Ethyl Corporation

Gary S Ragan

Jesse D Jones

The impact strength of thermoplastic poly(ethylene terephthalate) molding compositions containing a reinforcing filler (preferably glass fiber), an epoxidized crystallization promoter (e.g., an epoxidized vegetable oil) and a nucleating agent (e.g., sodium stearate) is markedly improved by including in the composition a small amount of an organofunctional silane, i.e., a compound characterized by having a functional substituent at the end of a methylene chain bound to a silicon atom to which are also bonded a plurality of readily hydrolyzable groups. A few such compounds are gamma-aminopropyltriethoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-aminopropyltriethoxysilane and gamma-glycidoxypropyltrimethoxysilane. The formulations may also contain a warp-reducing filler such as mica. Organofunctional silanes typically have application in thermoplastic polymers only as coupling agents, i.e., agents that act to bind the resin to a reinforcing filler so that improved tensile strength and tensile modulus are obtained. However, in the present compositions the organofunctional silanes appear to function in a new and different way--they serve as effective impact modifiers for the PET blends and in so doing, provide significantly improved Izod Impact results. Normally the tensile strength and tensile modulus are not materially changed by the addition of the organofunctional silanes.

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Baton Rouge, LA, United States of America

Gary S Ragan