Abstract

ABSTRACT The melt crystallization characteristics of a compound of coconut lignocellulosic fibers dispersed in poly(butylene adipate terephthalate) (PBAT), a fully biodegradable copolyester matrix, was studied by differential scanning calorimetry (DSC). PBAT/coconut fiber compounds with 10% and 20% filler content were prepared in a laboratory internal mixer; torque rheometry showed negligible degradation during processing. Nonisothermal melt crystallization of the matrix was thoroughly studied by DSC in 10% compounds at cooling rates between 2 and 32°C/min, and quantitative information was provided on crystallization temperatures and rates, as well as the crystallinity developed, which turned out to be higher than expected at the high cooling rates. Crystallization kinetic results were correlated using classical macrokinetic Pseudo-Avrami, Ozawa, and Mo models, in order to obtain quantitative analytical expressions appropriate for processing applications. Pseudo-Avrami and Mo models were found to represent well the experimental data. A detailed analysis of the model fitting is presented, in order to assess the expected uncertainties. Despite its failings at the onset and end of the crystallization process, Mo model is recommended as best overall empirical correlation of the experimental data for the intended purpose.

Highlights

  • Persistent polymers are an important source of environmental pollution

  • The melt crystallization characteristics of a compound of coconut lignocellulosic fibers dispersed in poly(butylene adipate terephthalate) (PBAT), a fully biodegradable copolyester matrix, was studied by differential scanning calorimetry (DSC)

  • PBAT/coconut fiber compounds with 10% and 20% filler content were prepared in a laboratory internal mixer; torque rheometry showed negligible degradation during processing

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Summary

INTRODUCTION

New materials with environmentally friendly characteristics, included biodegradable polymers, have attracted considerable attention in last decades. PBAT is a biodegradable, semi-crystalline, random aliphatic-aromatic copolyester based on the monomers 1,4-butanediol, adipic acid and terephthalic acid. Particular applications of PBAT include cling wrap for food packaging, compostable plastic bags for gardening and agricultural use, water resistant coatings for other materials, etc. In Europe, the automobile industry upholsters cars with pads of brown coir bonded with rubber latex. It has been successfully used in polymeric and ceramic compounds. The addition of a natural filler, such as coconut fiber, may affect PBAT morphology and crystallization behavior. Crystallization kinetics affects optimum processing protocols and the viability of manufacturing particular items, and allows the rational control of the compound morphology. Activation energy was estimated using a modified Friedman isoconversional model-free kinetics approach

EXPERIMENTAL
RESULTS AND DISCUSSION
Melt crystallization
Pseudo-Avrami model
Ozawa model
Mo model
Activation energy
CONCLUSIONS
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