Percolation Phenomenon And Critical Behaviour Of The Crosslink Networks Evolution Process Of Rubber Vulcanization

Rubber vulcanization,due to their direct relation to the development of rubber network during its curing and the final effect on the performance of products, has always been the focus. At the same time, the model which based on the percolation theory is an effective theoretical model to deal with disordered systems that has been applied in many areas. In our study, we associate the percolation theory with the vulcanization process of cross-linked network, comprehensively analyze the crosslink density and torque of NR, BR and SBR under variable accelerant, and curing systems through Rubber Process Analyzer(RPA2000), Magnetic Resonance Cross-link Density Spectrometer (NMR-CDS 3500), MSC. Marc Software, and other conventional test methods.The analysis results show that the mutation phenomenon which is percolation translation in fact really existe in the cross-linked network. It is similar to classical percolation theory, while has its own characteristics.Critical translation time was obtained by the dissolved/swelling and tangent methods, they reach the same value. The critical transition time obtained by cross-linking density is generally slightly less than the critical transition time obtained by the dissolution/swelling method or torque curves. The percolation threshold related to many factors, including the types of rubber (rubber structure), curing conditions and curing systems.The percolation thresholds and critical exponents are obtained respectively by analyzing the vulcanization curves and the crosslink density curves of the NR, BR and SBR with the aid of percolation theory. The results show that, the critical exponents achieved in the same vulcanization periods by the same method are in agreement with each other, the value is one, which is in good agreement with the exponents derived by De Genns with Ginsbury and Potts models. Hence, the evolutions of their crosslink networks in vulcanization process obey the same scale law. The critical exponents are not so regular before the percolation translation, there is big gap before and after percolation translation.The addition of carbon black impact the development of cross-linked network. Carbon black network and rubber cross-linked network interact with each other. The vulcanization network is no longer follow the same scaling law, the critical index is greater than one, higher carbon black content get the smaller critical exponents.MSC.Marc Software Simulation of cross-linked network strain under the same stress proved that the SBR network percolation threshold is about 0.3.The amount of sulfur can directly affect the cross-linked density further affect the mechanical properties of vulcanized rubber when the sulfur during 0.3-2.0 phr, the sulfur is a bridge linking the macro-performance and microstructure of the rubber. It is linear relationship of NR, BR, SBR in a certain range of concentration of sulfur between vulcanization torque and crosslink density statistically.