Processing of thermoplastics

BERNHARDT, E. c. (Ed.), Processing of Thermoplastic Materials, Reinhold, New York (1959) BLACKLEY, D. c.. High Polymer Latices, Maclaren, London (1966)... 

Vulcanised rubbers possess a range of very desirable properties such as resilience, resistance to oils, greases and ozone, flexibility at low temperatures and resistance to many acids and bases. However, they require careful (slow) processing and they consume considerable amounts of energy to facilitate moulding and vulcanisation. These disadvantages led to the development of thermoplastic rubbers (elastomers). These are materials which exhibit the desirable physical characteristics of rubber but with the ease of processing of thermoplastics. 

Thermoplastic elastomers are materials that have the properties of vulcanized rubbers but can be processed by techniques associated with thermoplastics. The commercial importance of TPEs is due to their superior processing properties and economic advantages over conventional rubbers and plastics. TPEs from rubber-plastic blends became important because they combine the superior processability of thermoplastics and the... 

Ionic polymers are a special class of polymeric materials having a hydrocarbon backbone containing pendant acid groups. These are then neutralized partially or fully to form salts. lonomeric TPEs are a class of ionic polymers in which properties of vulcanized rubber are combined with the ease of processing of thermoplastics. These polymers contain up to 10 mol% of ionic group. These ionomeric TPEs are typically prepared by copolymerization of a functionalized monomer with an olefinic unsamrated monomer or direct functionalization of a preformed polymer [68-71]. The methods of preparation of various ionomeric TPEs are discussed below. 

TPEs from thermoplastics-mbber blends are materials having the characteristics of thermoplastics at processing temperature and that of elastomers at service temperature. This unique combination of properties of vulcanized mbber and the easy processability of thermoplastics bridges the gap between conventional elastomers and thermoplastics. Cross-linking of the mbber phase by dynamic vulcanization improves the properties of the TPE. The key factor that controls the properties of TPE is the blend morphology. It is essential that in a continuous plastic phase, the mbber phase should be dispersed uniformly, and the finer the dispersed phase the better are the properties. A number of TPEs from dynamically vulcanized mbber-plastic blends have been developed by Bhowmick and coworkers [98-102]. 

Reactive macroalkyl radicals are formed during stress-initiated scission of the polymer backbone occassioned by the application of mechanical shear during industrial processing of thermoplastic polymers. These radicals undergo further reactions with other species or reactive sites, most important of which is molecular oxygen (dissolved or trapped in the polymer feed), with deleterious consequences. 

The determination of flow properties taken during the pigmentation and processing of thermoplastics are described in the literature on polymers [132,133],... 

The other difference [21] is fhaf fhermosef composife shows higher balanced sfrength and toughness compared to thermoplastic composite, with a little brittleness. Thus, thermoset composite plates can be fabricated relatively thinner and have more applications. On the other hand, as mentioned before, a well developed injection molding process has been applied as the fabrication process of thermoplastic-based composite plates to assure high quality and low cost. 

Bernhardt, E.C., Processing of Thermoplastic Materials, Reinhold Publishing Company, New York, 1959. 

Kalinchev EL, Sakovtzeva MB (1983) Properties and processing of thermoplastics, Chimia, Leningrad... 

Design considerations for air knives are discussed by Senecal (ibid.). Design procedures for extrusion dies when the flow is laminar, as with highly viscous fluids, are presented by Bernhardt (Processing of Thermoplastic Materials, Rheinhold, New York, 1959, pp. 248-281). 

A comparatively new group of materials— thermoplastic elastomers or thermoplastic rubbers —combines the ease of processing of thermoplastics with qualities of traditional vulcanized rubbers, especially elasticity. Because of convenience in processing there is much interest too in blends of plastics with elastomers, which may be modified by the inclusion of filler or glass fibre. As an example, a rubber-like material that can be processed as a thermoplastic can be made by blending and melt-mixing an ethylene-propylene rubber with polypropylene. The use of such blends may be helpful when there are needs to reclaim and re-process material, and in order to obtain products with qualities intermediate between those of the main components of the blends. 

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