Synergistic Effect Of Graphene/Boron Nitride 3D Structure For Thermal Conductive Properties Of Polyamide Composite

Graphene and boron nitride nanosheets are promising to be used as thermal conductive filler in composites due to their unique two-dimensional structure.So far,people do a lot of efforts to enhance the thermal conductivity of polymer composites by combining layered materials in polymer matrix.But the thermal conductivity of composites is far from the desired targets.It is because that the layered materials are hard to be dispersed in polymer matrix and the nanosheets will be wrapped in polymer chains.Making layered materials into a 3D framework is an effective way to build a continuous thermal conductive path.Here,we make graphene oxide?GO?and boron nitride nanosheets?BNNSs?into a hybrid framework.The framework is combined in PA6 matrix by“grafting to”strategy.The thermal conductivity of obtained composite is enhanced with low filler content.The main results were as follows:?1?The foams and reduced graphene foams were prepared by using GO as original material,which underwent hydro-thermal self-assembly and freeze drying.And two PA6 composites were obtained by in-situ polymerization of PA6 chains in rGO foams and GO foams respectively.Thermal conductivity of PGF composite was improved to 0.48 W·m^-1·K^-1 with 6.8wt%rGO loading.Thermal conductivity of PGOF composite was improved to 0.57 W·m^-1·K^-1 with 2.0wt%GO loading.The GO foam have higher advantages than rGO foam due to the fact that the surface oxygen groups on GO could covalently connect to PA6 chains.?2?The 3D BN/Graphene framework was self-assembled by embedding BNNSs into 3D graphene framework.And the PA6 composites were obtained by in-situ polymerization of PA6 chains in the pores of the 3D framework.The thermal conductivity of PA6 composites with 3D framework?1.6 wt%BNNSs/6.8 wt%graphene?was improved to 0.891 W·m^-1·K^-1.This value indicated that additional introduction of 1.6 wt%BNNSs could increase the TC up to 87.6%and 350%compared with the composites containing 6.8 wt%3D GF(0.475 W·m^-1·K^-1)and neat PA6(0.196 W·m^-1·K^-1),respectively.The high efficiency of BNNSs on the TC enhancement could be attributed to the factors,including the unobstructed 3D thermal conductive paths constructed by BNNSs,favorable PA6 grafting on the 3D BGF,and the morphology-promoted synergistic effect between BNNSs and graphene nanosheets.?3?BN nanosheets were first amino-functionalized.The amino-BN and GO were made into a hybrid aerogel with the crosslinking of glutaraldehyde and resorcinol.The obtained aerogel was compound with PA6.The thermal conductivity of PBGA composite is 0.856 W·m^-1·K^-1 with 0.75 wt%amino-BN loading.This result indicates that the interaction between graphene and BN is in favor of the thermal conductivity.