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Liu H.,Center for Polymers from Renewable Resources | Yu L.,Center for Polymers from Renewable Resources | Yu L.,CSIRO | Chen L.,Center for Polymers from Renewable Resources
Starch/Staerke | Year: 2010

The retrogradation process of the biphasic endotherms Gr and M1r for waxy cornstarch was systematically investigated using differential scanning calorimetry (DSC). The high temperature endotherm M1r developed significantly within 2-5 h, while the retrograded endotherm Gr appeared after 5 h storage and increased with time. The single endotherm Gr was separated using an analytical software, and the enthalpy was found to be ∼36% of the total enthalpy of the retrograded starch. Compared to normal cornstarch (∼77% amylopectin content), the final retrogradation ratio of the waxy cornstarch was higher. Both the waxy and normal cornstarches investigated showed a similar pattern of retrogradation process, which developed quickly in the initial stage (up to 1 day) and then gradually came to a near-constant value in the second stage (from 1 to 20 days). © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Liu X.,Center for Polymers from Renewable Resources | Ma H.,Center for Polymers from Renewable Resources | Yu L.,Center for Polymers from Renewable Resources | Yu L.,CSIRO | And 2 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2014

Thermal oxidation degradation of high-amylose (80 %) cornstarch has been studied using thermogravimetry analyser coupled to Fourier transform infrared spectroscopy (TG-FTIR). The linear structure of amylose provides a modal material to understand how the starch microstructure affects on the decomposition mechanisms. Kinetics of the thermal oxidation has been studied using different methods. It is found that the thermal oxidation degradation is more complex than thermal degradation, thermal oxidation degradation kinetics of the starch can be interpreted in terms of multi-step degradation mechanism, the activation energies obtain from Flynn-Wall-Ozawa (F-W-O) method and modified Coats-Redfern method are in good agreement. TG-FTIR and FTIR results confirm that the thermal oxidation mechanism of starch is a process containing long chain scission and glowing combustion. © 2013 Akadémiai Kiadó, Budapest, Hungary. Source

Liu X.,Center for Polymers from Renewable Resources | Wang Y.,Center for Polymers from Renewable Resources | Yu L.,Center for Polymers from Renewable Resources | Yu L.,CSIRO | And 3 more authors.
Starch/Staerke | Year: 2013

The objectives of this paper are to review the thermal degradation and stability of starch and starch-based materials, including both fundamental sciences such as detecting techniques, the effect of amylose/amylopectin content in starches and starches modifications, as well as the effect of different processing environments, such as an open or sealed system, and shearless or shear stress conditions. The decomposition temperature of starches was increased with increasing amylopectin content in an open system. In the open system, the initial water content did not affect the decomposition temperature because all water had evaporated from samples prior to reaching the decomposition temperature. Two decomposition temperatures were observed in the sealed system: the first at lower temperature represents long chain scission; and the second at higher temperature involves decomposition of glucose ring. In the sealed system, the first degradation was increased with increasing amylopectin content. There is no observable difference of the second degradation for the samples containing different amylose/amylopectin ratios. The higher the moisture content is, the lower the second decomposition temperature is detected in the sealed system. Significant shear degradation was observed in amylopectin component of starch, while high amylose starch proved less sensitive to shear stress. The achievements in this area have increased the knowledge of polymer science, in particular to understand the degradation of natural polymers. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Liu X.,Center for Polymers from Renewable Resources | Liu X.,CSIRO | Liu X.,Monash University | Khor S.,CSIRO | And 6 more authors.
Thermochimica Acta | Year: 2010

From a commercial viewpoint, the two most promising methods of producing biodegradable polymer materials are: (i) to blend poly(lactic acid) (PLA) with starch and (ii) to reinforce it with cellulose fibres, since both additives are commercially available and are derived from renewable resources. This paper reports on a study of the effects of starch and wood flour (WF) on the thermal stability of PLA using thermogravimetric analysis (TGA) in a nitrogen atmosphere, and TG-FTIR to investigate the effects of degraded products from the two fillers on the thermal degradation of PLA. Both fillers accelerated decomposition by releasing chemicals, in particular those with polar groups that can act as chain scissors in PLA. The lower decomposition temperature of the starch resulted in lower decomposition temperatures for PLA/starch blends compared to PLA/WF composites. In addition, the smaller particle size of the starch compared to the WF, facilitated greater interfacial contact with the PLA matrix, thus enhancing its function in accelerating decomposition. © 2010 Elsevier B.V. Source

Petinakis E.,CSIRO | Petinakis E.,Monash University | Liu X.,CSIRO | Liu X.,Monash University | And 8 more authors.
Polymer Degradation and Stability | Year: 2010

The effect of hydrophilic fillers (starch and wood-flour) on the degradation and decomposition of poly(lactic acid) (PLA) based materials was investigated. Biodegradation was evaluated by composting under controlled conditions in accordance with AS ISO 14855. Thermal decomposition was studied by thermogravimetry (TGA). Morphological variations during biodegradation were investigated by SEM examination. It was found that biodegradation rates of PLA/starch blends and PLA/wood-flour composites were lower than that of pure cellulose but higher than that of pure PLA. The biodegradation rate was increased from about 60% to 80% when the starch content was increased from 10% to 40% after 80 days. Both starch and wood-flour accelerated thermal decomposition of PLA, and starch exhibited a relatively stronger affect then wood-flour. The decomposition temperature of PLA was decreased about 40 °C when the filler content was increased to 40%. Small polar molecules released during thermal decomposition of starch and wood-flour were attributed to the thermal decomposition behaviours of the PLA based blends and composites and their role is further discussed in this paper. © 2010 Elsevier Ltd. All rights reserved. Source

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