Influence of nucleation and growth mechanisms on the heat deflection temperature of a reactively processed polypropylene nanocomposite

The development of a reactively processed polypropylene nanocomposite (PPNC) with consequential improvements in the heat deflection temperature (HDT), Vicat softening temperature (VST), and crystallization peak temperature (T_c) is reported herein. Neat PP without nanoclay was also reactively processed to elucidate the effects of fillers on the improvement in physical properties. The results show a considerable improvement in the HDT of PPNC (77.9 °C) compared to those of neat PP (62.6 °C) and reactively processed branched PP (BPP; 69.2 °C). Moreover, the T_c of PP in PPNC improved by ~14% compared to that of neat PP. Various models of nonisothermal crystallization kinetics were employed to elucidate the nucleation and crystal growth mechanisms, and to correlate them with the observed HDT improvement in PPNC. Thermal transitions investigated by modulated differential scanning calorimetry explained the changes observed in the VSTs of all the samples. To the best of our knowledge, this is the first report on a significant improvement in HDT along with a marked increase in Tc. Such simultaneous improvements in HDT, VST, and T_c are highly desirable for applications involving the use of PP-based materials in rigid packaging.     

The synthesis and testing of thin film ZSM-5 catalysts

The synthesis and catalytic testing of thin ZSM-5 films on glass and alumina beads is described. The thickness of the ZSM-5 films was controlled to 150, 350, 800 and . The samples were characterised by SEM, gas adsorption and p-xylene isomerisation and 1,3,5-tri-isopropyl benzene cracking test reactions. A reaction-diffusion model adequately described the p-xylene isomerisation data. Estimates of model parameters were obtained by fitting the model to the experimental data. In both cases, the reaction rate constant increased with increasing film thickness. The xylene reaction data showed that secondary reaction products increased as expected with increasing diffusion limitations, but the increase was less than that predicted by the variation of thickness only. The trends in the reaction data could be explained by more defects in the thicker films and/or partial poisoning of the zeolite by mobile support cations in thinner films and/or orientation effects.