Application Of Anti-reversion Agent In Natural Rubber

Natural rubber is widely used in various industries due to its high elasticity and high module.Reversion is however one of the strictest problems that cause serious damage to physical-mechanical properties and service life for thick natural rubber products.In this paper,there are two ways to improve the anti-reversion properties of natural rubber.On the one hand,three sulfur-containing anti-reversion agent O,O-dibutyldithiophosphate disulfide(TBuPD),1,6-bis(dibutyl dithiophosphorol)hexane(DBPH),1,6-bis(dibenzyl dithiocarbamoyl)hexane(DBTH)are synthesized.On the other hand,a set of compensatory anti-reversion agents containing carbon-carbon double bonds are synthesized.Effect of two sets of anti-reversion agent on the cure properties and physical-mechanical properties of carbon black filled natural rubber are measured.Combined with crosslink distribution,the reactivity and mechanism of the anti-reversion agent are analyzed.The results show that the mechanism of DBTH and DBPH is different.The mechnism of former is to form more mono-sulphur,while that of the later is to transfer poly-sulphur to more mono-sulphur.The reversion percentage of vulcanizates within DBTH and DBPH reduce from8.2% to less than 1% after cured at 150°C for 60 minutes,DBTH can also significantly maintain the physical-mechanical properties,and the temperature rise of vulcanizates with DBTH is about 62% of contrast.The reactivity and mechanism of the compensatory anti-reversion agent are affected by the electron cloud density on the carbon-carbon double bond.N.N-m-phenylene dimaleimide(BMB)with high reactivity take part in crosslinking through free radical reaction during vulcanization.The carbon-carbon double bond of 1,3-bis(maleimide)benzene(BCDB)shows weak activity and only exerts an anti-reversion effect during overcuring.So BCDB has the best anti-reversion performance and maintain optimum tensile strength and tensile stress of vulcanizates during overcuring.Besides,1,6-bis(maleimide)hexane(BCH)and 1,3-bis(maleimide)isobutane(BIB),whose molecular structure are more flexible,show higher elongation at break,as well as better performance in temperature rise and fatigue resistance of the vulcanizates.