Thermoplastic/rubber blends

A number of methods [11,13-17] have been applied in an attempt to solve the problem and to find more effective ways of tire rubber recycling and waste rubber utilization. These methods include retreading, reclaiming, grinding, pulverization, microwave and ultrasonic processes, pyrolysis, and incineration. Processes for utilization of recycled rubber are also being developed, including the use of reclaimed rubber to manufacture rubber products and thermoplastic-rubber blends and the use of GRT to modify asphalt and cement. 

Butadiene and styrene may be polymerised in any proportion. The Tfs of the copolymers vary in an almost linear manner with the proportion of styrene present. Whereas SBR has a styrene content of about 23.5% and is rubbery, copolymers containing about 50% styrene are leatherlike whilst with 70% styrene the materials are more like rigid thermoplastics but with low softening points. Both of these copolymers are known in the rubber industry as high-styrene resins and are usually used blended with a hydrocarbon rubber such as NR or SBR. Such blends have found use in shoe soles, car wash brushes and other mouldings but in recent times have suffered increasing competition from conventional thermoplastics and to a less extent the thermoplastic rubbers. 

Another area of recent interest is covulcanization in block copolymers, thermoplastic rubbers, and elasto-plastic blends by developing an interpenetrating network (IPN). A classical example for IPN formation is in polyurethane elastomer blended acrylic copolymers [7]. 

Compatibilization along with dynamic vulcanization techniques have been used in thermoplastic elastomer blends of poly(butylene terephthalate) and ethylene propylene diene rubber by Moffett and Dekkers [28]. In situ formation of graft copolymer can be obtained by the use of suitably functionalized rubbers. By the usage of conventional vulcanizing agents for EPDM, the dynamic vulcanization of the blend can be achieved. The optimum effect of compatibilization along with dynamic vulcanization can be obtained only when the compatibilization is done before the rubber phase is dispersed. 

Blend of (1) and (2) type categories mostly include the modification of engineering thermoplastics with another thermoplastic or rubber. PS-EPDM blends using a low-molecular weight compound (catalyst) Lewis acid have been developed [126]. Plastic-plastic blends, alloys of industrial importance, thermoplastic elastomers made by dynamic vulcanization, and rubber-rubber blends are produced by this method. 

Handbook of elastomers , A.K. Bhowmick and H.L. Stephens Marcel Dekker (1988) Series Plastics Engineering, Volume 19 ISBN 0824778006. This handbook systematically addresses the manufacturing techniques, properties, processing, and applications of rubbers and rubber-like materials. The Handbook of Elastomers provides authoritative information on natural rubbers, synthetic rubbers, liquid rubbers, powdered rubbers, rubber blends, thermoplastic elastomers, and rubber-based composites— offering solutions to many practical problems encountered with rubber materials. 

Typical Properties of Thermoplastic Elastomers Developed from Nylon-6-Acrylate Rubber Blends... 

Jha and Bhowmick [51] have reported the development and properties of thermoplastic elastomeric blends from poly(ethylene terephthalate) and ACM by solution-blending technique. For the preparation of the blend the two components, i.e., poly(ethylene terephthalate) and ACM, were dried first in vacuum oven. The ACM was dissolved in nitrobenzene solvent at room temperature with occasional stirring for about three days to obtain homogeneous solution. PET was dissolved in nitrobenzene at 160°C for 30 min and the rubber solution was then added to it with constant stirring. The mixture was stirred continuously at 160°C for about 30 min. The blend was then drip precipitated from cold petroleum ether with stirring. The ratio of the petroleum ether/nitrobenzene was kept at 7 1. The precipitated polymer was then filtered, washed with petroleum ether to remove nitrobenzene, and then dried at 100°C in vacuum. 

Jha A. and Bhowmick A.K., Thermoplastic elastomeric blends of nylon 6/acrylate rubber Influence of interaction of mechanical and dynamic mechanical thermal properties. Rubber Chem. TechnoL, 70, 798, 1997. 

Jha A., Dutta B., and Bhowmick A.K., Effect of fillers and plasticizers on the performance of novel heat and oil-resistant thermoplastic elastomers from nylon-6 and acrylate rubber blends, J. Appl. Polym. Sci., 74, 1490, 1999. 

Roy Choudhury N. and Bhowmick A.K., Adhesion between individual components and mechanical properties of natural rubber-polypropylene thermoplastic elastomeric blends, J. Adhes. Sci. Technol., 2(3), 167, 1988. 

Kresge E.N., Polyolefin thermoplastic elastomer blends. Rubber Chem. TechnoL, 64, 469, 1991. 

Jha, A. and Bhowmick, A.K., Thermoplastic elastomeric blends of poly(ethylene terephthalate) and acrylate rubber I. Influence of interaction on thermal, dynamic mechanical and tensile properties. Polymer, 38, 4337, 1997. 

Ismail, H. and Suryadiansyah, S., Thermoplastic elastomers based on polypropylene/natural rubber and polypropylene/recycle rubber blends. Polymer Test., 21, 389, 2002. 

Anandhan, S., De, P.P., Bhowmick, A.K., Bandyopadhyay, S., and De, S.K., Thermoplastic elastomeric blend of nitrile rubber and poly(styrene-co-acrylonitrile). n. Replacement of nitrile rubber by its vulcanizate powder, J. Appl. Polym. Set, 90, 2348, 2003. 

Presents current research activities on new rubbers, thermoplastic elastomers, nanocomposites, biomaterials, and smart polymers, as well as rubber blends, composites, and rubber ingredients... 

Thermoplastic elastomers (TPE), 9 565-566, 24 695-720 applications for, 24 709-717 based on block copolymers, 24 697t based on graft copolymers, ionomers, and structures with core-shell morphologies, 24 699 based on hard polymer/elastomer combinations, 24 699t based on silicone rubber blends, 24 700 commercial production of, 24 705-708 economic aspects of, 24 708-709 elastomer phase in, 24 703 glass-transition and crystal melting temperatures of, 24 702t hard phase in, 24 703-704 health and safety factors related to, 24 717-718... 

Kocsis (1999) In Shonaike GO, Simon GP (eds) Polymer blends and alloys - thermoplastic rubbers via dynamic vulcanization. Marcel Dekker, Ne w York... 

Other thermoplastic elastomer combinations, in which the elastomer phase may or may not be cross-linked, include blends of polypropylene with nitrile (30,31), butyl (33), and natural (34) rubbers, blends of PVC with nitrile mbber (35,36), and blends of halogenated polyolefins with ethylene interpolymers (29). Collectively, thermoplastic elastomers of this type are referred to herein as hard polymer/elastomer combinations. Some of the more important examples of the various types are shown in Table 3. 

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. 

In the last years of the history shown in Table II we see the announcements of new commercial thermoplastic rubbers. Uniroyal TPR appeared in 1971. (This thermoplastic rubber many not be a block polymer. Presumably it is a blend that achieves its properties by virtue of interpenetrating networks between the plastic and rubber constituents. The exact structure has not been disclosed.) Du Pont s Hytrel, an (A-B) polyetherpolyester thermoplastic rubber, came out in 1972. Also in 1972, Shell announced a second generation block polymer, Kraton-G, which is a three-block S-EB-S thermoplastic rubber (EB represents an ethylene-butylene rubbery midblock). 

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