Gregor Bruce Yeo Christie

Preparation, surface modification and characterisation of solution cast starch PVA blended films

Several blends have been prepared of polyvinyl alcohol, starch and glycerol. The blend containing 20% polyvinyl alcohol has been modified by application of chitosan to the surface. The blend, and its modified form have been characterised by atomic force microscopy, x-ray diffraction, Fourier transform infra-red spectroscopy, contact angle measurements, 13C-NMR spectroscopy and scanning electron microscopy. The blended films were flexible and homogeneous on a macroscopic scale but on a microscopic scale there seemed to be small patches of individual components. Surface modification altered some of the characteristics of the film. The blends had surface roughness intermediate between that of the pure components. The addition of chitosan made the film more hydrophobic than the unmodified film but slightly less than the starch film. There was no evidence of new bond formation among the individual components. Solution casting reduced the overall crystallinity in the blended films.

Developing biodegradable mulch films from starch-based polymers

This paper examines the development of starch-based plastics for use as biodegradable mulch film. A variety of starch-based polymers are blended with high performance biodegradable polyester polymers in order to determine the applicability of films to be processed on a film blowing line and to perform well in mulch film field trials. The process of material formulation, film blowing processing and scale-up and performance properties are highlighted for a successful material. Insights into future developments of starch-derived biodegradable polymers are given.

Biodegradation by Composting of Surface Modified Starch and PVA Blended Films

Several starch/PVA/glycerol polymer blends were prepared by a solution casting technique and examined for biodegradation by composting over 45 days. Within this time frame, the starch and glycerol components were fully degraded, leaving the PVA component essentially intact. The lowest PVA content film (20%) was selected as a polymer with enough PVA to impart important physical characteristics, but also enough starch to be considered biodegradable. The film characteristics were further improved by surface modification with chitosan. This modification did not interfere with the biodegradation of the starch component. Furthermore, there was slight evidence that PVA biodegradation had been initiated in composted, surface modified starch/PVA blends.

Bacteria immobilised in Gels: Improved methodologies for antifouling and biocontrol applications

A range of bacteria, including the marine bacterium Pseudoalteromonas tunicata which produces antifouling compounds, and Escherichia coli were used to investigate methods for immobilising bacteria in gels. Different types of matrices were screened using the survival of barnacle nauplii as a bioassay. A Dupont® polyvinylalcohol (PVOH) 10% gel was found to be the optimal matrix. This non‐toxic gel remained stable in seawater while allowing for an outflux of active biological compounds from the bacterial cells. The presence of active bacterial cells in the matrix was tested by CTC‐staining, green fluorescent protein (GFP) expressing bacteria and a barnacle larvae bioassay. The Dupont® PVOH 10% gels containing P. tunicata cells were inhibitory against larvae for a period of up to 2 weeks. In further studies using gels containing immobilised bacteria, the E. coli strain C600 was employed based on its cell size, stress resistance and the fact that a plasmid for the expression of GFP could be transferred and maintained in the cells. Immobilised E. Coli cells maintained their viability in the Dupont® PVOH 10% gels for as long as 2 months, and the life‐span of these “biologically active”; gels was increased to more than 2 months by the incorporation of small beads into the gels. The results indicate that bacteria can be immobilised in coatings for periods of time consistent with the needs of some antifouling and antibacterial applications.

Oxidative and immersional heating on low rank coal surfaces

Abstract The low temperature heating of low rank coal was examined by both differential thermal/thermogravimetric analysis (DTA/TGA) and immersional calorimetry. The effect of surface composition was examined by modifying the oxygen-containing functional groups and the exchangeable metal cation contents. It was seen that a smooth decline in the heat of immersion resulted from a reduction in surface polarity. The heat of immersion was related to a generalized expression that demonstrated the relative contributions of exchangeable metal ion, carboxylic acid and phenolic groups. It was found that brown coals produced highly characteristic heat release profiles on DTA/TGA analysis and that the initial lowest temperature peak and the second exothermic peak could be correlated to the cation content. Removal of a large part of the cations in the high cation Morwell coal transformed it into a coal with a low temperature heating profile almost identical to the low cation Loy Yang coal.