Preparation of EPDM/SAN Dry Blends by Reactive Processing

Autor: Oskar Nuyken, Norbert Steinhauser, Werner Obrecht, Mario Vierle
Rok vydání: 2003
Předmět:
Zdroj: Macromolecular Materials and Engineering. 288:209-218
ISSN: 1439-2054
1438-7492
DOI: 10.1002/mame.200390019
Popis: Reactive blending of the rubber EPDM (a terpolymer consisting of ethylene, propylene and a diene) and the thermoplastic material SAN (a copolymer of styrene and acrylonitrile) is reinvestigated with special attention to EPDM/SAN blends with a 50/50 blend ratio. A resin cure system based on a low molecular weight phenol formadehyde condensate, which primarily consists of dimethylolphenol and stannous dichloride, is used for compatibilization of EPDM and SAN, as well as for crosslinking of the EPDM phase. The amounts of phenolic resin and SnCl 2 .2H 2 O as well as the EPDM grade and the EPDM/SAN blend ratio are varied. The blends are characterized by stress-strain measurements, transmission electron microscopy (TEM) and scranning electron microscopy (SEM). Unreacted EPDM, unreacted SAN and gelplus graft copolymer are quantitativelydetermined by fractionation of the blends with a binary solvent mixture which exhibits phase separation at room temperature. Blends prepared from EPDM grades that are amorphous and have a high molar mass exhibit high levels of gel and rather poor mechanical properties. With these blends, gel formation is favored over the formation of EPDM/SAN graft copolymer. Even with low levels of the resin cure sytem, the formation of gel cannot be avoided. It is therefore not possible to prepare graft copolymers without some gelling. Blends prepared from an EPDM grade with high crystallinity and a low Mooney viscosity exhibit substantially better mechanical properties than blends based on amorphous and higher viscosity EPDM grades. TEM and SEM micrographs reveal good dispersion of the two polymrs, as well as good interfacial adhesion between the EPDM and the SAN phase. This electron microscopic evidence, in combination with low gel contents, supports the view that the tendency towards graft copolymer formation and gelling strongly depends on the EPDM grade used. Variation of the EPDM/SAN blend ratio between 5-90 wt.-% results in blends which cover the product range from toughened thermoplastics to thermoplastic elastomers.
Databáze: OpenAIRE
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