Injection molding of cotton fiber–filled HNBR is commonly used in the rubber industry. A microscopic technique was used to monitor level of fiber alignment as affected by varied scorch time, injection pressure, and flow distance in mold cavity. The results obviously reveal an increase in thickness of orderly alignment layer of fiber when injection pressure and flow distance in mold cavity increase, attributed to the increased magnitude of shear strain. On the other hand, a disorderly alignment of fiber is found in the system having relatively long scorch time. The molecular relaxation process via strain recovery causes a misalignment of cotton fibers. Stress relaxation results exhibit an increasing tendency of residual stress when injection pressure and flow distance in mold increase while scorch time decreases. Unexpectedly, the increase in creep strain with increasing injection pressure and flow distance, in association with a decrease in scorch time, arises from poor filler–rubber interaction.

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