Thermoplastic elastomers dynamic vulcanization

A.Y. Coran s research on the melt-mixed blends of elastomer and thermoplastics with dynamic vulcanization... 

A. Y. Coran, Thermoplastic elastomers based on elastomer-thermoplastic blends dynamically vulcanized, in Thermoplastic Elastomers—A Comprehensive Review, N. R. Legge, G. Holden, and H. E. Schroeder (eds.), Hanser Publishers, Munich, 1987. 

The more important grades of thermoplastic natural mbber, which fall into the olefinic class of thermoplastic elastomers, are prepared with the natural mbber phase partially cross-linked during blending, a process known as dynamic vulcanization. The hardness of the soft blends is controlled by the natural mbber content, and typical properties of those of 50—90 hardness (Shore A) are shown in Table 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. 

For the compatible elastomer-thermoplastic blends, melting of the two polymers is the first step followed by subsequent vulcanization of the elastomeric phase. A typical mixing cycle for dynamically vulcanized NR-PE blend (DVNR) in a Brabender mixer is as follows [58] ... 

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. 

Prut, E.V. and Erina, N.A., Dynamic vulcanization and thermoplastic elastomers, Macromol. Symp., 170, 73, 2001. 

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]. 

Microstructure-property correlations in dynamically vulcanized thermoplastic elastomers based on polypropylene (PP)/EPDM have shown that clay was nearly exfoliated and randomly distributed into the continuous polypropylene phase [23]. SEM photomicrographs revealed that the size of rubber particles increased with clay incorporation. Also, the clay layers act as nucleating agents, resulting in higher crystallization temperature and reduced degree of crystallinity. 

Recent Developments on Thermoplastic Elastomers by Dynamic Vulcanization... 

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

Recently, a new concept in the preparation of TPVs has been introduced, based on the reaction-induced phase separation (RIPS) of miscible blends of a semicrystalline thermoplastic in combination with an elastomer, with the potential for obtaining submicrometer rubber dispersions. This RIPS can be applied to a variety of miscible blends, in which the elastomer precursor phase was selectively crosslinked to induce phase separation. Plausible schematic representation of the morphological evolution of dynamic vulcanization of immiscible and miscible blends is shown in Fig. 9. For immiscible blends, dynamic vulcanization leads to a decrease in the size... 

Naskar (2004) Dynamically vulcanized PP/EPDM thermoplastic elastomers. Ph.D. thesis, University of Twente, The Netherlands... 

In 2004, Berstorff introduced a combined rubber extruder/gear pump, patent pending, for the production of dynamically cross-linked vulcanized thermoplastic elastomers (TPE-V) (DE 101340701 Al). A short rubber extruder, with a gear pump connected downstream,... 

Chorvath I et al. (2002) Thermoplastic elastomer compositions containing silicone rubber and nylon resins and the dynamically vulcanizing method. US Patent... 

Dynamically vulcanized blends Dynamically vulcanized blends are produced by melt mixing an elastomer phase with a thermoplastic (the elastomer being the major component) and then curing the elastomer during melt mixing. The resulting blend comprises the thermoplastic resin filled with high concentration of rubber particles well bonded to the matrix. Examples include EPDM/PP (Santo-... 

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