Thermoplastic vulcanisates

Obviously, there exists severe interplastics competition, e.g. PP vs. ABS, clarified PP vs. PS, PA, PVC, HDPE and PS (Table 10.7). A wide range of cross-linked and thermoplastic elastomer applications, from footware to automotive parts and toothbrushes, are adopting new metallocene-catalysed polyolefin elastomers (POEs). These low-density copolymers of ethylene and octene were first accepted as impact modifiers for TPOs, but now displace EPDM, (foamed) EVA, flexible PVC, and olefinic thermoplastic vulcanisates (TPVs). Interpolymer competition may also result from... 

There has been an increasing global trend in the wire and cable industry to restrict and remove the presence of lead in materials used for insulation and jacketing applications. The various standards that apply to lead in electrical applications are discussed. One of the issues is how to define the low levels of lead. Many minerals contain trace levels of lead as a chemical impurity. These minerals are used in rubber and plastics and thus the final composition is likely to contain trace amounts of lead. With modem analytical techniques, lead can be found at levels lower than five parts per million. Therefore, to satisfy increasing demands on wire and cable materials, a new series of thermoplastic vulcanisates (TPV) has been introduced that contains no added lead chemicals. These TPV materials have recently been granted a UL listing for flexible cord applications. The properties of these materials are presented and highlighted. 6 refs. 

The majority of these systems are crosslinked, so are thermosets. The term thermoplastic vulcanisates (TPV) is also used (a.8). Copolymers are made from ethylene, propylene and a small fraction of unsaturated diene, so allowing the crosslinking of the foam. Eor applications such as mouse mats, the foam density is... 

By rapid expansion of supercritical propane solution (RESS), and isobaric crystallisation (ICSS), isotactic polypropylene and ethylene-butylene copolymers were precipitated from the supercritical solution. The RESS process produced microfibres with a trace of microparticles, while the ICSS process produced microcellular products. Improvement in thermal stability was achieved by first synthesising a thermoplastic vulcanisate from polypropylene and ethylene-propylene-diene terpolymer from a supercritical propane solution, followed by RESS. 28 refs. 

As a result of its saturated polymer backbone, EPDM is more resistant to oxygen, ozone, UV and heat than the low-cost commodity polydiene rubbers, such as natural rubber (NR), polybutadiene rubber (BR) and styrene-butadiene rubber (SBR). Therefore, the main use of EPD(M) is in outdoor applications, such as automotive sealing systems, window seals and roof sheeting, and in under-the-hood applications, such as coolant hoses. The main drawback of EPDM is its poor resistance to swelling in apolar fluids such as oil, making it inferior to high-performance elastomers, such as fluoro, acrylate and silicone elastomers in that respect. Over the last decade thermoplastic vulcanisates, produced via dynamic vulcanisation of blends of polypropylene (PP) and EPDM, have been commercialised, combining thermoplastic processability with rubber elasticity [8, 9]. 

EPDM was developed and commercialised in the late 1950s. With an annual production capacity of more than 1,000 kt in 1998 [10]. EPDM is currently the fourth elastomer by volume and has become more or less a commodity rubber. Actually, EPDM is the largest non-tyre rubber. The annual growth rate is about 4%. DSM and Exxon are market leaders with a combined market share of approximately 40%. PP/EPDM-based thermoplastic vulcanisates which have currently the fastest growing rubber market (8% per year). 

Resols (phenol-formaldehyde resins) are commercially used for effective crosslinking of EPDM in the production of thermoplastic vulcanisates [8]. General studies on rubber crosslinking for different diene rubbers are presented here. 

Thermoplastic vulcanisates (TPV), blends of polypropylene with ethylene propylene diene (EPDM) copolymer, have replaced conventional rubbers in... 

Naskar, K., Gohs, U., Wagenknecht, U., Heinrich, G., PP-EPDM thermoplastic vulcanisates (TPVs) by electron induced reactive processing. Express Polymer Letters 2009,3(11), 677-683. 

The structure and physical properties of the thermoplastic vulcanisates (TPE-V) produced in the process of the reactive processing of polypropylene (PP) and ethyl-ene-octene elastomer (EOE) in the form of alloy, using the cross-linking system was analyzed. With the DMTA, SEM and DSC it has been demonstrated that the dynamically produced vulcanisates constitute a typical dispersoid, where semicrystal PP produces a continuous phase, and the dispersed phase consists of molecules of the cross-linked ethylene-octene elastomer, which play a role of a modifier of the properties and a stabilizer of the two-phase structure. It has been found that the mechanical as well as the thermal properties depend on the content of the elastomer in the blends, exposed to mechanical strain and temperature. The best results have been achieved for grafted/cross-linked blends with the contents of iPP/EOE-55/45%. 

Automotive and electrical/electronics industries are the largest markets for engineering polymers which include Crastin PBT polyesters, Hytrel thermoplastic polyester elastomers, Rynite PET, high-temperature Thermx PCT (polycyclohexylene dimethyl terephthalate), Tribon composites and Tynex filaments, Vespel polyimide parts and shapes, Zenite liquid crystal polymers and Zytel PA resins. In July 2005, DuPont launched the DuPont Vespel SP-202 composition whose properties include the prevention of static charge build-up. Other products include Delrin acetal resins, engineering thermoplastic vulcanisates. Minion mineral reinforced PA resins and Teflon PTFE fluoropolymer resins. 

The use of a gear pump feed of solid rubber compoimd is an ideal way for adding the rubber component to thermoplastic vulcanisates (the so-called TPV materials), once calibration of the gear pump for throughput has been completed. 

Deutsches Institut fur Kautschuktechnologie in Hanover has been carrying out interesting work on the continuous mixing of both curable rubbers and thermoplastic vulcanisates, with published papers comparing different screw designs, for example (39). 

Philadelphia, Pa., 28th-29th Sept. 1999, p. 171-85 COMPOUNDING OF RUBBER CONCENTRATE THERMOPLASTIC VULCANISATES... 

Another group in Malaysia [10] have looked into the viability of using reclaimed rubber from rejected NBR gloves in blends of PP for the production of thermoplastic vulcanisate(s) (TPV). The reclaimed NBR was evaluated as a partial replacement for virgin NBR in the blends in the range 40-70 phr. The TPV were prepared from the starting materials using a Banbury internal mixer, with... 

Whilst newer material types have emerged in recent years, primary TPE types can be categorized into two generic classes, block copolymers (styrenics, copolyesters, polyurethanes and polyamides) or thermoplastic/elastomer blends and alloys (thermoplastic polyolefins and thermoplastic vulcanisates). These TPE types are known as two-phase systems as essentially, a hard thermoplastic phase is coupled mechanically or chemically with a soft elastomer phase. The result is a TPE that has the combined properties of the two phases. 

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