Yield strength various polymers

Fig.2.21. Stress-strain diagram for various types of polymers (for explanation, see text) Og = yield strength Og = tensile strength at break...

The following polymer characteristics were obtained on the variously irradiated test specimens melt index (ASTM 1238-62T), Vicat softening temperature (modified ASTM 1525-58T) heat distortion (ASTM D 1220-63T) physical strength yield strength ultimate tensile strength percent elongation at break (ASTM D 412-64T) chemical resistance to boiling toluene. 

Supercritical or high pressure carbon dioxide can induce polymer crystallization and plasticize polymers. The systematic study on the interaction of carbon dioxide with twenty different crystalline and amorphous polymers has been performed and various influencing parameters have been determined. Through the examination, analysis and comparison of the yield strength, ultimate elongation and modulus both before and after treatments in supercritical carbon dioxide at 3000 psi and 70°C, it was found that two main factors, i.e., degree of crystallinity and the presence of a polar side chain group, e g., ester. 

Stress-strain data collected for many rigid polymers deformed at various conditions revealed stronger dependence of the yield strength cfy on temperature and strain rate... 

A comparison of the crystal structures, NMR and IR spectra of various Yb(ll) and calcium complexes demonstrated that they were strikingly similar, a reflection of the nearly identical radii of Ybz+ and Ca2+.25 Nevertheless, the dibenzylytterbium(ll) analog of 127 produces polystyrene of high syndiotacticity (r= 94.9%, rr= 90.0%), whereas 127 itself yields only atactic or slightly syndiotactic polymer. A difference in Yb-L and Ca-L bond strengths, despite their similar lengths, has been proposed as the source of the difference.315... 

Most polystyrene products are not homopolystyrene since the latter is relatively brittle with low impact and solvent resistance (Secs. 3-14b, 6-la). Various combinations of copolymerization and blending are used to improve the properties of polystyrene [Moore, 1989]. Copolymerization of styrene with 1,3-butadiene imparts sufficient flexibility to yield elastomeric products [styrene-1,3-butadiene rubbers (SBR)]. Most SBR rubbers (trade names Buna, GR-S, Philprene) are about 25% styrene-75% 1,3-butadiene copolymer produced by emulsion polymerization some are produced by anionic polymerization. About 2 billion pounds per year are produced in the United States. SBR is similar to natural rubber in tensile strength, has somewhat better ozone resistance and weatherability but has poorer resilience and greater heat buildup. SBR can be blended with oil (referred to as oil-extended SBR) to lower raw material costs without excessive loss of physical properties. SBR is also blended with other polymers to combine properties. The major use for SBR is in tires. Other uses include belting, hose, molded and extruded goods, flooring, shoe soles, coated fabrics, and electrical insulation. 

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