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Fibers & Textiles

PHB properties for By: Pavan Kumar Manvi, Mustafa Salih Korkmaz Gunnar Seide, Thomas Gries Institut fĂźr Textiltechnik, RWTH Aachen Aachen, Germany

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HAs are polyesters produced by the bacterial fermentation of sugar or lipids. PHB is one of the well-known members of the PHA family with the largest volume in the market compared to other PHAs. However, the market demand for biopolymers like PHB is strongly influenced by factors such as a limitation of processing possibilities and the possibility to adopt the PHB for textile-based applications. There is, therefore, a definite need for further research to improve the processing technologies. One significant aspect is the thermal instability of PHB, which has a negative impact on melt processing as well as on the end product properties. PHB is characterized by a very large spherulite size, which is generally the result of a high level of purity and presence of very low number of nuclei. The low glass transition temperature of PHB results in post crystallization of PHB and large spherulites are formed. [1] The biggest problem in the processing of PHB is the low degradation temperature with regards to its melting temperature.

Thermal degradation of PHB The thermal degradation of PHB is characterized by nonradical random chain scission reactions in a six member ring ester decomposition process. The mechanism of degradation is explained in the Fig 1. The PHB molecule consists of a ring structure with three resonance positions, as shown in the figure. At elevated temperatures this resonance becomes stronger and results in the breakage of a chemical bond. This in turn results in the gradual decrease in the molecular weight. The thermal degradation of the PHB takes place above 200 °C, which is not far from melting temperature (178°C). [2]

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One way of improving the melt processability of PHB is to add a thermal stabilizer to enhance its thermal properties. In this study various concentrations of thermal stabilizer are added to analyze the thermal stability through melting and crystallization behaviour of the polymer.

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Fig. 1: Mechanism of thermal degradation of PHB

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bioplastics MAGAZINE [05/13] Vol. 8

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Experimental PHBs (Biomer P209) from the company BIOMER GmbH (Krailing) were mixed with a thermal stabilizer mechanically, in various fractions from 0.1 % to 2.0 % These samples were tested for their thermal properties with the help of Differential Scanning Calorimetry (DSC). For heating/ cooling cycle measurements, the following thermal procedure

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bioplastics MAGAZINE is the only independent trade magazine worldwide dedicated to bioplastics (i.e. plastics made from renewable resources...

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bioplastics MAGAZINE is the only independent trade magazine worldwide dedicated to bioplastics (i.e. plastics made from renewable resources...

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