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Crystallization of poly(hydroxybutrate‐co‐hydroxyvalerate) in wood fiber‐reinforced composites
Author(s) -
Reinsch Veronika E.,
Kelley Stephen S.
Publication year - 1997
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19970531)64:9<1785::aid-app15>3.0.co;2-x
Subject(s) - materials science , crystallization , composite material , crystallinity , microcrystalline cellulose , differential scanning calorimetry , composite number , cellulose , nucleation , crystallite , kraft paper , fiber , chemical engineering , chemistry , organic chemistry , physics , engineering , metallurgy , thermodynamics
Wood fiber‐reinforced composites were prepared from poly(hydroxybutyrate) (PHB) and poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHB/HV) copolymers containing 9 and 24% valerate. The effects of fibers on crystallization were investigated. Thermomechanical pulp, bleached Kraft fibers, and microcrystalline cellulose filler were used as the reinforcing phase. The crystallization of PHB/HV in composite materials was examined using Modulated Differential Scanning Calorimetry (MDSC) and hot‐stage microscopy. Hot‐stage microscopy showed that polymer crystallites are nucleated on the fiber surface and that the density of nuclei was greater in fiber‐reinforced composites than in unfilled material. Dynamic crystallization experiments showed that bleached Kraft, thermomechanical pulp, and microcrystalline cellulose increased the crystallization rate of PHB and PHB/HV both from the glass and melt. However, ultimate crystallinity determined from the heat of crystallization was the same in unreinforced and reinforced materials. The kinetics of PHB/HV crystallization were examined using nonisothermal Avrami‐type analysis. Unreinforced and Kraft‐reinforced PHB were characterized and compared with unreinforced PHB/9%HV. The Avrami exponent of crystallization, related to nucleation mechanism and growth morphology, is 2.0 for unreinforced PHB, 2.8 for kraft‐reinforced PHB, and 3.0 for unreinforced PHB/9%HV. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1785–1796, 1997