Preparation And Performance Improvement Of Thermoplastic Polyurethane Filled With Phosphorus Modified BN Nanosheets

Recently,the electron device possess the characteristics of miniaturization,high power and high frequency,which make the device release a lot of heat.Which will affect the performance or reduce the life of device.To ensure the device can work steadily,it is necessary to develop high thermal conductivity composites to dissipated the heat.Here,We developed a kind of thermal conductivity composite,thermoplastic polyurethane?TPU?prepared by prepolymerization chain expansion,was blended with surface-modified boron nitride nanosheets?P-BNNSs?to fabricate P-BNNSs/TPU composites.The results showed that the thermal conductivity of the P-BNNSs/TPU composite exhibited an enhancement in thermal conductivity at P-BNNSs content of 1 wt.%-7.5 wt.%,the thermal conductivity of the composite up to 0.398 W/mK,the mechanical properties improved significantly.The research mainly includes the following two aspects:?1?Surface modification of BNNSsBoron nitride?BN?has a stable structure,it is not easy to form chemical bonds and has poor affinityin with polymer matrices.To improve the affinity and dispersion between BNNSs wiht thermoplastic polyurethane matrix.In this paper,the surface modification of BNNSs by phosphorus is carried out,P-BNNSs is perpared by POCl₃ as bridging agent to P grafted on BNNSs by covalent modification.Fourier transform infrared spectromete?FTIR?test showed that the P-BNNSs sample apperaed new characteristic peaks,such as P=O?B-O-P;Nuclear magnetic resonance?NMR?test showed that the-CH₂CH₂-?-OH groups in hydrogen sample,respectively from Et₃N and EG,the P element in phosphorus sample;X-ray photoelectron spectroscopy?XPS?test showed that the B?N?O?P elements in all samples,while P_2pp of P-BNNSs can be deconvoluted into P=O and P-O bonds.In a word,the P element grafted on BNNSs,the surface modification of BNNSs by POCl_3.?2?Preparation of the composite materialsThe P-BNNSs/TPU composites were synthesized by using polycaprolactone?PCL?as soft materia,4,4-diphenylmethane diisocyanate?MDI?as hard material,1,4-butanediol?BDO?as chain extender,P-BNNSs as thermal conductive filler.Dynamic thermal mechanical analysis?DMA?test showed that the storage modulus and loss modulus of the composites has been improved with the amination boron nitride nanosheets addition.At the temperature of-70?,the material is in glass state,1 wt.%P-BNNSs/TPU composites?T2?storage modulus increased by 1.7 GPa,loss modulus increased by 0.02 GPa.At the temperature of 40?,the material is in rubber state,P-BNNSs/TPU composites storage modulus increased by 0.12 GPa,loss modulus increased by 0.011 GPa.The thermal conductivity test showed that the P-BNNSs can improve the thermal conductivity of P-BNNSs/TPU composite,when the P-BNNSs concentration was 7.5 wt.%,the thermal conductivity is increased form 0.19 W/mK to 0.398 W/mK.The mechanical test showed that P-BNNSs can improve the mechanical properties of P-BNNSs/TPU composite,when the P-BNNSs concentration was 3 wt.%,the tensile strength is increased form 3.3 MPa to6.3 MPa.