Full text
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| Author(s): |
Fernanda Miranda Mendes
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT) |
| Defense date: | 2009-10-30 |
| Examining board members: |
Antonio Aprigio da Silva Curvelo;
José Augusto Marcondes Agnelli
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| Advisor: | Antonio Aprigio da Silva Curvelo |
| Abstract | |
The aim of this work was the study of thermoplastic starch (TPS) prepared from potato and its blends with biodegradable polyhydroxyalcanoates as homopolymer - Poly (β-hydroxibutirate) (PHB) and/or copolymer - Poly (β-hydroxybutirate-co-valerate) (PHBV). To reach the objectives of this study, there were developed formulations of TPS, TPS/PHB, TPS/PHBV, TPS/PHBV, TPS/PHB/PHBV and of the polymers themselves. The content of polyhydroxyalcanoates in the mixtures were 25, 50 and 75 %. The TPS and the blends were prepared by physical mixture of the polymers with water and glycerol. The study of starch\'plasticization, performed with 30 % of glycerol, was carried out in an intensive mixer and the determined parameters of the process (160°C, 10 min and 60 rpm ) were effective for the production of the parent thermoplastic starch. The water absorption tests showed that the TPS can present gain of mass up to 37 %. The blends prepared with higher amounts of the polymer (PHB and/or PHBV) presented higher resistance to the absorption of water. Thermogravimetric analysis (TG) of the blends revealed the existence of two mass loss stages, correspondents to the degradation of TPS and the polyesters. Data from calorimetry (DSC) demonstrated that the potato starch present 23.6% of amylose. The traces of DSC from TPS revealed only events related to the elimination of water and glycerol. For the blends two thermal endothermic events were observed. The first one corresponds to the elimination of water and glycerol from TPS and the second to the melting of the PHB and/or PHBV. The analysis performed by using scanning electron microscopy showed the presence of residual grains of starch in the formulations containing 50% or higher amounts of PHB and/or PHBV. The Dynamic Mechanical Thermal Analysis of TPS revealed the occurence of two tan δ peaks, being the first one correspondent to transitions in the glycerol rich phase and a second peak described as Tg of the plasticized starch. The Mechanical Tests showed for the TPS sample the highest value of elongation, the lower value of tensile strength and a low value of Young\'s modulus, when compared to the blends TPS/PHB, TPS/PHBV and TPS/PHB/PHBV. The behaviour of the TPS appeared strongly influenced by the content of water in the samples. (AU) | |
| FAPESP's process: | 07/06406-8 - PREPARATION AND CHARACTERIZATION OF BIOPLASTICS FROM POTATO STARCH |
| Grantee: | Fernanda Miranda Mendes |
| Support Opportunities: | Scholarships in Brazil - Master |