Surface Modification Of Carbon And Boron Nitride And Their Application Research On The Modification Of Polyhydroxyalkanoayes

Polyhydroxyalkanoates(PHA) has attracted significant attention because of its excellent biocompatibility and biodegradability. Although PHA has the potential to substitute petroleum-based plastics with its thermoplasticity and mechanical strength, there still exist some disadvantages, notably the high costs and poor mechanical properties. Boron nitride(BN) and carbon have high thermal conductivity, outstanding thermal stability and excellent mechanical performance therefore are idea fillers for PHAs. This thesis has extensively studied on the surface functionalizes of boron nitride nanosheets(BNNPs), boron nitride nanofibers(BNNFs), carbon nanotubes(MWNTs) and carbon fibers(CFs) and investigated the effect of doping the nano-materials on the properties of PHA.Firstly, the surface of fillers(BNNPs, BNNFs, MWNTs and CFs) were treated with silane coupling agent, concentrated sulfuric acid, concentrated nitric acid and polyaniline to improve their dispersibility in PHA matrix. The surface functionalizion of the fillers were clearly illustrated by the SEM images.Sequentially, the treated fillers were filled into PHA matrix to prepare PHA based composites. The results from Instron 3365 and TGA indicated that the addition of treated fillers distinctly enhanced the tensile strength, stiffness and thermal stability. For example, at the loading of 2%, the tensile strength and Young’s modulus of composites with CFs treated with acid and polyaniline achieved 200% and 150% increase, respectively, and the thermal stability of the composites were also improved accordingly. Meanwhile, the effect of BNNFs and CFs on the mechanical and thermal properties of BNNFs/PHA and CFs/PHA composites was desirable. With the addition of the stiff and stable reinforcement, the strength and stiffness as well as the thermal stability of BNNFs/PHA or CFs/PHA composites were improved.