Study On The Preparation And Performance Of Inorganic Nano-composites Of PP/PBS

Isotactic polypropylene (iPP), as one of the commodity plastics, has been used in manyareas such as packaging, households, and automotives, for its low price, excellentperformance, good electrical insulation and chemical stability, and ease of processing. IPP isa kind of typical biological aliphatic polyester for its degradability, and has a high growthrate. Poly(butylene succinate)(PBS) is one of the most promising materials for theproduction of high-performance, environment-friendly and biodegradable. It has particularlyattracted more commercial interests because of its significant properties, including meltprocessability, thermal and chemical resistance, and biodegradability. However, its softnessand low gas-barrier properties have restricted further applications of PBS. Therefore, addingother polymers, fillers, and the compatibilizing agent can improve the material properties.Up to now, the research and application of nanocomposites have attracted enormous interestsin academia and industry.(1) Polypropylene-graft-maleic anhydride (PP-g-MAH) is used as interfacecompatibilizing agent, and the surface of calcium sulphate whisker is treated with silanecoupling agent to reinforce and toughen polypropylene. The effects of compatibilizerPP-g-MAH and rare earth β-phase nucleating agent have been studied systematically toknow the influence of crystallization, melting behavior and mechanical properties onpolypropylene/calcium sulfate whisker composites. It is found that the calcium sulfatewhisker has a heterogeneous nucleation effect on the polymer matrix and induced theformation of β-crystal, thus increases the peak crystallization temperature and the overallrate of crystallization of PP. PP-g-MAH content improves the interfacial compatibility andtensile strength, which also enhance the nucleation activity of the whisker in the PP matrix,and suppress the formation of β-iPP. The results shows that rare earth β-phase nucleatingagent resulted in dominant β-PP and improved the strength effectively. The analysis of the crystallization process shows that the Mo model can describe the kinetics data ofnonisothermal crystallization successfully. To achieve the identical degree of crystallinity,the composites need a lower cooling rate than pure PP. The results shows that the crystallinestructure and melting behavior of the composites depend on their component and coolingrate. Lower cooling rate is favorable for the formation of β-crystals.(2) Crystallization behavior of isotactic polypropylene (iPP)/magnesium salt whisker(MSW) composites modified by compatibilizer PP-g-MAH is studied under both isothermaland nonisothermal conditions. It is observed that the addition of MSW affected thecrystallization rate and melting behavior of iPP/MSW composites remarkably. The additionof MSW and/or PP-g-MAH has strong nucleation activity and accelerates the nucleation rateand the overall crystallization rate. Analysis of the isothermal crystallization shows that theAvrami model successfully described the crystallization process.(3) Biodegradable poly(butylene succinate)(PBS) and layered double hydroxide (HT)nanocomposites are prepared. By means of TEM and SEM,conclusions are drawed: HTnanoparticles dispersed well in PBS, PBS crystallization rate has been improved with theaddition of the HT nanoparticles greatly. HT nanoparticles in the PBS/HT nanocompositeshave heterogeneous nucleation effect on crystallization of PBS matrix, through experimentalresults of DSC, and the results show that the crystallization rate increases with the growth ofthe HT content, and the HT nanoparticles act as the heterogeneous nucleation agents topromote the crystallization process. Adding HT to PBS material can not greatly change themechanism of nucleation and crystal growth morphology. Furthermore, The non-isothermalcrystallization processes is analyzed by methods of Jeziorny, Ozawa and Mo, and found thatthe method proposed by Mo could successfully analyze the non-isothermal crystallizationkinetics of PBS and its nanocomposites. The experimental results of POM show that thespherulitic morphologies did not change, but the spherulite size of PBS and itsnanocomposites decreases with the addition of HT nanoparticles.(4) Poly(butylene succinate)(PBS) and aminopropylisobutyl polyhedral oligomericsilsesquioxanes (POSS) nanocomposites are prepared by solution-casting method. The effects of POSS on the microstructure, crystal structure, crystallization behavior, spheruliticmorphology and spherulite grow rate, mechanical properties, and thermal stability ofPBS/POSS nanocomposites are investigated with various techniques. Scanning electronmicroscope measurements reveals that POSS particles are well-dispersed uniformly on thenanoscale in the PBS matrix and has a good interfacial interaction with PBS chains.Wide-angle X-ray diffraction patterns shows that the POSS molecules are able to crystallizein PBS matrix, but do not affect the crystalline structure of PBS matrix. Differential scanningcalorimetry results indicate that the incorporation of POSS particles into PBS matrix,unexpectedly, decrease the crystallization temperature during nonisothermal meltcrystallization and prolong the crystallization time during isothermal crystallization. Thenucleation effect of such POSS on the crystallization of PBS is extraordinary limited;furthermore, it hinders the motion of PBS chains and decelerated the spherulite growth rate,as confirmed by polarized optical microscopy. Mechanical properties are evaluated byInstron and dynamic mechanical analysis. The Young’s modules and storage modules of thenanocomposites are enhanced relative to PBS by the addition of POSS, however, the tensilestrength is not much improved and the elongation at break is reduced in the nanocomposites.Glass transition temperature (Tg) of the PBS/POSS nanocomposites increased slightly withincreasing POSS content, which indicated that the molecular mobility of amorphous PBSchains is constrained in the nanocomposites. The above results indicate that the retardedcrystallization of PBS and the effect of mechanical properties of the nanocomposites in thepresence of POSS are ascribed the stronger hydrogen-bonding interactions between thePOSS molecules and the PBS matrix as well as the network formation based on the POSSphysical crosslinking points in the PBS/POSS nanocomposites.