Preparation Of Quaternary Ammonium Salt Grafted Polypropylene And Application In PP/PVC Blends

Polypropylene (PP) had advantages such as excellent mechanical properties and chemical erosion resistance. However, its high molecular integrity and low polarity led to poor properties of dyeing, adherence, antistatic and hydrophilicity, and low compatibility with other polar polymers or inorganic additives. Polyvinylchloride (PVC), an inexpensive polar polymer, was of high strength and fireproof. The striking difference between polarity of PP and PVC resulted in the low compatibility, and the inferiorities originated from it could be counteracted by blending. Recently, the preparation of PP/PVC blends with excellent properties and the enhancement of their compatibilization by additives had been the focus of research interests all around the world.In this paper, preparation, crystallization kinetics and compatibility PP/PVC blends of a quaternary ammonium bearing graft copolymer, PP-g-(St-co-DMC), had been investigated. In addition, compatibilization of PP-g-(St-co-DMC)/HBP on PP/PVC had been studied in detail. This work was of fundamental and technological importance in the theoretical investigation and the application of those polymers.A quaternary ammonium bearing graft copolymer, PP-g-(St-co-DMC) had been prepared by a suspension solid-state grafting process using a cationic monomer with quaternary ammonium groups, methacryloxyethyltrimethyl ammonium chloride (DMC), as a material. The grafted PP was systematically characterized using FT-IR, TGA and DSC. It was then suggested that DMC was successfully grafted onto the PP backbone. The effects of monomer concentration, swelling time, initiator concentration, the second monomer dosage, reaction time, and reaction temperature on the grafting yield were examined. In addition, the grafting mechanism of this reaction was proposed.The isothermal (non-isothermal) crystallization kinetics of PP-g- (St-co-DMC) sample was investigated using Avrami equation (modified Avrami equation and Mo's method). It was indicated that the induction of DMC chain could result in the modification of the crystallization mode and hence the acceleration of the crystallization under both the isothermal and the non-isothermal conditions. In the samples with low grafting yield, DMC chain led to the heterogeneous nucleation and acceleration of crystallization, and whereas, the rate of crystallization decreased. The aforementioned results might originate from the effects of quaternary ammonium groups bearing DMC. On the one hand, electrostatic attraction promoted nucleation and enhanced the crystallization. On the other hand, the increased intermolecular interaction between ions could hinder the migration of the crystallization chain, and therefore increase the diffusion activation energy of PP chain, which decreased the rate of crystallization. Furthermore, the crystallization kinetics of PP-g-(St-co-DMC) /PP(10/90) blends was discussed.The effect of compatibility of quaternary ammonium bearing PP-g- (St-co-DMC) on PP/PVC (80/20) blends was investigated systematically. The measurements of SEM, tensile strength and impact strength indicated that the PP-g- (St-co-DMC) could enhance compatibility of PP/PVC blend remarkably. The tensile strength and the impact strength of PP/PVC blends with a concentration of PP-g-(St-co-DMC) at 4%(wt) increased up to19.15% and 74.48%, respectively. The subsequent increase in the concentration of PP-g-(St-co-DMC) decreased the mechanical properties remarkably. The apparent melt viscosity of PP/PVC blends increased by the addition of PP-g-(St-co-DMC) and reached its maximum at a concentration of 4%. Study on the effect of the degree of grafting (DG) of PP-g- (St-co-DMC) on the compatibility of PP/PVC blends suggested that it should reach a peak at DG of 16.78%.For clarifying the compatibility capacity of hyperbranched polymer (HBP) on PP/PVC/PP-g-(St-co-DMC)/ blend, the effect of AB2 typed HBP on the crystallization kinetics of polypropylene (PP) was investigated. The crystallization kinetics under isothermal and non-isothermal conditions indicated that the introduction of HBP could modify its crystallization mode, and therefore accelerate the crystallization process of PP, and increase the Avrami exponent. This might be because the HBP with fractal structure had an effect on the crystal growth and diffusion mode of the crystal chain. It was indicated that, in the examined range of concentration (1-5%) of HBP, this additive with low concentration could accelerate the crystallization remarkably, and whereas, the rate of crystallization decreased. In addition, the study of molecular weight of HBP on PP crystallization kinetics indicated that, in blend samples, the increase in molecular weight reduced the rate of crystallization.The compatibility of the HBP on PP/PVC/PP-g- (St-co-DMC) (80/20/4) was further studied on the basis of effect of HBP on the crystallization behavior of PP. The measurement of SEM, tensile strength and impact strength indicated that PP-g-(St-co-DMC)/HBP could enhance the compatibility of PP/PVC blends. The addition of the mixture of PP-g-(St-co-DMC) and HBP into PP/PVC blends facilitated the modification of melt apparent viscosity of the latter. With comparison to those of the blend free of HBP, the tensile strength and the impact strength of the PP/PVC/PP-g- (St-co-DMC) (80/20/4) blends could reach up to 8.16% and 53.41% at the most, respectively, and meanwhile the apparent melt viscosity of blends reached the less value when the content of HBP was 1%. Furthermore, the influence of the molecular weight of HBP on the compatibility of PP/PVC/PP-g-(St-co-DMC) blend was discussed.