I. Natural rubber
Water absorption: The water absorption of natural rubber varies with the coagulation concentration of latex, the type of preservative and coagulant, washing pressure and drying conditions in the rubber making process, so there are obvious differences in the water absorption of different product types.
II. Styrene butadiene rubber
Water absorption: similar to natural rubber.
III. Butadiene rubber
Low water absorption: The water absorption of butadiene rubber is lower than that of styrene butadiene rubber and natural rubber, which can make butadiene rubber used for insulating electric wire and other rubber products that need water resistance.
IV. Butyl rubber
Butyl rubber has very low water permeability, excellent water resistance in general temperature, and the water absorption rate at room temperature is 10-15 times lower than other rubbers. This excellent performance of butyl rubber is an important contribution to electrical insulation. Butyl rubber reinforced with carbon black and vulcanized with resin can obtain low water absorption performance under high temperature and long-term exposure conditions. In order to enable butyl rubber to be exposed to water or high temperature for a long time, the following considerations should be made in principle:
1, the filler should be non-hydrophilic and meta-electrolytic.
2, the water-soluble substances of the vulcanization system should be as little as possible
3、 The selected reinforcing filler and vulcanization conditions should make the vulcanized rubber have high elastic modulus and other physical properties.
V. Ethylene propylene rubber
Hot water and water vapor resistance. Ethylene propylene rubber has better steam resistance, even better than its heat resistance. Its high-pressure steam resistance is better than butyl rubber and general rubber. Ethylene propylene rubber also has better resistance to hot water, but is closely related to the vulcanization system used. The use of peroxide and effective vulcanization system of ethylene propylene rubber vulcanization rubber peroxide performance is much better than the sulfur vulcanization of ethylene propylene rubber or butyl rubber, but the sulfur vulcanization of ethylene propylene rubber vulcanization rubber peroxide performance is worse than the sulfur vulcanization of butyl rubber.
VI. Neoprene rubber
Water resistance is better than other synthetic rubber, gas tightness is second only to butyl rubber.
Preparation of neoprene water-resistant rubber, should pay attention to the choice of vulcanization system and filler. Vulcanization system is best to use lead oxide system, avoid using magnesium oxide, zinc oxide system. Lead oxide dosage in 20 parts or less, there is a role in improving water resistance, but the dosage is too much but ineffective. When using lead sulfide, the best choice of filler reinforcement carbon black, carbon black in the slot method carbon black is better, the furnace method carbon black is second. Inorganic filler is best to use calcium silicate, followed by barium sulfate, clay, etc. All the hydrophilic agents should not be used. Also should not use sulfur vulcanization. Water-resistant rubber scorch performance is generally poor, should be noted when processing.
VII. Nitrile rubber
Water resistance is good: with the increase of acrylonitrile content, water resistance becomes worse.
VIII. Silicone rubber
Hydrophobicity: the surface energy of silicone rubber is lower than most organic materials, therefore, it has low moisture absorption, long-term immersion in water, its water absorption rate of only about 1%, physical and mechanical properties do not decline, mold resistance is good.
IX. Fluorine rubber
Stable performance for hot water. There is excellent resistance to high temperature steam.
Fluorine rubber on the role of hot water stability, not only depends on the nature of the raw rubber itself, but also determined by the rubber material with. For fluorine rubber, this performance depends mainly on its vulcanization system. Peroxide vulcanization system is better than amine, bisphenol AF type vulcanization system. 26 type fluoroelastomer using amine vulcanization system rubber performance is worse than the general synthetic rubber such as ethylene propylene rubber, butyl rubber. G-type fluorine rubber using peroxide vulcanization system, the cross-linked bonds of the vulcanized rubber than amine, bisphenol AF type vulcanized rubber cross-linked bonds to hydrolysis stability is better.
X. Polyurethane
One of the outstanding weaknesses of polyurethane: poor hydrolysis resistance, especially at slightly higher temperatures or the presence of acid and alkali media hydrolysis more quickly.
XI. Chlorine ether rubber
Homopolymerized chloroether rubber and nitrile rubber has similar water resistance, copolymerized chloroether rubber water resistance between nitrile rubber and acrylate rubber. Formulation has a greater impact on water resistance, containing PB3O4 rubber water resistance is better, containing MGO water resistance significantly worse, improve the degree of vulcanization can improve water resistance.
XII. Chlorosulfonated polyethylene rubber
Cross-linking chlorosulfonated polyethylene rubber with epoxy resin or more than 20 parts of lead monoxide can make the vulcanized rubber have good water resistance. The filler used in addition to calcium carbonate, ordinary filler to precipitate barium sulfate, hard clay and thermal cracking carbon black is more suitable. In addition, in order to make the vulcanized rubber obtain good water resistance, close vulcanization is very important.
For intermittent exposure in water or a short time exposure products, generally available barium oxide as vulcanizing agent, such as in the chlorosulfonated polyethylene rubber with about 5 parts of silicone oil, then cross-linked with magnesium oxide vulcanization rubber in the water swelling rate is also quite small.
XIII. Acrylate rubber
Because the ester group is easy to hydrolyze, making acrylate rubber in water swelling rate is large, BA type rubber in 100 ℃ boiling water after 72h weight gain of 15-25%, volume expansion of 17-27%, steam resistance is worse
