Study On Thermal Oxidative Aging Mechanism Of Rubber And Silicon Rubber Modified Thermal Oxidative Aging Performance Of EPDM

Rubber as a polymer, the aging of rubber products has been the focus of the rubber enterprises. Rubber aging performance in appearance is soft-sticky or hard-brittle, mechanical performance is gradually decreased under aging process, therefore fully understanding the mechanism of rubber aging can effectively inhibit the aging of rubber product, to avoid unnecessary casualties and economic losses. Using environment of rubber products is very complex, therefore many factors can cause rubber aging, such as heat, light, oxygen, ozone, metal ions and so on. Thermal oxygen aging is one of the main ways of rubber aging which has also been the focus of many scholars'research and exploration. This paper selects the general synthetic rubber-styrene butadiene rubber (SBR) as the research object of thermal oxygen aging. Colloid containing antioxidants is prepared by liquid phase mixing. Testing Mooney viscosity, yellow index and infrared spectrum of samples with different aging time can explore the SBR aging mechanism and antioxidant mechanism. Using condensed phase reaction kinetics and temperature function predicts SBR rubber storage life under different ambient temperature and cofactor between primary and auxiliary antioxidants, and comparing the storage life with Mooney viscosity rules verifies the feasibility of thermal analysis method.First preparing antioxidant emulsions, the milk and SBR latex mixing by liquid phase, and colloid containing antioxidants prepared by flocculation process. Mooney viscosity results show that the aging behaviors of SBR is mainly first degradation after crosslinking, the addition of antioxidants can slow down the process of rubber thermal oxidative aging, which the best antioxidant effect is primary and auxiliary antioxidant compounds, followed by a single primary antioxidant and a single auxiliary antioxidant. Mooney viscosity results combined with the infrared spectrum of blank sample shows that the SBR thermal oxygen aging mainly concentrated in the butadiene chain segment and will produce a lot of aldehyde and ketone ester structure in the reaction process, belonging to the autocatalytic free radical reactions. Yellow index shows that antioxidant added can delay the ageing process, but phenolic antioxidants can form of quinone structure, the yellow index of colloid increasing.The differential thermal analysis (DTA) can determine oxidation onset temperature (Ti) of colloid in the air atmosphere under different heating rates, using condensed phase reaction kinetics in combination with Arrhenius temperature function or experience function of temperature to predict storage life of 100 and 25 Celsius temperature of colloid containing different antioxidants. The results are consistent with the Mooney viscosity law, verifying the feasibility of the thermal analysis method. Further using SBR storage life under different ambient temperature calculates cofactors (IS) between primary and auxiliary antioxidant, and shows the antioxidant synergy factor increase with the decrease of ambient temperature. Thermal gravimetric (TG) show the temperatures of weightlessness five percent have no difference among colloid containing different antioxidants, verifying the aging behavior of cross-linking of SBR.The high temperature resistant conveyor cover glue matrix material is EPDM, which can be used for a long time under the high temperature of 150 Celsius temperature, but because our country is the largest producer of cement, iron and steel, clinker temperature for a long time keep 200 to 400 Celsius temperature, part material instantaneous temperature can be obtained more than 600 Celsius temperature, thus the preparation of more high level resistance to high temperature cover gum is particularly important. Domestic silicon rubber synthetic technology has a big breakthrough in 2005, breaking the monopoly of international prices of silicon rubber, silicone rubber prices fell sharply, but the melt strength of silicone rubber itself is too low, unable to achieve the requirements of engineering structure, while EPDM/MVQ can effectively blend, the blend will having good mechanical properties and resistance to high temperature level more high. The viscosity of MVQ is too low to blend with EPDM and their solubility parameter difference >0.5, which belongs to the thermodynamically incompatible system, those are difficult problems for EPDM/MVQ blending. In this paper, we first explore the effect of MVQ on the performance of the product before and after aging in the formula of high temperature resistant covering rubber. Optimizing mixing process of the blend and investigating the effect of different silane coupling agents successfully prepare EPDM/MVQ blending, which has excellent performance.