| Epoxy resins are considered as one of the most important thermosetting polymers and wildly used in various fields,such as adhesives,coatings,electronic packaging and composite materials etc.However,unmodified epoxy resin cured products have poor toughness and insufficient adhesive properties.Several routes have been proposed to improve toughness of epoxy resin,such as the addition of second-phase particles,the structure transformation from rigidness to flexibility by chemical modification,and the reduction of the crosslinking density of the cured epoxy resin.In this study,epoxy resin were toughened by natural renewable cardanol.The cardanol glycidyl ether with long unsaturated aliphatic side chain was used as internal toughening agent for epoxy resin,to improve the toughness and performance of epoxy resin.Cardanol glycidyl ether epoxy resin,bisphenolA-cardanol-glycidyl ether epoxy resin and cardanol glycidyl ether-polyamine adducts were prepared in this paper.The ratio of reactants,reaction temperature,reaction time and the catalyst were optimized.The structure of the synthesized products were characterized by IR.The adhesive properties(shear strength,peel strength),mechanical properties(impact strength,tensile strength,compressive strength,hardness),thermal properties(TG,DMA)and curing reaction(DSC)of the modified epoxy system were studied.The cardanol glycidyl ether epoxy resin modified epoxy E-51 blend has longer pot life,higher room temperature curing reaction degree and bonding performance and impact strength,than the unmodified epoxy E-51 system.When the content of cardanol glycidyl ether epoxy resin is 10%,the 24 hours room temperature curing degree of modified epoxy E-51 system is 81.97%,which increased by 18.20%,and the corresponding shear strength is 15.42 MPa,which increased by 164.41%.The peel strength a room temperature cure for 7 days is 1.31 N/mm,which increased by178.13%,and the corresponding impact strength is 10.36 kJ/m~2,which increasedby157.71%.The addition of cardanol glycidyl ether had a great negative effect on 80°C the compressive modulus of modified epoxy resin,and had limited effect on the 5%weight loss temperature and glass transition temperature.The compression modulus at80°C of modified epoxy resin can be significantly increased when cardanol glycidyl ether modified epoxy resin was cured at 90℃.bisphenolA-cardanol-glycidyl ether epoxy resin modified epoxy E-51 blend had higher the room temperature curing speed,the curing reaction degree and the room temperature curing adhesion performance,than the cardanol glycidyl ether modified E-51 system.When the content of bisphenolA-cardanol-glycidyl ether epoxy resin is20%,the 5 hours room temperature curing degree of modified epoxy E-51 system is63.6%,which increased by 10.40%,and the shear strength measured at room temperature and 80℃are 7.43 MPa and 14.89 MPa,increased by 79.11%and191.90%respectively.The modified system at room temperature curing or at high temperature curing,had outstanding high-temperature shear strength,peel strength and impact strength.The E-51 epoxy resin was cured using a cardanol glycidyl ether-triethylene tetraamine adduct curing agent,instead of a partial triethylene tetraamine curing agent.The cardanol glycidyl ether modified amine curing epoxy system had excellent heat curing properties.When the content of cardanol glycidyl ether epoxy resin is 10%,the shear strength at150°C、room temperature、80°C and-150°C were 9.78 MPa,25.71MPa,22.35 MPa and 17.50 MPa,respectively.The peel strength is 2.80 N/mm,the impact strength is 12.33kJ/m~2,respectively.Increased by 183.51%,59.10%,63.87%,75.71%,55.60%,and 98.91%.The modified amine curing epoxy system had higher room temperature curing Tg than above two cardanol glycidyl ether modified epxoy system. |
PDF Full Text Request