シリカ表面の疎水化処理を用いないシリカ／ポリプロピレンナノコンポジットの調製および本系コンポジットの結晶化温度

抄録

A simple method for the fabrication of silica/polypropylene (PP) nanocomposites was investigated, whereby silica particles of 190nm in diameter without any surface modification were dispersed uniformly through mechanical breakdown of loosely packed agglomerates of silica nanoparticles with low fracture strength in a kneaded PP melt during direct melt-compounding. The method consists of two stages. The first stage involves preparation of the loosely packed silica agglomerate by destabilizing a colloidal aqueous solution of nanometer-size spherical silica via pH control and KBr addition, and the second stage involves melt-compounding of an isotactic PP with the silica agglomerates. The pore structure and strength of the silica agglomerate prepared in the first stage were found to control the dispersion state of the silica nanoparticles in the silica/PP composite, and the use of loosely packed silica agglomerates with numerous large pores was shown to be effective for achieving a uniform dispersion of isolated primary silica nanoparticles in the PP matrix. Non-isothermal differential scanning calorimetry (DSC) analyses of the fabricated composites revealed that the crystallization temperature of the PP matrix phase shifts towards higher one with decreasing dispersion size of silica and increasing content of distributed nano-silica. A DSC analysis may be a potential candidate for useful method to evaluate the dispersion characteristics of the inorganic nano-fillers in crystalline polymer-based nanocomposites.