Influence of particle size of isotactic polypropylene (iPP) on barrier property against agglomeration of homogenized microcrystalline cellulose (HMCC) in iPP/HMCC composites

摘要

Isotactic polypropylene (iPP) powders were treated by a colloid mill for different times to obtain a series of particle sizes ranging from 682 mu m to 89 mu m. The relative crystallinity degree index (X c, %) calculated by X- ray diffraction, and the initial degradation temperature measured by thermogravimetry, were all reduced after the milling process, which revealed that the structure of iPP molecular chains was destroyed during the powerful shearing and friction action. Furthermore, the increasing melt flow rate (MFR) index indicated that the molecular weight of iPP had reduced during the mechanical treatment. Scanning electron micrographs showed the inevitable agglomeration of homogenized microcrystalline cellulose (HMCC) fibers after being dried directly without iPP powders. However, the addition of achieved superfine iPP powders presented a good barrier property against the agglomeration phenomenon and consequent improvement in mechanical performance of the iPP/ HMCC composites.