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Maleic anhydride grafting onto polypropylene was conducted in a twinscrew extruder according to an experimental design in which the maleic anhydride and peroxide concentrations were varied. The modified polypropylene was characterized by FTIR spectroscopy, melt-flow index measurements, size-exclusion chromatography, differential scanning calorimetry, and nuclear magnetic resonance. The results showed that only the independent variable peroxide concentration influenced the amount of reacted maleic anhydride, whereas the two variables studied influenced the molecular weight of the grafted polypropylene.

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PHB was characterized after different industrial processes by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Melt Flow Index (MFI), Complex Dielectric Relaxation (CDR) and Size Exclusion Chromatography (SEC). Some properties of PHB were investigated before and after processing, in order to understand how temperature and other extrusion or injection conditions affect the polymer degradation. All the processed samples showed an increasing in the melt flow index, a decreasing of the dynamic crystallization temperature, and a reduction in the molar mass, suggesting some degradation. The molar mass reduction after processing, predicted when only thermal degradation is considered, was calculated in function of the kinetic parameters, such as constant thermal degradation and residence time during the industrial processing. It was found that the real molar mass reduction was higher than the theoretical value, indicating an important contribution of the shearing of polymeric chains during processing in the PHB degradation.

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Blends of starch and zein plasticized with glycerol were prepared by melting processing in an intensive batch mixer connected to a torque rheometer at 160 °C. The resulting mixtures were compression molded and then characterized by scanning electron microscopy, differential scanning calorimetry, wide-angle X ray diffraction and water-absorption experiments. The blends were immiscible, showing two distinct phases of starch and zein. The water uptake at equilibrium and its diffusion coefficient were determined. The water uptake at equilibrium decreased with increasing zein content. The diffusion coefficient fell sharply on addition of 20% zein and remained constant as zein content was increased. No appreciable effect of zein on starch crystallization was observed by X ray diffraction. The use of zein in thermoplastic starch compositions causes a decrease in the water sensitivity of these materials and lower its melt viscosity during processing making zein a suitable and very promising component in TPS compositions

ABSTRACT:Grafting reactions were performed in a Haake torque rheometer, according to a central composite experimental design, where the maleic anhydride and peroxide concentrations, rotor speed, and reaction time were varied. The 27 formulations were analyzed by Fourier transformed infrared spectroscopy and melt-flow index measurements (MFI). An increase in peroxide concentration caused an increase in the percentage of reacted maleic anhydride and in MFI. The effect of initial maleic anhydride concentration presented different types of behavior, depending on the peroxide level.