AN INNOVATIVE METHOD OF
DYNAMIC VULCANIZATION OF EVA IN THE PRESENCE OF P P:
CHEMICAL, PROCESSING AND MECHANICAL PROPERTIES.
1Laboratoire des Matériaux Polymères et Biomatériaux,
UMR5627,
ISTIL, Université Claude Bernard, Lyon 1, 43 Bvd du 11
Novembre 1918
69622 Villeurbanne cedex (France)
2GEMICO, ENSIC, 1 Rue Grandville, BP 451, 54001 Nancy
cedex (France)
ABSTRACT
The elaboration of a thermoplastic elastomer vulcanizated (TPV) based on copolymer of ethylene and vinyl acetate (EVA) and polypropylene (PP) as thermoplastic phase was investigated in a batch mixer and in a twin screw extruder. The crosslinking reaction is carried out through a two step process. First, silane groups from vinyl trimethoxysilane (VTMOS) are radically grafted onto an EVA chain in the presence of dicumyl peroxide (DCP). And secondly, when PP thermoplastic phase is added, elastomer phase is crosslinked at higher temperature by an exchange reaction between acetate function of EVA and grafted silane functions. This chemical way of EVA crosslinking improves mechanical properties of such a TPV compared to the one tailored by the exchange reaction between tetrapropoxy-orthosilicate (TPOS) and acetate function of EVA. In order to improve elongation and tensile strength at break, a third component, the Kratonâ polystyrene-block-poly(ethylene-stat-butylene) was added. Furthermore, a compatibilizing effect of plastol oil (paraffinic and naphtenic hydrocarbons oil) through the SEBS phase explains the improvement of the tensile mechanical properties. Lastly, compression set and tensile properties are better when TPV is tailored in extruder than in batch mixer.