Polyme Analysis 2010 Part 5 doc

üThe specimen is placed between compressive plates parallel to the surface.. Compression test Compressive strength maximum compressive load minimum cross-sectional area = Compressive mod

Impact Testing

üCompressive properties describe the behavior of a

material when it is subjected to a compressive load

üLoading is at a relatively low and uniform rate

üCompressive strength and modulus are the two most

common values produced

Compression test

üBlocks or cylinders üFor ASTM D695:

+The typical blocks: 12.7 x 12.7 x 25.4mm +The cylinders:12.7mm diameter and 25.4mm long üFor ISO 604: the preferred specimens:

+50 x 10 x 4mm for modulus +10 x 10 x 4mm for strength

Specimen size:

Scope:

üThe specimen is placed between compressive plates

parallel to the surface

üThe specimen is then compressed at a uniform rate

üThe maximum load is recorded along with stress-strain

data

üAn extensometer attached to the front of the fixture is

used to determine modulus

Compression test

Compressive strength maximum compressive load

minimum cross-sectional area

=

Compressive modulus

change in stress change in strain

=

Test Procedure:

Rockwell Hardness tester

üStandard specimen of 6.4mm thickness

ü is molded or cut from a sheet

Specimen size:

ü A hardness measurement based on the net increase in depth of impression as a load is applied

üHardness numbers have no units and are commonly given in the R, L, M, E and K scales

üThe higher the number in each of the scales, the harder the material

üThe harder the material → better resistance to plastic deformation or cracking in compression, better wear properties

Scope:

Durometer Hardness - Shore Hardness

üDetermine the relative hardness of soft materials,

usually plastic or rubber

üThe test measures the penetration of a specified

indentor into the material under specified conditions of

force and time

üThe hardness value is often used to identify or

specify a particular hardness of elastomers or as a

quality control measure on lots of material

Scope:

üGenerally 6.4mm (¼ in) thick for ASTM D 2240

Specimen size:

Durometer Hardness - Shore Hardness

üThe specimen is first placed on a hard flat surface

üThe indentor for the instrument is then pressed into the specimen making sure that it is parallel to the surface

üThe hardness is read within one second (or as specified by the customer) of firm contact with the specimen

Test Procedure:

üThe hardness numbers are derived from a scale

üShore A and Shore D hardness scales are common, with the A scale being used for softer and the D scale being used for harder materials

Data:

ü Density is the mass per unit volume of a material.

ü Specific gravity is a measure of the ratio of mass of a given volume of material at 23°C to the same volume of deionized water.

üSpecific gravity and density are especially relevant because plastic is sold on a cost per pound basis and a lower density or specific gravity means more material per pound or varied part weight.

Density and Specific Gravity

ASTM D792, ISO 1183 Scope:

ü For sheet, rod, tube and molded articles.

üThe specimen is weighed in air then weighed when immersed in distilled water at 23°C using a sinker and wire to hold the specimen completely submerged as required Density and Specific Gravity are calculated

üAny convenient size

+Specific gravity = a/[(a + w)-b]

a = mass of specimen in air

b = mass of specimen and sinker (if used) in water

W = mass of totally immersed sinker if used and partially immersed wire

+Density, kg/m3 = (specific gravity) x (997.6)

Test procedures:

üBulk density is defined as the weight per unit volume of material.

üBulk density is primarily used for powders or pellets

üThe test can provide a gross measure of particle size and dispersion which can affect material flow consistency and reflect packaging quantity

üA funnel is suspended above a measuring cylinder

üThe funnel is filled with the sample and allowed to freely flow into the measuring cylinder

üThe excess material on top of the measuring cylinder is scraped off with a straight edge

üThe sample and the cylinder is then weighed and the weight / volume (Bulk Density) is determined

üApparent density value is recorded as g/cm3

Bulk Density ASTM D1895B