Le Duc Minh, Nguyen Thuy Chinh, Nguyen Vu Giang, Tong Cam Le, Dau Thi Kim Quyen, Le Duc Giang, Thai Hoang 2017, Study on change of color and some properties of high density polyethylene
Trang 1NATURALLY IN NORTH CENTRAL
SUMMARY OF CHEMISTRY DISSERTATION
Sepcialization: Organic chemistry
NGHE AN - 2018
Trang 2Department of Physico – Chemistry of non - metallic materials
Institute for tropical technology – Vietnam Academy of Science and Technology and Specialized Lab Organic Chemistry - Faculty of Chemistry -
Vinh University
Supervisors: Prof Dr Thai Hoang
Assoc Prof Dr Le Duc Giang
Dissertation is stored in:
National libarary of Vietnam
Nguyen Thuc Hao Library and Information Center of Vinh University
Trang 3PUBLISHED WORKS
1 Le Duc Minh, Nguyen Thuy Chinh, Nguyen Thi Thu Trang, Nguyen Vu
Giang, Tran Huu Trung, Mai Duc Huynh, Tran Thi Mai, Le Duc Giang, Thai Hoang (2016), Study on change of some characters and morphology of polyethylene
compound exposed naturally in Dong Hoi-Quang Binh, Vietnam Journal of
Chemistry, 54(2), 153-159
2 Le Duc Minh, Nguyen Thuy Chinh, Nguyen Vu Giang, Tong Cam Le, Dau
Thi Kim Quyen, Le Duc Giang, Thai Hoang (2017), Study on change of color and some properties of high density polyethylene/organo-modified calcium carbonate
composites exposed naturally at Dong Hoi-Quang Binh, Vietnam Journal of
Chemistry, 55(4), 417-423
3 Le Duc Minh, Nguyen Thuy Chinh, Le Duc Giang,Tong Cam Le, Dau Thi Kim Quyen, Thai Hoang (2018), Prediction of service half-life time of high density polyethylene/organo-modified calcium carbonate composite exposed naturally at
Dong Hoi – Quang Binh, Vietnam Journal of Chemistry 56(6), pp 767-772
4 Le Duc Minh, Nguyen Thuy Chinh, Nguyen Vu Giang, Le Duc Giang,
Tong Thi Cam Le, Dau Thi Kim Quyen, Tran Huu Trung, Mai Duc Huynh, Thai Hoang (2017), Study on the change in characteristics and morphology of high density polyethylene/organo-modified calcium carbonate composites exposed naturally at
Dong Hoi – Quang Binh, Asian Workshop on Polymer Processing 2017, Hanoi
University of Science and Technology, Program & Proceedings book, 154-159
5 Le Duc Minh, Nguyen Thuy Chinh, Le Duc Giang, Tong Thi Cam Le, Dau
Thi Kim Quyen, Thai Hoang (2019), Study on the change in characteristics and prediction of service half-life time of high density polyethylene/organo-modified
calcium carbonate composite exposed naturally at Dong Hoi – Quang Binh, Journal
Chemical industry (accepted)
Trang 51 Preamble
High density polyethylene (HDPE) is the typical polymer hydrocarbon of
thermoplastic and is widely used in technical and life Under different methods, HDPE is applied in the manufacture of food containers, covers for electric wires and cables, communication cables, hard tubes, twisted pipes for construction, architecture, electricity, telecommunication, etc
In the process of use, especially in the outdoors, polymers in general and HDPE,
PE composites in particular are always affected by sunlight and other environmental factors Oxidation reactions occurring when polymer is illuminated play an important role in polymer aging and affect the lifetime of HDPE
The results of research on the photo-oxidation process of HDPE under the influence of sunlight in some parts of the world show that the mobility of HDPE macromolecular is changed, HDPE circuit is broken, the mechanical properties are greatly reduced over time
In Vietnam, the study on the changes in properties and morphology of PE, PVC and rubber under natural exposure has been conducted in Hanoi, Quang Ninh, Da Nang and Ho Chi Minh City following different times However, natural exposure of HDPE with additive CaCO3 modified with steatic acid has not been conducted in Dong Hoi (Quang Binh), which is one of the locations showing the typical climate of the North Central region With average rainfall and number of rainy days are small in the year, meanwhile, relative humidity and average annual temperature are large, Dong Hoi (Quang Binh) has quite a harsh natural conditions Therefore, the process
of thermal oxidation degradation, photodegradation, photo-oxidation degradation, ozone degradation for polymer composites may occur more strongly than other parts
in our country In addition, there has not been any study in Vietnam that conducts both natural exposure and accelerated weather testing for HDPE/m-CaCO3 composite
to compare the change of characteristics (infrared spectra, ultraviolet-visible spectra, nuclear magnetic resonance, molecular weight of products formed when HDPE was degraded, crystallinity percentage, etc.), mechanical properties, thermal properties, durability heat and morphology of HDPE Thus, no correlation coefficient has been determined between natural exposure and accelerated weather testing of HDPE as well as the lifetime prediction of this polymer
From the research results in the country as well as the world, we found the study
on changes in characteristics, properties, morphology, determining the lifetime of composites based on HDPE natural exposure in Dong Hoi (Quang Binh) combined with accelerated weather testing is very necessary, with both scientific and practical meaning Therefore, researcher has chosen to implement the thesis with the topic:
“Study on the change in characteristics, properties and morphology of high density polyethylene exposed naturally in North Central”
Trang 62 Objects
The research object of the thesis is the high density modified calcium carbonate composites exposed naturally at Dong Hoi City, Quang Binh province
polyethylene/organo-3 Tasks
- The natural exposure the HDPE/m-CaCO3 composites was conducted at Dong Hoi City, Quang Binh province; The accelerated weather testing the HDPE/m-CaCO3composites was carried out in a UV condensation weather device
- Study on the change in characteristics, properties and morphology of high density polyethylene/organo-modified calcium carbonate composites exposed naturally and accelerated weather testing
- Determining the correlation coefficient between the accelerated weather testing and natural exposure for lifetime prediction of the HDPE/m-CaCO3 composites
- Proposing solutions to improve weather durability and increase the lifetime of the HDPE/m-CaCO3 composites exposed naturally in North Central
4 New contributions of the thesis
- The natural exposure the HDPE/m-CaCO3 composites were the first studied
at Dong Hoi City, Quang Binh province (Viet Nam) - is a typical climate location of the North Central region
- The change in characteristics, properties and morphology of the CaCO3 composites is closely related to weather factors, especially solar radiation and temperature during natural exposure
HDPE/m The correlation coefficient between the accelerated weather testing and natural exposure were determined for lifetime prediction of the HDPE/m-CaCO3composites when studying the remained percentage of tensile strength, the remained percentage of elongation at break and the molecular weight of HDPE in HDPE/m-CaCO3 composites
5 Structure of the thesis
It is displayed in a total of 133 pages with 21 tables, 58 figures, 7 diagrams and
136 references Its major sections include: Introduction (3 pages), overview (45 pages), methods and experiment (12 pages), results and discussion (52 pages), conclusion (2 pages), published works (1 page) and references (17 pages) Morever, there is an appendix with 49 spectra, tables, figures and diagrams of the high density polyethylene/organo-modified calcium carbonate composites
Trang 7CHAPTER 1: OVERVIEW
The thesis has conducted a literature review content:
1 Basic information about polyethylene: introdution about polyethylene; photodegradation reaction and photo-oxidation degradation reaction of polyethylene
2 High density polyethylene (HDPE): introdution about HDPE; structure,
characteristics and properties of HDPE
3 High density polyethylene/organo-modified calcium carbonate composites
4 Natural exposure and accelerated weather testing of polymer
5 Lifetime of polymer: effect of temperature; effect of humidity, steam; effect
2.1.1 Chemicals: High density polyethylene, calcium carbonate, acid stearic
2.1.2 Equipment: Preparation of the HDPE/m-CaCO3 composites samples (Haake internal mixer); measuring instrument IR, UV-Vis, 13C-NMR, XRD, DSC, TGA, SEM; instrument used for the accelerated weather testing (Atlas UVCON); measuring instrument the tensile properties (Zwich Z2.5), the color parameters (ColourTec PCM), electric properties (TR-10C) and viscosity (Ubbelohde)
2.2 Methods for polymer composite preparation
Composites containing high density polyethylene, 30 wt.% calcium carbonate and 1 wt.% acid stearic were prepared by melt mixing in a Haake internal mixer at
160oC for 5 minutes Immediately after melt mixing, the composites were hot-pressed
in melting state at 160oC with the pressure of about 5 MPa into about 1-1.2 thickness sheets
mm-2.3 Natural exposure and accelerated weather testing
- Natural exposure: The HDPE/m-CaCO3 composites were exposed on outdoor testing shelves at the Natural Weathering Station of the Institute for Tropical Technology in Dong Hoi sea atmosphere region (Quang Binh) The inclining angle of shelves in comparison with the ground was 450 Total exposure time of the samples was 36 months
- Accelerated weather testing: The instrument used for accelerated weather testing was the UV-CON 327 (USA) Test conditions were set according to the ASTM D 4329-99 Each cycle of the accelerated weathering test included 8 hours of
UV irradiation at 60oC and 4 hours of condensation (with evaporation) at 50oC Total testing time was 720 hours (60 cycles) The UV-CON 327 was set on the automatic irradiance control mode with an irradiance level of 0.8 w/m2 at 313 nm After every six cycles, the samples were withdrawn and stored under standard condition
2.4 Methods
Infrared (IR), ultraviolet (UV), nuclear magnetic resonance spectroscopic 13C-NMR, X-ray diffraction (XRD), Scanning Electronic Microscopy (SEM), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), electric properties measurement, tensile properties measurement, color measurement, viscosity measurement
Trang 8CHAPTER 3: RESULTS AND DICUSSION
3.1 The change in morphology and structure of HDPE/m-CaCO 3 composites exposed naturally
3.1.1 Infrared spectra (IR)
IR spectra of M0, M12, M24, M36 samples of HDPE/m-CaCO3 composites presented in Fig 3.1
In the IR spectrum of M0, M12, M24 and M36 samples, some peaks characterize for stretching and bending vibrations of CH groups in HDPE were found
at 2921, 2854, 1465 and 1380 cm-1 Beside, a peak corresponding to out-of-plane bending vibration of CH group appears at 725 cm-1 The absorption peak around 1735
cm-1 characterizes for the stretching vibrations of carbonyl groups was seen clearly in
IR spectra of the exposed samples In addition, photolysis of ketones results in the formation of vinyl-type unsaturations with absorption band appearing at 1639 cm-1
A small increase in the region of 3300-3500 cm-1 was attributed to hydroxyl groups This is caused by the formation of the carbonyl groups such as ketone, lactone carbonyl and aliphatic ester occurring in photodegradation process of HDPE according to the Norish 1 and Norish 2 reaction and mechanism has been well described in the scheme 3.1
Trang 9h
CH2 CH2 C CH2 CH2
O H
carboxylic acid ester lactone
H2C CH CH2
CH2 CH2 C CH3
O +
h
saturated ketone
CH CH3CH
Scheme 3.1 Simplified photo-degradation mechanism of HDPE
To quantify relatively the carbonyl group content existed in the exposed samples, carbonyl index (CI) was calculated using the following equation:
Trang 10Figure 3.2 exhibits a increase of CI index as increasing the natural exposure time After 6 months of natural exposure, the CI index of composite sample increase 1.7 times compared with the initial value and increase 3.0 times after 36 months of natural exposure The significant increase of the CI was observed for the samples exposed from 0 to 6 months, from 12 to 18 months and from 24 to 30 months (hot season) while from 6 to 12 months, from 18 to 24 months and from 30 to 36 months (cold season) the CI varies more slowly
3.1.2 UV-Vis spectra
The UV-Vis spectra showed an increase of the absorption intensity of HDPE in the composites between 200 and 300 nm wavenumber In the UV-Vis spectrum of initial sample (M0 sample), there was one very strong absorption band at 226 nm The absorption at 226 nm must be associated with the π – π* transition of the ethylenic group of the α,β-unsaturated carbonyl of impurity chromophores of the enone type in photo-oxidation degraded HDPE
3.1.3 Nuclear magnetic resonance spectroscopic 13 C-NMR
Nuclear magnetic resonance spectroscopic 13C-NMR of HDPE sample (M0n), HDPE/m-CaCO3 composites samples before natural exposure (M0) and HDPE/m-CaCO3 composites samples after 36 months natural exposure (M36) were performed
Trang 11Figure 3.5 13C-NMR spectra of M0 sample before natural exposure
Figures 3.4 and 3.5 showed that, the resonances at 30.04 ppm and 32.80 ppm of M0n sample, 30.02 ppm and 32.86 ppm of M0 sample assigned to amorphous regions and to orthorhombic crystalline regions, respectively For the M36 sample, the 13C-NMR spectra also indicate the resonances at 30.05 ppm and 32.83 ppm assigned to amorphous regions and to orthorhombic crystalline regions, respectively Besides, the new peaks between 25 and 175 ppm were found in the spectrum of the M36 sample
Trang 12Characteristic peaks are 25.12, 43.18, 75.06 and 175.16 ppm could be assigned as follows The peak at 25.12 ppm is from carbons alpha (-*C-CO-) to carbonyl group The peak at 43.18 ppm is from carbons alpha to carboxyl group (-*C(R)-COO-) The peak at 75,06 ppm was assigned as carbon alpha to ester oxygen (-COO-*C-) and the peak at 175,16 ppm as carboxyl acid or ester carbons (-*COO-)
Samples Pic (ppm) Carbon position
-*
CH2- amorphous region 32,80 -*CH2- orthorhombic crystalline region
-*
CH2- amorphous region 32,86 -*CH2- orthorhombic crystalline region
M36
25,12 -*C-COO- 30,05 -*CH2- amorphous region 32,83 -*CH2- orthorhombic crystalline region 43,18 -*C(R)-COO-
75,06 -COO-*C- 175,16 -*COO-
Trang 13Figure 3.8 XRD patterns of M36 sample
Before natural exposure, the M0 sample mainly exhibited a strong reflection peak
at 21.6° followed by a less intensive peak at 23.9°, which correspond to the typical orthorhombic unit cell structure of (110) and (200) reflection planes, respectively The two weak peaks at around 30.0° and 36.2° were attributed to reflection planes (210) and (020), respectively In addition, there were several other weak reflection planes in the range of 40° to 50° angle In the XRD pattern of M0 sample, there was a peak at 29.5°, representing the planes (104) of distance 3.038 Å for m-CaCO3 The shape of XRD patterns for the M36 sample was almost similar to that of the M0 sample The diffraction peak position of all samples was not changeed while the intensity and width
of each peak were different, depending on the exposure time of the samples
The intensity of the peaks observed corresponding to (110) and (200) was used
to determine percentage of crystallinity and crystallite size of the samples by Eqs 1 and 2
a C
C C
I I
k
It was seen that the crystallinity percentage ( C) of HDPE/m-CaCO3 composites was increased with rising natural exposure time, from 43.06% to 49.86% (table 3.3)
In the first 12 months of natural exposure, it may be attributed to the strong increase
in the crystallinity of the samples (5.26%) After 12 to 36 months 12 natural exposure, the crystallinity percentage of the samples was slightly increased (from 48.32% to 49.86%) The crystallite size (for (110) plane) was increased from 9.8 to 12.5 nm when increasing natural exposure time
versus natural exposure time Samples 2 (o) d110 (nm) C (%)
Trang 143.1.5 Morphology
Figure 3.9 SEM images of M0 (a); M6 (b); M12 (c); M18 (d); M24 (e); M30 (g);
M36 (h) samples versus natural exposure time Figure 3.9 demonstrates the surface images of the samples before and after natural exposure Before natural exposure, the sample surface was relatively smooth, only had some small cracks (M0 sample) After 6 - 36 natural exposure months, there were more cracks found on the surface of the exposed samples The number and size
of cracks were increased with increasing natural exposure time The cracks also became bigger and deeper
3.1.6 Color change
composites according to natural exposure time
(h)