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74 BURIED PLASTIC PIPE TECHNOLOGY
I m p a c t S t r e n g t h : F a l l i n g w e i g h t i m p a c t t e s t s b o t h at r o o m t e m p e r a t u r e 2 0 ~ 1 7 6 a n d at 0~ (32~ h a v e d e m o n s t r a t e d s u b s t a n t i a l i m p r o v e m e n t s in f a i l u r e l e v e l of P V C O p i p e c o m p a r e d w i t h PVC m a n u f a c t u r e d to A S T M D2241, " S t a n d a r d S p e c i f i c a t i o n for P o l y ( V i n y l Chloride) (PVC) P r e s s u r e - R a t e d Pipe (SDR S e r i e s ) , " or B r i t i s h S t a n d a r d BS3505, " B r i t i s h S t a n d a r d S p e c i f i c a t i o n for U n p l a s t i c i z e d P o l y v i n y l C h l o r i d e (PVC-U) P r e s s u r e P i p e s for C o l d F o t a b l e W a t e r . " T e s t i n g at 0~ d e m o n s t r a t e s t h a t PVC has f r o m 3 to 5 t i m e s g r e a t e r i m p a c t c a p a b i l i t y t h a n PVC, of the same
p r e s s u r e rating, m a d e to D 2 2 4 1 a n d B S 3 5 0 5 r e s p e c t i v e l y .
F a t i g u e R e s i s t a n c e : F i g u r e 5 r e v e a l s t h e t e s t d a t a c o m p a r i n g P V C O a n d PVC, for c y c l e s to f a i l u r e v e r s u s c y c l i c stress. This g r a p h d e m o n - s t r a t e s t h a t P V C O can s u s t a i n s u b s t a n t i a l l y m o r e c y c l e s for a g i v e n m a x i m u m c y c l i c s t r e s s t h a n PVC. F r o m t h e s e data, P V C O d e m o n s t r a t e s
r o u g h l y 50 t i m e s g r e a t e r r e s i s t a n c e . Or, g i v e n a s p e c i f i e d n u m b e r of cycles, P V C O can s u s t a i n a m u c h h i g h e r m a x i m u m c y c l i c s t r e s s t h a n PVC:
a p p r o x i m a t e l y two t i m e s g r e a t e r .
This m e c h a n i c a l s t r e s s w o r k was c o n d u c t e d b y P r o f e s s o r P.P. B e n h a m at Q u e e n s U n i v e r s i t y , B e l f a s t .
T y p i c a l a p p l i c a t i o n s w h e r e f a t i g u e b e c o m e s a c r i t i c a l d e s i g n v a r i a b l e are f o r c e m a i n s or g o l f c o u r s e i r r i g a t i o n s y s t e m s w h e r e p u m p s come on a n d off, or v a l v e s o p e n a n d close, at f r e q u e n t i n t e r v a l s .
S t r e s s C r a c k i n g (Crazing): A n o t h e r v e r y p o s i t i v e p r o p e r t y e n h a n c e m e n t r e s u l t i n g f r o m o r i e n t a t i o n is d r a m a t i c a l l y i n c r e a s e d r e s i s t a n c e to c r a z i n g [2,3]. O r i e n t a t i o n of s a m p l e s p r i o r to t e n s i l e tests, r e s u l t s in s t e e p e r e l a s t i c d e f o r m a t i o n c u r v e s t h a n n o r m a l l y e x t r u d e d PVC, a h i g h e r y i e l d stress, a l o w e r r e d u c t i o n in s t r e s s d u r i n g y i e l d i n g a n d less n e c k i n g of the s a m p l e s . A t a g i v e n o r i e n t a t i o n l e v e l (~=1.75) t h e y i e l d p o i n t d i s a p p e a r s , t h e r e is no d r o p in s t r e s s a n d no n e c k i n g of the s a m p l e w i l l t a k e place. T h i s m e a n s t h e p o s s i b i l i t y of l o c a l y i e l d i n g , w h i c h is n e c e s s a r y for the f o r m i n g of f i b r i l s in the crazes, has
d i s a p p e a r e d a n d c r a z e i n i t i a t i o n is no l o n g e r p o s s i b l e . T h e r e f o r e , PVC is m u c h m o r e l i k e l y to e x h i b i t a d u c t i l e f a i l u r e m o d e r a t h e r t h a n a p r e m a t u r e b r i t t l e failure. This p r o v i d e s g r e a t e r s a f e t y a n d c e r t a i n t y a b o u t the l i f e t i m e of P V C O pipes.
F ~ ( P E B / K ~ C E
Y o r k s h i r e I m p e r i a l P l a s t i c s (YIP) Ltd. f i r s t d e v e l o p e d P V C O p i p e s u n d e r the t r a d e n a m e '~uperpolyorc," f o l l o w i n g o r i g i n a l w o r k c a r r i e d out b y I m p e r i a l C h e m i c a l I n d u s t r i e s PLC. E x t e n s i v e d e v e l o p m e n t was u n d e r t a k e n b y YIP, b e g i n n i n g in 1972, a n d the p r o d u c t p r o v e n in d i a m e t e r s r a n g i n g f r o m i00 m m (4") to 450 ram (18"). T h e f i r s t i n s t a l l a t i o n s w e r e m a d e in the U.K. in 1974. Full s c a l e p r o d u c t i o n , b e g i n n i n g w i t h 150 m m (6") d i a m e t e r , b e g a n in 1982. In 1987, Y I P w a s a c q u i r e d b y U p o n o r a n d full s c a l e p r o d u c t i o n of 200 m m (8") b e g a n . O v e r the p a s t f i f t e e n years, s e v e r a l h u n d r e d t h o u s a n d feet of 150 m m a n d 200 m m (6" a n d 8") P V C O h a v e b e e n i n s t a l l e d t h r o u g h o u t Europe.
V i n i d e x b e g a n p r o d u c t i o n a n d d e l i v e r y o f P V C O in 1984 in A u s t r a l i a . S i n c e then, o v e r two h u n d r e d k i l o m e t e r s (over a h a l f m i l l i o n feet) h a v e b e e n i n s t a l l e d t h r o u g h o u t A u s t r a l i a .
BAUER ON ORIENTED PVC PIPE 75 E x t r u s i o n T e c h n o l o g i e s , Inc. (ETI) b e g a n i n s t a l l i n g test p r o j e c t s a c r o s s t h e U.S. in t h e s p r i n g of 1991. F u l l s c a l e p r o d u c t i o n of 150 m m a n d 200 m m (6" a n d 8") P V C O b e g a n in l a t e 1992. B y t h e t i m e this p a p e r was w r i t t e n , s e v e r a l t h o u s a n d feet h a d b e e n i n s t a l l e d w i t h i n the U.S. Plans are c u r r e n t l y u n d e r w a y to i n c r e a s e the d i a m e t e r range.
T h e e x p e r i e n c e s w i t h P V C O h a v e b e e n v e r y f a v o r a b l e . B e c a u s e it is e x p a n d e d u n d e r a u n i f o r m i n t e r n a l p r e s s u r e , b o t h t h e i n t e r n a l a n d e x t e r n a l f i n i s h of t h e p i p e are e x t r e m e l y s m o o t h . W h i l e p r i m a r i l y an a e s t h e t i c q u a l i t y , it is one w h i c h is h i g h l y t h o u g h t of b y the e n d user.
B e c a u s e the o u t s i d e d i a m e t e r is t h e same as t h e e x i s t i n g p r o d u c t s in the local, the f i t t i n g a v a i l a b i l i t y a n d r e q u i r e m e n t s are i d e n t i c a l to c u r r e n t l y s p e c i f i e d P V C p r o d u c t s . T h e r e f o r e , t h e r e are no s p e c i a l i t e m s r e q u i r e d for PVCO. B e c a u s e the O.D. is t h e s a m e as e x i s t i n g PVC, yet t h e w a l l t h i c k n e s s is reduced, P V C O has a l a r g e r I.D. w h i c h a l l o w s for g r e a t e r f l o w c a p a b i l i t y for a g i v e n d i a m e t e r . L i g h t e r w e i g h t a n d i n c r e a s e d i m p a c t r e s i s t a n c e h a v e m e a n t g r e a t e r h a n d l e a b i l i t y . P V C O c a n n o t be s o l v e n t c e m e n t e d . H o w e v e r , the g a s k e t e d b e l l a n d s p i g o t j o i n t a r e p r e f e r r e d for m o s t u n d e r g r o u n d a p p l i c a t i o n s due to e a s e of a s s e m b l y .
C O N C L U S I O N S
P V C O p i p e o f f e r s s e v e r a l p r o d u c t p r o p e r t y e n h a n c e m e n t s w h i c h are b e n e f i c i a l for its i n t e n d e d a p p l i c a t i o n s as a p r e s s u r e pipe. I n c r e a s e d t e n s i l e strength, i m p a c t r e s i s t a n c e , f a t i g u e r e s i s t a n c e a n d r e s i s t a n c e to c r a z i n g a r e all s i g n i f i c a n t i m p r o v e m e n t s to a p r o d u c t w h i c h has p e r f o r m e d e x t r e m e l y w e l l for o v e r f i f t y y e a r s - PVC pipe.
A t a t i m e w h e n t h e g l o b a l e c o n o m y d i c t a t e s e f f i c i e n c y , q u a l i t y a n d p e r f o r m a n c e , i n n o v a t i o n s s u c h as P V C O d e s e r v e s o u r e v a l u a t i o n a n d a c c e p t a n c e .
R E F E R E N C E S
Eli R i c h a r d C. S t e p h e n s o n , " S o m e R e c e n t D e v e l o p m e n t s in the P r o c e s s i n g of P o l y ( V i n y l C h l o r i d e ) , " J o u r n a l of V i n y l T e c h n o l o g y , Vol. 5, No. i, 1983.
[2] T . G . M e i j e r i n g , "The P r o d u c t i o n a n d A p p l i c a t i o n of B i o r i e n t e d PVC P i p e , " P l a s t i c s Pipe VII, B o o k of P r o c e e d i n g s , Europe, 1990.
[3] Dr. It. L.C.E. Struik, " C r a z i n g & F r a c t u r e , " T N O report, Nov.
1981.
[4] T. G. M e i j e r i n g a n d P. B e n j a m i n , " M o l e c u l a i r e B i o r i e n t a t i e v a n P V C / C P E G a z b u i z e n , " Gas 9, 1986.
Rehabilitation
Douglas G. Klewenol
P H Y S I C A L P R O P E R T I E S A N D C H E M I C A L R E S I S T A N C E O F S E L E C T E D RESINS FOR CURED-IN-PLACE P I P E REHABILITATION
REFERENCE: Kleweno, D.G., "Physical Properties and Chemical Resistance of Selected Resins for Cured-in-Place Pipe Rehabilitation,"
Buried Plastic PiDe Technoloav: 2nd Volume, ASTM STP 1222, Dave Eckstein, Ed., American Society for Testing and Materials, Philadelphia, 1994.
ABSTRACT: This report is a summary of the basic chemistry, physical properties, and chemical resistance of six commercially available resins (i.e. vinyl ester, polyester, and epoxy) used for making cured-in-place pipe (CIPP). Flexural and tensile properties are included and chemical resistance from a one year study for each resin.
system as a CIPP resin/felt composite in acids, bases, and oxidizing agents currently found or introduced into municipal sanitary sewer systems [1,2,1,41.
Conclusions drawn from this report indicate the three different types of resin had measurably different flexural and tensile properties that ranged the from stiff, brittle behavior to very flexible. Among the test group the two polyesters were relatively stiff, the two epoxy vinyl esters had a balance of high stiffness and strength, one epoxy system was extremely flexible, while the other was similar to the epoxy vinyl esters. The one year chemical resistance also clearly
distinguished the performance of the three types of resins. Overall, the two polyester resins performed at an intermediate level, the two epoxy vinyl ester resins demonstrated superior broad range chemical resistance, and the epoxy performance ranged from poor to excellent depending on the type of curing agent used.
KEY WORDS: physical properties, chemical resistance, thermoset resins, cured-in-place pipe, pipe
Accelerated aging caused by hydrogen sulfide-related corrosion has generally caused premature failure of our nation's sanitation
infrastructure. Awareness of the existence of corrosion and concern about its effect on the sewer system has been an issue since concrete first started displacing clay and brick as the primary materials of sewer construction. Even though it was known that some corrosion would take place, precautions taken in the sewer design and pipe thickness were intended to produce the 100+ year life expectancy of the sewer system [l]. However, within the last 15 years, hydrogen sulfide-related 'Sr. Development Engineer, Chemical Resistance Application Development Labs, The Dow Chemical Company, Texas Division, 2301 N. Brazosport Blvd., B-2009, Freeport, Texas 11541-3251
79
80 BURIED PLASTIC PIPE TECHNOLOGY
c o r r o s i o n has a c c e l e r a t e d at an a l a r m i n g r a t e t h r o u g h o u t the U.S. a n d h a s b e e n d o c u m e n t e d by the E n v i r o n m e n t a l P r o t e c t i o n A g e n c y (EPA) in a n u m b e r of s t u d i e s [!,~,~,~]- T h e p r i m a r y c a u s e of the a c c e l e r a t e d c o r r o s i o n has b e e n a t t r i b u t e d to t h e p r o l i f e r a t i o n of s e v e r a l s t r a i n s of D e s u l f o v i b r i o b a c t e r i a in r e s p o n s e to the r e d u c t i o n of c y a n i d e a n d o t h e r h e a v y m e t a l p o l l u t a n t s r e g u l a t e d b y the E P A [l,~]- An a n a e r o b i c
b a c t e r i a l i v i n g in the s l i m e l a y e r on the l o w e r h e m i s p h e r e of the p i p e r e d u c e s s u l f u r - c o n t a i n i n g c o m p o u n d s to h y d r o g e n s u l f i d e (H2S) . A n a e r o b i c s t r a i n l i v i n g in the s l i m e on t h e c r o w n of the p i p e o x i d i z e s h y d r o g e n s u l f i d e to s u l f u r i c a c i d (H2SO4). T h e a e r o b i c b a c t e r i a h a v e b e e n o b s e r v e d to p r o d u c e s u l f u r i c a c i d u p to 5% b y w e i g h t (i.e., p H 0.28) a n d r e m a i n s v i a b l e in c o n c e n t r a t i o n s as h i g h as 7% (i.e., p H <
0.15) [[,!].
S e w a g e o v e r f l o w r e s t r i c t i o n s , o v e r f l o w m o n i t o r i n g , a n d s t i f f fines for n o n c o m p l i a n c e i m p o s e d by the E P A a n d s t a t e w a t e r a g e n c i e s h a v e m o t i v a t e d m u n i c i p a l s a n i t a t i o n d e p a r t m e n t s to d e v e l o p a g g r e s s i v e p r o g r a m s to m a i n t a i n a n d / o r r e h a b i l i t a t e t h e i r s y s t e m s [~]. T h e s e p r o g r a m s h a v e f o s t e r e d the g r o w t h a n d a c c e p t a n c e of n u m b e r of t r e n c h l e s s p i p e r e h a b i l i t a t i o n t e c h n i q u e s , as w e l l as c r e a t i v e m a i n t e n a n c e
s o l u t i o n s [~,~,~].
T h e c u r r e n t e m p h a s i s on r e b u i l d i n g i n f r a s t r u c t u r e has c r e a t e d the e n v i r o n m e n t for t h e d e v e l o p m e n t a n d a c c e p t a n c e o f a number of d i f f e r e n t m e t h o d s of p e r f o r m i n g CIPP. A l t h o u g h the c o n s t r u c t i o n a n d i n s t a l l a t i o n o f e a c h t e c h n i q u e v a r i e s slightly, t h e y all i n c o r p o r a t e the u s e of non- w o v e n a n d / o r w o v e n f a b r i c f o r m e d i n t o a t u b e t h a t is i m p r e g n a t e d w i t h a t h e r m o s e t t i n g r e s i n a n d s u b s e q u e n t l y c u r e d in p l a c e to f o r m a n e w p i p e i n s i d e the o l d c o n d u i t . O n c e the j o b is c o m p l e t e d the c l i e n t has a n e w p i p e c o m p o s e d of a p p r o x i m a t e l y 6 5 - 8 5 % t h e r m o s e t t i n g r e s i n a n d 1 5 - 3 5 % f i b e r s or fabric. A s s u m i n g c o n s i s t e n t i n s t a l l a t i o n , the long t e r m p e r f o r m a n c e of that p r o d u c t w i l l b e s t r o n g l y c o n t r o l l e d by t h e t y p e of r e s i n used, n o m a t t e r w h a t f i b r o u s m a t e r i a l w a s u s e d to c o n s t r u c t the t u b e itself.
In o r d e r to e x t e n d the life o f e x i s t i n g i n t a c t c o n c r e t e s e w e r systems, m a n y s a n i t a t i o n d i s t r i c t s h a v e d e v e l o p e d c h e m i c a l t r e a t m e n t p r o t o c o l s a n d i n v e n t i v e a p p l i c a t i o n t e c h n i q u e s to c o n t r o l h y d r o g e n s u l f i d e c o r r o s i o n [~,4,~]. D e p e n d i n g o n the p r o g r a m o b j e c t i v e s , r e g u l a r a d d i t i o n of o n e or m o r e c h e m i c a l s c a n r e d u c e e x i s t i n g h y d r o g e n sulfide, n e u t r a l i z e the acids, t e m p o r a r i l y s h o c k the b a c t e r i a , or a c c o m p l i s h all three. C h e m i c a l s c o m m o n l y u s e d for this p u r p o s e i n c l u d e s s t r o n g o x i d i z i n g a g e n t s (i.e., h y d r o g e n p e r o x i d e , s o d i u m h y p o c h l o r i t e
(active i n g r e d i e n t in bleach), c h l o r i n e , p o t a s s i u m p e r m a n g a n a t e ) , w e a k o x i d i z i n g a g e n t s (i.e., o x y g e n a n d a i r i n j e c t i o n ) , a c i d n e u t r a l i z i n g b a s e s (i.e., s o d i u m h y d r o x i d e ) , a n d iron s a l t s [~,!]-
In general, this n a t i o n ' s s a n i t a t i o n s y s t e m has c h a n g e d
d r a m a t i c a l l y w i t h i n the last t w o d e c a d e s a n d w i l l c o n t i n u e to evolve.
S t u d i e s d e m o n s t r a t e that d e c r e a s e d f l o w s i n c r e a s e the c o r r o s i v e e n v i r o n m e n t in s e w e r s y s t e m s [~]. It is s u g g e s t e d that m u n i c i p a l e f f o r t s to r e d u c e i n f l o w a n d i n f i l t r a t i o n (I/I) t h r o u g h r e h a b i l i t a t i o n w i l l a l s o i n c r e a s e h y d r o g e n s u l f i d e - r e l a t e d c o r r o s i o n a n d c o n c e n t r a t e all o t h e r c h e m i c a l a g e n t s p r e s e n t . T h e s e a n d o t h e r u n p r e d i c t a b l e c h a n g e s m a y n e c e s s i t a t e c h e m i c a l t r e a t m e n t w i t h i n s a n i t a t i o n s y s t e m s t h a t p r e s e n t l y are not c h e m i c a l l y t r e a t e d . H o w e v e r , m o s t c h e m i c a l s u s e d for h y d r o g e n s u l f i d e r e d u c t i o n c a n be m u c h m o r e c h e m i c a l l y a g g r e s s i v e to g e n e r a l p u r p o s e t h e r m o s e t p o l y m e r s t h a n h y d r o g e n s u l f i d e or s u l f u r i c acid. To date, o n l y m u n i c i p a l i t i e s u s i n g the " G r e e n Book" r e q u i r e c h e m i c a l r e s i s t a n c e q u a l i f i c a t i o n for C I P P that w i l l be e x p o s e d to c h e m i c a l s i n t r o d u c e d into the s a n i t a t i o n s y s t e m [8,~].
KLEWENO ON CURED-IN-PLACE PIPE REHABILITATION 81
C u r e d - i n - p l a c e p i p e has b e n e f i t t e d t r e m e n d o u s l y b y the d e v e l o p m e n t of A S T M s t a n d a r d i z a t i o n a n d c o n t r a c t o r s p e c i f i c d o c u m e n t a t i o n d e t a i l i n g the m e t h o d of c o n s t r u c t i o n a n d i n s t a l l a t i o n . H o w e v e r , a r e v i e w of S t a n d a r d P r a c t i c e for R e h a b i l i t a t i o n of E x i s t i n g P i p e l i n e s a n d C o n d u i t s b y the I n v e r s i o n a n d C u r i n g of a R e s i n - I m p r e g n a t e d T u b e (F 1216) a n d m o s t m u n i c i p a l m a t e r i a l of c o n s t r u c t i o n s p e c i f i c a t i o n s for C I P P o f f e r t h e m u n i c i p a l w a s t e w a t e r e n g i n e e r v e r y l i t t l e g u i d a n c e for the
c l a s s i f i c a t i o n , r e l a t i v e p e r f o r m a n c e , or s e l e c t i o n o f the thermosetting r e s i n s u s e d for CIPP. A s a result, m o s t m u n i c i p a l w a s t e w a t e r e n g i n e e r s a r e left w i t h no a l t e r n a t i v e but to r e l y e x c l u s i v e l y on the c o n t r a c t o r to s e l e c t the t h e r m o s e t t i n g resin. T h e c i v i l e n g i n e e r i n g c o m m u n i t y s p e c i f y i n g CIPP n e e d s t h i s i n f o r m a t i o n a n d m u s t b e c o m e m o r e
k n o w l e d g e a b l e . P r o p e r s c r e e n i n g a n d s e l e c t i o n of the r e s i n s y s t e m s u s e d for all a s p e c t s of s e w e r r e h a b i l i t a t i o n w i l l m a x i m i z e u s e of p r o j e c t funds for the p r e s e n t c o n d i t i o n s of the s e w e r a n d m a y a l s o p r o v i d e i n s u r a n c e a g a i n s t a n t i c i p a t e d a n d u n a n t i c i p a t e d e n v i r o n m e n t a l c h a n g e s that w i l l be o c c u r r i n g in the n e x t I00 y e a r s [~]. T h e d a t a in t h i s p a p e r is i n t e n d e d as o n e g e n e r a l s o u r c e of i n f o r m a t i o n a b o u t t h e r m o s e t t i n g r e s i n s u s e d for c u r e d - i n - p l a c e pipe.
E X P E R I M E N T A L M E T H O D S
M a t e r i a l s
The r e s i n s u s e d in this s t u d y a r e all c o m m e r c i a l l y a v a i l a b l e a n d h a v e b e e n or are c u r r e n t l y b e i n g u s e d for C I P P r e h a b i l i t a t i o n .
i. I s o p h t h a l i c p o l y e s t e r r e s i n - i (PER-I) 2. I s o p h t h a l i c p o l y e s t e r r e s i n - 2 (PER-2)
3. B i s p h e n o l A e p o x y r e s i n - i / F l e x i b i l i z e d a m i n e c u r i n g a g e n t (ER-I) 4. B i s p h e n o l A e p o x y r e s i n - 2 / M u l t i a m i n e / I m i d a z o l e c u r i n g a g e n t (ER-2) 5. B i s p h e n o l A e p o x y v i n y l e s t e r - i (VER-I)
6. B i s p h e n o l A e p o x y v i n y l e s t e r - 2 (VER-2)
The PER-I, PER-2, VER-I, a n d V E R - 2 r e s i n s w e r e c a t a l y z e d w i t h a c o b a l t p r o m o t e r a n d the c o m b i n a t i o n o~ t w o p e r o x i d e i n i t i a t o r s . T h e s a m e b i s p h e n o l A (bis A) e p o x y r e s i n W a s c u r e d w i t h t w o d i f f e r e n t a m i n e b a s e d c u r i n g a g e n t s a c c o r d i n g to p r o p e r r e a c t i v e e q u i v a l e n t
s t o i c h i o m e t r i c ratios. C u r e d - i n - p l a c e p i p e c o m p o s i t e s a m p l e s m a d e w i t h t h e s e six r e s i n s w e r e c o m p o s e d of r e s i n i m p r e g n a t e d p o l y e s t e r felt that w a s v a c u u m i m p r e g n a t e d w i t h c a t a l y z e d r e s i n a n d c u r e d 4.5 h o u r s at 1 0 0 ~ (212~ b e t w e e n s p a c e d a l u m i n u m p l a t e s . T h e p o l y e s t e r felt c o n s i s t s of s h o r t p o l y e s t e r f i b e r s n e e d l e d into a d e n s e felt. P o l y e s t e r felt w a s c h o s e n b e c a u s e it is c u r r e n t l y the m o s t c o m m o n m a t e r i a l of c o n s t r u c t i o n for C I P P r e h a b i l i t a t i o n .
T e s t M e t h o d s
T h r e e p o i n t b e n d f l e x u r a l t e s t i n g w a s c a r r i e d out a c c o r d i n g to the A S T M Test M e t h o d for F l e x u r a l P r o p e r t i e s of U n r e i n f o r c e d a n d R e i n f o r c e d P l a s t i c s a n d E l e c t r i c a l I n s u l a t i n g M a t e r i a l s (D 790) test m e t h o d I. A s t a n d a r d L / d r a t i o of 16:1 w a s u s e d a n d s p e c i m e n d i m e n s i o n s , s u p p o r t span, a n d rate of l o a d i n g was d e t e r m i n e d f r o m T a b l e 1 in D 790.
S p e c i m e n d i m e n s i o n s w e r e h e l d c o n s t a n t at 12.7 m m x 3.2 m m x 76.2 m m a n d t e s t e d w i t h a 50.8 m m (2 in.) s u p p o r t s p a n at a r a t e of 1.3 m m / m i n (0.05 in/min). T a n g e n t m o d u l u s of e l a s t i c i t y , m a x i m u m s t r e s s a n d s t r a i n w e r e d e t e r m i n e d as d e s c r i b e d b y test m e t h o d I c o n d i t i o n s w i t h i n D 790.
T e n s i l e p r o p e r t i e s w e r e e v a l u a t e d a c c o r d i n g to A S T M M e t h o d for T e n s i l e
82 BURIED PLASTIC PIPE TECHNOLOGY
P r o p e r t i e s of P l a s t i c s (D 638). S p e c i m e n s w e r e a p p r o x i m a t e l y 3 . 1 7 5 m m {0.125 in.) t h i c k a n d w e r e dog b o n e d to c o n f o r m w i t h T y p e I d i m e n s i o n s g i v e n in Fig. 1 of D 638. A 50.8 m m (2 in.) e x t e n s o m e t e r w a s a t t a c h e d to the n a r r o w s e c t i o n of e a c h s p e c i m e n for a c c u r a t e m e a s u r e m e n t of p e r c e n t e l o n g a t i o n a n d slope. S p e c i m e n s w e r e l o a d e d at a c o n s t a n t r a t e of 5.08 m m / m i n (0.2 in./min.). All s p e c i m e n s b r o k e in a b r i t t l e m a n n e r w i t h o u t a n y y i e l d and t h i s is s h o w n in Fig. A I . 2 of D 638. M o d u l u s of e l a s t i c i t y , s t r e n g t h a n d e l o n g a t i o n at b r e a k w e r e d e t e r m i n e d as
d e s c r i b e d in D 638. All f l e x u r a l a n d t e n s i l e s p e c i m e n s w e r e
e q u i l i b r a t e d at 7 0 ~ a n d 50% r e l a t i v e h u m i d i t y for 40 h o u r s p r i o r to t e s t i n g . T e s t i n g was d o n e w i t h an I n s t r o n l o a d frame (model 4505) e q u i p p e d w i t h a u t o - r a n g i n g 1 kN (224 ibf) a n d 50 kN (11.2 kip) load c e l l s for f l e x u r a l and t e n s i l e testing, r e s p e c t i v e l y .
The c h e m i c a l r e s i s t a n c e of C I P P c o m p o s i t e s w e r e e v a l u a t e d in e x t r e m e s of a c i d i t y a n d b a s i c i t y , as w e l l as to o x i d i z i n g a g e n t s . T h e a c i d s t e s t e d a r e 25% sulfuric, 5% nitric, a n d 20% h y d r o c h l o r i c (having l o w pH), the b a s e s are 5% a m m o n i u m a n d 5% s o d i u m h y d r o x i d e (having h i g h pH), a n d t h e o x i d i z i n g a g e n t s are 0.5% a n d 5% s o d i u m h y p o c h l o r i t e (i.e., b l e a c h ) , 5% h y d r o g e n p e r o x i d e , a n d 5% p o t a s s i u m p e r m a n g a n a t e . T h e c h e m i c a l b a t h s w e r e m a i n t a i n e d at 49~ (120~ s i n c e t h i s is w i t h i n the 1 4 0 ~ i n p u t t e m p e r a t u r e limit f r e q u e n t l y e n f o r c e d by m o s t s a n i t a t i o n d e p a r t m e n t s . C h e m i c a l r e s i s t a n c e t e s t i n g w a s a c c o m p l i s h e d w i t h 3 . 1 7 5 m m
(0.125 in.) t h i c k r e s i n / p o l y e s t e r felt c o m p o s i t e s h a v i n g e x p o s e d e d g e s a n d a n o m i n a l s u r f a c e a r e a of 5806 m m 2 (9 in.2). C h e m i c a l e x p o s u r e a n d c o u p o n e v a l u a t i o n w a s c a r r i e d out in a m a n n e r c o n s i s t e n t w i t h the A S T M S t a n d a r d P r a c t i c e for D e t e r m i n i n g C h e m i c a l R e s i s t a n c e of T h e r m o s e t t i n g R e s i n s U s e d in G l a s s - F i b e r - R e i n f o r c e d S t r u c t u r e s I n t e n d e d for L i q u i d S e r v i c e (C 581). Once r e m o v e d f r o m the c h e m i c a l baths, t h e c o u p o n s w e r e r i n s e d w i t h t a p water, a n d p a t t e d d r y w i t h p a p e r t o w e l s b e f o r e m e a s u r i n g w e i g h t a n d t h i c k n e s s . T h e c o u p o n s w e r e t h e n cut a n d e v a l u a t e d for
f l e x u r a l p r o p e r t i e s as r ~ e v i o u s l y d e s c r i b e d . C h e m i c a l r e s i s t a n c e c o u p o n s w e r e not e q u i l i b r a t e d , but w e r e t e s t e d u n d e r c o n d i t i o n s of 7 0 ~ a n d 50% r e l a t i v e h u m i d i t y w i t h i n 24 h o u r s u p o n r e m o v a l f r o m the c h e m i c a l bath. T h e m a j o r i t y of s p e c i m e n s w e r e e v a l u a t e d at i n t e r v a l s of i, 3, 6, a n d 12 m o n t h s . S o m e of the ER-I, PER-l, a n d PER-2 s p e c i m e n s p r e m a t u r e l y f a i l e d in s o m e of the c h e m i c a l s b e f o r e t h e 12 m o n t h e v a l u a t i o n . O n l y 6 m o n t h s of d a t a is c u r r e n t l y a v a i l a b l e for the ER-2 r e s i n s y s t e m b e c a u s e
it w a s s t a r t e d at a l a t e r time a n d the s t u d y has not b e e n c o m p l e t e d . D I S C U S S I O N A N D R E S U L T S
R e s i n C h e m i s t r v a n d P r o c e s s i n q
I n t r o d u c t i o n - - T h e t h r e e t y p e s of t h e r m o s e t t i n g r e s i n s m o s t c o m m o n l y u s e d for c u r e d - i n - p l a c e p i p e a r e p o l y e s t e r , v i n y l ester, a n d e p o x y resins. 2 o l y e s t e r s are the least e x p e n s i v e a n d a r e b y far the m o s t c o m m o n l y u s e d t h e r m o s e t w i t h v i n y l e s t e r s a n d e p o x y r e s i n s u s e d to a l e s s e r d e g r e e . Just as "concrete" is a g e n e r a l i z e d n a m e for that m a t e r i a l of c o n s t r u c t i o n , p o l y e s t e r , v i n y l ester, a n d e p o x y a r e g e n e r i c n a m e s for a w i d e v a r i e t y of r e s i n s that fall into e a c h c a t e g o r y . In a d d i t i o n , just as a g g r e g a t e size, shape, a n d v o l u m e m i g h t d e t e r m i n e the p r i c e a n d p e r f o r m a n c e of concrete, the m o l e c u l a r c o m p o n e n t s of
t h e r m o s e t t i n g r e s i n s a l s o d e t e r m i n e p r i c e a n d p e r f o r m a n c e .
P o l y e s t e r - - U n s a t u r a t e d t h e r m o s e t t i n g p o l y e s t e r r e s i n s a r e the p r o d u c t of a p o l y c o n d e n s a t i o n r e a c t i o n b e t w e e n s p e c i f i c g l y c o l s a n d s a t u r a t e d a n d u n s a t u r a t e d d i c a r b o x y l i c a c i d s . T y p i c a l g l y c o l s ,
s a t u r a t e d a n d u n s a t u r a t e d d i c a r b o x y l i c a c i d s h a v e b e e n l i s t e d in F i g u r e
KLEWENO ON CURED-IN-PLACE PIPE REHABILITATION 83
I. It is the s a t u r a t e d a c i d by w h i c h the p o l y e s t e r r e s i n d e r i v e s its n a m e a n d a n e l e m e n t of its i n h e r e n t p e r f o r m a n c e . T h e u n s a t u r a t e d d i c a r b o x y l i c a c i d c o n t r i b u t e s the r e a c t i v e p o l y m e r i z a t i o n site. The g l y c o l l i n k s the two t y p e s of d i c a r b o x y l i c a c i d s t o g e t h e r . A c o m m o n
( a l t h o u g h not the only) c l a s s of p o l y e s t e r s u s e d for C I P P is that p r o d u c e d w i t h i s o p h t h a l i c acid, a n d is t h e r e f o r e c a l l e d an u n s a t u r a t e d
i s o p h t h a l i c (Iso) p o l y e s t e r resin. T h e g e n e r i c s t r u c t u r e of an Iso p o l y e s t e r is g i v e n in F i g u r e 2 w h e r e a n u m b e r o f t h e p r e d o m i n a n t f e a t u r e s of the p o l y m e r h a v e b e e n l a b e l l e d . T h e t e r m " u n s a t u r a t e d "
r e f e r s to the (-C=C-), w h i c h are the p o l y m e r i c r e a c t i o n s i t e s that f a c i l i t a t e cross l i n k i n g d u r i n g the c u r i n g p r o c e s s . T h e m u l t i p l e e s t e r g r o u p s (-CO0-) a r e the w e a k link in the p o l y m e r , p r o v i d i n g s i t e s for h y d r o l y s i s in the p r e s e n c e of s t r o n g a c i d s a n d b a s e s .
E p o x y - - E p o x y r e s i n s are the r e a c t i o n p r o d u c t of v a r i o u s t y p e s of p h e n o l s a n d e p i c h l o r o h y d r i n , w h i c h p r o v i d e s the p o l y m e r i c r e a c t i o n site.
T h e t y p e of p h e n o l u s e d is t y p i c a l l y h o w the n a m e of the e p o x y is d e r i v e d . T h e m o s t c o m m o n e p o x y is t h a t m a d e w i t h b i s p h e n o l A (bis A) a n d is o f t e n r e f e r r e d to as a bis A e p o x y r e s i n (Fig. 4). A l i s t i n g of some of t h e m o s t c o m m o n p h e n o l s are g i v e n in the f l o w c h a r t in F i g u r e 3.
T h e b i s A e p o x y b a c k b o n e (Fig. 4) p r o v i d e s t o u g h n e s s a n d the p o l y m e r i c r e a c t i o n s i t e s a r e o n l y l o c a t e d at e a c h e n d of t h e m o l e c u l e . H y d r o x y l (-OH) g r o u p s in the m i d d l e a n d h y d r o x y l g r o u p s p r o d u c e d at the r e a c t i o n s i t e c a n p r o v i d e i m p r o v e d a d h e s i o n (Fig. 4). H o w e v e r , the p o l a r h y d r o x y l groups, c h o i c e of c u r i n g agent, a n d / o r p r e s e n c e of r e a c t i v e d i l u e n t s (see P r o c e s s i n g ) are a l s o s o u r c e s for c h e m i c a l d e g r a d a t i o n .
V i n y l E s t e r - - E p o x y v i n y l e s t e r r e s i n s a r e t h e r e a c t i o n p r o d u c t of a n e p o x y r e s i n w i t h m e t h a c r y l i c acid. T h e m e t h a c r y l i c a c i d p r o v i d e s the u n s a t u r a t e d (-C=C-) p o l y m e r i c r e a c t i o n site a n d a s i n g l e e s t e r g r o u p
(Figures 3 a n d 5). The formal n a m e of the v i n y l e s t e r is d e r i v e d b y the t y p e of e p o x y used. W h e n s t a r t i n g w i t h a bis A e p o x y resin, t h e r e s u l t is a b i s A v i n y l e s t e r (Fig. 5) that h a s the t o u g h n e s s a n d i m p r o v e d w e t t i n g of the p a r e n t e p o x y a n d the r e a c t i v e p o l y m e r i z a t i o n s i t e s of a p o l y e s t e r . F r o m a m o l e c u l a r basis, b i s A e p o x y v i n y l e s t e r s h a v e b e t t e r c h e m i c a l r e s i s t a n c e t h a n p o l y e s t e r s b e c a u s e t h e r e a r e t y p i c a l l y o n l y two r e a c t i o n s i t e s a n d o n l y t w o e s t e r g r o u p s p e r m o l e c u l e . In a d d i t i o n , all t h e e s t e r g r o u p s a r e s h i e l d e d w i t h m e t h y l g r o u p s (Fig. 5), t h e r e b y p r o v i d i n g a d d i t i o n a l r e s i s t a n c e to c h e m i c a l d e g r a d a t i o n v i a h y d r o l y s i s .
P r o c e s s i n a - - W i t h r e g a r d to p r o c e s s i n g , e a c h r e s i n h a s its o w n a d v a n t a g e s or d i s a d v a n t a g e s , d e p e n d i n g o n the a p p l i c a t i o n . P o l y e s t e r s a n d v i n y l e s t e r s are d i l u t e d w i t h s t y r e n e m o n o m e r w h i c h a l s o
p a r t i c i p a t e s in the free r a d i c a l i n i t i a t e d p o l y m e r i z a t i o n . F r e e r a d i c a l s for the c u r e a r e g e n e r a t e d w i t h the u s e o f a s m a l l a m o u n t
(i.e., 0 . 5 - 2 . 5 % b y weight) of a p e r o x i d e . S t y r e n e a l s o a l l o w s
m a n u f a c t u r e r s to p r o v i d e v e r y l o w v i s c o s i t y r e s i n s that e a s i l y w e t out r e i n f o r c i n g fibers, fabric, a n d / o r m i n e r a l f i l l e r s . E p o x y r e s i n s r e q u i r e a r e a c t i v e e q u i v a l e n t of a c u r i n g a g e n t (i.e., 1 0 - 1 1 5 % b y w e i g h t ) , w h i c h a l s o s t r o n g l y d i c t a t e s c u r e times, the f i n a l p h y s i c a l p r o p e r t i e s , a n d c h e m i c a l r e s i s t a n c e . By far the m o s t c o m m o n c u r i n g a g e n t s a r e the f a m i l y of m o d i f i e d a m i n e s . E p o x y r e s i n s a r e g e n e r a l l y m u c h m o r e v i s c o u s a n d are s o m e t i m e s d i f f i c u l t to w e t - o u t f i b e r s a n d f i l l e r s at a m b i e n t t e m p e r a t u r e s , but p r o c e s s i n g c a n be o p t i m i z e d w i t h the u s e of r e a c t i v e d i l u e n t s a n d l o w v i s c o s i t y c u r i n g a g e n t s .
84 BURIED PLASTIC PIPE TECHNOLOGY
SATURATED DICARBOXYLIC ACIDS
ORTHOPHTHALIC ACID ISOPHTHALIC ACID TEREPHTHALIC ACID
ADIPIC ACID +
UNSATURATED DICARBOXYLIC ACIDS
MALEIC ANHYDRIDE FUMARIC ACID
MALEIC ACID
GLYCOLS PROPYLENE GLYCOL DIETHYLENE GLYCOL DIPROPYLENE GLYCOL
~ I 0 N ~ 0 ~ o ~ ~,~ I j
FIG. i - - F l o w c h a r t of c o m m o n c h e m i c a l c o m p o n e n t s a v a i l a b l e for m a n u f a c t u r i n g d i f f e r e n t t y p e s of u n s a t u r a t e d p o l y e s t e r r e s i n s .
MULTIPLE ESTER GROUPS WITHIN MOLECULE
.[ o 01
Ho-c-~=~-~-o-~,~-o~-o-~. - ~ - o - ~ - ~ - o - & ~ = c , - g o-c~-~-o,
t t ":.~,o0
I MULTIPLE INTERNAL REACTIVE POLYMERIZATION SITES AROMATIC RING PROVIDES RIGIDITY
TERMINAL ACID OR HYDROXYL GROUPS PROVIDE GOOD WETI'ING & ADHESION
FIG. 2 - - G e n e r i c s t r u c t u r e of a n i s o p h t h a l i c p o l y e s t e r resin.
PHENOL I BISPHENOL A I TETRABROMO BISPHENOL A ] PHENOL FORMALDEHYDE NOVOLAC I RIPHENOL FORMALDEHYDE
I
+ I EPICHLOROHYDRIN I
I EPOXYRES,N I + I METHACRYLIC ACID I ACRYLIC ACID
l
I EPOXY VINYL ESTER RESINS I
FIG. 3 - - F l o w c h a r t of c o m m o n c h e m i c a l c o m p o n e n t s a v a i l a b l e to m a n u f a c t u r e e p o x y a n d e p o x y v i n y l e s t e r t h e r m o s e t t i n g r e s i n s .
K L E W E N O ON C U R E D - I N - P L A C E PIPE R E H A B I L I T A T I O N
[ o 9 1 6 9 ] o
O CH 3 (}4 t / \
/ \
H2C- CH- OH 2 - - C - - O - OH 2 - CH- CH 2 O- CH2 - C H - CH2
~ N
I t N = l t o 3
HYDROXYL GROUP ~ IMPROVEDWEI-rING
AND ADHESION
BISPHENOL A EPOXY RESIN BACKBONE ~ TOUGHNESS
TERMINAL REACTIVE POLYMERIZATION SITES
85
FIG. 4 - - G e n e r i c c h e m i c a l s t r u c t u r e of a b i s p h e n o l A e p o x y resin.
o r c., q o
~C=C-~-O-CH2-CH-CH2 1 O- ~ C ('~-">-O-CH2*CH-CH~/ O-~-C=CH2
N CH.
/ / | EPOXY RESIN BACKBONE ~ TOUGHNESS
/ | HYDROXYL GROUP ~ IMPROVED WETTING & ADHESION
/ ONLY TWO ESTER GROUPS PER MOLECULE - - ~ .MPROVED CHEM.OA. RES METHYL GROUP SH,ELDS T . E ESTER - - - " ,MPROVED C.EM,CAL RES,STANOE REACTIVE POLYMERIZATION SITE ONLY AT THE ENDS OF THE MOLECULE
FIG. 5 - - G e n e r i c s t r u c t u r e of a b i s p h e n o l A e p o x y v i n y l e s t e r resin.
Short a n d L o n a T e r m P h y s i c a l P r o p e r t i e s
I n t r o d u c t i o n - - A s m e n t i o n e d in the i n t r o d u c t i o n of this paper, t h e r e is a d i s t i n c t d i f f e r e n c e b e t w e e n short a n d long t e r m p h y s i c a l p r o p e r t i e s , as w e l l as the test m e t h o d o l o g i e s u s e d to d i s t i n g u i s h the two. T h r o u g h the u s e of e x a m p l e s a n d data, the d i s t i n c t i o n b e t w e e n the t w o a n d t h e type of i n f o r m a t i o n o b t a i n e d w i l l be c l a r i f i e d . T y p i c a l l y , short t e r m p r o p e r t i e s are c o n f i r m a t o r y or q u a l i f y i n g m e a s u r e s of m i n i m u m m a t e r i a l p r o p e r t i e s o b t a i n e d by r e l a t i v e l y q u i c k t e s t m e t h o d s .
Flexural, tensile, a n d c o m p r e s s i o n t e s t s are e x a m p l e s of m a t e r i a l e v a l u a t i o n t e c h n i q u e s that r a p i d l y load a s p e c i m e n to f a i l u r e a n d r e q u i r e m i n u t e s to p e r f o r m . Short t e r m p r o p e r t i e s are i m p o r t a n t for m i n i m u m r e q u i r e m e n t s but a r e not n e c e s s a r i l y an i n d i c a t o r of long t e r m m a t e r i a l p e r f o r m a n c e . L o n g t e r m p r o p e r t i e s such as c r e e p (flexural, tensile), c h e m i c a l resistance, a n d s t r a i n c o r r o s i o n a r e are i n t e n d e d to a s c e r t a i n t h e p e r f o r m a n c e of a m a t e r i a l or m a n u f a c t u r e d a r t i c l e e x p o s e d
86 BURIED PLASTIC PIPE TECHNOLOGY
to lower level, or "real w o r l d " e n v i r o n m e n t a l s t r e s s e s . W h e n u s i n g l o n g t e r m t e s t i n g p r o t o c o l s it is a l s o d e s i r a b l e to test a m a t e r i a l to failure, e x c e p t f a i l u r e s h o u l d o c c u r s l o w l y o v e r a long p e r i o d of time.
U n f o r t u n a t e l y , l o n g t e r m t e s t i n g can r e q u i r e y e a r s to o b t a i n m e a n i n g f u l d i s t i n c t i o n s a n d is o f t e n a c c e l e r a t e d to a r e a s o n a b l e d e g r e e to o b t a i n m e a n i n g f u l c o m p a r i s o n s in m o n t h s i n s t e a d of d e c a d e s . P r a c t i c a l e x p e r i e n c e w i t h t h e test m e t h o d s , m a t e r i a l s , k n o w l e d g e of the a c t u a l s e r v i c e c o n d i t i o n s , and c o m m o n s e n s e are a r e s e a r c h e r ' s g u i d e in
d e t e r m i n i n g r e a s o n a b l e a c c e l e r a t e d test c o n d i t i o n s that y i e l d m e a n i n g f u l d a t a w i t h i n a lifetime. O n l y t h r o u g h c a r e f u l l y d e s i g n e d a n d c o n t r o l l e d e x p e r i m e n t s can o n e m a k e c o n c l u s i o n s a b o u t l o n g t e r m m a t e r i a l
p e r f o r m a n c e w i t h the use of short t e r m test d a t a .
F l e x u r a l a n d T e n s i l e - - T h e f l e x u r a l a n d t e n s i l e d a t a g i v e n in T a b l e 1 is that of neat r e s i n p r o p e r t i e s not h a v i n g a n y f i l l e r s o r f i b e r s a d d e d . T h e d a t a in T a b l e 2 w a s g e n e r a t e d by t e s t i n g C I P P r e s i n / f e l t c o m p o s i t e s p r e p a r e d as d e s c r i b e d in the M a t e r i a l s s e c t i o n of the paper.
B o t h sets of d a t a have b e e n p r o v i d e d to b e t t e r i l l u s t r a t e d i f f e r e n c e s b e t w e e n n e a t r e s i n and r e s i n / f e l t c o m p o s i t e p r o p e r t i e s , as w e l l as p r o v i d i n g a r u d i m e n t a r y b a s i s b y w h i c h o n e m i g h t e s t i m a t e r e s i n / f e l t
c o m p o s i t e p r o p e r t i e s from neat r e s i n d a t a that is m o r e r e a d i l y
a v a i l a b l e . T h e r e are four key a r e a s of i n t e r e s t in t h e s e t w o d a t a sets that w i l l b e e m p h a s i z e d . First, t h e r e is not a t r e m e n d o u s d i f f e r e n c e b e t w e e n the f l e x u r a l and t e n s i l e m o d u l i of the neat r e s i n s (Table i) a n d t h e C I P P r e s i n / f e l t c o m p o s i t e s (Table 2). T h e p o l y e s t e r felt does not s t i f f e n the c o m p o s i t e a n d p r i m a r i l y f u n c t i o n s to c a r r y a n d h o l d the resin, as w e l l as form the t h i c k n e s s a n d d i a m e t e r of the tube.
T h e r e f o r e , the m o d u l u s for any neat r e s i n w o u l d be e x p e c t e d to be s i m i l a r to that o f a C I P P r e s i n / f e l t c o m p o s i t e . S e c o n d l y , the f l e x u r a l a n d t e n s i l e s t r e n g t h s of t h e s e C I P P r e s i n / f e l t c o m p o s i t e s a r e less t h a n the neat resins. T h e r e d u c t i o n of s t r e n g t h is a r e s u l t of the s h o r t p o l y e s t e r felt f i b e r s p u l l i n g a p a r t f r o m one a n o t h e r , b r e a k i n g , a n d / o r r e s i n d i s b o n d i n g f r o m the fibers. Thirdly, t h e f l e x u r a l a n d t e n s i l e p r o p e r t i e s of the t h r e e r e s i n c l a s s i f i c a t i o n s d o h a v e r e c o g n i z a b l e d i f f e r e n c e s . Of t h e s e r e p r e s e n t a t i v e samples, the t w o Iso p o l y e s t e r s h a d h i g h m o d u l i a n d the l o w e s t a v e r a g e s t r e n g t h a n d e l o n g a t i o n s c o m p a r e d to the o t h e r r e s i n s . B o t h bis A e p o x y v i n y l e s t e r s h a d a b a l a n c e of h i g h m o d u l i a n d a l s o had t h e h i g h e s t a v e r a g e s t r e n g t h s a n d e l o n g a t i o n s at f a i l u r e a m o n g t h e test group. The bis A e p o x y r e s i n / c u r i n g a g e n t systems h a d q u i t e d i f f e r e n t p r o p e r t i e s as a r e s u l t of the d i f f e r e n t c u r i n g a g e n t s u s e d to cure the e p o x y resin. T h e ER-I s y s t e m h a d the l o w e s t m o d u l u s a n d h i g h e s t e l o n g a t i o n in the t e s t group. T h e ER-2 s y s t e m w a s s l i g h t l y stiffer, but h a d l o w e r s t r e n g t h a n d f l e x i b i l i t y t h a n E R - I a n d m o r e or less b e h a v e d s i m i l a r l y to V E R - I . In g e n e r a l , b e c a u s e of the t o u g h n e s s a n d f l e x i b i l i t y i m p a r t e d by t h e bis A m o l e c u l a r b a c k b o n e (Figures 4 and 5) the e p o x y a n d e p o x y v i n y l e s t e r r e s i n s h a d the h i g h e s t s t r e n g t h s a n d e l o n g a t i o n s a m o n g t h e test group. The
m u l t i p l e i n t e r n a l r e a c t i o n s i t e s a n d r i g i d i t y of the i s o p h t h a l i c a c i d in the Iso p o l y e s t e r s (Fig. 2) r e s u l t s in r e s i n s h a v i n g h i g h m o d u l u s , but c o m p a r a t i v e l y l o w e r s t r e n g t h s a n d e l o n g a t i o n s . Lastly, the d a t a of all r e s i n t y p e s g i v e n in T a b l e 2 is s o m e w h a t h i g h e r t h a n an a v e r a g e d a t a set o b t a i n e d f r o m f i e l d s a m p l e s u s e d to q u a l i f y i n s t a l l e d CIPP. One m i g h t t y p i c a l l y e x p e c t f l e x u r a l a n d t e n s i l e d a t a f r o m C I P P f i e l d s a m p l e s to be in the r a n g e of 6 0 - 9 0 % of that w h i c h c a n be o b t a i n e d t h r o u g h c a r e f u l p r e p a r a t i o n in the l a b o r a t o r y . U n c o n t r o l l a b l e f a c t o r s s u c h as the e q u i p m e n t , g e o m e t r i c , and e n v i r o n m e n t a l c o n d i t i o n s i n f l u e n c e p r o p e r t i e s . C o n t r o l l a b l e f a c t o r s such as p r o p e r t i e s of the c h o s e n resin, c u r e system, c u r e schedule, a n d contractor e x p e r i e n c e a l s o c o n t r i b u t e to the v a r i a b i l i t y of this p r o c e s s .
KLEWENO ON CURED-IN-PLACE PIPE REHABILITATION
T A B L E l - - F l e x u r a ! (Flex.) a n d t e n s i l e (Tens.) m o d u l u s (Mod.) a n d S t r e n g t h (Stro} of n e a t r e s i n s a m p l e s m a d e w i t h the g i v e n resins.
87
T e s t
Prop. V E R - I V E R - 2 E R - I E R - 2 P E R - I PER-2
Flex. 3.59 G P a 3.52 G P a 3.03 G P a 3.24 G P a 3.65 G P a 3.24 G P a
Mod. (520 Kpsi) (510 Kpsi) (440 Kpsi) (470 Kpsi) (530 Kpsi) (470 Kpsi)
Flex. 130.3 M P a 130.3 M P a 86.9 M P a 1 0 7 . 6 M P a 124.1 M P a 117.2 M P a Str. (18.9 Kpsi) (18.9 Kpsi) (12.6 Kpsi) (15.6 Kpsi) (18 Kpsi) (17 Kpsi) Tens. 3.45 G P a 3.45 G P a 2.69 G P a 2.89 G P a 3.59 G P a 3.45 G P a Mod. (500 Kpsi) (500 Kpsi) (390 }<psi) (420 Kpsi) (520 Kpsi) (500 Kpsi) Tens. 63.4 M P a 64.1 M P a 48.9 M P a 64.1 M P a 60.0 M P a 58.6 M P a
Str. (9.2 Kpsi) (9.3 Kpsi) (7.1 Kpsi) (9.3 Kpsi) (8.7 Kpsi) (8.5 Kpsi)
T A B L E 2 - - F l e x u r a l (Flex.) a n d t e n s i l e (Tens.) m o d u l u s (Mod.), s t r e n g t h (Str), a n d p e r c e n t s t r a i n (Stn.) or e l o n g a t i o n (Elon.) for r e s i n / p o l y e s t e r felt C I P P c o m p o s i t e s m a d e w i t h the g i v e n resins.
T e s t
Prop. V E R - I ~ R - 2 E R - I E R - 2 P E R - I PER-2
Flex.
Mod.
F l e x . Str.
Max.
Stn.
T e n s . Mod.
Tens.
Str.
Tens.
Elon.
3.45 G P a 3.41 G P a 2.72 G P a 2.99 G P a 3.54 G P a 3.57 G P a (500 Kpsi) (495 Kpsi) (394 Kpsi) (433 Kpsi) (513 Kpsi) (518 Kpsi)
76.5 M P a 85.5 M P a 73.8 M P a 61.4 M P a (ii.i Kpsi) (12.4 Kpsi) (i0.7 Kpsi) (8.9 Kpsi)
65.5 M P a 58.6 M P a (9.5 Kpsi) (8.5 Kpsi)
2.5 % 3.0 % 3.5 % 2.2 % 2.0 % 1.7 %
3.45 G P a 3.17 G P a 2.52 G P a 2.65 G P a 2.83 G P a ...
(500 Kpsi) (460 Kpsi) (365 Kpsi) (384 Kpsi) (410 Kpsi) ...
44.8 M P a 55.2 M P a 48.9 M P a 42.1 M P a 35.2 M P a ...
(6.5 Kpsi) (8.0 Kpsi) (7.1 Kpsi) (6.1 Kpsi) (5.1 Kpsi) ...
1.8 % _ 2.6 % 2.8 % 1.8 % 1.5 % ...
C h e m i c a l R e s i s t a n c e - - T h e acids, bases, a n d o x i d i z i n g a g e n t s s e l e c t e d for this s t u d y w e r e c h o s e n b e c a u s e t h e y are n a t u r a l l y f o u n d in the s e w e r s y s t e m or are i n t r o d u c e d by h o m e o w n e r s , b u s i n e s s e s , or s a n i t a t i o n d e p a r t m e n t s [l,~,~,~]- This i d e a l i z e d t e s t i n g p r o t o c o l i n c l u d e s i d e n t i c a l sample p r e p a r a t i o n a n d t e s t i n g c o n d i t i o n s in o r d e r to p r o v i d e a g o o d c o m p a r i s o n of the r e l a t i v e c h e m i c a l r e s i s t a n c e of the six r e s i n s e v a l u a t e d in a b r o a d r a n g e of c h e m i c a l e f f l u e n t s . T h e c h e m i c a l
88 BURIED PLASTIC PIPE TECHNOLOGY
r e s i s t a n c e data in F i g u r e s 6-14 represent r e t e n t i o n of f l e x u r a l m o d u l u s v e r s u s t i m e up to 12 m o n t h s of e x p o s u r e to the a f o r e m e n t i o n e d c h e m i c a l s , a n d the r e s i n s w e r e a b b r e v i a t e d as p r e v i o u s l y n o t e d in the M a t e r i a l s section. C o u p o n t h i c k n e s s a n d w e i g h t c h a n g e i n f o r m a t i o n o b t a i n e d at the i, 3, 6, a n d 12 m o n t h e v a l u a t i o n s is p r e s e n t e d in T a b l e 3. T h e d a t a in F i g u r e s 7 - 1 4 is r e p r e s e n t e d in l o g - l o g p l o t s a n d s t a t i s t i c a l l y fit to r e p r e s e n t r e t e n t i o n cf f l e x u r a l m o d u l u s as a f u n c t i o n of time.
S t a t i s t i c a l l y fit data s u c h as this c a n t h e n b e u s e d to m a k e p r e d i c t i o n s a b o u t f u t u r e p e r f o r m a n c e b y e x t r a p o l a t i n g f o r w a r d in time [i0]. The f l e x u r a l m o d u l i (Figures 7-14) a n d s t r e n g t h d a t a (not g r a p h i c a l l y r e p r e s e n t e d ) w e r e e x t r a p o l a t e d to o b t a i n e s t i m a t e s of the 25 y e a r
r e t e n t i o n of t h e s e two p r o p e r t i e s (Table 4). I m p l i c i t w i t h this d a t a is the a s s u m p t i o n t h a t the s p e c i m e n s c o n t i n u e to p e r f o r m in a c o n s i s t e n t m a n n e r as t h e y d i d in t h e first 12 m o n t h s of the e v a l u a t i o n . However, t h e r e a r e s e v e r a l e x a m p l e s (Table 4) w h e r e the f l e x u r a l p r o p e r t i e s of VER-I, VER-2, or ER-2 w e r e g r e a t e r t h a n o r e q u a l to the c o n t r o l a f t e r 12 months' e x p o s u r e to some o f the c h e m i c a l s t e s t e d . T h e r e f o r e , 25 y e a r
f l e x u r a l p r o p e r t y r e t e n t i o n p r e d i c t i o n s t h a t w o u l d h a v e b e e n g r e a t e r t h a n 100% w e r e g i v e n as i00+ in T a b l e 4, s i n c e it u n r e a l i s t i c to p r e d i c t a c o n t i n u e d increase a f t e r long t e r m c h e m i c a l exposure.
A n u m b e r of g e n e r a l i z e d t r e n d s a r e r e a d i l y a p p a r e n t f r o m the d a t a in F i g u r e s 6-14 a n d T a b l e s 3 a n d 4. First, the r e t e n t i o n of f l e x u r a l m o d u l u s a n d s t r e n g t h c l o s e l y c o r r e l a t e for all the r e s i n s in this e x p e r i m e n t a l g r o u p (Table 4) [11,12]. T h e o n l y e x c e p t i o n s to this g e n e r a l i z a t i o n a r e the p e r f o r m a n c e of ER-I, PER-I, a n d P E R - 2 in p o t a s s i u m p e r m a n g a n a t e , w h i c h w i l l be a d d r e s s e d later. S e c o n d l y , the b a s i c c h e m i c a l s (i.e., s o d i u m h y d r o x i d e a n d a m m o n i u m h y d r o x i d e ) a n d the o x i d i z i n g a g e n t s (i.e., b l e a c h a n d p o t a s s i u m p e r m a n g a n a t e ) w e r e in g e n e r a l m o r e s e v e r e than the a c i d s for a l l t h r e e c l a s s i f i c a t i o n s of resin. T h i r d l y , r e d u c t i o n of f l e x u r a l p r o p e r t i e s c o r r e l a t e d c l o s e l y w i t h l a r g e c h a n g e s in t e s t c o u p o n t h i c k n e s s a n d w e i g h t c h a n g e (Table 3).
Lastly, t h e p e r f o r m a n c e o f b o t h e p o x y v i n y l e s t e r s w e r e e x t r e m e l y s i m i l a r to one another, a s w a s the p e r f o r m a n c e of b o t h Iso p o l y e s t e r s . However, t h e c h e m i c a l r e s i s t a n c e of t h e h i s h e p o x y r e s i n w a s e x t r e m e l y d e p e n d e n t o n the t y p e of c u r i n g a g e n t u s e d to c u r e the resin.
In g e n e r a l , the P E R - I a n d PER-2 r e s i n s w e r e m o s t r e s i s t a n t to the acids, m i l d l y s u s c e p t i b l e to h y d r o g e n p e r o x i d e , a n d v e r y s u s c e p t i b l e to bleach, p o t a s s i u m p e r m a n g a n a t e , s o d i u m h y d r o x i d e , a n d a m m o n i u m
h y d r o x i d e . Of the c h e m i c a l s that m o s t a f f e c t e d b o t h Iso p o l y e s t e r s , p o t a s s i u m p e r m a n g a n a t e w a s the m o s t s u b t l e s i n c e t e s t i n g t h r o u g h 12 m o n t h s d i d not s h o w s e v e r e loss of f l e x u r a l p r o p e r t i e s (Fig. 8, T a b l e 4). H o w e v e r , l a r g e i n c r e a s e s in c o u p o n t h i c k n e s s a n d w e i g h t g a i n (Table 3) i n d i c a t e s e v e r e p o l y m e r s w e l l i n g w h i c h t y p i c a l l y leads to p r e m a t u r e f a i l u r e o f the r e s i n system. A m o n g the c h e m i c a l s t e s t e d the m o s t s e v e r e is the s o d i u m h y p o c h l o r i t e , w h i c h is t h e a c t i v e i n g r e d i e n t m o s t o f t e n u s e d in h o u s e h o l d bleach, b a t h r o o m , a n d d r a i n c l e a n e r s . I n i t i a l l y this p r o t o c o l w a s s t a r t e d w i t h 2.5% b l e a c h (Fig. 7), but r e s i n f a i l u r e o c c u r r e d so q u i c k l y that a s e c o n d e v a l u a t i o n w a s s t a r t e d w i t h 0.5%
b l e a c h (Fig. 6) so that t h e s t u d y w o u l d last a full 12 m o n t h s . However, e v e n the 0.5% b l e a c h r e s u l t e d to c o m p l e t e f a i l u r e by 9 m o n t h s .
A m o n g the t w o bis A e p o x i e s the m u l t i a m i n e / i m i d a z o l e c u r i n g a g e n t u s e d in the ER-2 s y s t e m is m u c h m o r e c h e m i c a l l y r e s i s t a n t to all the c h e m i c a l s t e s t e d t h a n the f l e x i b i l i z e d a m i n e c u r i n g a g e n t u s e d to cure the ER-I system. The E R - I a n d E R - 2 r e s i n s y s t e m s w e r e b o t h r e s i s t a n t to the b a s i c c h e m i c a l s (sodium h y d r o x i d e a n d a m m o n i u m h y d r o x i d e ) . The E R - I s y s t e m w a s m i l d l y r e s i s t a n t to the acids, but e x t r e m e l y s u s c e p t i b l e to the o x i d i z i n g a g e n t s (bleach, h y d r o g e n p e r o x i d e , a n d p o t a s s i u m
permanganate). Exposure o f ER-I to b o t h c o n c e n t r a t i o n s o f b l e a c h a n d
120
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FIG. 8--Chemical resistance of CIPP to 5% potassium permanganate.
8
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FIG. 9 - - C h e m i c a l r e s i s t a n c e of C I P P to 5% h y d r o g e n p e r o x i d e .
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FIG. l l - - C h e m i c a l r e s i s t a n c e of C I P P to 5% a m m o n i u m h y d r o x i d e .
K L E W E N O O N C U R E D - I N - P L A C E P I P E R E H A B I L I T A T I O N 91
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25 Yrs
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T A B L E 3 - - T e s t c o u p o n p e r c e n t "change of t h i c k n e s s a n d w e i g h t c h a n g e s m e a s u r e d at i, 3, 6, a n d 12 m o n t h s (Mon.) d u r i n g e x p o s u r e t o t h e g i v e n c h e m i c a l s .
B i s A E p o x y B i s A E p o x y
C h e m i c a l V i n y l E s t e r - i V i n y l E s t e r - 2 B i s A E m o x y - i
T e s t e d P r o p e r t y 3 Mon. 6 M o n . 12 M o n . 3 Mon. 6 Mon. 12 Mon. 1 M o n . 3 Mon. 6 M o n . W C m -u
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0.5% S o d i u m C o u p o n T h i c k n e s s -0.4 -0.2 0.0 0.0 -0.4 -0.4 ... - 4 . 5 -6.1
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2 . 5 % S o d i u m C o u p o n T h i c k n e s s 0.0 -i.i -i.i 0.0 -0.4 -i.i 0 - 0 . 8 - i i . i
H y p o c h l o r i t e C o u p o n W e i g h t 0.i -0.9 -2.0 0.2 -i.i -1.8 - 1 8 . 8 - 4 7 . 8 - 8 4 . 7
5% H y d r o g e n C o u p o n T h i c k n e s s -0.4 0.0 -0.4 0.4 0.0 0.0 2 0 . 2 40.7 ...
P e r o x i d e C o u p o n W e i g h t 0.6 0.6 0.5 0.5 0.5 0.5 18.0 4 4 . 5 ...
3 Mon. 6 M o n . 12 Mon.
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H y d r o x i d e C o u p o n W e i g h t -3.7 -3.8 -5.7 -2.3 -4.8 -7.0 2 . 2 2.2 1.3
5% P o t a s s i u m C o u p o n T h i c k n e s s P e r m a n g a n a t e C o u p o n W e i g h t
0.8 0.8 1.8 0.0 0.4 2 . 2 16.6 2 7 . 8 2 9 . 8
0.8 2 . 5 4.6 0.8 2 . 1 3.2 3 5 . 0 4 7 . 6 5 0 . 4
5% A m m o n i u m C o u p o n T h i c k n e s s H y d r o x i d e C o u p o n W e i g h [
0.8 0.0 0.8 0.4 0.0 0.4 2 . 1 2.1 9.4
0.6 -2.7 -4.1 0.0 -3.1 -5.1 1.8 -i.i - 8 . 6
2 5 % S u l f u r i c C o u p o n T h i c k n e s s 0.4 0.4 0.0 0.4 -0.4 0.0 12.4 14.2 12.4
A c i d C o u p o n W e i g h t 0.3 0.3 0.3 0.2 0.2 0.2 2 5 . 5 3 0 . 9 3 2 . 1
2 0 % H y d r o - C o u p o n T h i c k n e s s c h l o r i c A c i d C o u p o n W e i g h t
0.0 0.0 0.0 -0.4 0.0 0.0 6.7 8.9 6.7
0.3 0.4 0.4 0.3 0.2 0.3 9.9 11.4 12.1
5% N i t r i c C o u p o n T h i c k n e s s 0.0 0.0 0.0 -0.4 0.0 -0.4 4.9 7 . 9 2 5 . 9
A c i d C o u p o n W e i g h t 0.4 0.5 0.5 0.4 0.4 0.5 6.6 1 1 . 6 2 7 . 2
T A B L E 3 ( C o n t i n u e d ) - - T e s t c o u p o n t h i c k n e s s a n d w e i g h t c h a n g e s m e a s u r e d at i, 3, 6, a n d 12 m o n t h s (Mon.) d u r i n g c h e m i c a l e x p o s u r e to t h e g i v e n c h e m i c a l s .
I s o p h t h a l i c I s o p h t h a l i c
C h e m i c a l B i s A E p o x y - 2 P o l v e s t e r - i P o l v e s t e r - 2
T e s t e d P r o p e r t y 1 Mon. 3 Mon. 6 Mon. 1 Mon. 3 M o n . 6 Mon. 1 M o n . 3 M o n . 6 M o n .
0 . 5 % S o d i u m C o u p o n T h i c k n e s s 0.4 H y p o c h l o r i t e C o u p o n W e i g h t 1.2 2 . 5 % S o d i u m C o u p o n T h i c k n e s s 0.0 H y p o c h l o r i t e C o u p o n W e i g h t 0.9 5% S o d i u m C o u p o n T h i c k n e s s 0.4 H y d r o x i d e C o u p o n W e i g h t 1.6
5% H y d r o g e n C o u p o n T h i c k n e s s 0.0 P e r o x i d e C o u p o n W e i g h t 2.3 5% P o t a s s i u m C o u p o n T h i c k n e s s i.I P e r m a n g a n a t e C o u p o n W e i g h t 3.4 5% A m m o n i u m C o u p o n T h i c k n e s s 0.4 H y d r o x i d e C o u p o n W e i g h t 1.9 2 5 % S u l f u r i c C o u p o n T h i c k n e s s 0.4 A c i d C o u p o n W e i g h t 1.3 2 0 % H y d r o - C o u p o n T h i c k n e s s 0.4 c h l o r i c A c i d C o u p o n W e i g h t 1.6 5% N i t r i c C o u p o n T h i c k n e s s 0.7 A c i d C o u p o n W e i g h t 2.0
-0.8 0.0 ... -0.7 0.4 ... 0.0 - 0 . 4
0.9 -0.i ... -5.4 - 1 2 . 0 ... - 4 . 1 - 1 2 . 2
0.0 - 0 . 4 0.8 0.7 ... 0.0 - 0 . 8 ...
-1.9 -6.6 -0.8 -1.8 ,-78.0 -1.2 - 6 . 5 - 4 7 . 7
0.4 0.4 -0.7 - 0 . 4 0.4 -0.7 - 1 . 5 - 1 . 5
1.7 1.9 -4.6 -6.6 - 7 . 5 -3.2 -7.9 -6.9
3 M o n . 6 M o n . 12 M o n . 3 Mon. 6 M o n . 12 M o n .
1.2 0.8 0.0 -0.4 - 0 . 4 -0.4 0.4 - 0 . 4
3.3 3.7 0.8 0.3 -2.2 0.7 0.4 - 1 . 4
1.8 2 . 5 2 . 8 11.3 1 4 . 4 1.2 3.9 1 1 . 2
4.3 4.7 4.1 2 2 . 8 2 8 . 1 2 . 0 6.9 18.7
0.0 0.4 0.7 - 1 . 4 ... i.i - 0 . 8 ...
1.9 - 0 . 4 -3.4 - 1 1 . 2 ... 1.0 - 7 . 6 ...
0.4 0.4 0.4 -0.8 0.4 0.0 - 0 . 8 -0.4
1.3 1.5 0.8 0.8 1.0 0.4 0.4 0.4
0.4 0.7 0.7 0.4 0.4 0.4 - 0 . 4 - 0 . 4
1.7 2.0 1.4 1.4 0.9 0.5 0.5 0.6
0.7 0.7 0o0 0.0 0.4 -0.4 -0.8 0.0
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T A B L E 4 - - E s t i m a t e d p e r c e n t r e t e n t i o n o f f l e x u r a l p r o p e r t i e s I a f t e r 2 5 y e a r s (Yrs) o f c h e m i c a l e x p o s u r e f o r resin~polyester f e l t C I P P composites m a d e w i t h t h e g i v e n r e s i n s .
~D 4~
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C h e m i c a l F l e x u r a l V E R - I V E R - 2 E R - I E R - 2 P E R - I P E R - 2
T e s t e d P r o p e r t y 25 Y r s 2 5 Y r s 2 5 Y r s 25 y r s 2 5 Y r s 2 5 Y r s
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2 . 5 % S o d i u m M o d u l u s 97 96 0 ... 0 0
H y p o c h l o r i t e S t r e n g t h 99 86 0 ... 0 0
5% S o d i u m M o d u l u s 66 60 73 88 0 0
H y d r o x i d e S t r e n g t h 77 53 7 6 7 2 0 0
5 % H y d r o g e n M o d u l u s 2 94 i 0 0 + 0 84 65 7 1
P e r o x i d e S t r e n g t h i 0 0 77 0 84 7 6 7 4
5% P o t a s s i u m M o d u l u s 99 97 ... 83 73 81
P e r m a n g a n a t e S t r e n g t h 89 86 27 60 47 65
5% A m m o n i u m M o d u l u s 66 66 42 65 22 2 6
H y d r o x i d e S t r e n g t h 64 55 3 8 54 2 5 2 4
2 5 % S u l f u r i c M o d u l u s i 0 0 + i 0 0 + 0 93 89 94
A c i d S t r e n g t h 96 92 0 i 0 0 + 88 94
2 0 % H y d r o - M o d u l u s I 0 0 + 99 2 1 89 7 7 92
c h l o r i c A c i d S t r e n g t h i 0 0 + 91 3 1 95 70 95
5 % N i t r i c M o d u l u s i 0 0 + 97 0 85 77 90
A c i d S t r e n g t h i 0 0 + 9 4 0 82 7 2 93
-0 m m O -r Z O O -<
i F l e x u r a l p r o p e r t y r e t e n t i o n e s t i m a t e s b a s e d o n 12 m o n t h c o r r o s i o n d a t a .
2 ( 1 0 0 + ) i n d i c a t e s t h e c u r v e f i t w o u l d p r e d i c t p h y s i c a l p r o p e r t y r e t e n t i o n g r e a t e r t h a n 1 0 0 %
KLEWENO ON CURED-IN-PLACE PIPE REHABILITATION 95
h y d r o g e n p e r o x i d e r e s u l t e d in c o m p l e t e d e s t r u c t i o n of the r e s i n w i t h i n a f e w m o n t h s ( F i g u r e s 6, 7, T a b l e 3). Also, e x p o s u r e to p o t a s s i u m
p e r m a n g a n a t e w a s e q u a l l y d e s t r u c t i v e to this resin. T h e f l e x u r a l
m o d u l u s i n i t i a l l y dropped, t h e n i n c r e a s e d (Fig. 8), w h i c h is b e l i e v e d to b e c a u s e d b y the s e v e r e s w e l l i n g a w e i g h t g a i n of the resin. The ER-2 s y s t e m g e n e r a l l y has e x c e l l e n t c h e m i c a l r e s i s t a n c e to the w i d e r a n g e of e f f l u e n t s tested, but s h o w s s o m e s i g n s of susceptibility to the
o x i d i z i n g a g e n t s t h r o u g h 6 m o n t h s of t e s t i n g . T h e i m p o r t a n c e of s l i g h t a c c e l e r a t i o n of the test p r o t o c o l is e v i d e n t for ER-2. F r o m Fig. 6 a n d T a b l e 3 ER-2 a p p e a r s q u i t e r e s i s t a n t to b l e a c h . H o w e v e r , t h e r e s u l t s s h o w n in Fig. 7 a n d the w e i g h t l o s s e s in T a b l e 3 i n d i c a t e a m u c h g r e a t e r s u s c e p t i b i l i t y to b l e a c h t h a n o r i g i n a l l y m i g h t h a v e b e e n a n t i c i p a t e d b y e v a l u a t i n g the r e s i n o n l y at 0.5% b l e a c h c o n c e n t r a t i o n .
B o t h b i s A e p o x y v i n y l e s t e r s h a d e x c e l l e n t c h e m i c a l r e s i s t a n c e to the a c i d s a n d t h e o x i d i z i n g agents, a n d g o o d r e s i s t a n c e to t h e b a s e s tested. Of the c h e m i c a l s t e s t e d the bis A e p o x y v i n y l e s t e r s w e r e m i l d l y s u s c e p t i b l e to s o d i u m a n d a m m o n i u m h y d r o x i d e (Fig. i0, ii a n d T a b l e 3) but w e r e not s i g n i f i c a n t l y d i f f e r e n t f r o m that of the e p o x y resins. H o w e v e r , note t h a t the bis A e p o x y r e s i n s g a i n w e i g h t w h e n e x p o s e d to c a u s t i c a n d t h e e p o x y v i n y l e s t e r s lose w e i g h t .
C O N C L U S I O N
In summary, t h e r e w e r e d e m o n s t r a t e d d i f f e r e n c e s in t h e p h y s i c a l p r o p e r t i e s a n d c h e m i c a l r e s i s t a n c e of the t h r e e c l a s s e s of t h e r m o s e t t i n g r e s i n s e v a l u a t e d . The f l e x u r a l a n d t e n s i l e p r o p e r t i e s of t h e s e r e s i n s w e r e c o n s i d e r e d to be g o o d q u a l i f y i n g m e a s u r e s of t h e u l t i m a t e
p e r f o r m a n c e of e a c h resin. W i t h i n this test g r o u p b o t h Iso p o l y e s t e r s h a d h i g h m o d u l i , but low s t r e n g t h a n d strain. T h e e p o x y v i n y l e s t e r s h a d a b a l a n c e of h i g h m o d u l i , strength, a n d strain. T h e b i s A e p o x y r e s i n s w e r e v e r y d e p e n d e n t on the c u r i n g agent, w i t h E R - I h a v i n g the h i g h e s t f l e x i b i l i t y a n d E R - 2 h a v i n g p r o p e r t i e s s i m i l a r to V E R - I . T h e o n e y e a r c h e m i c a l r e s i s t a n c e e v a l u a t i o n s s h o w e d a n u m b e r of c o m m o n t r e n d s for the C I P P r e s i n / f e l t c o m p o s i t e s . T h e p e r c e n t r e d u c t i o n of f l e x u r a l m o d u l u s g e n e r a l l y c o r r e l a t e s w e l l w i t h the p e r c e n t r e d u c t i o n o f f l e x u r a l s t r e n g t h for e a c h r e s i n in e a c h c h e m i c a l c h o s e n for t e s t i n g . L o w f l e x u r a l p r o p e r t y r e t e n t i o n o r f a i l u r e c o r r e l a t e d w i t h r e l a t i v e l y l a r g e w e i g h t a n d t h i c k n e s s changes, a n d w e i g h t c h a n g e m e a s u r e m e n t s a r e c r i t i c a l in i n t e r p r e t i n g m o r e s u b t l e c h a n g e s . E v a l u a t i n g t w o bis A e p o x y v i n y l e s t e r s a n d t w o Iso p o l y e s t e r s d e m o n s t r a t e d h o w s i m i l a r c h e m i s t r y t y p e s a p p e a r to h a v e s i m i l a r p e r f o r m a n c e f e a t u r e s . However, the same bis A e p o x y c u r e d w i t h a d i f f e r e n t c u r i n g a g e n t s i g n i f i c a n t l y a f f e c t s p h y s i c a l p r o p e r t i e s a n d c h e m i c a l r e s i s t a n c e .
B a s e d o n a 12 m o n t h c h e m i c a l r e s i s t a n c e s t u d y the Iso p o l y e s t e r s w e r e g o o d in acids, but f a i l e d in the b a s i c c h e m i c a l s , b l e a c h , a n d p o t a s s i u m p e r m a n g a n a t e . T h e b i s A e p o x y r e s i n s are g o o d in b a s i c c h e m i c a l s , but r a n g e d f r o m p o o r to e x c e l l e n t in the a c i d s a n d o x i d i z i n g a g e n t s d e p e n d i n g on the t y p e of c u r i n g a g e n t u s e d . T h e b i s A e p o x y v i n y l e s t e r s s h o w e d an a b i l i t y to r e s i s t acids, bases, a n d o x i d i z i n g a g e n t s w i t h l i t t l e or no loss of p h y s i c a l p r o p e r t i e s d u r i n g study.
Lastly, t h i s s t u d y d e m o n s t r a t e d the d i s t i n c t i o n b e t w e e n s h o r t a n d long t e r m p r o p e r t i e s . G i v e n the short t e r m d a t a (Tables 1 a n d 2), o n e c o u l d not h a v e p r e d i c t e d the long t e r m c h e m i c a l r e s i s t a n c e w i t h o u t m o r e k n o w l e d g e a b o u t the c h e m i c a l c o m p o s i t i o n of t h e i n d i v i d u a l r e s i n s a n d p r e v i o u s l y c o n d u c t e d c h e m i c a l r e s i s t a n c e s c r e e n i n g . A l t h o u g h all the r e s i n s e v a l u a t e d h a v e a c c e p t a b l e short t e r m p h y s i c a l p r o p e r t i e s , t h e y are c e r t a i n l y n o t all a c c e p t a b l e for u s e in t h e full r a n g e of c h e m i c a l a g e n t s t e s t e d .
96 BURIED PLASTIC PIPE TECHNOLOGY
R E F E R E N C E S
[i] " H y d r o g e n S u l f i d e C o r r o s i o n in W a s t e w a t e r C o l l e c t i o n a n d T r e a t m e n t S y s t e m s , " R e p o r t P B 9 2 - I 1 7 9 8 5 , R e p o r t to C o n g r e s s , Sept. 1991.
[2] " P r o c e s s D e s i g n M a n u a l for S u l f i d e C o n t r o l in S a n i t a r y S e w e r a g e S y s t e m s , " R e p o r t E P A 625/1-74-005, U.S. E P A T e c h n o l o g y T r a n s f e r , Oct.
1974.
[3] "Sewer S y s t e m I n f r a s t r u c t u r e A n a l y s i s a n d R e h a b i l i t a t i o n H a n d b o o k , " R e p o r t C E R I - 9 1 - 4 2 , U.S. E P A O f f i c e for E n v i r o n m e n t a l R e s e a r c h Information, J u l y 1991.
[4] " T e c h n o l o g y T r a n s f e r Seminars: S e w e r S y s t e m I n f r a s t r u c t u r e A n a l y s i s a n d R e h a b i l i t a t i o n , " R e p o r t C E R I - 9 1 - 5 1 , U.S. E P A O f f i c e for E n v i r o n m e n t a l R e s e a r c h Information, J u l y 1991.
[5] Parker, C.D., "Species of B a c t e r i a A s s o c i a t e d w i t h the C o r r o s i o n of C o n c r e t e , " Nature. Vol. 159, 1947, p p 439-40.
[6] Badia, Jaime, et. al., "Caustic S p r a y for S e w e r C r o w n C o r r o s i o n C o n t r o l " , P r o c e e d i n q s of the A S C E I n t e r n a t i o n a l C o n f e r e n c e on P i p e l i n e I n f r a s t r u c t u r e , Aug. 1993.
[7] M a r s h a l l , G., Batis, G., " P r e p a r i n g C o l l e c t i o n S y s t e m s for W a t e r C o n s e r v a t i o n " , W a t e r E n v i r o n m e n t & T e c h n o l o q v , Vol. 5, No. 8, 1993, p p 52-57.
[8] S t a n d a r d S p e c i f i c a t i o n for P u b l i c W o r k s C o n s t r u c t i o n (Green Book), BNi B u i l d i n g News, Los Angeles, 1991.
[9] J e y a p a l a n , J.K., " P r e d i c t i o n a n d C o n t r o l of S u l f i d e C o r r o s i o n in C o n c r e t e S e w e r I n f r a s t r u c t u r e and R e h a b i l i t a t i o n " , C o r r o s i o n Forms a n d C o n t r o l for I n f r a s t r u c t u r e , STP 1137, V i c t o r Chaker, Ed., A m e r i c a n S o c i e t y for T e s t i n g a n d Materials, P h i l a d e l p h i a , 1992, p p 273-283.
[i0] "How I n g r e d i e n t s I n f l u e n c e U n s a t u r a t e d P o l y e s t e r P r o p e r t i e s , "
B u l l e t i n IP-70a, A m o c o C h e m i c a l Company.
[ii] Kleweno, D.G., " C h a r a c t e r i z a t i o n of R e s i n s u s e d for C u r e d - i n - P l a c e Pipe R e h a b i l i t a t i o n " , P r o c e e d i n q s of the N o r t h A m e r i c a n N O - D I G '93 C o n f e r e n c e , M a y 1993.
[12] Kleweno, D.G., "Chemical R e s i s t a n c e of T h e r m o s e t t i n g R e s i n s u s e d for C u r e d - i n - P l a c e Pipe", P r o c e e d i n a s of the A S C E I n t e r n a t i o n a l
C o n f e r e n c e on P i p e l i n e I n f r a s t r u c t u r e , Aug. 1993.
King H. Lo’, and Jane Q. Zhang’
COLLAPSE RESISTANCE MODELING OF ENCASED PIPES
REFERENCE: Lo, K. H. and Zhang, J. Q., “Collapse Resistance Modeling of Encased Pipes,” wried P lastic Pipe Technolovv: 2nd Volume, ASTM STP
m, Dave Eckstein, Ed., American Society for Testing and Materials, Philadelphia, 1994.
ABSTRACT: Two different collapse models are developed for predicting the collapse resistance of encased pipes for pipe rehabilitation
applications. One model corresponds to an unsymmetrical collapse mode and the other one corresponds t o a symmetrical collapse mode. Attention is focused here on modeling the effect of the small radial gap between the encased pipe and the host pipe on encased pipe collapse resistance.
This small radial gap is assumed t o have developed when installing the encased pipe into the host pipe. It increases in size when subjected to temperature change, swelling, and application of external hydrostatic pressure. The predictions by the models correlate well with some collapse test results on encased pipes.
KEYWORDS: encased pipe, collapse pressure, progressive buckling, radial gap effect
Plastic pipes and cured-in-place pipes are used more and more to rehabilitate buried pipes. For such applications, the ability of the plastic pipes and cured-in-place pipes (from here on will be referred to as the encased pipes) t o resist collapse by external hydrostatic
pressure and/or vacuum loading is an Fmportant design concern. Due to the constraint exerted by the host (rehabilitated) pipe, the collapse behavior of an encased pipe will be significantly different from that of an unsupported (stand-alone) pipe. In particular, the collapse
resistance of an encased pipe can be many times higher than that of an unsupported pipe. This paper presents two simple engineering models for assessing the relative enhancement in collapse resistance that can be obtained with encased pipes. One model corresponds to ,an unsymmetrical collaspe mode and the other one corresponds to a symmetrical collapse mode.
Analytical modeling of the collapse behavior of radially constrained circular rings and pipes had been carried out by various researchers. Some representative examples of these modeling studies can be found in [L-g]. The general conclusion from these investigations is that the collapse resistance of a n encased pipe is strongly influenced by the geometry of the initial imperfection in the pipe. The type of
initial imperfection, used in all these studies, was in the form of an assumed crown deflection and an assumed detached length. The rest of the pipe was assumed, in the stress free state, to be in perfect contact with the confining medium.
’Shell Development Company, Westhollow Research Center, P. 0. Box 1380, Houston, TX 77251-1380
97
98 BURIED PLASTIC PIPE TECHNOLOGY
In this study, no d i s t i n c t i v e initial g e o m e t r i c i m p e r f e c t i o n is a s s u m e d to exist in t h e e n c a s e d pipe. Instead, a t t e n t i o n is f o c u s e d here on m o d e l i n g the e f f e c t of the small radial g a p b e t w e e n the e n c a s e d pipe and t h e host pipe on the collapse resistance. This small radial g a p is a s s u m e d to have d e v e l o p e d w h e n installing the e n c a s e d p i p e into t h e host pipe. It can increase or d e c r e a s e in size due to d i f f e r e n t i a l t h e r m a l expansion, swelling, and/or h y d r o s t a t i c p r e s s u r e t r a p p e d b e t w e e n the e n c a s e d pipe and the host pipe.
T h e first part of t h e p a p e r gives a brief d e s c r i p t i o n of t h e models. This is f o l l o w e d by c o r r e l a t i o n b e t w e e n m o d e l p r e d i c t i o n s and a v a i l a b l e test results.
COLLAPSE P R E S S U R E MODELS FOR ENCASED P I P E S
The effect of t h e radial g a p b e t w e e n the e n c a s e d pipe and the host p i p e is the key e l e m e n t in the d e v e l o p m e n t of t h e c o l l a p s e models.
Intuitively, a s m a l l e r radial g a p w o u l d lead to a larger improvement in c o l l a p s e r e s i s t a n c e d u e to t h e stronger constraint imposed b y t h e host pipe. Conversely, a larger radial g a p w o u l d impose a w e a k e r constraint on t h e e n c a s e d p i p e and thus w o u l d give rise to a smaller i m p r o v e m e n t in c o l l a p s e resistance.
T h e p r o b l e m considered here is m o d e l e d as a t w o d i m e n s i o n a l plane strain b u c k l i n g p r o b l e m of the c r o s s - s e c t i o n of t h e e n c a s e d pipe. A schematic d i a g r a m of the e n c a s e d p i p e inside the host pipe is shown in F i g u r e i. The c o l l a p s e p r o c e s s is m o d e l e d as a p r o g r e s s i v e b u c k l i n g process. It starts w i t h the e n c a s e d p i p e first c o m i n g into contact w i t h the host p i p e at one or two locations due to l o c a l i z e d b u c k l i n g of the e n c a s e d pipe. As t h e h y d r o s t a t i c p r e s s u r e b e t w e e n the e n c a s e d p i p e and the host p i p e increases, the contact area or b u c k l e d c i r c u m f e r e n t i a l length increases. This process is initially stable since an increase in p r e s s u r e is needed to induce b u c k l i n g in the r e m a i n i n g u n b u c k l e d segment of t h e e n c a s e d pipe. This process continues until no additional p r e s s u r e increase can be t a k e n and final c o l l a p s e of t h e e n c a s e d p i p e has
occurred. Model analysis starting w i t h one contact location leads to an u n s y m m e t r i c a l c o l l a p s e mode (Figure 2) and w i t h t w o contact locations gives rise to a symmetrical c o l l a p s e m o d e (Figure 3). In the following, t h e g o v e r n i n g e q u a t i o n s for t h e u n s y m m e t r i c a l c o l l a p s e m o d e w i l l be d e r i v e d first to be followed by t h e equations for t h e symmetrical c o l l a p s e mode.
U n s y m m e t r i c a l C o l l a p s e M o d e
To construct t h e p r o g r e s s i v e collapse model, t h e c i r c u m f e r e n t i a l length of the e n c a s e d pipe is a s s u m e d to remain u n c h a n g e d d u r i n g the b u c k l i n g process. Further, we assume that once t h e b u c k l e d p o r t i o n of t h e e n c a s e d pipe comes into contact w i t h the host p i p e it will c o n f o r m to t h e g e o m e t r y of t h e host p i p e w h i l e the r e m a i n i n g u n b u c k l e d segment of t h e e n c a s e d p i p e assumes t h e shape of an arc of a n e w circle. This n e w circle has an e f f e c t i v e radius p and a n e w center O" as shown in F i g u r e 2(b). N o t e t h a t the location of O' will be different from that of the center of the circular c r o s s - s e c t i o n of t h e host pipe. A s s u m i n g that t h e host pipe is rigid, t h e f o l l o w i n g geometric r e l a t i o n s can be
o b t a i n e d for the u n s y m m e t r i c a l b u c k l i n g mode.
2=R2-2RI(~- ~) =2~p (I)
psin==R1sin ~ (2)