A Study On The Activation And Combination Of Blowing Agents And Its Application In The Foaming Of Natural Rubber

Natural rubber (NR) foam is one of the earliest polymer foam materials, which has currently been used in plenties of industries. In the foaming technology, it is important to use various methods to decrease the decomposition temperature of blowing agents to a suitable range to make the curing process of NR could match well with foaming process. In this paper, we used NR as the polymer matrix, H (N,N′-dinitroso pentamethylene tetramine), AC (Azodicarbonamide), OBSH (p,p′-Oxybis Benzene Sulfonyl Hydrazide) as blowing agents, Urea as activator and Sulfur as crosslink agent. We systematicly studied the activation mechanism of blowing agent H with Urea, the decoposition characteristics of AC/OBSH, AC/H, H/OBSH compounds. We also studied the influence of blowing agents on curing and foaming process of NR. Finally, we prepared NR foam materials and studied the influences of blowing agents and process conditions to pore structure and compression performance of foam materials.Activation mechanism of blowing agent H with Urea in NR matrix was qualitatively and quantitatively characterized by DSC, TGA and FTIR analysis, and their effects on the foaming performance for NR were also investigated. The results show that the decomposition mechanism of blowing agent H and Urea mixture is different from their own decomposition reactions, they react at a temperature range from 130°C to 180°C, and the peak decomposition temperature is 150°C. The optimum ratio for the two compounds is at their equivalent weight or with a little excess of Urea. Both of blowing agent H and Urea show great accelerating effects on the cure of NR. The pore uniformity of NR foam is closely related to the dispersion of Urea.The DSC, TGA and FTIR analysis showed that the combination of AC/OBSH and H/OBSH had positive synergy effects and could made good pore structure, but the combination of AC/H had no obvious synergy effects. The optimum curing temperature of NR with blowing agent blends was about 160°C.The compressive behavior of NR foam through compressive stress-strain curves was also investigated by the means of energy absorption efficiency (E). Results show that foams with low density have better absorption efficiency in a wide range.In this paper, valuable parameters of the activation and blending characteristic of blowing agents in polymeric matrix were provided, which could give the guidance for blowing system selection and for the improvement of pore structure and performance of NR foams.