Dynamic vulcanization of fluorocarbon elastomers containing peroxide cure sites

Abstract

Processable rubber compositions contain a vulcanized elastomeric material dispersed in a matrix of a thermoplastic polymeric material. The vulcanized elastomeric material is a peroxide cure polymeric material containing repeating units derived from fluorine-containing monomers and at least one peroxide cure site monomer. In one embodiment the matrix forms a continuous phase and the vulcanized elastomeric material is in the form of particles forming a non-continuous phase. The compositions are made by combining a radical curing system, a fluorocarbon elastomer material, and a fluoroplastic material, and heating the mixture at a temperature and for a time sufficient to effect vulcanization of the elastomeric material, while mechanical energy is applied to mix the mixture during the heating step. Shaped articles may be readily formed from the rubber compositions according to conventional thermoplastic processes such as blow molding, injection molding, and extrusion. Examples of useful articles include seals, gaskets, O-rings, and hoses.

Description

FIELD OF THE INVENTION [0001] The present invention relates to thermoprocessable compositions containing cured fluorocarbon elastomers. It also relates to seal and gasket type material made from the compositions and methods for their production by dynamic vulcanization techniques. BACKGROUND OF THE INVENTION [0002] Cured elastomeric materials have a desirable set of physical properties typical of the elastomeric state. They show a high tendency to return to their original size and shape following removal of a deforming force, and they retain physical properties after repeated cycles of stretching, including strain levels up to 1000%. Based on these properties, the materials are generally useful for making shaped articles such as seals and gaskets. [0003] Because they are thermoset materials, cured elastomeric materials can not generally be processed by conventional thermoplastic techniques such as injection molding, extrusion, or blow molding. Rather, articles must be fashioned from...

AI Technical Summary

Benefits of technology

[0008] A method for making a rubber composition comprises combining a radical curing system, a curable elastomeric material having cure sites highly reactive to radical initiators, and a thermoplastic material, and heating the mixture at a temperature and for a time sufficient to effect vulcanization of the elastomeric material, while mechanical energy is applied to mix the mixture during the heating step. The elastomeric material is a fluorocarbon polymer and the thermoplastic material comprises a fluorine containing polymeric material that softens and flows upon heating.

Problems solved by technology

Because they are thermoset materials, cured elastomeric materials can not generally be processed by conventional thermoplastic techniques such as injection molding, extrusion, or blow molding.

Although these and other rubber compounding operations are conventional and known, they nevertheless tend to be more expensive and require higher capital investment than the relatively simpler thermoplastic processing techniques.

Another drawback is that scrap generated in the manufacturing process is difficult to recycle and reuse, which further adds to the cost of manufacturing such articles.

Articles made from elastomeric materials, such as seals and gaskets, are in contact with such fluids during use, and are subject to a wide variety of challenging environmental conditions, including exposure to high temperature, contact with corrosive chemicals, and high wear conditions during normal use.

As a thermoset material, the cured fluorocarbon rubber is subject to the processing disadvantages noted above.