Investigation On Plastic-Base Elastomer Material For High Temperature Applications

Based on the polymer entropy elasticity theory and from the two major factors molecular weight and flexibility which are influencing the rubber elastic performance, this paper explored the plastic-base elastomer for high temperature applications. The proposed plastic-base elastomer mainly refers to the materials which are after crosslinking modification of the base materials which are of high glass transition temperature or are the crystal materials.Firstly, in order to obtain the crosslinking network with ultrahigh molecular weight, the ultra-high molecular weight polyethylene (UHMWPE) fiber was crosslinked by means of high energy electron beam irradiation. The results showed that the largest gel content was up to77%under irradiation dose of1000kGy. Rheological properties results of collosol showed that chain scission effect existed in the process of irradiation and it was more obvious under the larger irradiation dose. The samples after irradiation showed high dimensional stability under high temperature. The break elongation of materials at high temperature increased due to crosslinking, but because of the shortage of gel content or serious chain scission effect, the enhancement of the strength is not obvious.Secondly, the relationship among the test temperature, mechanics performance and glass transition temperature of the material was studied by measuring the tensile properties of two common elastomers styrene-butadiene rubber and nitrile rubber at different temperature. Results showed that for the same rubber material, when the difference value between the test temperature and the glass transition temperature of the elastomer rising, the strength and modulus value of the vulcanized rubber reduced. That meant high glass transition temperature could help to achieve the high temperature resistant performance.On the basis of the above, this thesis made the crosslinking modification of the crystal material high density polyethylene (HDPE). Results showed that HDPE could be crosslinking modified by the curing agent. Under the condition of high temperature, the crosslinking modified HDPE showed a dramatic rise in the elongation at break. But because of the low crosslinking degree, stress value of modified HDPE was too low to measure at high temperature. In order to guarantee high crosslinking degree, the tensile performance of four type of epoxy resin curing product with different degree of curing were tested above the glass transition temperature. The results showed that with the increasing of glass transition temperature, sample strength increased significantly. While high curing degree would affect the elongation at break seriously. In order to achieve the higher crosslinking degree and the control of the molecular weight between the crosslinking points, styrene and maleic anhydride alternate copolymer (A-SMA) and styrene and maleic anhydride random copolymer (R-SMA) with about10%maleic anhydride were synthesized. A-SME and R-SME were got by crosslinking modification of A-SMA and R-SMA through esterification. Infrared spectrum analysis proved the crosslinking reaction. Crosslinking modified products in tetrahydrofuran solvents just swelled. The glass transition temperature and thermal performance of A-SME and R-SME were influenced by the crosslinking modification through esterification.Through the above research, the influence factors of high temperature resistant performance of elastomer were further clarified and provided the theoretical basis and experimental evidence for the successful preparation of the elastomer for high temperature applications.