Synthesis Of Tung Oil-based Epoxy System And Their Structures And Properties

Tung oil tree belongs to Euphorbiaceae deciduous tree.It is an important woody oil tree in China.The oil content of its seeds is about 50-70%.Tung oil is rich in many kinds of unsaturated fatty acids such as ?-earonic acid,which can be used as a kind of high-quality dry vegetable oil.However,the application of tung oil is still in the primary product stage,and there are few types of high value-added products.This study first analyzed the physical and chemical properties of tung oil and the composition and content of fatty acids,and then used the active groups such as conjugated double bonds,carboxyl groups,and ester groups in the molecular structure to adopt Diels-Alder reaction,esterification reaction,saponification reaction and Epoxidation reaction,etc.to carry out chemical modification,synthesize tung oil-based epoxy resin,epoxy curing agent and epoxy resin toughening agent,and use differential scanning calorimetry(DSC),mechanical properties,thermal stability,Dynamic thermomechanical properties(DMA)and scanning electron microscopy(SEM)and other analytical methods have carried out detailed research and analysis on the relationship between its structure and performance.The specific research results are as follows:1.Extraction of tung oil seed kernel oil and analysis of fatty acid composition The three-year tung seeds cultivated in Yongshun,Hunan Province were used as experimental materials,and the physical and chemical properties,fatty acid composition and content of tung oil were determined and analyzed by Soxhlet extraction and gas chromatography.The results of physical and chemical properties show that the acid value of three-year tung oil is 0.811 ±0.11 mg/g,the iodine value is 180.24±1.97 mmol/kg,the saponification value is 189.97±2.13 mg/g,the refractive index is 1.521 ±0.001,and the color is light.Yellow;by gas chromatography analysis,it is found that in addition to the fatty acids mainly elenic acid,tung oil oil also contains 5 fatty acids such as oleic acid,linoleic acid,linolenic acid,palmitic acid and stearic acid,which are not saturated The fatty acid content is as high as 93.08%.The above data values all indicate that tung oil contains multiple unsaturated double bonds,which is active in nature and is beneficial to chemical modification.2.Study on structure and properties of tung oil based epoxy resins with different crosslinking densities.Using tung oil as raw material,through methyl esterification,Diels-Alder addition,epoxidation and other reactions to synthesize two-functionality and three-functionality epoxy resins and characterize the products,and then combine them with methyl tetrahydrophthalic anhydride(MTHPA).),methylnadic anhydride(MNA),diaminodimethyl benzene(DDM),m-phenylenediamine(MPD),m-xylylenediamine(MXDA)are cured to prepare tung oil-based rings with different crosslinking densities Oxygen resin,and explored the influence of crosslinking density vc on the performance of epoxy resin.The results show that as the crosslinking density increases,the tensile strength and elastic modulus of the tung oil-based epoxy resin also increase linearly.The linear fitting equations are?=60.79vc-36.7 and E=3075.39vc-2129.12,respectively.,The elongation at break decreases with the increase of the cross-linking density and finally tends to be stable.It does not show a linear relationship.It satisfies the boltzmann equation?=7.37+74.87/(+e(vc-1.19)/0.03);glass The chemical transition temperature Tg shows a linear increase trend with the increase of the crosslink density,and its linear equation is Tg=55.1vc-7.4;thermogravimetric analysis found that the thermal stability of the material does not have a linear relationship with the crosslink density.Mainly due to the molecular structure of the curing system.If the curing system contains a benzene ring structure,the thermal stability of the material is better than that of the curing agent without benzene ring structure.In addition,analysis found that for curing agents containing the same structure,such as curing agents containing a benzene ring structure,as the crosslinking density increases,the initial decomposition temperature also linearly increases.The linear equation is T5%=40.21vc+228.95.3.Study on high-performance tung oil-based anhydride epoxy curing agent.Using tung oil as raw material,through transesterification,esterification,diene addition and other reactions,tung butyric acid anhydride containing two carbox yl groups and one anhydride was synthesized,and the target product was chara cterized by FT-IR and 1H-NMR.DSC was used to study the curing reaction ki netics of the tarbutyric anhydride epoxy curing system.The results show that t he apparent activation energies of three epoxy curing systems of tung butyric a nhydride,tung oil anhydride and tung maric anhydride are 72.82 kJ/mol,84.33 kJ/mol,66.42 kJ/mol,respectively,and the index factor is 3.25×108 s-1,7.87×109 s-1,9.04×108 s-1,the reaction order is 0.91,0.92,0.90,the optimal curing condition of the synthetic tung oil-based acid anhydride curing agent is 120?/2 h+140?/2 h+160?/2 h;The mechanical properties show that the synthesized epoxy cured product of tonbutyric anhydride has the characteristics of high str ength,high modulus,and high flexibility:its tensile strength is 49.61 MPa,an d the elongation at break is 14.86%,The modulus of elasticity is 2364.48 M Pa,the shear strength is 16.78 MPa,and its comprehensive properties are bette r than those of commercially available tung oil-based acid anhydride curing ag ents.4.Study on the reinforcement and toughening of epoxy resin based on ?-?interaction in eleonic acid.Tung oil is hydrolyzed,acidified,and finally purified to produce oleic acid.After characterizing its molecular structure by FT-IR and 1H-NMR,the prepared oleic acid is added to the bisphenol A epoxy resin,and the ?-?interaction is proved by ultraviolet spectroscopy.The existence of,and finally curing with polyetheramine D230,the modulus and tensile strength of the cured product have been improved,and its flexibility has also been improved.When the addition amount of eleonic acid is 5 wt.%,the prepared epoxy resin has the best mechanical properties,the tensile strength is 73.98 MPa,and the elongation at break is 8.68%;DMA shows that the introduction of eletric acid can effectively improve the glass Transition temperature,when the addition amount is 5 wt.%,Tg can reach 83.4 ?,but the addition amount should not be large.If too much eleonic acid is introduced,the crosslink density of the cured product will decrease,thereby reducing the glass transition temperature;The heavy results showed that the addition of oleic acid did not improve the thermal stability of the epoxy resin;the SEM characterization results showed that the system did not phase separate,and the addition of oleic acid would make the cross section of the epoxy resin rough,which indicated that the oleic acid The addition of can improve the flexibility of epoxy resin.