STUDY ON VARIATION OF STRUCTURE AND PROPERTIES OF NATURAL-RUBBER DURING ACCELERATED STORAGE

The dynamic variations of molecular structure and properties of natura l rubber (NR) during the accelerated storage have been studied. The re sults showed that, with the prolonging of the storage time, the averag e molecular weight and the gel content increased, the width index of m olecular weight distribution decreased, the gel size increased gradual ly, but the crosslinking density of gel fluctuated only within a narro w range. Besides, the initial plasticity increased, whereas the plasti city retention index decreased. The studies with thermal analyses and infrared spectroscopy showed that the thermal degradation temperature dropped, the thermal degradation rate increased, and the thermal stabi lity has decreased after the storage of NR. The molecular structure an d properties of NR are in a state of dynamic variation during accelera te storage. (C) 1998 John Wiley & Sons, Inc.