Preparation Of Polyurethane Modified Chlorinated Polypropylene And Its Properties

Chlorinated polypropylene (CPP) has excellent adhesive power to polypropylene substrates, so it is often used as adhesion promoter in special coating for polypropylene. Nevertheless, CPP still has some effects, such as insufficient weatherability, low adhesive capacity for polar materials, poor mutual solubility for other polar resins and polar solvents, etc. Polyurethane (PU) is a polar polymer and possesses excellent flexibility at low temperature. When it is used to modify CPP, CPP is provided with satisfactory weatherability, high impact strength and a better mutual solubility for other polar resins and polar solvents. The preparation of PU modified CPP can be carried out by a physical modification preprocess or a chemical ones. The performance of CPP will be improved more by grafting with PU. In this article, the synthesis of PU grafted CPP was studied firstly. When it was proved that PU had been grafted with CPP successfully, the adhesive capacity and the solidifying characteristics of graft mixture were investigated in order to enhance its application.Several inter-chain polymer reactions to prepare PU grafted CPP were introduced. Considering maleic anhydride(MAH) grafted CPP (MCPP) having been studied in our laboratory, PU grafted CPP was designed to synthesize via a new inter-chain polymer reaction between MCPP with PU prepolymers with free isocyanate.In the process of synthesis of MCPP,the effects of reaction temperature, charging manner, reaction time and the amount of initiator on the grafting ratio and grafting efficiency of maleic anhydride were studied. The grafting efficiency was advanced by improving the grafting technology and optimizing the reaction conditions. When consuming a lower amount of maleic anhydride, the grafting yield could arrive to about 2% and the efficiency could be up to 80%, which was good to reduce the raw material consumption.The significance of determining the maleic anhydride content in MCPP was discussed, and the merits and demerits of several methods for measuring the acid value of MCPP were analyzed. According to the special structure, a method for exactly measuring the.acid value of MCPP was researched to solve such the problem as emulsification and precipitation. The parameters of method for determining the malefic anhydride content in MCPP were established by using CPP as blank and investigating influence factors of dechlorinating of tertiary carbon chlorine, and the error conditions were analysized. This work assisted in optimizing the synthesis and the further modification of MCPP.Poly(oxypropylene) diols (N210 and N220) and liquefacient MDI were designed to prepare PU prepolymers, and several samples with different molecular weight and different flexible linkage were obtained by controlling the polymerizing technology. Then the inter-chain polymer reaction between MCPP and PU prepolymers was investigated in the presence of xylene as solvent and tertiary amine as catalyst. The potential crosslinking and gelation were avoided successfully by dropping MCPP and controlling reaction time and the mole ratio of PU prepolymers to MCPP. Three target graft products with different PU content were obtained, and they were characterized by FT-IR spectroscopy and differential scanning calorimetry (DSC) techniques.The solubility parameter of PU grafted CPP was estimated by the method of turbidimetric titration. The viscosity and the densities for binary mixture of PU grafted CPP with xylene at 25℃were determined by Ubbelohde viscometer and the vibrating tube densimeter respectively. Then the intrinsic viscosities of PU-g-CPP were obtained. The effects of PU content on the densities for binary mixture and the intrinsic viscosity were studied. This work will provide the foundational physical data for the application of PU grafted CPP.The graft mixture was divided into PU-CPP composites and PU-CPP-MAH composites on the basis of MCPP being purified or not, and the preparation and performance of them were investigated. Allowing a mild crosslinking and using PU prepolymers with lower molecular weight and higher polarity and maintaining PU prepolymers/MCPP(mol)= 4/1, the PU-CPP composites and the PU-CPP-MAH composites behaved a satisfactory solidifying characteristic and adhesive capacity. This work also indicated that, when diols/diamines introduced as extenders, PU-CPP composites and PU-CPP-MAH composites could have a better adhesion to polyolefin resins without any loss of gloss.