The quality of magnesium oxide has a great influence on the properties of rubber chlorinated polyethylene.As the acid acceptor of halogenated polymer series, it not only affects the curing speed, but
The quality of magnesium oxide has a great influence on the properties of rubber chlorinated polyethylene.As the acid acceptor of halogenated polymer series, it not only affects the curing speed, but also has a great influence on the physical and mechanical properties of vulcanizates.
In recent years, rubber chlorinated polyethylene (hereinafter referred to as CPE) is more and more widely used in the wire and cable industry, and its dosage accounts for more than 85% of rubber CPE, which has a tendency to replace neoprene rubber (CR).Production of rubber CPE is also growing at a rate of 40%.Magnesium oxide is an important complexing agent for halogenated rubber. The high activity (iodine adsorption value) of magnesium oxide has a great influence on the coke resistance of CR, as well as the tensile strength of CR.In chlorosulfonated polyethylene rubber (CSM), magnesium oxide can be used as a crosslinker and as an acid acceptor to prevent the HCl gas from being released during CSM crosslinking and being absorbed once it appears.In the processing of rubber CPE, the role of magnesium oxide should be attached great importance.
As is known to all, CPE itself has no double bond, no point of crosslinked structure, completely by peroxide crosslinking, at high temperatures of sulfide make peroxide decomposition produces free radicals, seize the CPE long-chain molecules of hydrogen and CPE free radicals, with the help of the vulcanizing agent TAIC, for connecting the two free radical of macromolecular chain, form a network structure, so that the CPE rubber vulcanization.Therefore, it is not suitable to use acid compounding agent in the rubber formula to prevent the destruction of acid compounding agent to peroxides and affect the vulcanization of CPE rubber.In this process, due to the action of polar molecules, HCl molecules will be produced. This HCl gas not only hinders the vulcanization of the colloid, but also tends to make CPE rubber produce similar cavernous pores and its physical and mechanical properties deteriorate.The addition of active magnesium oxide effectively overcomes this problem.Therefore, magnesium oxide is a good acid absorber, sulfur accelerator, CPE thermal stabilizer.
However, not all magnesium oxide can be used for CPE, because the quality of magnesium oxide has an important impact on the properties of rubber chlorinated polyethylene.Magnesium oxide is generally divided into light magnesium oxide and heavy magnesium oxide according to its accumulation density, and can be divided into high activity magnesium oxide, medium activity magnesium oxide, low activity and relatively inert magnesium oxide according to its chemical activity.Generally speaking, light active magnesium oxide can be used as a CPE vulcanization assistant, in the selection of magnesium oxide and can not only pay attention to the content of the mistaken idea that the content of the higher the better.However, the quality of magnesium oxide should be comprehensively considered from the aspects of accumulation density, activity degree (iodine absorption value or citric acid value), content, particle size, surface modification or not, and then screened through experimental comparison.A large number of tests have proved that the comprehensive quality of magnesium oxide and CPE rubber curing speed, curing degree, as well as the rubber tensile strength, elongation at break and other physical properties have a significant relationship, generally speaking, lightweight activity of magnesium oxide, is used in most formulations.At the same time, the finer the particle size of magnesium oxide, the better its acid absorption rate, the more conducive to improve the tensile strength, promote the curing.
If the surface is modified by coating with appropriate coupling agent, the dispersion of magnesium oxide and its compatibility with rubber can be increased, and it is more suitable for adding in rubber.