The Synthesis And Properties Of PP-g-PVAc And PP-g-PVOH

In this thesis, solid phase graft polymerization of vinyl acetate (VAc) in porous polypropylene (PP) granule was studied in water where benzyl peroxide was used as initiator and PP-g-PVAc was prepared with high graft percentage (GP). Then, PP-g-PVAc granule was saponified to PP-g-PVOH by heterogeneous saponification technique with NaOH/KOH as catalyst in alcohol dispersing medium. During our investigation, some methods to prepare PP-g-PVOH with high saponification percentage (SP) were explored.Results showed that porous PP granule was in favor of solid phase graft polymerization for its' high porosity and large inner surface area as substrate and reactor, by using what the graft percentage (GP) and efficiency (GE) of PP-g-PVAc could be as high as 16% and 90%, respectively. During the polymerization processes, GP increased rapidly at the initial stage and then, the increasing rate slowed down gradually, while GE was always decreased. Elevating the reaction temperature could raise both GP and GE in efficiency. A peak relationship was lied between GP and BPO concentration, while GE was always decreased. Less than the inner porous volume in PP granule, increasing the amount of monomer could enhance GP dramatically along with high GE; on the contrary, GP was not enhanced and GE decreased markedly because more homopolymer formed. Using smaller granules as substrate, GP and GE were higher than these using smaller granules for their larger porosity. In our investigation, the improvement of graft polymerization was not observed by using tetrahydronaphthalene as swelling agent and it was probably because of its' inhibiting property to free radicals.As PP-g-PVAc was achieved from PP granule by solid phase graft polymerization, the grafting layer was mainly distributed at the surface region which provides the possibility to saponify PP-g-PVAc into PP-g-PVOH with high saponification percentage (SP). When catalysts concentrations lower than 2%, NaOH was more efficient to catalyze saponification reaction; on the contrary, KOH was in efficiency. For both catalysts, there exists a best concentration range. Increasing reaction temperature, saponification rate and degree were both improved. For PP-g-PVAc granule with various GP, the higher GP led to a lower SP which meant more graft chains distributed at the inner regain on PP substrate. The species for reaction mediums influenced reaction degree greatly for the low swelling ability of lower alcohol and high viscosity of higher alcohol and a peak relationship between SP and alcohol carbon number was laid. The system of lower/higher bi-alcohol system was firstly studied and it was found that the reaction rate and degree were both increased. The conditions to produce PP-g-PVOH with the highest SP 60% were: ethyl alcohol/butyl alcohol=30/70 (v/v), NaOH%=0.5% (g/ml), refluxing at 90℃ for 16hr.FTIR confirmed graft and saponification reactions, and it was identified that graft reaction influence porosity and morphology very little, but microparticles in PP granule were sightly swelled. There was a peak relationship between melt flowing index (MFI) and GP and the flowing property was decreased with sponification reactions. The studies of non-isothermal crystallization kinetics for PP-g-PVAc and PP-g-PVOH showed that: for PP-g-PVAc, the crystallization behavior was not changed, the best crystallization temperature was increased at higher GP, the crystallization rate and enthalpy were decreased; for PP-g-PVOH, the crystallization behavior was changed from homo to hetero nucleation with SP increased, the best crystallization temperature and enthalpy was increased dramatically, but the crystallization rate was decreased because the integrity of molecular chain was decreased. The photographs of polarizing microscope showed the number of spherocrystal was increased and the diameter was decreased after saponification reaction which was agreed with the studies of DSC.