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Compatibilization of low-density polyethylene/cassava starch blends by potassium persulfate and benzoyl peroxide

Authors

  • Varaporn Tanrattanakul,

    Corresponding author
    1. Bioplastic Research Unit, Polymer Science Program, Faculty of Science, Prince of Songkla University, Hatyai, Songkla, Thailand 90112
    • Bioplastic Research Unit, Polymer Science Program, Faculty of Science, Prince of Songkla University, Hatyai, Songkla, Thailand 90112
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  • Wannarat Panwiriyarat

    1. Bioplastic Research Unit, Polymer Science Program, Faculty of Science, Prince of Songkla University, Hatyai, Songkla, Thailand 90112
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Abstract

Low-density polyethylene (LDPE) was melt-blended with native cassava starch in an internal mixer. The unplasticized starch content was in the range of 30–70 wt %. Potassium persulfate and benzoyl peroxide were used as initiators to generate free radicals in starch and LDPE, leading to graft copolymerization during melt blending. An enhancement of interfacial adhesion due to initiators was observed directly in scanning electron micrographs and was proven indirectly with many experiments, including tensile property testing, tear strength testing, water absorption testing, dynamic mechanical thermal analysis, thermogravimetric analysis, and soil burial testing. The tensile strength and Young's modulus of all blend compositions increased with the addition of initiators, whereas the tear strength increased in blends containing 50 wt % or more starch. The water uptake of the samples decreased significantly when initiators were added. Starch exhibited a strong effect on the α-relaxation process of LDPE. Blends containing initiators provided higher α-relaxation temperatures than blends without initiators. The increase in the interfacial adhesion of the blends also affected the biodegradation of starch. A lesser biodegradation rate of starch was observed in the blends containing initiators; this was shown by a reduction in the weight loss and more starch left in the samples after soil burial testing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

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