Poly block copolymer tensile strength

In order to achieve the desired fiber properties, the two monomers were copolymerized so the final product was a block copolymer of the ABA type, where A was pure polyglycoHde and B, a random copolymer of mostly poly (trimethylene carbonate). The selected composition was about 30—40% poly (trimethylene carbonate). This suture reportedly has exceUent flexibiHty and superior in vivo tensile strength retention compared to polyglycoHde. It has been absorbed without adverse reaction ia about seven months (43). MetaboHsm studies show that the route of excretion for the trimethylene carbonate moiety is somewhat different from the glycolate moiety. Most of the glycolate is excreted by urine whereas most of the carbonate is excreted by expired CO2 and uriae. 

Multiblock copolymers based on poly(a-methylstyrene) also show significantly better oxidative thermal stability than the block copolymers based on polystyrene. Thus, polystyrene-polydimethyldisiloxane multiblock copolymers lose half of their tensile strength after 80 hours with considerable yellowing at 150°C in air, but corresponding materials based on poly( -methylstyrene) show no discoloration or loss in tensile properties under the same conditions. 

The experimental results that will be examined consist of studies that look at the ability of a random copolymer to improve the properties of mixtures of the two homopolymers relative to the ability of a block copolymer. The three different systems that are examined include copolymers of poly(styrene-co-methyl methacrylate) (S/MMA), poly(styrene-co-2-vinyl pyridine) (S/2VP), and poly(styrene-co-ethylene) (S/E) in mixtures of the two homopolymers. The experiments that have been utilized to examine the ability of the copolymer to strengthen a polymer blend include the examination of the tensile properties of the compatibilized blend and the determination of the interfacial strength between the two homopolymers using asymmetric double cantilever beam (ADCB) experiments. 

ABA coil-rod-coil copolymers of poly(p-phenylene ter-ephthalamide) (PPTA) or poly(p-benzamide) (PBA) rods and nylon 6 or nylon 6,6 coils were prepared and used to reinforce nylon 6 and nylon 6,6 homopolymers. Materials with 5% total rod in the block copolymer/homo-polymer blend showed improved modulus and tensile strength over the homopolymer and much better elongation to break than similar composition blends of rod and coil homopolymers. The dispersed nature of the rod blocks in the block copolymer prevents the initiation of cracks at the macrophase-separated rod-coil phase interface that would normally occur in a rod/coil homopolymer blend. 

Lin and co-workers [47] reinforced PU elastomers with an entirely rigid aromatic polyamide, poly(w-phenyleneisophthalamide). The block copolymers formed exhibited glass transition temperatures (Tg) under 0 °C. Such block copolymers have improved reinforcing affect as shown by both their tensile strength and elongation when compared with the virgin PU. 

Hard PhaS6. The choice of the hard phase determines the upper service temperature and also infiuences the solvent resistance. In styrenic block copolymers, those based on poly(a -methylstyrene) [25014-31-7] have higher upper service temperature and tensile strength than analogues based on polystyrene [9003-53-6] (6) both are soluble in common solvents. Replacing the polystyrene end segments in S-EB-S by polyethylene (giving E-EB-E block copolymer) improves solvent resistance the phases are not separated in the melt (6). 

As a continuation of this work, various analogs of these triblock copolymers were synthesized, such as a-methylstyrene-b-isoprene-b-a-methylstyrene, a-methylstyrene-b-(propylene sulfide)-b-a-methylstyrene and a-methylstyrene-b-dimethylsiloxane-b-a-methylstyrene. All of these showed similar morphology and structure-property relations as the styrene-diene triblocks, as might have been expected. It was noteworthy, however, that when the polystyrene end blocks were replaced by poly-a-methylstyrene, there was a noticeable increase in modulus and tensile strength, at any given temperature. This was presumably due to the enhanced ability of the poly-a-methylstyrene domains to withstand greater stresses and higher temperatures,... 

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