The biodegradation of the above copolymer (PBSA) by Aspergillus versicolor isolated from compost was studied and its mechanism examined. Analysis of weight loss showed that more than 90% of PBSA film was assimilated within 25 days. There was also a rapid decrease in molec.wt. characterised by GPC. Several cracks and round holes were observed on the eroded film surface by SEM. These results showed the fast degradation of PBSA film in the presence of A.versicolor. For comparison, the hydrolysis of the same sample was much slower in the corresponding abiotic medium. The analyses by PMR and DSC indicated that the preferred degradation took place in the adipate units and that the succinate units were relatively resistant to A.versicolor. 20 refs.

Gelatin was modified using various amounts of stearic acid using different reaction times in aqueous media at 60C and pH 5.5. By casting the modified gelatin solutions, slightly yellow films were formed. It was found that all modified gelatin films had longer drying time, lower TS, lower percentage moisture absorption and better biodegradability than unmodified ones. Their oil resistance was comparable. It was also found that the amount of stearic acid and the reaction time significantly affected these properties. As the amount of stearic acid increased, the films exhibited longer drying time, lower TS and lower moisture absorption. With increasing reaction time, the films exhibited shorter drying time, higher TS and lower moisture absorption. The results suggested that the film prepared from 15% stearic acid-modified gelatin using the reaction time of 8 h had the highest potential for applications in environmentally-friendly packaging. 11 refs.

A high-content starch/LDPE blend with acceptable biodegradation and mechanical properties was produced by adjusting the compatibility of the blend system and processing plasticisation through the compatibiliser and different processing methods. Two types of compatibilisers, maleic anhydride-grafted LDPE after plasma treatment (MA-g-PLDPE) and acrylic acid-grafted LDPE after plasma treatment(AAc-g-PLDPE), were used. MA-g-PLDPE gave better compatibility than AAc-g-PLDPE by the anhydride groups. The plasticisation effect by the oligomer resulted from a different process by mixing the MA-g-PLDPE and/or MA with glycerol before compounding was investigated. As the MA and compatibiliser/LDPE were premixed with glycerol for 30 min, the LDPE particle size of the blends decreased with increasing compatibiliser content. If free MA was not added, the PE blends showed irregular shapes. The weight loss of all the samples was achieved above 65 wt % after two weeks of biodegradation. 17 refs.

Sodium caseinate-based films were prepared by casting from aqueous solutions containing 5% (w/v) protein and different proportions of plasticiser (plasticiser:protein ratios of 25-100 wt%) to give biodegradable films for packaging applications. Glycerol, triethanolamine and other glycols were examined and the effects of plasticiser type and proportion and relative humidity (RH) on the mechanical properties of the films were determined. Enhanced tensile properties were obtained using glycerol or triethanolamine. Increased RH reduced the elastic modulus and the stress at break of the films, whereas the elongation at break increased when RH was increased from 11 to 53%, then decreased at RH 84%. Chemical crosslinking between the free amino groups in the protein and added formaldehyde was also carried out to reduce the solubility of the protein films in water. Crosslinked films prepared with a formaldehyde-free amino group ratio of more than 1.35 improved the mechanical strength, strain at break and Young's modulus. In crosslinked samples, solubility was due to the plasticiser exuding from the film. 27 refs.

The internal plasticisation of cellulose acetate was accomplished by grafting with caprolactone in the presence of a tin bis(2-ethylhexanoate) catalyst to produce biodegradable natural polymers. Reaction proceeded very slowly below 180 degC but at greater temperatures, the degree of grafting increased with temperature and reaction time. The product was washed with toluene to remove unreacted caprolactone and the small amounts of polycaprolactone formed and characterised by SEC, proton NMR, FTIR, colorimetry and dynamic mechanical thermal analysis. The weight loss after toluene extraction was small, indicating that grafting efficiency was high. The average caprolactone chain length was three, confirming that oligomeric side chains were grafted onto cellulose acetate. Although high temperatures and long reaction times were required for good grafting efficiency, they initiated degradation of the product, as evidenced by increased yellowing. Grafting lowered the glass transition temperature. 41 refs.

Blends of caprolactone and lactide with a linear oligocaprolactone were prepared and characterised as a possible biodegradable injectable drug delivery system. The melting characteristics, melt viscosity and degree of crystallinity of the blends were measured, and an in vitro degradation study was performed. Characterisation was undertaken using proton NMR, GPC, light scattering and DSC. 25 refs.

Details are given of the use of a microfabrication method for a controlled release drug delivery system. Microholes were made in a polylactic acid plate and dyes were cast in each well. The wells were sealed with polymers having different biodegradation rates. The polymers were prepared by mixing polylactides with lactide-glycolide copolymers and lactide-caprolactone-glycolide copolymers. Upon polymer degradation the dye was released and detected spectrophotometrically. 8 refs.

Details are given of the preparation of a novel diacid monomer. Copolyanhydrides composed of this monomer and sebacic acid were further prepared by melt copolycondensation and characterised by FTIR, NMR, UV vis spectroscopy, DSC and fluorescence. Microspheres fabricated from the copolymer were visualised using fluorescence microscopy. Biodegradation characteristics were investigated. 31 refs.

Details are given of processing procedures, mechanical properties and a structural analysis of polyhydroxybutyrate fibres and films. Highly ordered structures in mono-filaments and films were revealed by micron-beam or time-resolved X-ray diffraction. The enzymatic degradation and biodegradation of fibres and films are discussed. 47 refs.

Preparation of biodegradable polyurethanes by copolymerisation of polycaprolactone (PCL) or polyethylene glycol (PEG) with glycidol, using thermal polymerisation, is described. Hexamethylene diamine was used as a crosslinking agent. Elastomeric polymers were characterised using Fourier transform infrared and nuclear magnetic resonance spectroscopies, thermogravimetric analysis, dynamic mechanical thermal analysis, hardness, contact angle measurement, saline solution degradability and tensile properties. Mechanical properties of the PCL based polyurethane were better than those of the PEG based polymer, but degradation rates were inferior. 39 refs.

The opportunities for designing polymers and developing polymerisation processes that are safe, prevent pollution and are more efficient in the use of materials and energy are enormous, judging by the breadth of topics discussed several weeks ago at a symposium on green polymer chemistry. Iowa State University described how novel rubbers can be prepared from a renewable feedstock, soybean oil. The approach relies on the catalyst boron trifluoride diethyl etherate to initiate the cationic polymerisation of the oil. Work at Eindhoven University of Technology has shown that microwave irradiation provides a green alternative to conventional heating for the cationic ring-opening polymerisation of 2-oxazoline monomers from soybean oils. The Colorado School of Mines, Golden, presented a paper on a new class of green materials referred to as ecobionanocomposites. The composites consist of polylactic acid, derived from cornstarch, grafted onto cellulosic nanowhisker fillers produced by acid hydrolysis of cellulose.