Optical and mechanical properties of polypropylene modified by metal oxides

Films of polypropylene (PP)/SiO2, PP/ZnO and PP/SiO2-ZnO nanocomposites have been prepared. SiO2 and ZnO were prepared by the sol-gel method and mixed with dispersant (Efka) and coupling agent (thiocyanatopropyltriethoxysilane) before being introduced to melted PP in an internal mixer. The transmission of UV, visible light and NIR radiation of the nanocomposite films was less than that of the PP films. Efka and silane made the film clearer to all rays since they hindered the particle agglomeration. PP/ZnO film had a unique property as it blocked UV while transmitted visible light better than PP/SiO2. The modulus of PP mixed with metal oxide increased whereas the elongation to break decreased, indicating that the metal oxides increased the film strength and brittleness. The PP/SiO2 gave higher tensile strength and modulus than the PP/ZnO due to the greater hardness of SiO2. The silane improved the tensile strength and modulus of PP/SiO2. Copyright (C) 2004 John Wiley Sons, Ltd.