CALCIUM CARBONATE SURFACE COATING MODIFICATION AND IT'S EFFECT ON THE MECHANICAL PROPERTIES OF FILLED POLYPROPYLENE

Abstract

Recently,polypropylene toughened and strengthened by ultrafine calcium carbonate(CaCO_3) has become more and more popular.But for its high surface energy,the compatibility between CaCO_3 and polypropylene is poor,so the surface of CaCO_3 must be modified before use.In this article,CaCO_3 whose surface was pretreated first by acrylic acid(AA) to introduce active double bond groups,was coated chemically by polypropylene wax(PPW) via solid-phase coating polymerization.Compared to traditional solid-phase grafting polymerization,this method has some differences.First,the reaction is not between monomers of small molecular weight and polymer,but between CaCO_3 pretreated by AA and PPW;Second,the polymer is usually a solid phase mass under the reaction temperature in the traditional solid-phase grafting polymerization,but in this method PPW is in the liquid phase,and the CaCO_3 pretreated by AA in the solid phase.Third,in traditional method the reaction is the monomers grafting to the polymer's surface,but in this method the coating reaction is PPW to the AA on the CaCO_3's surface.As this method can occur in high-speed mixer,it is more convenient and feasible comparing to the traditional grafting reaction which is usually in extruder or reactor.In this article,it is found that coated CaCO_3 can stand the treatment of both methyl benzene and dilute hydrochloric acid.Combined the results of FTIR and TGA,the conclusion can be made that PPW has been coated successfully with polyacrylic acid on the surface of CaCO_3.After filling the coated CaCO_3 into polypropylene(PP),it shows that the impact and tensile properties of PP are improved in somewhat degree.When the content of the coated CaCO_3 is 15 phr,the notched impact strength of the PP composite is 1.68 times as high as that of PP.When the content is 10 phr,the tensile strength of PP filled with coated CaCO_3 is 1.22 times higher than that of PP filled with uncoated CaCO_3 at same contents.