Abstract
Concerns over the persistence of plastics in the environment, this research focuses on the effects of surface modified nanozeolite on polyhydroxybutyrate (PHB) a biodegradable polyester polymer and polypropylene (PP) a non-biodegradable synthetic polymer with a particular interest in the improvement of mechanical, morphological and thermal properties towards packaging products. Surface modified nanozeolite filled PP/PHB composites were prepared in a melt-mixing process and followed by compression molding using hot press machine according to standard test specifications. Nanozeolite was modified through a cationic exchange method using alkyl ammonium ions prior to melt-mixing. The effects of nanozeolite/surface modified nanozeolite loadings of 0.1, 0.25, 0.5, 1.0 wt. % on the properties of 70% PP/ 30% PHB blend composites was studied. Firstly, by characterizing the structure and confirming the functional group on surface modified nanozeolite using x-ray diffraction (XRD), fourier transform infrared radiation spectroscopy-attenuated total reflection (FTIR-ATR). Dynamic mechanical analysis and tensile test were performed to study the mechanical properties of the nanocomposites. Comparative studies on gas barrier properties, biodegradation and antimicrobial activity were conducted. PP/PHB filled with surface modified nanozeolite showed high tensile modulus than unmodified nanocomposites. Thermal properties of all the nanocomposites were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results showed that 0.5wt% surface modified nanozeolites is most thermally stable at 400°C while 1wt% surface modified nanozeolite showed fast decomposition rate. PP/PHB blend showed good thermal stabilities at low and high temperature which means poor processability and low thermal stability of PHB has been enhanced by the better properties of PP. Moreover, the morphological study evaluated using SEM revealed fewer cavities and little agglomeration with modified nanocomposites as compared to unmodified nanocomposites which might be an indication of much improved dispersion of modified nanozeolite in the polymer matrix. Surface modified nanozeolite filled composite exhibited improved oxygen and vapour transmission rate, also surface modified nanozeolite composite showed improved weight lost during biodegradation studies.
M.Sc. (Chemistry)