Study On The Destruction And Formation Of Natural Rubber Crosslinking Network Structure Under High Temperature And Humidity

Due to the inherent characteristic of the molecular structure(unsaturated molecular chain structure),natural rubber is prone to molecular chain degradation or cross-linking and other molecular structure changes under the action of external environmental factors(light,oxygen,heat,etc.),resulting in performance degradation.The aging phenomenon of natural rubber is particularly prominent in the high temperature and high humidity environment of tropical islands.Therefore,it is of great significance to study the destruction and formation mechanism of natural rubber network structure under high temperature and high humidity environment,to grasp the rules of destruction and formation of the network,and to understand its molecular mechanism.This paper analyzes the changes and mechanism of the network structure of natural rubber before and after aging through a variety of test methods,formulates corresponding anti-aging strategies according to the thermal and oxygen aging mechanism,and studies the anti-aging effect of 1,3-diisopropenylbenzene on natural rubber.And the anti-aging mechanism,to study the anti-aging effect of nitroxide free radical piperidinol on natural rubber and the strengthening and toughening effect on natural rubber and the corresponding mechanism.The main contents are summarized as follows:1.High temperature and high humidity aging research(1)Research on thermal oxygen agingUnder thermal oxidative aging conditions,the changes in the cross-linked network structure,static mechanical properties and dynamic mechanical properties of natural rubber have been studied.The results show that the tensile strength and elongation at break of natural rubber continue to decrease after thermal oxidative aging.The glass transition temperature continues to rise,the crosslink density first rises and then falls,the oxygen-containing groups continue to increase,and the double bond content continues to decrease.At the same time,a polyisoprene simulation method is used to explore the aging process of natural rubber.According to the structural changes and thermal cracking products,the thermal oxidative aging mechanism of natural rubber is inferred.(2)Research on the structure change of natural rubber crosslinking network in high humidity environmentUnder high humidity aging conditions,the cross-linked network structure,static mechanical properties and dynamic mechanical properties of natural rubber have been studied.The results show that the tensile strength of natural rubber after high humidity aging has decreased,but the fracture elongation The growth rate has little change,and the glass transition temperature and cross-linking density have no obvious changes.The color of the water will change when natural rubber is extracted with water.Humidity has little effect on natural rubber.(3)Research on the change of cross linking network structure of natural rubber under high temperature and humidityUnder high temperature and high humidity aging conditions,the changes in the cross-linked network structure,static mechanical properties and dynamic mechanical properties of natural rubber have been studied.The results show that the tensile strength of natural rubber first increases and then decreases,and the elongation at break is somewhat Decrease,the glass transition temperature continues to rise,and the crosslink density continues to increase.Combining the mechanism of thermal oxygen aging and high humidity aging with the changing law of high temperature and high humidity aging,we can infer the aging mechanism of high temperature and high humidity compound conditions.2.Research on the anti-aging effect of 1,3-diisopropenylbenzene on natural rubber1,3-Diisopropenylbenzene is added to natural rubber as an anti-aging additive.After aging,the natural rubber exhibits excellent tensile strength and elongation retention at break,and the best amount of natural rubber after aging The tensile strength of the material is even higher than the original tensile strength.1,3-Diisopropenylbenzene has a good ability to react with free radicals,and can also reduce the damage of oxygen to the internal structure of rubber.The method of comparing different substances is used to reveal the excellent aging resistance of 1,3-diisopropenylbenzene.3.Research on the anti-aging effect of nitroxide radical piperidinol on natural rubber and research on strengthening and tougheningNitrox free-radical piperidinol is added as an anti-aging additive to natural rubber.With reference to the aging retention rate,the material does not have good anti-aging ability,but the nitrox free-radical piperidol can greatly improve the natural rubber material.Tensile strength and fracture toughness make the material have excellent properties,and it can also play a role in partial replacement of vulcanization aids.