Microcellular Poly(hydroxybutyrate-co-hydroxyvalerate)-Hyperbranched Polymer Nanoclay Nanocomposites

The effects of incorporating hyperbranched polymers (HBPs) and different nanoclays [Cloisite (R) 30B and halloysite nanotubes (HNT)] on the mechanical, morphological, and thermal properties of solid and microcellular poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) were investigated. According to the X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, Cloisite 306 exhibited a combination of exfoliation and heterogeneous intercalation structure for both solid and microcellular PHBV-12% HBP-2% Cloisite 306 nanocomposites. TEM images indicated that HNTs were uniformly dispersed throughout the PHBV matrix. The addition of 2% nanoclays improved the thermal stability of the resulting nanocomposites. The addition of HBP+poly(maleic anhydride-alt-1-octadecene) (PA), Cloisite 30B, and HNT reduced the average cell size and increased the cell density of the microcellular components. The addition of (HBP+PA), Cloisite 306, and HNT also increased the degree of crystallinity for both solid and microcellular components in comparison with neat PHBV. Also, with the addition of 12% (HBP+PA), the area under the tan-delta curve, specific toughness, and strain-at-break of the PHBV-HBP nanocomposite increased significantly for both solid and microcellular specimens, whereas the storage modulus, specific Young's modulus, and specific tensile strength decreased. The addition of 2% nanoclays into the PHBV-HBP nanocomposites improved the storage modulus, specific Young's modulus, and specific tensile strength of the PHBV-HBP-nanoclay-based nanocomposites, but they were still lower than those of the neat PHBV. POLYM. ENG. SCI., 51:1815-1826, 2011. (C) 2011 Society of Plastics Engineers