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Master's Dissertation
DOI
10.11606/D.75.2009.tde-11032010-104107
Document
Author
Full name
Fernanda Miranda Mendes
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2009
Supervisor
Committee
Curvelo, Antonio Aprigio da Silva (President)
Plepis, Ana Maria de Guzzi
Agnelli, José Augusto Marcondes
Title in Portuguese
Produção e caracterização de bioplásticos a partir de amido de batata
Keywords in Portuguese
Amido termoplástico
Blendas poliméricas
Poli-hidroxialcanoatos
Abstract in Portuguese
O presente trabalho teve por objetivo estudar o amido termoplástico (TPS) proveniente de batata e suas blendas com os polímeros biodegradáveis da classe dos poli (hidroxialcanoatos), como o homopolímero Poli (β-hidroxibutirato) (PHB) e o copolímero Poli (β-hidroxibutirato-co-valerato) (PHBV). Para tanto, foram desenvolvidas formulações de TPS, TPS/PHB, TPS/PHBV, TPS/PHBV, TPS/PHB/PHBV e dos próprios polímeros. Os teores de poli(hidroxialcanoatos) nas misturas foram iguais a 25, 50 e 75%. O TPS e as blendas foram preparados via mistura física dos polímeros base com água e glicerol. O estudo da plasticização do amido com 30 % de glicerol foi realizado em um misturador intensivo e os parâmetros de processo determinados (160°C, 10 min e 60 rpm) mostraram-se eficientes para a obtenção do termoplástico TPS. Os ensaios de absorção de água revelaram que o TPS pode apresentar ganho de massa de até 37%. As blendas preparadas com maiores teores do polímero (PHB e/ou PHBV) apresentaram maior resistência à absorção de água. A análise termogravimétrica (TG) das blendas revelou a existência de dois estágios de perda de massa, correspondentes à degradação do TPS e aos poliestéres. Dados de calorimetria demonstraram que o amido de batata possui teor de amilose de 23,6%. A curva DSC das blendas foram observados dois eventos térmicos endotérmicos, sendo o primeiro relacionado à saída de água e glicerol do TPS e o segundo correspondente à fusão do PHB e/ou PHBV. A análise por microscopia eletrônica de varredura evidenciou a presença de grãos de amido residuais nas formulações contendo maiores conteúdos de PHB e/ou PHBV. A análise térmica dinâmico-mecânica do TPS revelou a ocorrência de dois picos em tan δ, sendo o primeiro correspondente a transições na fase rica do plasticizante glicerol e um segundo pico definido como Tg do amido plasticizado. Os Ensaios Mecânicos de Tração mostraram para a amostra TPS o maior valor de deformação máxima, menor valor de módulo de elasticidade e baixo valor de tensão máxima, quando comparado às blendas TPS/PHB, TPS/PHBV e TPS/PHB/PHBV. O comportamento do TPS mostrou-se fortemente influenciado pelo teor de água presente na amostra.
Title in English
Production and characterization of bioplastics from potato starch
Keywords in English
Poly-hydroxyalcanoates
Polymer blends
Thermoplastic starch
Abstract in English
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.
 
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Publishing Date
2010-08-17
 
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