Study On The Vulcanization System Of Epichlorohydrin Rubber

Epichlorohydrin rubber possesses outstanding combination of properties including heat resistance, fuel and oil resistance, ozone resistance. However, vulcanized forms of epichlorohydrin rubber have disadvantages in terms of strength and generally become softer after thermal oxidative aging. In this paper, in order to improve the overall performance of epichlorohydrin rubber and expand the application fields, study on curing system (vulcanization, assistant and filler) have been made. Details are as follows:1. Effects of three kinds of vulcanization assistants (glycerol, trimethylolpropane, pentaerythritol) on the curing characteristics, crosslinking densities and mechanical properties of epichlorohydrin rubber have been evaluated. The experimental results indicated that under the same conditions during processing and curing, as the melting point of assistants decrease, the mobility of rubber got better, the vulcanization velocity improved, the crosslinking density, the tensile strength, the300%modulus and the shore "A" increased.2. Effects of three kinds of thiol vulcanizing agents (2,3-dithiolquinoxalines, trithiocyanuric acid and ethylene thiourea) on the curing characteristics, crosslinking densities, mechanical properties and thermo-oxidative aging properties of epichlorohydrin rubber have been evaluated. The experimental results indicated that structure of the curing agent on the molecular affects vulcanization reaction. Under the same conditions during processing and curing, the vulcanization velocity slowed according to TCY, DNR-12A, NA-22, the crosslinking density decreased according to DNR-12A, TCY, NA-22. When fixed carbon black as the filler, the rubber cured with ethylene thiourea possess the best mechanical properties and the worst thermo-oxidative aging properties. Because the rubber vulcanized using DNR-12A and TCY formed rigid structure which improved thermo-oxidative aging properties. While the rubber vulcanize using NA-22formed monosulfur bond which is easy to break when exposed under high temperature.3. Effects of three kinds of fillers (carbon black, lignin-montmorillonite complex and alkalescent lignin) on the curing characteristics, crosslinking densities, mechanical properties and thermo-oxidative aging properties of epichlorohydrin rubber have been evaluated. The experimental results indicated that when fixed ethylene thiourea as the vulcanizing agent, the rubber filled with alkalescent lignin possess the best mechanical properties and thermo-oxidative aging properties. The tensile strength of rubber composite is15.5MPa; the elongation at break is394%; the100%modulus is6.4MPa; after aging at100℃for72h, the retention of tensile strength is103%. Both XRD and TEM data showed that the filler particles were well dispersed in the ECO/BL-MMT composites. Adding30phr MMT to the composites, the retention of tensile strength is106%after aging at100℃for72h. BL-MMT will be a promising filler for ECO rubber composites.4. Effects of the loadings of acid acceptor (magnesium oxide), the proportion of fillers and the proportion of anti-aging agents on the mechanical properties and thermo-oxidative aging properties of epichlorohydrin rubber have been evaluated. The experimental results indicated that when the loading of MgO, white carbon black, carbon black, and nickelous N, N-dibutyldithiocarbamate were10phr,30phr,10phr and2phr respectively, the over-all properties of rubber are the best. The tensile strength of rubber composite is13.9MPa; the elongation at break is644%; the100%modulus is2.6MPa and the hardness is71. After aging at125℃for1000h, the percent retention of tensile strength was100%and the percent retention of elongation at break was26.4%.