The choice of polyurethane rubber vulcanizing agent | polyurethane rubber
polyurethane rubber as UR, polyurethane rubber vulcanizing agent mainly of sulfur, peroxide and diisocyanate. Usually used in the preparation of casting polyurethane rubber pre polymers containing isocyanate, add more hydroxyl content in pre polymers or multiple amine, they are both chain extender and crosslinking agent, after heated and mixed casting molding, continue to heat can cure, do not need to add other vulcanizing.
for mixed type polyurethane rubber, such as the base of isocyanate group, also don't need to join other vulcanizing agent. Such as the base for isocyanate group, will be expected to join the vulcanizing agent can only be carried out after vulcanization. Of sulfur, peroxide and diisocyanate as vulcanizing agent, now the points mentioned below:
mixing type polyurethane cyanogen different acid ester as vulcanizing agent, the income of the vulcanizates with good abrasion resistance, the advantage of high strength and hardness, but are prone to bubbles, require cold demoulding and performance were some shortcomings, and two different cyanide
acid ester volatile and toxic, and larger in the process of using all needs to tighten. When using peroxide as curing agent, the commonly used with tertiary butyl peroxide isopropyl benzene, dicumyl peroxide, 2. 5 - Dimethylhexane, etc. Using these peroxides rubber, its operation safety is extremely high, with properly, they can - in 90 - Within the range of 100 ℃ without charred dangerous operation.
when using peroxide alone, degree of cure is often not satisfactory enough. Cyanuric acid is added as in formula 3 allyl esters as crosslinking agent, can greatly improve the crosslinking degree of the rubber and the tensile modulus, and can reduce the dosage of peroxide. With peroxide vulcanized rubber, compression permanent deformation is small, low hardness, strength is moderate, does not need after curing, the disadvantage is that the tear strength and low temperature resistance. When in the molecular chain of polyurethane rubber containing unsaturated bond, can be vulcanized with sulfur. In this case, the accelerator dosage should be larger, general sulphur dosage is 1. 5 ~ 2, 6 copies of accelerator, common promoter for M and DM. Sulfur curing polyurethane rubber can be like common plastic processing, rubber storage time is longer, the comprehensive performance is good, can fill carbon black increase the hardness, but no more than 30, or performance degradation. This kind of defect is permanent deformation of the rubber is bigger.
polyurethane rubber with belong to the bolt-on analysing. Therefore, in the general case to join carbon black and have no obvious reinforcement effect. When adding carbon black filler such as more than a certain amount of scope, reduce strength quickly. In order to reduce cost, add no more than 30 cases of filler, generally will not affect performance, and for some analysing can improve tensile strength, wear resistance of the rubber and the tear strength, but lower the elasticity. Carbon black under a certain amount of casting polyurethane rubber increase tensile modulus, hardness and enhance the role of weathering. Used as filling agent of polyurethane in addition to carbon black ( Spray is commonly used in carbon black) , there are white carbon black, kaolin in other mineral filler. When using mineral filler, calls for strengthened vulcanization system. Molded urethane expansion coefficient is bigger, is easy to cause the size of the finished product is super bad, so often use zirconium silicate, calcium carbonate, aluminium powder etc packing to overcome the shortcoming of expansion coefficient is larger.
also can be used in mixing glue with plasticizer, its purpose is to improve process performance and improve the low temperature properties of the vulcanizates, reduce the hardness and tensile modulus, commonly used plasticizer such as phthalic acid dibutyl. Plasticizer dosage is too large will reduce the wear resistance of vulcanized rubber.
polyurethane rubber product recommendations: PU optimal force lugs, hardware plastic bags
the relevant article recommended:
mixing type polyether polyurethane raw rubber and mixing rubber
mixing performance differences between each batch of rubber glue reason
polyurethane material, epdm material, what is the difference between cr material?
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