DEVELOPMENT OF NANO CALCIUM CARBONATE - POLYPROPYLENE COMPOSITE FOR AUTOMOTIVE APPLICATION

摘要

The objective of the study is to develop an automotive bumper grade nanocomposite by modifying polypropylene (PP) with nano-sized precipitated calcium carbonate (NPCC) filler and polyethylene elastomer (POE). Ternary polypropylene/polyolefin elastomer (POE)/calcium carbonate nanocomposites were prepared via melt blending in a corotating twin screw compounder using maleated PP (PP-g-MA) as a coupling agent. The NPCC added has an average measured primary particle size of 50 nm while the POE used was an ethylene-octene copolymer. Two NPCC filler loadings of 10 and 15 weight % were studied while the POE contents were varied between 0-30 weight %. Phase structures of both etched and unetched fractured surfaces of the nanocomposites were observed using a scanning electron microscope (SEM). At both NPCC levels studied, the impact strength of the homopolymer PP increases dramatically with increasing POE content. The maximum impact enhancement achieved for the neat PP was 450 J/m obtained for the nanocomposite with 15 wt. % NPCC and 30 wt. % POE. SEM photomicrographs of the nanocomposites showed a three-phase morphology of the dispersed POE and the nano-sized filler particles in the continuous PP matrix, except for the nanocomposite with the highest impact properties which showed evidence of a better adhesion between the POE and the PP. To obtain PP-NPCC composite of the required grade, it was crucial that the filler loading and POE content need to be delicately balanced. These factors greatly affect the properties of interest viz., the tensile, impact and modulus values as specified in the automotive specification of the bumper grade material.