Study On Preparation And Properties Of High-Elasticity Eucommia Ulmoides Gum

In recent decades,as the most viable alternative resource for natural rubber,Eucommia ulmoides gum(EUG)has been widely concerned by researchers with respect to its development potential and business prospects.With the modification of EUG by chemical method,a similar or even better developed performance can be achieved than that of natural rubber and synthetic materials,which has been a key issue of domestic and international research at present.This study explored the preparation method of highly elastic EUG.Addition and modification for alkene in double bonds of EUG backbone were carried out by Alder-ene reaction with 1,2,4-triazoline-3,5-diones(TAD)to destroy the crystallinity of EUG itself.Thus,a modified EUG with high elasticity was synthesized at room temperature.Meanwhile,related research was also performed on its physical and mechanical properties.The contents and results of the present study were described in details as follows:The second chapter expounded the synthesis of three modifiers firstly.Three kinds of different TAD were synthesized according to the approach provided in previous literature.Secondly,the further description was performed focusing on the preparation process of modified EUG and modified degradative EUG.As for the Alder-ene reaction of EUG,the addition and modification on double bonds in EUG backbone was carried out through the classical Alder-ene reaction by TAD.The molecular weight of products was evaluated by GPC test.Alder-ene reaction of EUG with different molecular weights was conducted with different modifiers.The structures of obtained products were tested by NMR,IR,GPC,and UV-vis,respectively.NMR,UV-vis,and IR spectra showed that products different from EUG were obtained after Alder-ene reaction.GPC data showed that the hydrogen bonds between the pendant group of urazole,introduced by the modifier,led to the molecular weight of the product far less than the theoretical molecular weight.The results of test indirectly confirmed that the modification degree of EUG was strengthened with the increase of modifier.Finally,the research results were analyzed and discussed from the thermal properties,crystallinity properties,and mechanical properties of these products.The properties of obtained products were studied by TGA,DSC,WAXD,and tensile tests.Data related to TGA showed that the molecular weight of EUG was positively correlated with its thermal stability.DSC data indicated that there was an increased trend in the glass-transition temperature of modified EUG obtained from Alder-ene reaction of monofunctional modifier with EUG.The glass-transition temperature of modified EUG increased with the elevation of the amount of monofunctional modifier.The crystallinity of modified EUG was analyzed by DSC and WAXD.The sequence of carbon-carbon double bonds on EUG backbone was destroyed by the modifier,accompanied by reduced crystallinity,showing similar properties of this type of EUG to the natural rubber.The mechanical properties of modified EUG were obtained through tensile tests.The experimental results showed that with the increase of modifier loading,the elongation at break of the product increased first and then decreased,while its tensile strength continued to decrease.The tensile data of modified EUG and modified degradative EUG revealed that the degradative EUG had poor mechanical properties than EUG,which in turn suggested an intimate connection between mechanical properties and molecular weight.To sum up,the above investigation proved that Alder-ene reaction could change the physical and chemical properties of EUG by changing the backbone structure of EUG,and finally resulting in the acquisition of high elastic EUG that could replace the natural rubber.As indicated in the previous chapter,the trans carbon-carbon double bonds of EUG was not stable,besides,the microstructure of EUG changed and the mechanical properties of modified degradative EUG decreased significantly with time.Therefore,in the third chapter,it was expected to get rubber material with better performance by increasing the molecular weight of EUG.Firstly,according to the Alder-ene reaction,it was proposed to conduct chain extension reaction of EUG with difunctional modifier(bisTAD)first.Molecular weight of chain-extended EUG increased,which was tested by GPC.The properties of chain-extended EUG were then discussed from three aspects of thermal properties,crystallinity properties,and mechanical properties.The conclusion was that with the increase of modifier,the glass-transition temperature of chain-extended EUG was lower than EUG,and mechanical properties were improved,while crystallinity decreased.In addition,the chain-extended EUG was further modified to obtain the modified chain-extended EUG using monofunctional modifier.The rubber with higher elongation at break was obtained by exploring properties of modified chainextended EUG.Then,the modifier introduced hydrogen bonds into the EUG backbone.The interaction of hydrogen bonds in both modified EUG and methanol had more obvious effect on the mechanical properties.Therefore,further exploration emphasized the influence of residual solvent content on the mechanical properties of modified chain-extended EUG.The study indicated that the amount of residual solvents was positively correlated with the elongation at break,whereas a negative correlation was observed with the tensile strength.Finally,different rubbers were modified by monofunctional modifiers,which indicated that Alder-ene reaction could improve the mechanical properties of rubber containing unsaturated double bonds.