Sunil,K Narayanankutty(Technomic Publishing Co., Inc., April , 1998)
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Abstract:
The stress relaxation behavior of polyurethane elastomer and
short polyester fiber filled elastomer composites with and without bonding
agents at different strain levels and strain rates was studied. It was found that
these compounds exhibit a multistage relaxation mechanism and that the rate
of relaxation and cross-over time depend on the strain level and strain rate.
The incorporation of fibers reduced the stage-I relaxation rate and increased
the cross-over time of the gum vulcanisate. A higher rate of relaxation (first
stage) was shown by the composites with longitudinal fiber orientation and
composites with bonding agents.
The cure characteristics of short fiber-polyurethane elastomer
were studied with respect to different fiber-matrix bonding agents. A hexamethylenetetramine-
resorcinol -hydrated silica based bonding agent was found to affect
the stability of the composite. A new bonding agent, TP resin, based on polymeric
toluenediisocyanate and polypropylene glycol has been developed. Cure characteristics
of the composite with and without TP resin at different fiber loadings were
also compared. Minimum torque, scorch time and optimum cure time increased
with fiber content. Maximum torque was consistently higher with TP resin at all
fiber loadings.