Nitrile Rubber Introduction 2

by Dongrubber on November 18, 2006 · 0 comments

(2) Oil resistance and solvent resistance. In ordinary rubber, oil resistance of NBR rubber is the best: nitrile rubber oil resistant base oil, benzene and other non polar solvent, is far superior to natural rubber, styrene butadiene rubber, butyl rubber and so on nonpolar rubber, neoprene rubber is also better than that of polarity neoprene rubber. But the oil resistance of NBR polar and polar solvent ability is bad, such as the ability of the ethanol tolerance is poorer than nonpolar rubber.

(3) Resistance to aging performance. Nitrile rubber sheets without protective agent has very poor aging resistance, its weather resistance and ozone resistance are in one level with natural rubber, while slightly lower than natural rubber. Adding PVC in nitrile rubber, however, can improve the ability of its weather resistance and ozone resistance.

Nitrile rubber under the radiation will be destroyed, increase the hardness, elongation decreased. But the nitrile rubber is smaller influenced by irradiation than other synthetic rubber, combination acrylonitrile content at 33% – 38% of the nitrile rubber is with good irradiation resistance. High acrylonitrile content of NBR rubber after nuclear radiation, its tensile strength can be increased by 140%, this is due to the low content of acrylonitrile butadiene acrylonitrile rubber will happen degradation under the effect of irradiation, and high acrylonitrile containing amount of NBR under nuclear irradiation will generate crosslinking reactions.

(4) Low temperature performance. In general rubber, nitrile rubber has poor low temperature performance. Nitrile rubber sheet after appropriate coordination, can make its glass transition temperature reduce, so as to improve its performance in low temperature.

(5) Heat resistant performance. Nitrile rubber has better heat resistance than natural rubber, styrene-butadiene rubber. Choosen appropriate formula, nitrile rubber products can be in continuous use under 120 ℃; In the hot oil can apply to 15 ℃; In 191 ℃ for 70h oil bath it still has flexible resistance performance.

(6) Ozone resistance. Ozone resistance of NBR is bad, generally we add resistant to ozone agent to improve, but the products in use contacting oil is easy to take out ozone resistant agent, thereby it loses resistance to ozone. But with polyvinyl chloride material then the effect is remarkable.

(7) Water resistance. Nitrile rubber water resistance is better, and the higher acrylonitrile content, the better its resistance to water.

(8) Electrical insulation performance. Because NBR rubber sheeting has polarity, so its electrical insulating performance is bad, belonging to the semiconductor rubber, should not be used for insulation material.

(9) The permeability. Nitrile rubber air tightness is superior to natural rubber and styrene butadiene rubber, but not as good as thiokol, about same with the butyl rubber. Nitrile rubber airtight performance are improved significantly with the increase of combined acrylonitrile.

To sum up, the effect of acrylonitrile content are big on properties of NBR. Universal NBR acrylonitrile content is between 15%~50%, if the acrylonitrile content increased to more than 60%, then it gets harden, similar to leather and not again has the performance of the rubber.

Effect of acrylonitrile content on properties of NBR is as follows:

(1) Acrylonitrile content increases, oil resistance of NBR increased; The tensile strength, tensile modulus and hardness increased; Increased wear resistance; Increase the water resistance, permeability is decreased; Affinity with the polar polymer increases; Solubility increased in polar solvent.

(2) Acrylonitrile content decrease, low temperature resistance performance of nitrile rubber improved, hardness changes small along with the change of temperature; Flexibility increased; With softener, the intermiscibility of plasticizers increases; Solubility in the non-polar solvents increased.

2. Special nitrile rubber

1) Carboxyl nitrile rubber. Its basic features are as follows:

(1) Vulcanization rate higher than NBR, easily burnt.

(2) Pure rubber showed a high tensile strength after coordinate.

(3) Vulcanization heat resistance, abrasion resistance is good.

(4) Good compatibility with phenolic resin.

(5) Good viscosity. Mainly for the production of rubber hose, seal, gasket, oil seal, all kinds of model products, adhesives and so on.

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