Tensile properties, copolymers poly

Copolymers of S-caprolactone and L-lactide are elastomeric when prepared from 25% S-caprolactone and 75% L-lactide, and rigid when prepared from 10% S-caprolactone and 90% L-lactide (47). Blends of poly-DL-lactide and polycaprolactone polymers are another way to achieve unique elastomeric properties. Copolymers of S-caprolactone and glycoHde have been evaluated in fiber form as potential absorbable sutures. Strong, flexible monofilaments have been produced which maintain 11—37% of initial tensile strength after two weeks in vivo (48). 

Table 4. Tensile properties of the poly(CL-[7-DXO-[7-CL) ABA triblock copolymers (see Scheme 39) ...

Ethylene copolymers were compared with liquid plasticisers for use as additives to improve the flexibility of poly(vinyl chloride) (PVC) for electrical cable insulation applications. The PVCs were assessed by determining smoke generation, flammability, tensile properties and the low temperature brittle point. The ethylene copolymers gave similar peak heat release rates, but the peak smoke and the total smoke generation were lower. They also gave similar or increased strength, similar elongation and flexural modulus, and lower brittle point temperatures. 4 refs. 

Thus, Hope and his coworkers concluded for the solid-state extrusion of linear poly-ethylenes that increasing the molecular wei t reduced both the maximum degree of deformation and the tensile properties of the jaoduct. Hie sother hand, increased the maximum degree of deformation. The degree of stiffness enhancement upon extrusion and the melting points of the products were reduced. 

In the early 1950 s, B.F. Goodrich introduced the first commercial elastomer based on ionic interactions, a poly(butadiene-co-acry-lon1trile-co-acrylic acid). Typically less than 6% of carboxylic monomer 1s employed in order to preserve the elastomeric properties inherent in these systems. When neutralized to the zinc salt, these elastomers display enhanced tensile properties and improved adhesion compared to conventional copolymers. This enhancement of properties can be directly attributed to ionic associations between the metal carboxylate groups. 

Block copolymers constituted so that the hard A blocks show increased glass temperatures might be expected to show better ultimate tensile properties than comparable block copolymers of a lower Tg in the glassy phase (12). This is demonstrated in the present system by substituting the major portion of the polystyrene in the present system for poly (a-methylstyrene). A short length of polystyrene is included at each chain end of the hard block to facilitate the second step of the synthesis and to give a more stable polymer. The effect of replacing... 

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. 

Some physical properties of polyethylene ionomers are compared with those of polyethylene and the acid copolymer, poly(ethylene-co-methacrylic acid) in Table 5.15. lonomer is generally tougher and, as shown in Table 5.15, relative to the acid copolymer, its tensile strength is increased by 27—53% and its stiffness is nearly tripled. 

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. 

In copolymers of poly(ethylene terephthalate-co-naphthalate)s with low amounts of naphthalate, a melting point depression is observed, while the glass transition temperatures are higher than that of PET. The crystallization rates of the copolymers decrease with increasing comonomer content. The tensile properties of the copolymers with 3 % of naphthalate are significantly improved compared to PET. Thus, the properties of PET can be improved with the use of small amounts of naphthalate, with no significant increase of cost [29]. 

An increase in the high temperature (200 °C) tensile properties of the ethylene-tetrafluoroethylene copolymer, ETFE, after irradiation in nitrogen at room temperature followed by heat treatment at 162 °C in nitrogen for 20 min indicates some crosslinking [118]. On the other hand, irradiatimi carried out in air showed very little cross-linking [119]. ETFE behaves in some ways similar to poly-vinyUdene fluoride (PVDFO in that there is competition between crosslinking and scissimi. Some of the tensile properties, measured at 200 °C, of irradiated ETFE are shown in Table 52.14 [119]. 

PET/LCP, PBT/LCP Tensile properties PET-LCP copolymer as compatibilizer was used Poli et al. 1996... 

Extrusion of the poly (p-dioxanone-co-L(-) lactide) segmented and random copolymers was performed in a similar fashion as that of poly (p-dioxanone). The tensile properties were determined with an INSTRON tensile tester. The breaking strength retention (BSR) in vivo of the fibers was determined by implanting two strands of the fiber in the dorsal subcutis of each of a number of Long-Evans rats. 

Wootthikanokkhan and Tongrubbai examined the tensile properties of NR/ACM vulcanizates. It was found that increasing the NR content in the recipe improved the mechanical properties. However, that was not the case when the same specimens were heated for 24 h at 140 °C. After this thermal treatment, the vulcanizates with increased ACM weight ratio maintained to a greater extent their initial strain percentage compared to these with lower ACM content. To improve the mechanical response of NR/ACM sulfur-cured vulcanizates, incorporation of CB or compatibilization with poly(isoprene-butyl acrylate) block copolymer (at 5 wt%) has been proposed. ... 

Elanthikkal et al. investigated the effect of CNCs (from banana waste fibers) (0-10% w/w) on the morphological, thermal, and mechanical properties of poly(ethylene-co-vinyl acetate) (PEVA)/cellulose composites. The produced composites showed superior thermal and mechanical properties as compared to that of the EVA copolymer alone. In this study, three different theoretical models (Halpin-Tsai model, the Kemer model and the Nicolais-Narkis model) have been employed to compare the results with observation of tensile data from mechanical tests. Here, experimental results showed better agreement with the prediction given by the use of the Halpin-Tsai model, assuming that there is perfect wetting of filler by the polymer matrix [217]. 

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