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Poly(3-hydroxybutyrate) (PHB)/babassu compounds were prepared in a laboratory internal mixer with 10, 30, and 50 % by mass of fiber content. Nonisothermal melt crystallization behavior of PHB/babassu compounds was investigated using differential scanning calorimetry, and crystallization parameters were determined at cooling rates ranging between 2 and 32°C min -1 . Adding babassu fiber affected the melt crystallization behavior of PHB, and increasing filler content from 10 to 30 % has significant effects on the thermal characteristics of the system. Further increase in filler content from 30 to 50 % filler content has no effect on crystallization temperature and rate, but it has important positive consequences, once there is a considerably latitude in choosing the actual filler level in highly loaded PHB/babassu compounds without affecting processing characteristics. The melt crystallization kinetics of PHB/babassu compounds was analyzed by three empirical models widely used to represent nonisothermal polymer crystallization data: Pseudo-Avrami, Ozawa, and Mo. Kinetics analyses indicate that the Pseudo-Avrami model represented well the experimental data for both compounds in a wide interval of temperature, conversion, and cooling rates; the Ozawa model with two different sets of parameters, for low and high cooling rates, was found to correlate the data equally well, but over limited ranges of the variables, and the model proposed by Mo and collaborators did not adequately represent the experimental data for the systems and conditions tested. List of symbols cCrystallization rate c 0.1-99.9% Crystallization rate measured between 0.1 and 99.9 % of mass transformation c 20-80% Crystallization rate measured between 20 and 80 % of mass transformation c max Maximum crystallization rate (at T c ) E 0 Total latent heat released or absorbed by the sample during the crystallization or melting event F Mo rate parameter J DSC output heat flow rate of thermal energy exchanged between sample and the surroundings J 0 Virtual baseline during a phase change event K 0 Pseudo-Avrami rate parameter m Ozawa exponente MFR Melt flow rate M n Number average molar weight n 0 Pseudo-Avrami exponente t 1Onset time of the crystallization event t 2Endtime of the crystallization event T Temperature T 0.1% Temperature to attain 0.1 % of crystallized fraction T 50%

ABSTRACT:The present work studies the thermal properties of composites of poly(3-hydroxybutyrate) (PHB) -a fully biodegradable semi-crystalline thermo-plastic obtained from renewable resources through lowimpact biotechno-logical process, biocompatible and non-toxic -and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB is a highly crystalline resin and this characteristic leads to suboptimal properties in some cases. Consequently, thermal properties, in particular those associated with the crystallization of the matrix, are important to judge the suitability of the compounds for specific applications. PHB/babassu composites with 0-50% load were prepared in an internal mixer. Two different types of babassu fibers with two different particle size ranges were compounded with PHB and test specimens molded by compression. Melting and crystallization behavior were studied by differential scanning calorimetry (DSC) at heating/cooling rates between 2 and 30 C/min. Several parameters, including melting point, crystallization temperature, crystallinity, and rate of crystallization, were estimated as functions of load and heating/cooling rates. Results indicate that fibers do not affect the melting process, but facilitate crystallization from the melt. Crystallization temperatures are 30 to 40 C higher for the compounds compared with the neat resin. However, the amount of fiber added has little effect on crystallinity and the degree of crystallinity is hardly affected by the load. Fiber type and initial particle size do not have a significant effect on thermal properties.