Evolution Of Network Based On General-purpose Diene Rubbers During Vulcanization And Interact With The Carbon Black Network

The elastic torque, crosslink density, gel content, swelling index, dissolution/swelling, and dynamic rheological properties during vulcanization process under different sulfur curing system of generally used diene rubbers, including natural rubber (NR), polybutadiene rubber (BR), and styrene butadiene rubber (SBR) were studied by means of Rubber Process Analyzer(RPA2000), Magnetic Resonance Cross-link Density Spectrometer(MR-CDS 3500), with the aim to discuss the evolution of crosslink network for generally used diene rubbers.First, the elastic torque, crosslink density, gel content and the dissolution / swelling were investigated under different sulfur curing system of unfilled-compounds in the vulcanization process. Combined with previous studies, the evolution law of cross-linked network structure of unfilled-generally used diene rubbers was explored. Secondly, the evolution of the sulfur cross-linking network of carbon black filled systems were explored, combined with rheological properties and the research on the changes of torque, cross-linked microstructure parameters in vulcanization process. And the relation between cross-link network and carbon black network was further researched in the vulcanization process of the carbon black filler system. And the effects of the addition of carbon black on the crosslink density and its parameters were also researched.The results showed that the evolution process of cross-linked network of general polydiene rubber in different vulcanization systems including BR, NR, SBR's Sulfur(S)/ 2,2'-Dibenzothiazoledisulfide(DM)system, SBR's S/N-t-butylbenzothiazole- 2-sulfenamide (NS) effective, semi-efficient vulcanization system, BR, NR, SBR's S/NS/Carbon(CB) system, BR's different filling volume of S/NS/CB systems were the same as the previous research work in the BR, NR, SBR's S/NS system. The local primary cross-linked structure was produced in the scorch period, which was similar with branch, and could be called local primary network. The fundamental cross-linked network structure was formed at the beginning of curing. Then the network was improved on top of the formation of fundamental cross-linked network at the beginning of hot cure which could be called improving network period, which could be divided into two stages. And the rates of change of cross-linking parameters were the same at the time when formed the fundamental cross-linked network under various systems. The change of crosslink density was about 36%, and the change of gel content was about 25%. But in different systems, the speeds of evolution were different.The results also show that the viscous torque value of compound changed abruptly in the curing process,which can characterizatie the time when fundamental cross-linked network was formatted, and it was in good agreement with other methods.In the study of network development of Carbon black filled rubber, discovered that filled rubber vulcanization torque in the induction period showed apparent increase which was different with unfilled rubber. The result of experiment without adding sulfur to rubber showed that this phenomenon was caused by a high-temperature condensation of carbon black or the increase of gel content, and this effect was enhanced as the increase of the amount of carbon black.The result of dynamic rheological properties showed that the evolution of sulfur cross-linked network and the change of carbon black network in the curing process can be analyzed according to the difference of elastic modulus (G′), the loss factor (tanδ) dependence on frequency (ω) and strain (ε) of curing compound with different degree and compound filled with different content of carbon black. The results of evolution process compared with the analysis of cross-linking parameters were consistent. The results of strain scans showed that Payne effect of vulcanizate materials filled with carbon black became clear with increasing degree of vulcanization, which indicated the cohesive effect among carbon black particles was further increased by the role of sulfur cross-linking.