Statistical Analysis of Plasticity Measurements of Natural and Synthetic Rubber

Abstract

The reliability of plasticity data on rubber is affected by (1) variance in precision of measurement by the instrument used and (2) heterogeneity of the rubber. While the relative precision of the instrument and observer error must be considered, the problem is somewhat complicated by the fact that each sample is used only once. Thus a single measurement is made on n like things rather than n like measurements on a single thing. Methods commonly used are the Williams parallel-plate, Dillon and Johnston extrusion, and Mooney shear. Rather meager data have been published on plasticity measurements of large numbers of samples (200–300) of elastomers. Riebl and Martin, Davey and Baker have reported no dispersion values, only averages of D30 plasticity values of smoked sheet and crepe being shown, using a parallel-plate plastometer. Aside from Mooney plasticity values of GR-S on 45–50 samples given in recent papers by Heide and Vila and Gross no statistical data for GR-S plasticity are available in the literature. It is the purpose of this paper to present a simple statistical analysis of the three types of plasticity measurements for GR-S and natural rubber (Hevea smoked sheet) based on 256 specimens.

The behavior of dithiocarbimate derivative as safety accelerator of natural rubber compounds

“…2‐Bisbenzothiazole‐2,2′‐disulfide (MBTS)‐accelerated sulfur vulcanization of rubber has been studied by various authors 15–18. Gradwell and McGill19 investigated the sulfur vulcanization of polyisoprene accelerated by MBTS.…”