Preparation And Properties Of Polyhedral Oligomeric Silsesquioxane Modified Poly-p-phenylene-benzobisoxazole Composite Fibers

Poly-p-phenylene-benzobisoxaole(PBO) fiber is widely applicable owing to its excellent properties such as heat resistance, high strength. However, there are also some shortcomings in PBO fiber because of its chemical structure. For example, there is little force interaction between PBO molecular chains, which leads to weak bonding effects between reinforcement and resin in fiber reinforced polymer composite material, and composite material with excellent properties will not be obtained without a good interface. Since PBO molecular is not chemically stable under UV for long time, the mechanical properties of PBO fiber will decrease rapidly when it’s exposed under UV. Therefore, it’s necessary to modify PBO fiber to enhance its properties for more applications.In the thesis, polyhedral oligomeric silsesquioxane(POSS) was added into polymerization and reacted with the monomers. POSS was connected with PBO molecule chain and a kind of cross-linked network structure has formed. The mechanical properties of PBO composite fiber improved obviously and the degradation of compoeite fiber was prevent on the surface.The molecular weight of PBO in the polymerization was tested b y viscometric method at first. Different spinning rates were investigated to get the optimal condition when PBO fibers were prepared, and the effects of treated temperature were researched by XRD and tensile test to study the lateral size of the crystallite and tensile strength of the PBO fibers subsequently. The best spinning rate was 78m/min and the treated tempuature was 340 oC. After that, the micro image, decomposition temperature, the lateral size of the crystallite, tensile strength and IFSS also were tested in a variety of testing methods to study the relation between the amount of POSS and the properties of PBO fiber. When the amount of POSS raised, the decomposition temperature and interfacial shear strength(IFFS) of PBO fiber also increased, while the lateral size of the crystallite decreased. The trend of tensile strength of POSS/PBO fiber was a fold line. The tensile strength of PBO fiber increased when the amount of POSS was lower than 0.2wt.%, otherwise it decreased. The maximum was 3.827 GPa which was obtained at 0.2wt.%. It’s 11.3% higher than that of PBO fiber. At last, the properties of PBO composite fibers which were treated under UV were also studied. The retention of tensile strength would improve and the rise of the IFFS would decrease while the mass of POSS increased.