Fabrication And Property Of Dicarboxylic Acid/diamine Cured Epoxidized Soybean Oil Thermosets

Vegetable oil is produced from oil-source plants and is a green chemical resource.Making full use of vegetable oil can reduce people’s pressure in petroleum resources,so as to cope with the threat posed by increasingly depleted oil resources.In recent years,the country has strongly supported related research work.However,due to the late start and relatively slow development in this field,there is a big gap between China and the developed countries,such as Europe and the United States.Replacing petroleum oil with vegetable oil is full of great significance for sustainable energy development in China.Therefore,it is necessary to develop study on vegetable oil-based platform compounds and macromolecule materials.China is rich in oil resources and has a wide variety of products.In particular,soybean oil production ranks among the top in the world,with cost advantages for development and in line with the country’s industrial orientation.And the unsaturated C=C double bonds in soybean oil fatty acids,it can promote the epoxidation reaction of epoxidized soybean oil（ESO）.ESO has been found that have important uses in materials science and industry.However,few studies have reported the use of dicarboxylic acids or diamines in ESO curing.In order to realize the sustainable polymer synthesis of renewable resources,research on vegetable oil-based polymer materials has attracted more and more people’s attention.In order to realize green development,the curing behavior of epoxidized soybean oil（ESO）with dicarboxylic acids and diamines was studied.The main content includes the following two aspects:（1）The dicarboxylic acids widely used in the current literature are usually derived from fossils,which reduces the sustainability of the resulting polymers.In this study,we synthesized fully sustainable polymers by curing different carbon chain-length bio-based dicarboxylic acids（DCAs）and epoxidized soybean oil（ESO）.Non-isothermal and isothermal curing process studies have shown that both the curing rate and activation energy decreased with increasing DCA chain length.The optimal-COOH/epoxy molar ratio for the ESO/DCA cured product with the highest degree of cross-linking was 0.7.The addition of 4-N,N-dimethylaminopyridine（DMAP）as a catalyst can effectively accelerate the curing rate and reduce the activation energy,and can be used to prepare the ESO/DCA curing with the fastest reaction by using no catalyst and changing amounts of catalysts.The best product was 1wt%4,4-N,N-dimethylaminopyridine（DMAP）,which can reduce the activation energy by 8—12kJ/mol.The specific value depends on the chain length of DCA.By using DMAP catalysis,the reaction time was reduced from 8 hours to 2 hours.The curing rate of the ESO/DCA polymer obtained by isothermal curing at 160°C for 3 hours can reach 90%or more.The chain length of the DCA also affects the physical properties of the ESO/DCA cured sample.As the crosslink density decreased,the glass transition temperature,tensile strength,and Young’s modulus decreased.As the DCA chain length increases,and the elongation at break increases.The feed ratio of DCA to ESO also affected the physical properties of the cured product.Due to the maximum degree of cross-linking,the samples with a molar ratio of-COOH to epoxy group of 0.7 exhibited the best physical properties,but the ESO/DCA tensile strength was only about 0.5 MPa,the elongation at break was only about 15%.The poor physical properties limited the application of ESO-DCA,and it was only use as binder in our laboratory.（2）In view of the limitations of the physical properties of ESO-DCA,the purpose of this chapter is to obtain polymer with physical properties stronger than ESO-DCA.Considering the glycerol ester aminolysis in the epoxidized soybean oil under high temperature,in this study,we acted based on the curing behavior of epoxidized soybean oil（ESO）and dicarboxylic acid（DCAs）,and 4,4-diaminodiphenyl methane is used as a curing agent instead of dicarboxylic acid.In addition,an effective catalyst was sought to accelerate the ring opening reaction.Through the exploration of various catalysts,the catalytic effect of tetra-n-butyl titanate（TT）was found optimal.The sample with the-NH₂ to epoxy molar ratio of 0.7 exhibits the best physical properties.The tensile strength of the obtained ESO-DDM polymer was about 2.15 MPa,the growth rate is approximately 5 times based on the ESO-DCA,the elongation at break was approximately 175%,and it was approximately 12 times that of the ESO-DAC.