Thermoplastics vulcanizates

We started this chapter with a description of the fundamental differences between thermoplastic and thermoset materials we will end it with an example of a subtle blend of their respective properties. A disadvantage of the three-dimensional network of EPDM, but actually of all thermoset materials, is the lack of recyclability. Crosslinked EPDM, both the waste from production and after use, cannot be processed in the melt again like thermoplastics. Reclaiming technologies have been developed for vulcanized mbber, degrading part of the network via high-temperature and shear treatment, but these technologies are less effective for EPDM vulcanizates, probably because the EPDM chains are so stable. A break- 

New York, 1992, Volumes I, II. c] T. Beock, M. Geotekiaes, P. Mischke, European Coatings Handbook, Vincentz Verlag, Hannover, 2000. d] W. F. 

Uleich, Reaction Polymers Polyurethanes, Epoxies, Unsaturated Polyesters, Phenolics, 

Special Monomers and Additives Chemistry, Technology and Applications, Hanser Gardner Publications, Munich, 2000. e] S. H. Goodman, Handbook of Thermoset Plastics, Noyes Publications, Norwich, 1999 (2nd edition). 

Nusseldee, Co-condensation of Melamine, urea and formaldehyde , in Proceedings of the 1998 TAPPI Plastic Laminates Symposium, Atlanta, Georg.a, Tappi Press, Atlanta. 

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In addition to dynamic vulcanization, the technological compatibilization technique was also adopted by Coran and Patel [34] to obtain thermoplastic vulcanizate having good mechanical integrity and elastic recovery. 

Han S.J., Lohse D.J., Radosz M., and Sperling L.H. Thermoplastic vulcanizates from isotactic olypro-pylene and ethylene-propylene-diene terpolymer in supercritical propane Synthesis and morphology. Macromolecules, 31, 5407, 1998. 

In an alternate synthesis, the formation of thermoplastic vulcanizate (TPV) is accomplished with two polymers, wherein one polymer is grafted with a carboxylic acid anhydride, which then is reacted with an aminosilane, which reacts with the acid anhydride and then cross-links with moismre. The vulcanizates exhibit good mechanical properties and lower melt-flow index than the starting polymers. 

Recent work on thermoplastic vulcanizates (TPVs) will not be included in this chapter since it is being reviewed elsewhere in the book. Abbreviations for some mbbers and accelerators will be used throughout in place of their full names as shown in Table 11.1. Acronyms for other polymers and additives wUl be provided in the text as required. A short discussion of polymer miscibility and compatibUization of polymer blends will be provided for better appreciation of the subject. 

Elastomers are often blended with plastics either to improve the impact resistance or to develop new materials having both plastic and elastic behavior. When the elastomer in the blend is dynamically vulcanized, the product is called a thermoplastics vulcanizate (TPV). Blends with unvulcanized mbber phase are usually known as thermoplastic elastomers. TPVs are discussed in another section of this book. This section will deal with recent developments in rubber-plastic blends. 

In this part, we will discuss AFM images and nanomechanical data obtained in smdies of natural and synthetic rubbers, thermoplastic elastomers (TPE), and their vulcanized counterparts— thermoplastic vulcanizates (TPV). 

Coran, A.Y. and Patel, R. Rubber-thermoplastic compositions. Part I. EPDM-polypropylene thermoplastic vulcanizates. Rubber Chem. TechnoL, 5, 141, 1980. 

Fig. 2 Compression set (elastic recovery under compressive deformation) at 70 °C for an ethyl-ene-LAO random copolymer, flexible polyvinylchloride (f-PVC) thermoplastic polyurethanes (TPUs), and thermoplastic vulcanizates (TPVs)...

Keywords Dynamic vulcanization Polymer blends and alloys Reactive processing Thermoplastic elastomers Thermoplastic vulcanizates... 

Fig. 1 Development of morphology in a thermoplastic vulcanizate from cocontinuous (left) to dispersed phase (right) [14]...

The contribution of Babu and Naskar gives a comprehensive overview on the recent developments of the thermoplastic vulcanizates (TPVs) with special reference to the technological advancement. TPVs combine high volume molding capability of thermoplastic with elastomeric properties of thermoset rubber. Therefore, they land themselves to broad area of applications in various fields. 

Medsker RE et al. (2000) Process for silicon hydride curing of thermoplastic vulcanizates. US Patent 6150464... 

First report on a conducting polymer, viz oxidised iodine doped polypyrrole by D.E. Weiss et al., a polyactetylene derivative Development of Thermoplastic Vulcanizates, a new class of thermoplastic elastomers by Gessler, Fisher, Coran and Patel. 

Thermoplastic Vulcanizates. These are a surprising improvement over conventional thermoplastic olefins. Vulcanized ethylene/... 

TPOs are basically two-component elastomer systems consisting of an elastomer finely dispersed in a thermoplastic polyolefin (such as polypropylene). The thermoplastic polyolefin is the major component. Thermoplastic elastomers (TPEs) include TPOs, TPVs (thermoplastic vulcanizates), etc. Properties of TPOs depend upon the types and amounts of polymers used, the method by which they are combined, and the use of additives such as oils, fillers, antioxidants, and colors. Blends and reactor-made products compete primarily with other TPEs and metals. There are vulcanizates (TPVs) that have higher elastomeric properties. They compete primarily with TS elastomers. 

The following TPs are the main thermoforming materials processed high-impact and high-heat PS, HDPE, PP, PVC, ABS, CPET, PET, and PMMA. Other plastics of lesser usage are transparent styrene-butadiene block copolymers, acrylics, polycarbonates, cellulosics, thermoplastic elastomers (TPE), and ethylene-propylene thermoplastic vulcanizates. Coextruded structures of up to seven layers include barriers of EVAL, Saran, or nylon, with polyolefins, and/or styreneics for functional properties and decorative aesthetics at reasonable costs.239-241... 

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