Marlene Cran

... Doctor of Philosophy December 2004 School of Molecular Sciences Victoria University Page 3. ... David B. Barry. Wayne Laughton, Olga Ki-avaritis, Marlene J. Cran and Stephen W. Bigger, "Properties of Metallocene and Low-Density Polyethylene Blends", presented at 22nd ...

The physicomechanical properties of polymer blend formulations comprising different grades of metallocene-catalyzed linear low-density polyethylenes (mLLDPEs) with high-density polyethylenes (HDPEs) or a low-density polyethylene (LDPE) were investigated. For blends with HDPE, the addition of mLLDPE improves the Izod impact strength and some tensile properties. For blends with LDPE, adding mLLDPE increases the ductility and the percent elongation at break.

ABSTRACT Composites of poly(lactic acid) (PLA) containing up to 40% (w/w) of kenaf fibre and up to 10% (w/w) of thymol were studied to evaluate the mechanical and thermal properties. These composites were compared with control systems containing either no fibre or no thymol and were prepared using melt blending and compression moulding techniques. The composites with 10% (w/w) thymol had the lowest tensile strength with slightly higher flexibility compared with those systems containing lower concentrations of this additive. The tensile properties of composites containing 5% (w/w) thymol demonstrated that the addition of fibre to the PLA/kenaf composites was affected more than the incorporation of the thymol alone. Thermogravimetric analysis of neat PLA and PLA/kenaf composites incorporated with 5% and 10% (w/w) thymol revealed no significant changes in the decomposition temperature. Analysis by differential scanning calorimetry, however, showed a decrease in all of the key thermal transitions with the addition of 5% and 10% (w/w) thymol into the neat PLA and PLA/kenaf composites. The results of the mechanical and thermal properties tests suggest that thymol acts as a plasticizing agent in this composite.

ABSTRACT The migration of antimicrobial (AM) agents carvacrol, thymol and linalool from heat pressed and coated starch-based packaging films into isooctane was investigated and the release of the agents consistently obeyed first-order kinetics. When the test temperature was increased from 15 to 35 degrees C, the diffusion coefficients increased from 6.3 x 10(-13) to 12.9 x 10(-13) m(-2) s(-1) for carvacrol, from 12.0 x 10(-13) to 29.7 x 10(-13) m(-2) s(-1) for thymol and from 9.5 x 10(-13) to 19.0 x 10(-13) m(-2) s(-1) for linalool from the heat pressed starch-based films. The diffusion coefficients of carvacrol, thymol and linalool from coated starch-based films containing increased from 2.2 x 10(-13) to 8.7 x 10(-13) m(-2) s(-1), from 2.7 x 10(-13) to 6.1 x 10(-13) m(-2) s(-1) and from 5.1 x 10(-13) to 9.4 X 10(-13) m(-2) s(-1) respectively between 15 and 35 degrees C. The activation energies for the migration of carvacrol, thymol and linalool from the heat pressed films were 26.2, 33.6 and 25.5 kJ mol(-1) respectively and those for the migration from the coated systems were 31.3, 3.0 and 22.5 kJ mol(-1) respectively. The results suggest that the AM agents show a potential for use as AM packaging materials.

The antimicrobial (AM) activity of starch‐based films coated with linalool, carvacrol or thymol against Saccharomyces cerevisiae in vitro and/or inoculated on the surface of Cheddar cheese was investigated. In solid medium using the agar diffusion method and in experiments ...

ABSTRACT Thermoplastic starch (TPS) films containing relatively low [0.75 ± 0.08% (w/w)], intermediate [1.08 ± 0.04% (w/w)] and high [3.20 ± 0.29% (w/w)] levels of the antimicrobial (AM) agents carvacrol, linalool and thymol were prepared, and their physico-mechanical and optical properties were evaluated. Addition of these AM agents to TPS film reduced the tensile strength with increasing AM agent content, with a significant effect observed at the highest AM agent concentration. The Young's modulus and elongation at break increased with increasing AM agent concentration, especially at the highest formulation concentration of AM agent. Films having a low or intermediate formulation concentration of AM agent exhibited no significant effect on their water vapour permeability, transparency and thermal properties when compared to the control film. Although scanning electron microscope imaging suggested a significant and progressive change in the surface morphologies of the films with AM agent concentration, the overall effects on the tested properties were not significant. This suggests that the direct incorporation of AM agents into TPS films did not adversely affect the films, particularly at lower AM agent concentrations. Copyright © 2013 John Wiley & Sons, Ltd.

ABSTRACT Summary A two-step isothermal annealing (TSIA) procedure is described that enables the endothermic peaks of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and their blends, to be satisfactorily resolved during analysis by differential scanning calorimetry. A modified form of multistep isothermal annealing, the TSIA procedure produces a highly characteristic profile of the blend components by facilitating the segregation of the phases based on branch density. It is proposed that the TSIA procedure may have significant merit in the identification and quantification of the components in an unknown blend as well as increasing the sensitivity in analytical procedures aimed at blend component quantification.

... Author to whom correspondence should be addressed. Email: Stephen.Bigger@vu.edu.au JOURNAL OF PLASTIC FILM & SHEETING, VOL. 22—APRIL 2006 121 8756-0879/06/02 0121–12 $10.00/0 DOI: 10.1177/8756087906064605 ß 2006 SAGE Publications ...

Spices and herbal plant species have been recognized to possess a broad spectrum of active constituents that exhibit antimicrobial (AM) activity. These active compounds are produced as secondary metabolites associated with the volatile essential oil (EO) fraction of these plants. A wide range of AM agents derived from EOs have the potential to be used in AM packaging systems which is one of the promising forms of active packaging systems aimed at protecting food products from microbial contamination. Many studies have evaluated the AM activity of synthetic AM and/or natural AM agents incorporated into packaging materials and have demonstrated effective AM activity by controlling the growth of microorganisms. This review examines the more common synthetic and natural AM agents incorporated into or coated onto synthetic packaging films for AM packaging applications. The focus is on the widely studied herb varieties including basil, oregano, and thyme and their EOs.

This study investigated the antimicrobial (AM) activity of starch-based films coated with linalool, carvacrol, or thymol against Staphylococcus aureus in vitro or inoculated on the surface of Cheddar cheese. In solid media using the agar diffusion method, the inhibitory effect of linalool, carvacrol, or thymol coated onto the films increased significantly (P≤ 0.05) with the increase in concentration of each AM agent. All the coated films effectively inhibited the growth of S. aureus on the surface of Cheddar cheese. The sensitivity of S. aureus to the AM agents tested in the concentration range of the study is in the order of thymol > carvacrol > linalool.

... KEY WORDS: LDPE, LLDPE, metallocene-catalyzed PE, film, blends, physicomechanical properties, downgauging, radar plots. *Author to whom correspondence should be addressed. E-mail: Stephen.Bigger@vu.edu.au JOURNAL OF ELASTOMERS AND PLASTICS Vol. ...

ABSTRACT The mechanical performance of thermoplastic starch (TPS) films and films made of TPS blended with an aliphatic polyester (APTPS) was investigated after exposure to water mixtures of various compositions and different levels of relative humidity (RH). Conditioning of TPS films at various RH levels resulted in a noticeable absorption of moisture, particularly at high RH levels, and their mechanical properties decreased significantly. High magnification imaging of the films revealed the presence of significant microcracking on the surface of the TPS films which could potentially result in the increased water absorption and consequent reduction in mechanical integrity. The APTPS film was free of any visible microscopic defects and was also less susceptible to water ingress. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013