| This paper introduces the development of a micro-crosslinked selfhealing tire sealant.The sealant is based on a blend of medium molecular weight polyisobutylene(MPIB)and butyl rubber(ⅡR),liquid poly isobutylene(PIB2300)and tackifying resin as a softening agent,mercaptan as a crosslinking density regulator,and sulfur as a vulcanizing agent.The sealant neither embrittles at low temperatures nor does it flow at high temperatures.The slope flow experiment verifies that the sealant has the resistance to flow at high temperature after being micro-crosslinked by heat treatment.The hot pressing experiment shows that the anti-liquidity and the body strength of the sample prepared according to a formula with more average performance in this paper are better than the commercial products in the comparison test at 80℃ or higher.In this paper,experiments based on the perspectives of preparation process,formula and characterization methods to study the influence of the types and amounts of various components in the sealant on the properties of the rubber.The research results are as follows:(1)Low-temperature and high-temperature methods were used to prepare rubber compounds in this paper.The reference formula was as follows:70 parts of butyl rubber,30 parts of PIB8950,120 parts of PIB2300,15 parts of carbon black,15 parts of CaCO3,3.75 parts of zinc oxide,2.5 parts of stearic acid,1.25 parts of accelerator TMTD,1.25 parts of accelerator DTDM,1.25 parts of sulfur,2 parts of antioxidant1010,4.5 parts of 1-dodecanethiol.Experiments showed that the preparation process of low-temperature blending and multi-step addition of low-molecular-weight polyisobutylene took less time,and was less likely to remain and easier to discharge.(2)A device to characterize the self-blocking performance of the sealant was innovatively produced in this paper.This device is composed of three parts:flange,valve,pressure gauge and air inlet.The sample preparation method is to cover 2mm thick sealant on a 2mm thick vulcanized natural rubber sheet.During the test,the sample is clamped in the flange,inflated from the air inlet,and precompressed.After the pre-pressure is over,let go of the gas,and use a needle to pierce the sample through the same position three times,submerge the flange holding the sample in the water,inflate it,and then read the air pressure when the gas leaks.(3)Adding 1-dodecanethiol to the sealant could consume the carboncarbon double bonds in the system through the Thiol-ene click reaction,so that the degree of crosslinking could be reduced more uniformly without reducing the amount of sulfur,and the initial adhesion and holding power of the sealant could be increased.When the added amount of 1-dodecanethiol was 4.5 parts,the holding power of the sealant was the maximum value obtained in the experiment,and the holding power of the 40mm sample was above 20min,which was far better than the sample without 1-dodecanethiol modification.At this situation,the self-blocking performance of the sealant was relatively ideal.The samples were prepared by applying 2 mm thick sealant on a 2 mm thick vulcanized rubber sheet.After the sample was pierced by the syringe at the same position 3 times,it could still withstand a pressure above 2.5 Bar without leakage.With the ratio of PIB8950 and butyl rubber Increased from 1:9 to 1:1,the shear storage modulus and complex viscosity of the sealant decreased.When the ratio of PIB8950 to butyl rubber was 3:7,the holding power of the sealant was the maximum value obtained in the experiment,and the holding power of the 40mm sample was more than 20 min,and through the method designed in this paper,we can see that the self-blocking performance test result can reach more than 2.5 Bar.The selfhealing performance,holding power and high-temperature anti-liquidity of the sample prepared with the reference formula described above were better than a kind of commercial product. |
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