High Performance Plant Oil-based Unsaturated Ester Resins:synthesis And Property Analysis

Due to the depletion of petroleum resources and the environment pollution,the use of renewable plant oil resources to synthesize unsaturated resin materials is of great significance.However,at present,plant oil-based unsaturated ester（UE）macromonomers or oligomers obtained via chemical modification generally have low carbon-carbon double bond（C=C）functionality and lack of rigid structure,resulting in the final materials with low crosslink-density and much inferior properties（such as stiffness and heat resistance）compared with petroleum-based products.In an effort to solve these problems,a series of research works based on the principle of molecular design were done:（1）New tung oil（TO）-based unsaturated co-ester（Co-UE）macromonomers bearing steric hindrance were synthesized by modifying a TO-based maleate（TOPERMA）monomer bearing anhydride structure with hydroxyethyl methacrylate（HEMA）and methallyl alcohol（MAA）,respectively.The obtained Co-UE monomers（TOPERMA-HEMA and TOPERMA-MAA）were then characterized by ¹H NMR and gel permeation chromatography（GPC）.For comparison,hydroxyethyl acrylate（HEA）-modified TOPERMA（TOPERMA-HEA）was also synthesized and characterized.Subsequently,the obtained Co-UEs were thermally cured with styrene and ultimate properties of the resulting materials were studied.The dynamic mechanical analysis（DMA）,thermogravimetric analysis（TGA）,mechanical property analysis and water absorption test showed that the C=C functionality of TOPERMA-HEMA and TOPERMA-MAAwere 1.56and 1.58,respectively,which were almost equivalent to TOPERMA-HEA（1.62）but clearly higher than unmodified TOPERMA（1.29）.The introduction of HEA,HEMA and MAA structures onto TOPERMA was beneficial to improve the stiffness,T_g,and water resistance of the TOPERMA resin.In addition,by introducing the structure of steric hindrance into the TO-based Co-UE monomer,tensile strength and Young’s modulus of the resulting materials were improved;by reducing the length of flexible chain in the Co-UE monomer,tensile strength,Young’s modulus,and glass transition temperature（T_g）of the resultant materials were also improved.The TOPERMA-MAA resin gave the best performance in these TO-based Co-UE resins,which showed the tensile strength of 32.2 MPa,Young’s modulus of 2.38 GPa,and T_g of 130.3℃.The developed eco-friendly materials show promise to be applied in structural plastics like molding compounds.（2）A novel soybean oil-based epoxy acrylate-like prepolymer（ESO-HEMAMA）was synthesized via ring-opening reaction of epoxidized soybean oil（ESO）with hydroxyethyl methacrylated maleate（HEMAMA）precursor,a synthesized unsaturated carboxylic acid having two active C=C groups and a side methyl group.The synthesis process of HEMAMA was investigated,and then the effects of feed ratio,reaction temperature,and reaction time on the synthesis process of ESO-HEMAMMA were also investigated.It was found that the optimal conditions for the synthesis of HEMAMA included a reaction time of 5 h at 90℃.The optimal conditions for the synthesis of ESO-HEMAMA included a feed molar ratio of 1.1:1（molar ratio of epoxy to carboxyl group）,reaction temperature of 110℃,and reaction time of 5 h.The optimal ESO-HEMAMA product possessed a C=C functionality up to 6.02 per triglyceride,which was much higher than an acrylate epoxidzed soybean oil（AESO）product（2.16 per triglyceride）used for comparison.The structures of HEMAMA and ESO-HEMAMA products were confirmed by FT-IR,¹H NMR,¹³C NMR,and GPC.In addition,the volatility of acrylic acid（AA）and HEMAMA was compared.The results show that the volatility of HEMAMA was much lower than that of AA,indicating that the process of synthesizing ESO-HEMAMA was more environmentally friendly.（3）A series of UV-curable resins were prepared by blending the optimal ESO-HEMAMA product with different diluents.The effects of different types of diluent on final properties of the UV-cured materials were investigated by DMA,TGA,tests of mechanic,coating,and swelling properties.The results showed that the obtained neat ESO-HEMAMA materials exhibited much superior properties than the neat AESO material.For instance,the ESO-HEMAMA material possessed a storage modulus at 25℃of 1.00 GPa,glass transition temperature（T_g）of 70.1℃,and tensile strength and modulus of 13.4 MPa and 592.1 MPa,which were 9.4,3.6,6.9,and 15.7times the values of the AESO material,respectively.Furthermore,as the increase of the C=C functionality of dilute monomer,the crosslink density,stiffness,and heat resistance of the resulting materials increased;as the introduction of steric hinderance structure into dilute monomer,the stiffness,heat resistance,and swelling properties of the obtained materials were also improved.Finally,photo-polymerization kinetics of the soybean oil-based UV-curable resins showed that the utilization of dilute monomer with higher C=C functionality or steric structure had a negative impact on the final C=C conversion of resin.In conclusion,the developed soybean oil-based EA resins are very promising to be applied in UV-curable coatings.（4）To further verify the applicability of the developed synthesis method for the new oil-based epoxidized acrylate,epoxidized rubber seed oil（ERSO）was employed to synthesize a similar epoxyidzed acrylate product,ERSO-HEMAMA.A series of new UV-curable resins were also prepared by blending ERSO-HEMAMA with different types of diluent.The resulting ERSO-HEMAMA had a C=C functionality of 4.85 per triglyceride and a biobased content of70.2%.Thermal,mechanical,and coating properties of ERSO-HEMAMA resin after UV curing were studied.The results showed that the thermal,mechanical and coating properties of pure ERSO-HEMAMA resin were greatly improved compared to the pure AESO resin.Moreover,by using the diluent with higher C=C functionality or steric hindrance,stiffness and T_g of the resulting UV-cured materials were significantly improved.The devloped rubber seed oil-based epoxidized acylate materials also showed great potential to be used in UV-curable coatings.