Thermally Reversible Cross-linking Of Carbon-carbon Double Bond Unsaturated Rubber

At present,the waste rubber is converted into recycled rubber by desulfurization and pulverization,and used the obtained sample for secondary use.This process has high energy consumption and risks of environmental pollution.The preparation of thermally reversible crosslinked rubber is expected to make the traditional crosslinked rubber into a thermoplastic elastomer,simplifying the processing process and recycling process of rubber product.So far,for unsaturated rubber,it has rarely been reported that thermal reversible crosslinking of rubber is based on classical mixing and hot press forming processes.Our research group has studied the in situ esterification cross-linking of unsaturated rubber with dicyclopentadiene dicarboxylic acid to achieve thermal reversible crosslinking of unsaturated rubber.The problem is that the crosslinking reaction activity is low and the glue sample performance is poor.In order to reveal the influencing factors of esterification cross-linking of unsaturated rubber,this paper mainly studies the esterification cross-linking behavior of unsaturated rubber which has different double bond structure with dicyclopentadiene dicarboxylic acid.On this basis,selecting the rubber with high reactivity,exploring the appropriate conditions and formulation system for the esterification reaction.The main research work includes:1.In order to explore the esterification activity,selecting five kinds of rubbers such as butadiene rubber(PB),styrene butadiene rubber(SBR)with trans structure,EPDM and natural rubber with high cis-structure(NR),high cis-structured eucommia gum(EUG)are reacted with DCPDCA.By Fourier infrared test(FTIR),swelling test and vulcanization curve test showed that unsaturated rubber with cis structure has high reactivity,double bond of the trans structure and the double bond with a methyl substituent have low esterification reactivity.2.Comparing clay-supported p-toluenesulfonic acid,phosphonium salt and titanium silica molecular sieves,the clay-supported p-toluenesulfonic acid was more suitable as a catalyst for esterification reaction by infrared characterization,swelling test and vulcanization curve test.3.Taking butadiene rubber as the research object,exploring the suitable temperature and time for PB and DCPDCA esterification reaction.Through the vulcanization curve and swelling degree test,it was found that the suitable temperature for rubber esterification reaction is 175℃.Comprehensive reversible rubber esterification cross-linking effect,high temperature de-crosslinking and double bond side reaction and determined the suitable hot pressing cross-linking time is 60min.4.The effect of the dispersion morphology of the cross-linking agent on the esterification reaction activity was investigated.The cross-linking agent was promoted by adding the interface agent PEG2000,using high-shear strengthening to mix the cross-linking masterbatch and using fine-grained cross-linking agent.By some test methods such as infrared spectrum,swelling degree test and tensile strength test of cross-linked samples,comparing the cross-linking effects of different processes.The results show that PEG2000 as an interface agent does not promote cross-linking effect on esterification when the cross-linking agent is not refined;by high-speed pulverization,the particle size is reduced by 1 μm by an order of magnitude.Before refinement,the swelling degree of DCPDCA cross-linked butadiene rubber is 14.After refining,the swelling degree of cross-linked butadiene rubber is 8,indicating that the refinement of cross-linking agent contributes to the improvement of esterification activity.The cross-linking agent masterbatch prepared by the substrate cross-links butadiene rubber,the obtained product has a swelling degree of 7,and the carbon black reinforces glue sample swelling degree to 3.5.The esterification cross-linking of PB/EPDM composite rubber was studied.The swelling degree of sample before repeated hot pressing was 7,and the swelling degree of sample after repeating hot pressing was 9,indicating glue sample has reproducibility.In this study,thermally reversible cross-linked rubber based on butadiene rubber has reworkability and can be reused.By adjusting the formulation and improving the process,it is possible to obtain a suitable catalyst and masterbatch matrix.The use of DCPDCA cross-linking agent particle refinement method is beneficial to the improvement of reversible rubber performance.