Construction Of Three-dimensional Network Of Nanoparticles And Its Effect On The Properties Of Epoxy Resin

Epoxy resin?EP?is a kind of thermosetting polymer with excellent chemical and corrosion resistance,strong adhesion,good stability and low cost.However,due to the random rotation and vibration of molecular chains during phonon transfer,the thermal conductivity of epoxy resin is low as 0.19?0.21 W·m^-1K^-1.And the brittleness and low impact resistance of EP resin caused by high crosslinking network greatly limit its application.Specific modification of EP resins is required depending on the desired properties of industry application.With the increasing demand for miniaturized electronic equipment and the development of electronic equipment toward integration and functionalization,the heat dissipation of electronic equipment has become a key problem in the field of electronic packaging.Electronic devices require higher thermal conductivity of polymer-based composites as widely used packaging or support materials.In order to enhance the thermal conductivity of polymer composites,it is necessary to add functional thermal conductivity filler into polymer matrix.The brittleness,low impact resistance and electrical insulation of EP resins limit their industrial applications.It is found that the construction of three-dimensional?3D?nanofiller network in polymer composites is an effective way to achieve high conductivity.In this paper,firstly,boron nitride?BN?and silica?SiO₂?nanoparticles were used as thermal conductivity nanofillers,and polyurethane?PU?sponge was used as 3D skeleton to prepare thermal conductive epoxy composites.Secondly,EP resin was toughened by thermoplastic resin polyetherimide?PEI?,and silver nanowires?Ag NWs?were used as conductive nanofillers to improve the both electrical conductivity and thermal conductivity of epoxy matrix composites.The main results are as follows:First,EP/PU@BN thermal conductive composite was prepared by BN nanofillers?40?m&500 nm?and PU sponge as 3D conductive skeleton.The morphology,thermal conductivity and thermal mechanical properties of composites were investigated.The thermal conductivity of EP/PU@BN?40?m?composite was higher than that of EP/PU@BN?500 nm?.When the loading of BN?40?m?was 5 wt%,the thermal conductivity of EP/PU@BN composite was 0.421 W·m^-1K^-1,110%to the pure epoxy.With the introduction of BN,the storage modulus of the composite system increased with the increase of filler content,but it had little effect on the glass transition temperature.Second,EP/PU@BN&SiO₂ thermal conductive composite was prepared by BN?40?m&500 nm?&SiO₂?20 nm&140 nm?nanofillers with PU sponge as 3D conductive framework.The morphology,thermal conductivity and thermal mechanical properties were studied.By comparing the thermal conductivity of EP/PU@BN?500 nm?&SiO₂?20 nm?,EP/PU@BN?500 nm?&SiO₂?140 nm?,EP/PU@BN?40?m?&SiO₂?20 nm?,EP/PU@BN?40?m?&SiO₂?140 nm?,the highest thermal conductivity was found in EP/PU@BN?40?m?&SiO₂?140 nm?composite.When the content of BN?40?m?&SiO₂?140 nm?was 5wt%,the thermal conductivity was 0.429 W·m^-1K^-1,which was increased by 145%compared with the pure epoxy resin.With the introduction of BN and SiO₂,the storage modulus of the composite system increased with the increase of filler content,and the glass transition temperature increased by 6?8oC.Third,the morphology,phase separation kinetics,thermal conductivity and thermal mechanical properties of the epoxy/polyetherimine?EP/PEI?binary system with low content silver nanowires were studied.During the reaction induced phase separation of EP/PEI blends,the system finally formed a cocontinuous phase structure.With selective distribution of the Ag NWs in continuous EP-rich phase,a low electrical resistivity was obtained at 3 wt%content of Ag NWs in EP/PEI composite.The glass transition temperature,electrical conductivity,and thermal conductivity were all enhanced by the addition of low content of Ag NWs.The surface resistivity of the EP/PEI blend decreased from 6.5×10¹⁶?to 9.6×10⁵?with the addition of 3 wt%Ag NWs,and meanwhile thermal conductivity was improved by 38.2%.Furthermore,the process of phase separation of the EP/PEI blends was characterized by optical microscopy?OM?,time-resolved light scattering?TRLS?,differential scanning calorimetry?DSC?,and scanning electron microscopy?SEM?.Ag NWs showed a critical impact on the kinetics of reaction-induced phase separation and the formation of co-continuous network structure.