tese
Characterization of poly-hydroxybutyrate-hydroxyvalerate (PHB-HV)/corn starch blend films
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UNIVERSIDADE FEDERAL DE LAVRAS
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Programa de Pós-Graduação
DCA - Departamento de Ciência dos Alimentos
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Blendas de polihidroxibutirato-hidroxivalerato (PHB-HV) com amido de milho em diferentes concentrações foram preparadas pelo processo "casting" com clorofórmio. As propriedades mecânica, térmica, morfológica e físico-química das blendas foram investigadas usando as análises de textura, calorimetria diferencial de varredura, espectroscopia no infra-vermelho com transformada de Fourier, difração de raio-X, microscopia ótica, microscopia eletrônica de varredura e colorimetria. As propriedades mecânicas, módulo de elasticidade, resistência à tração, alongamento na ruptura e punctura diminuíram com a adição de amido na blenda. As análises em FTIR indicaram que não houve interação molecular entre os dois polímeros, sendo as blendas imiscíveis. As blendas apresentaram baixa cristalinidade (<4%). Blendas de PHB-HV/ amido de milho obtidas pelo processo "casting" foram imiscíveis; entretanto, os dois componentes da blenda foram miscíveis na fase amorfa. Microscopia ótica dos filmes de PHB-HV/ amido de milho mostraram que as blendas não foram fundidas completamente durante a mistura. As blendas mostraram uma pobre adesão interfacial entre amido de milho e o PHB-HV. Uma dispersão heterogênea dos grânulos de amido na matriz rica em PHB-HV foi verificada nas superfícies dos filmes pela microscopia ótica e microscopia eletrônica de varredura. A diferença de cor e opacidade dos filmes apresentou pequena variação com o aumento do conteúdo de amido na blenda.
Blends of polyhydroxybutyrate-hydroxyvalerate (PHB-HV) with corn starch were prepared by solution casting from chloroform solutions at different compositions. The mechanical, thermal, morphological and physical-chemical properties were investigated using texture analyzer, differential scanning calorimetry, Fourier transform infrared spectrometry, X-ray diffractometry, optical microscopy, scanning electron microscopy and colorimetry. The Young´s Modulus, stress, strain and puncture decreased with increase in starch content in blend with PHB-HV. FTIR measurements indicated that no intermolecular interactions existed between the two polymers as no shift in the absorption peaks of the PHB-HV or starch in the blends was observed which suggests that PHB-HV and starch are immiscible. The blend showed low crystallinity (<4%). PHB-HV/ starch blends obtained by casting process were immiscible; however, the two components were completely miscible in the amorphous phase. Optical micrographs of PHB-HV/ starch blends films did not melt completely during blending. The blends showed a lack of interfacial adhesion between starch and PHB-HV and heterogeneous dispersion of starch granules over PHB-HV-rich matrix, as evidenced by SEM and optical micrographs of the surface. The colour difference and opacity showed small variation with increase of starch content.
Blends of polyhydroxybutyrate-hydroxyvalerate (PHB-HV) with corn starch were prepared by solution casting from chloroform solutions at different compositions. The mechanical, thermal, morphological and physical-chemical properties were investigated using texture analyzer, differential scanning calorimetry, Fourier transform infrared spectrometry, X-ray diffractometry, optical microscopy, scanning electron microscopy and colorimetry. The Young´s Modulus, stress, strain and puncture decreased with increase in starch content in blend with PHB-HV. FTIR measurements indicated that no intermolecular interactions existed between the two polymers as no shift in the absorption peaks of the PHB-HV or starch in the blends was observed which suggests that PHB-HV and starch are immiscible. The blend showed low crystallinity (<4%). PHB-HV/ starch blends obtained by casting process were immiscible; however, the two components were completely miscible in the amorphous phase. Optical micrographs of PHB-HV/ starch blends films did not melt completely during blending. The blends showed a lack of interfacial adhesion between starch and PHB-HV and heterogeneous dispersion of starch granules over PHB-HV-rich matrix, as evidenced by SEM and optical micrographs of the surface. The colour difference and opacity showed small variation with increase of starch content.
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REIS, K. C. dos. Caracterização de filmes de blenda de polihidroxibutirato-hidroxivalerato (PHB-HV)/amido de milho. 2007. 57 p. Tese (Doutorado em Ciência dos Alimentos)-Universidade Federal de Lavras, Lavras, 2007.