Study Of Toughening Epoxy Resin By Reactive Organic/Inorganic Hybrid Particles

With the development of technology,electronic products have become ubiquitous,which leads to an increase in the amount of epoxy resin as a common packaging material,and the requirements for the properties of epoxy thermosets increasing.Epoxy resin reacts with curing agent to form a three-dimensional network structure and the crosslinking density is increasing,resulting in poor toughness of epoxy thermosets,which cannot be suitable for the application of some high-end products.Therefore,it is necessary to toughen the epoxy resin.There are many types tougheners,each of which has its advantages and disadvantages.How to improve toughness of the epoxy resin without sacrificing other properties such as strength and thermal properties is currently a research hotspot.Organic/inorganic hybrid particles can combine the advantages of inorganic materials and organic materials.The inorganic structure can reduce the loss of the strength and modulus of the epoxy thermosets,the organic structure allows for good compatibility with the epoxy resin.The reactive organic/inorganic hybrid particles have a group that can react with the epoxy resin or the curing agent,which contributes to an improvement in the crosslinking density,and the strength of epoxy thermosets is increased to achieve the purpose of toughening and strengthening.Poly?styrene-alt-maleic anhydride?alternating copolymer is an industrial product that can be used as a curing agent,the obtained cured product has good heat resistance and excellent dielectric properties.Therefore,in this paper,poly?styrene-alt-maleic anhydride?alternating copolymer was reacted with an aminosilane coupling agent to prepare organic/inorganic hybrid particles with an acid anhydride and a carboxyl group,which were employed as a toughener for modifying epoxy resin/methyl hexahydrophthalic anhydride system.The main research contents are as follows:1.Polysiloxane/poly?styrene-alt-maleic anhydride?hybrid particles toughened epoxy resinFirst,the amidation reaction of poly?styrene-alt-maleic anhydride??SMA?and 3-aminopropyltriethoxysilane?APTES?were carried out and obtained partially ammoniated SMA;then followed by in-situ hydrolytic condensation of the silane,for inducing the self-assembly of SMA to prepare polysiloxane/poly?styrene-alt-maleic anhydride?hybrid particles?SMA-APTES?.The structure,size and morphology of the particles were characterized by infrared spectrometer,thermogravimetric analyzer,nanoparticle size analyzer,scanning electron microscope and transmission electron microscope,and the particles were added to the bisphenol A epoxy resin/methyl hexahydrophthalic anhydride system to study the curing behavior and mechanical properties,thermomechanical properties,thermal stability of the epoxy thermosets.The results showed that two kinds of spherical hybrid particles were obtained by controlling the molar ratio of SMA to APTES to be 1.5:1 and 2:1.After adding SMA-APTES particles,the tensile strength and impact strength of epoxy thermosets were significantly improved.It exhibited a simultaneous reinforcing and toughening performance.When the molar ratio of SMA to APTES was 2:1 and the loading of particles was 5 wt%,the epoxy thermosets showed the best overall performance.Compared to neat epoxy thermosets,the tensile strength,elongation at break,impact strength and fracture toughness of the above case were increased by 67.6%,159.0%,170.5%,and 230.9%,respectively.While the SMA-APTES particles themselves had relatively low glass transition temperatures?T_g?and poor thermal stability,but the T_g and thermal stability of the modified epoxy thermosets were comparable to the unmodified epoxy thermosets at this loading,which was beneficial to the fact that the reactive particles significantly improved the crosslink density of the epoxy thermosets.2.silica/poly?styrene-alt-maleic anhydride?hybrid particles toughened epoxy resinFirstly,the silica particles with amino groups on the surface were prepared by hydrolysis and condensation of tetraethyl orthosilicate and 3-aminopropylmethyldiethoxysilane under ammonia conditions;then the amidation reaction of it and poly?styrene-alt-maleic anhydride?was carried out and obtained organic/inorganic hybrid particles SiO₂-SMA.The structure,morphology and size of the particles were analyzed by infrared spectrometer,thermogravimetric analyzer,scanning electron microscopy,transmission electron microscopy,nanoparticle size analyzer,etc.Then the particles were added to the bisphenol A epoxy resin/methyl hexahydrophthalic anhydride system,the curing behavior of the system,mechanical properties,thermomechanical properties and thermal stability of the epoxy thermosets were investigated at different loadings.The results showed that the hybrid particles were spherical,the particle size distribution was narrow,the average particle size was 64.3 nm and the core-shell structure was composed of silica as the core and SMA as the shell.Compared to neat epoxy thermosets,the modified epoxy thermosets exhibited a simultaneous reinforcing and toughening performance.The thermal stability of the epoxy thermosets was improved.The modulus and T_g had no sacrifice,which was attributed to the rigid SiO₂ core structure and the reactive groups such as surface anhydride groups and carboxyl groups participated in the curing,which significantly increased the crosslinking density of the epoxy thermosets.In addition,the epoxy thermosets also had a lower water absorption rate and exhibited better water resistance.When the loading of hybrid particles was 0.5 wt%,the epoxy thermosets showed the best overall performance.The tensile strength and fracture toughness were increased by 14.1%and105.6%,respectively.The thermal stability was significantly improved.The T_g and modulus were comparable to the unmodified epoxy thermosets.