Shore hardness copolymers

The polyetherimide—polysdoxane multiblock copolymers are relatively hard (about 70 on the Shore D scale). Their main appHcation is flame-resistant wire and cable covering (24), where they combine very low flammabiUty with a low level of toxic products in the smoke. This unusual and vital combination of properties justifies their relatively high price, about 37/kg, at a specific gravity of about 1.2. 

Other Mechanical and Thermal Properties. Table IV shows that the tensile properties, the Shore D hardness, and the deflection temperature of a PVC graft copolymer alloy containing 13% of a VC/LD-PE (50-50) graft copolymer are only slightly lower than the corresponding properties of the pure PVC (Solvic 239). There is no difference between the heat stabilities of the PVC and of the alloy. 

Substitute for Conventional Vulcanized Rubbers, For this application, the products are processed by techniques and equipment developed for conventional thermoplastics, ie, injection molding, extrusion, etc. The S—B—S and S—EB—S polymers are preferred (small amounts of S—EP—S are also used). To obtain a satisfactory balance of properties, they must be compounded with oils, fillers, or other polymers compounding reduces costs. Compounding ingredients and their effects on properties are given in Table 8. Oils with high aromatic content should be avoided because they plasticize the polystyrene domains. Polystyrene is often used as an ingredient in S—B—S-based compounds it makes the products harder and improves their processibility. In S—EB—S-based compounds, crystalline polyolefins such as polypropylene and polyethylene are preferred. Some work has been reported on blends of liquid polysiloxanes with S—EB—S block copolymers. The products are primarily intended for medical and pharmaceutical-type applications and hardnesses as low as 5 on the Shore A scale have been reported (53). 

Similar results were obtained for cellulose acetate for which Rockwell hardness had linear correlation with the percentage of plasticizer in formulation. Shore A hardness of PVC/acrylate copolymer blends decreases with amounts of plasticizers but also incompatible liquids such as silicone oil. ... 

The tensile strengths of these TPEs are high, and they have hardnesses ranging from 40 to 63 Shore D (generally harder than conventional thermoset rubber compounds). As hardness increases, these copolymers become more like hard plastics and less like rubber vul-canizates. 

Styrenic block copolymer blends with polyolefins are among the most widely used blends and they vary in hardness from low Shore A on the softer side to >60 D on the harder side and are used in a wide variety of applications. EPDM blends with polyolefin that are made by compounding or by direct reactor polymerization have also found several applications in the automotive industry. At low concentrations ( 20% or less) EPDM and EPR have been used as an impact modifier for polyamides [16]. 

Polyamide/acrylate graft copolymers have a Shore D hardness range from 50 to 65, and continuous service temperature range from -40 to 329°F ( 0 to 165°C). The markets are... 

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