HIGH-STRAIN HYSTERESIS OF RUBBER VULCANIZATES OVER A RANGE OF COMPOSITIONS, RATES, AND TEMPERATURES

Hysteresis loss of natural rubber (NR) and styrene-butadiene rubber (S BR) vulcanizates having variations of loading of carbon black, silica, clay, resin, and curatives has been measured over a wide range of str ain rates and temperatures as well as under swollen conditions. Hyster esis loss increases with an increase in strain rate, filler loading, r esin loading (at high rates), crosslink density, and strain level. Hys teresis decreases with an increase in temperature, particle diameter o f filler, and resin loading at high testing temperature. All the data of hysteresis loss of filled NR and SBR compounds have been found to b e superimposable on single master curves with the help of the WLF shif t factor. The master curves can be divided into three regions. The slo pe of the intermediate region, Delta log(hysteresis)/Delta log(Ra-T) h as been found to be 0.1 for almost all the vulcanizates. Similar maste r plots have been obtained when the hysteresis loss has been measured at higher cycles and higher extensions and also by using the data of t he hysteresis loss ratio. The hysteresis loss ratio of all the vulcani zates follows a similar trend, except far the highly crosslinked syste m, which shows a lower value. Carbon black contributes significantly t o the hysteresis loss even when the energy dissipation is minimized by swelling. (C) 1997 John Wiley & Sons, Inc.