Polypropylene Composites Filled with Steam-Exploded Wood Fibers from Beetle-Killed Loblolly Pine by Compression-Molding
Keywords:Beetle-killed pine, steam explosion, polypropylene composite, compatibilizer, flexural properties
AbstractBeetle-killed loblolly pine chips were steam-exploded (SE) with a severity factor of 4.8 in a batch reactor into a fibrous mass followed by a sieve step to remove oversize pieces (>16 mesh). The sieved SE fibers (<16 mesh) contained 5%-10% water-soluble materials and were mainly composed of fiber fragments with lignin droplets on their surfaces. Composites were prepared by firstly compounding sieved SE fibers and polypropylene (PP) with or without maleic anhydride grafted polypropylene (MAPP) as a compatibilizer, and then by compression-molding the mixtures at 195°C. The MOE of the composites increased greatly, and the yield stress σy, was decreased slightly by inclusion of 50% SE fibers with no compatibilizer. Addition of 2.5% MAPP improved significantly the flexural properties of the composites, especially the σy which was eventually superior to that of neat PP. DMA and DSC measurements revealed that the SE fibers increased the crystallinity of PP by forming more crystalline fractions around wood fibers or fiber fragments. Addition of MAPP resulted in a reduction in the damping and an increase in the heat of fusion of the PP in the composites, suggesting a stronger interface between the matrix and SE fibers. The better interfacial adhesion was also demonstrated by SEM observations showing fiber breakage occurring on the fractured surfaces of the PP composites with MAPP as a compatibilizer.
Amash, A., and P. Zugenmaier. 2000. Morphology and properties of isotropic and oriented samples of cellulose fibre-polypropylene composites. Polymer41(4):1589-1596.nAnglè, M. N., J. Salvadó, and A. Dufresne. 1999. Steamexploded residual softwood-filled polypropylene composites. J. Appl. Polym. Sci.74:1962-1977.nBoyd R. H. 1985. Relaxation processes in crystalline polymers: Experimental behaviour—a review. Polymer26:323-347.nCanetti, M., A. D. Chirico, and G. Audisio. 2004. Morphology, crystallization and melting properties of isotactic polypropylene blended with lignin. J. Appl. Polym. Sci.91:1435-1442.nClemons, C. 2002. Wood-plastics composites in the United States. Forest Prod. J.52(6):10-18.nDonaldson, L. A., K. K. Y. Wong, and K. L. Mackie. 1988. Ultrastructure of steam exploded wood, Wood Sci. Technol.22:103-114.nFelix, J., and P. Gatenholm. 1991. The nature of adhesion in composites of modified cellulose fibers and polypropylene. J. Appl. Polym. Sci.42:609-620.nForest Products Laboratory. 2000. Forest Products Laboratory research program on small-diameter material. Gen. Tech. Rep. FPL-GTR-110 (Rev.). USDA, Forest Service. Madison, WI.nGenovese, A., and R. A. Shanks. 2004. Crystallization and melting of isotactic polypropylene in response to temperature modulation. J. Therm. Anal. Calorim.75:233-248.nHarper, D. 2003. A thermodynamic, spectroscopic, and mechanical characterization of the wood-polypropylene interphase. Doctoral Dissertation, Washington State University, Pullman, WA.nJosefsson, T., H. Lennholm, and G. Gellerstedt. 2002a. Steam explosion of aspen wood, characterisation of reaction products. Holzforschung56(3):289-297.nJosefsson, T., H. Lennholm, and G. Gellerstedt. 2002b. Changes in cellulose supramolecular structure and molecular weight distribution during steam explosion of aspen wood. Cellulose8(4):289-296.nKallavus, U., and J. Gravitis. 1995. A comparative study of the ultrastructure of steam exploded wood with light, scanning and transmission electron microscopy. Holzforschung49:182-188.nKardos, J. L. 1985. The role of the interface in polymer composites—some myths, mechanisms, and modifications. Pages 1-11 in H. Ishida and G. Kumar, eds. Molecular characterization of composites interfaces. Plenum Press, New York, NY.nKazayawoko, M., J. J. Balatinecz, R.T. Woodhams, and R. N. S. Sodhi. 1998. X-ray photoelectron spectroscopy of lignocellulosic materials treated with maleated polypropylenes. J. Wood Chem. Technol.18(1):1-26.nKazayawoko, M., J. J. Balatinecz, and L. M. Matuana. 1999. Surface modification and adhesion mechanisms in woodfiberpolypropylene composites, J. Mater. Sci.34:6189-6199.nKokta, B. V., and A. Ahmed. 1998. Steam explosion pulping. Pages 191-214 in R. A. Young and M. Akhtar, eds. Environmentally friendly technologies for the pulp and paper industry. John Wiley & Sons, Inc, New York, NY.nLeVan-Green, S. L., and J. Livingston. 2001. Exploring the uses for small-diameter trees. Forest Prod. J.51(9):10-21.nMi, Y., X. Chen and Q. Guo. 1997. Bamboo fiberreinforced polypropylene composites: Crystallization and interfacial morphology. J. Appl. Polym. Sci.64(7):1267-1273.nMichalowicz, G., B. Toussaint, and M. R. Vignon, 1991. Ultrastructural changes in poplar cell wall during steam explosion treatment. Holzforschung45:175-179.nMurayama, T. 1978. Dynamic mechanical thermal analysis of polymeric materials. Elsevier Scientific, Amsterdam, Netherlands. pp. 111-130.nNuñez, A. J., J. M. Kenny, M. M. Reboredo, M. I. Aranguren, and N. E. Marcovich. 2002. Thermal and dynamic mechanical characterization of polypropylenewoodflour composites. Polym. Eng. Sci.42(4):733-742.nOverend, R. P., and E. Chornet. 1987. Fractionation of lignocellulosics by steam-aqueous pretreatments. Phil. Trans. R. Soc. Lond. A321:523-536.nPanshin, A. J., and C. de Zeeuw. 1980. Textbook of wood technology, 4th ed. McGraw Hill, New York, NY. pp. 133-134.nQiu, W., F. Zhang, T. Endo, and T. Hirotsu. 2003. Preparation and characteristics of composites of highcrystalline cellulose with polypropylene: Effects of maleated polypropylene and cellulose content. J. Appl. Polym. Sci.87:337-45.nQuirk R. P., and A. A. Alsamarraie. 1989. Physical constants of poly(propylene). Page V/27 in J. Brandrup and E. H. Immergut, eds. Polymer Handbook. John Wiley & Sons, New York, NY.nSimpson, W., and A. TenWolde. 1999. Physical properties and moisture relations of wood. Pages 3-18t in Wood handbook—Wood as an engineering material. Gen. Tech. Rep. FPL-GTR-113. Madison, WI.nStamm, A. J., and E. E. Harris. 1953. Chemical processing of wood. Chemical Publishing Co. Inc., New York, N.Y. pp. 360-362.nTanahashi, M. 1990. Characterization and degradation mechanisms of wood components by steam explosion and utilization of exploded wood. Wood Research77:49-117.nToriz, G., F. Denes, and R. A. Young, 2002, Ligninpolypropylene composites, Part 1: Composites from unmodified lignin and polypropylene. Polymer Composites23(5):806-813.nYin, S., T. G. Rials, and M. P. Wolcott. 1999. Crystallization behavior of polypropylene and its effect on wood fiber composite properties. Pages 139-146 in Proc. 5th International Conference on Woodfiber-Plastic Composites. Madison, WI.n
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