Study On Modification Of Chlorinated Polypropylene

Due to excellent overall performance, PolyPropylene(PP) has gained great development in the production and application. It was widely used in the field of industrial products, daily necessities, packaging films, fibers, and so on. However, general adhesives are difficult to be adhered for PP, of which surface without special physical and chemical treatment, because of its non-polarity, low surface tension, high crystallinity and weak boundary layer. The good news is Chlorinated polypropylene(CPP) has good adhesion property to PP, because CPP and PP with the same main chain that will tangle with each other, when CPP applied to the PP surface. But the unmodified CPP have problems of compatibility with the other resin and environmental issues, since its low polarity and the use of organic solvents.In this paper, an aromatic-free and low volatile organic compounds(VOC) of water dispersive CPP was synthesized by reacting the CPP with acrylate monomer by way of solution grafting polymerization, and the influence of the polymerization conditions on grafting degree and the property of emulsion and coatings were investigated. The content and conclusions of this paper are as follows:1. Acrylate modified CPP emulsion, which has good adhesion to PP, can be diluted with water and is capable of producing water resistance film, was synthesized by solution graft polymerization, with acrylate as modified monomer, acrylic acid and perfluoroalkyl acrylate as functional monomers, butyl acetate as solvent, Benzoyl peroxide as initiator. The effects of factors such as reaction temperature, reaction time, adding method and quantify of initiator and the quantify of mixed acrylate monomers on grafting degree and the property of emulsion and coatings of the products were systematically investigated. The effects of quantity of acrylic acid and fluorine-containing monomer, and the ratio of soft monomer and hard monomer on the coatings properties were studied. It was found that:when the reaction temperature is95℃, the reaction time is3.5h, the method of added initiator was that the total quantify of BPO(mass percentage of CPP resin) is1.0%and divided into three parts:the first part(Ⅰ1) was added before adding monomers, the second part(Ⅰ2) was mixed with monomers and the third part(Ⅰ3) was added before the end of reaction, and the ratio of I1/(I1+I2+I3)=1/10, the interval of adding Ⅰ1and dropping mixed monomers is10min, the quantity of mixed acrylic monomers, acrylic acid and fluorine-containing monomer are30%,5%and4%, had higher grafting yield, and good overall performance of the water dispersion of chlorinated polypropylene can be obtained.The acrylate grafted CPP were analyzed by Fourier transform infrared(FT-IR) spectrometer. The results showed that acrylate and perfluoroalkyl acrylate effectively took part in the grafting copolymerization.2. Self-cross-linked and cross-linking system were investigated, and methods to improve the performance of the modified emulsion, especially water resistance, were explored. Self-cross-linked organosiloxane modified CPP emulsion was synthesized by solution grafting polymerization, with silane crosslinking agent containing unsaturated bonds as functional monomer. The influence of the adding method and amount of silane crosslinking agent on the property of emulsion and coatings were investigated. The effect of the type and quantity of the crosslinker on the coatings properties was also studied. The results showed that:when the organic silicon monomer added to the reaction system before the dropping of the other acrylic monomer and m(silane crosslinking agent)/m(Acrylate)=0.057, the modified CPP emulsion with good water resistance and storage stability can be obtained; choosing polyfunctional isocyanate as an external crosslinking agent and the amount of which is5%to the emulsion,the resulted coating has good water resistance.