Research Of Storage Hardening Mechanism And Storage Stability Of Natural Rubber

The slight intermolecular crosslinking and the increase in Wallace plasticity,Mooney viscosity and gel content that occurred in natural rubber on prolonged storage leads to bad processing properties and increase energy consumption of rubber processing. The variation of structure and performance of natural rubber during prolonged storage for different brands, the effect of external storage conditions (time, humidity) on structure and performance of natural rubber during prolonged storage, and the analysis of intermolecular crosslinking network structure of natural rubber during prolonged storage were carried out in this paper.The variation of structure and performance of natural rubber during prolonged storage for SCR 5, SVR 3L, RSS 1 and RSS 3 was analyzed. And the results showed that SCR 5,SVR 3L, RSS 1 and RSS 3 become storage hardening of different level with the prolonged storage time. The molecular weight, crosslinking density, total number of crosslink-point,gel content, P0 and Mooney viscosity of RSS 1 and RSS 3 were growing faster than SCR 5 and SVR 3L. On account of the P0 , the degree of hardening is RSS 3 > RSS 1 > SCR 5 >SVR 3L after accelerated storage for 48 h.The effect of storage time on structure and performance of natural rubber during prolonged storage was studied. The results indicated that the crosslinking density,molecular weight, gel content, P0 and Mooney viscosity all increased with the prolonged storage time, whereas the PRI significantly decreased. SEM showed that the formation of network-gel for natural rubber accompanied by the partial increasing and aggregation of rubber particles in batches.The effect of storage humidity on structure and performance of natural rubber during prolonged storage was carried out. The results showed that humidity had an effect on the crosslinking density, molecular weight, total number of crosslink-point, gel content, P0 and Mooney viscosity. And the influence order was 80% < 65% < 59% < 35%. Low humidity attributed to the storage hardening.The analysis of intermolecular crosslinking network structure of natural rubber during prolonged storage were studied. The results demonstrated that the presence of aldehyde groups or epoxy groups, proteins and lipids contributed to the molecular cross-linking during the accelerated storage, while the lipids of rubber was responsible for the formation of crosslink:ing during storage. And the results showed that the total degree of crosslinking decreases after accelerated storage by treating with alkaline protease. While the crosslinking density, total number of crosslink-point,gel content,molecular weight and P0 increased with the prolonging of the storage time. The crosslinking density, total number of crosslink-point,gel content,molecular weight and P0 increased slightly during accelerated storage from 0-12 h and showed little change after storage for 12 h by treating with lipase.