Butyl rubber is a low-unsaturated (unsaturated 1% to 3%) synthetic rubber made by copolymerization of isobutylene and a small amount of isoprene. It is widely used in the manufacture of inner tubes, radial tire inner liners, sealing products and shock absorbing products due to its high air tightness, high damping and heat resistance. However, there are many defects in the process performance, such as slow flow rate, difficult to stick, difficult to co-vulcanize and difficult to blend with other rubber types. Chlorinated butyl rubber, as its derivative rubber, can make up for the above shortcomings, so that it will come later and replace it.
The dry method and the wet method are both based on butyl rubber.
1 Dry method In the open mill, the chlorine carrier (activated chlorine adsorbing chlorine) is added to the butyl rubber, and the added amount of the activated carbon is 4 to 5 parts. If the amount of the activated carbon is further increased, the sulfur speed can be accelerated.
2 Wet method dissolves butyl rubber in carbon tetrachloride, then introduces chlorine gas at room temperature, and the combined chlorine content is controlled at 1%.
(3) Features and benefits
1 Air tightness is the same as butyl rubber; at room temperature, the air permeability is only 1/4 of NR or 1/9 of SBR.
2 There is no problem in co-vulcanization, blending and bonding with unsaturated rubber.
3 Heat resistance: The tensile strength retention rate after 130 ° C × 18 days is still 90%.
4 Ozone resistance is equal to butyl rubber and slightly worse than EPDM.
1 There are 10 kinds of vulcanization systems, among which zinc oxide system is used more. It is characterized by good heat resistance. If the sulfur rate is not fast enough, 1 part of stearic acid can be added. The advantage of this system is that it has good heat resistance and does not return to the original.
2 The tackifying system can be made of mineral rubber, but it is not needed in the inner tube formula.
It does not pollute high-unsaturated rubber and can be processed alternately on the same rubber mixer.
More easily adhered rolls, such as sticky rolls, can be sprinkled with stearic acid on the surface or raised in temperature to solve the problem.