Fabrication And Characterization of Biodegradable Polymer Composites For Packaging Applications

ABSTRACT

Environmental pollution by non-biodegradable plastics, gradual reduction and increase in cost of petroleum products used have affected lives over the years. With people using different kinds of packaging, it has a part of human daily living. Therefore, it is very important to find lasting and sustainable ways of producing and managing the wastes generated by these plastics. In this work, starch based biocomposites are fabricated and characterised to access its opportunities to replace petroleum based plastics. The modifiers that were considered for reinforcement purposes were nanokaolin and cellulose nanofibers extracted from rice husk. Stress strain diagrams were obtained from the tensile test method. From the stress-strain curve, the yield strength, ultimate tensile strength and the fracture strength of the various biocomposites were determined. The material that was shown to give good response to the tensile load in terms of the yield, and fracture was seen to be TPS-0.2kaolin biocomposite. This can be associated to goof interphase reaction between the nanoclay and the starch polymer at nanoclay volume fraction of 0.2. Water vapour transmission test also pointed to biocomposites of cellulose volume fraction 0.5 as the appropriate material with best water vapour barrier properties. This is associated to the reason that at cellulose volume fraction of 0.5, the cellulose whiskers are very compact and dispersed all over the biocomposites and hence restricts the escape of water in the form of gas from the film. This confirms the reason why the strength of the TPS-cellulose biocomposite is higher at volume fraction of 0.5. FTIR analysis was conducted for thermoplastic starch (TPS) only, TPS-nanokaolin biocomposites and TPS-cellulose biocomposites. The spectra for TPS only pointed to the presence of OH-stretching due to the water used during fabrication, CH- bending and some CC bonds. The spectra for TPS-nanokaolin was similar to that of thermoplastic starch, however, there was a new band showing the presence of Si-O-C bonds due to the chemical reaction of v the nanokaolin (alumino-silicate) to the water and starch. The spectra for TPS-cellulose showed the presence of OH- stretching bond, CH-bends, C-C bonds. The FTIR results showed the presence of water and other chemiclas that affect the strength of the biocomposites prepared. This gives an idea of what to expect for the results of the mechanical properties. Scanning Electron Microscope micrographs shows that nanokaolin particles were successfully introduced into the TPS matrix and it was uniformly dispersed in TPS-nanokaolin nanocomposite films at optimum nanokaolin volume fractions. The micrographs for TPScellulose biocomposites showed that cellulose fiber was successfully introduced into the TPS matrix but the fibers were not uniformly distributed. Energy Dispersive X-ray spectroscopy (EDX) also gave the representation of elements present in the TPS-nanokaolin and TPS-cellulose biocomposites. This analysis technique confirmed the presence of Al, Si, O (known to be present in nanokaolin), and C (known to be present in starch and glycerol) in TPS-nanokaolin biocomposites. Also, the presence of O, C, Ca, Si, Na was confirmed in TPS-cellulose biocomposites. With C, O representing the elements in cellulose, Ca and Si known to be elements which are present in rice husk. The Na was recorded as a traces left after the extraction process. Biocomposites prepared from starch, glycerol, and nanokaolin composites are seen to show broad peaks which is known for semi-crystalline materials. However, the degree of crystallinity increases as the volume fraction of nanokaolin increases.