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Age-induced changes in the microstructure and selected properties of extruded starch films plasticized with glycerol and stearic acid / Heartwin A. Pushpadass in Industrial & engineering chemistry research, Vol. 48 N° 18 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8457–8463 Titre : Age-induced changes in the microstructure and selected properties of extruded starch films plasticized with glycerol and stearic acid Type de document : texte imprimé Auteurs : Heartwin A. Pushpadass, Auteur ; Milford A. Hanna, Auteur Année de publication : 2010 Article en page(s) : pp. 8457–8463 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Extruded  starch  films  Water  vapor  permeability  Thermoplastic  starch Résumé : Aging of normal corn starch films processed by extrusion and stored at 20−22 °C and 50−56% RH was investigated over a period of 120 d. The changes in the structural, thermal, tensile, and water vapor permeability (WVP) properties of the films during aging were studied. The thermoplastic starch (TPS) just after extrusion processing (≈4 h) was nearly amorphous in character. However, aging above the Tg produced both B- and V-type crystalline structures in the TPS within 3 d of drying. The relative crystalline content of the TPS increased from 2.6 to 17.7%, depending on the glycerol content. Post-processing, the tensile strengths of the films increased by 39.3−134.1% while the tensile strains decreased by 48−81.1%. The rates of change in tensile strength and strain were faster during the first 30 d but stabilized thereafter. The biphasic transitions in the DSC thermograms suggested phase separation in the TPS. The Tg of glycerol-rich domains decreased while those of the starch-rich regions increased during storage. The band-narrowing and changes in peak styles and intensities in the 1400−800 cm−1 region of the Fourier transform infrared spectra suggested increases in the crystalline content of the TPS during aging. The WVP values tended to decrease with time as the crystallinity of starch increased and the free volume in the film network decreased. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801922z [article] Age-induced changes in the microstructure and selected properties of extruded starch films plasticized with glycerol and stearic acid [texte imprimé] / Heartwin A. Pushpadass, Auteur ; Milford A. Hanna, Auteur . - 2010 . - pp. 8457–8463. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8457–8463 Mots-clés : Extruded  starch  films  Water  vapor  permeability  Thermoplastic  starch Résumé : Aging of normal corn starch films processed by extrusion and stored at 20−22 °C and 50−56% RH was investigated over a period of 120 d. The changes in the structural, thermal, tensile, and water vapor permeability (WVP) properties of the films during aging were studied. The thermoplastic starch (TPS) just after extrusion processing (≈4 h) was nearly amorphous in character. However, aging above the Tg produced both B- and V-type crystalline structures in the TPS within 3 d of drying. The relative crystalline content of the TPS increased from 2.6 to 17.7%, depending on the glycerol content. Post-processing, the tensile strengths of the films increased by 39.3−134.1% while the tensile strains decreased by 48−81.1%. The rates of change in tensile strength and strain were faster during the first 30 d but stabilized thereafter. The biphasic transitions in the DSC thermograms suggested phase separation in the TPS. The Tg of glycerol-rich domains decreased while those of the starch-rich regions increased during storage. The band-narrowing and changes in peak styles and intensities in the 1400−800 cm−1 region of the Fourier transform infrared spectra suggested increases in the crystalline content of the TPS during aging. The WVP values tended to decrease with time as the crystallinity of starch increased and the free volume in the film network decreased. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801922z

Expansion, morphological, and mechanical properties of starch-polystyrene foams containing various additives / Heartwin A. Pushpadass in Industrial & engineering chemistry research, Vol. 47 n°14 (Juillet 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°14 (Juillet 2008) . - p. 4736-4742 Titre : Expansion, morphological, and mechanical properties of starch-polystyrene foams containing various additives Type de document : texte imprimé Auteurs : Heartwin A. Pushpadass, Auteur ; Robert W. Besant, Auteur ; Milford A. Hanna, Auteur Année de publication : 2008 Article en page(s) : p. 4736-4742 Note générale : Bibliogr. p. 4742 Langues : Anglais (eng) Mots-clés : Starch−polystyrene  --  expansion;  Azodicarbonamide Résumé : Starch and polystyrene (PS) were mixed at 70:30, 80:20, and 85:15 ratios with 0.5 and 1% talc and extruded into loose-fill packaging foams. Azodicarbonamide (ADC), at 0, 0.2, and 0.4 wt %, and citric acid, at 0, 0.25, and 0.5%, were added as blowing agents to enhance the radial expansion and functional properties of foams. As the concentration of ADC in the starch−PS mixtures was increased from 0 to 0.2%, the expansion ratios increased, and consequently the bulk densities decreased. However, with a further increase in the concentration of ADC to 0.4%, the expansion ratios dropped considerably. The effects of citric acid on radial expansion and other properties were similar to those of ADC. Compared to ADC, citric acid produced foams with higher radial expansion and correspondingly lower densities. Extrudates containing citric acid had large-sized cells, but the cell walls were structurally damaged due to degradation of starch. The spring indices of foams treated with various additives were not significantly different, indicating that spring index may not be a reliable measure of the elasticity. On the other hand, compressibility and modulus of elasticity varied depending on the starch, talc, and blowing agents. Foams extruded with ADC were superior in terms of their cushioning ability and other functional properties. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071049h [article] Expansion, morphological, and mechanical properties of starch-polystyrene foams containing various additives [texte imprimé] / Heartwin A. Pushpadass, Auteur ; Robert W. Besant, Auteur ; Milford A. Hanna, Auteur . - 2008 . - p. 4736-4742. Bibliogr. p. 4742 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°14 (Juillet 2008) . - p. 4736-4742 Mots-clés : Starch−polystyrene  --  expansion;  Azodicarbonamide Résumé : Starch and polystyrene (PS) were mixed at 70:30, 80:20, and 85:15 ratios with 0.5 and 1% talc and extruded into loose-fill packaging foams. Azodicarbonamide (ADC), at 0, 0.2, and 0.4 wt %, and citric acid, at 0, 0.25, and 0.5%, were added as blowing agents to enhance the radial expansion and functional properties of foams. As the concentration of ADC in the starch−PS mixtures was increased from 0 to 0.2%, the expansion ratios increased, and consequently the bulk densities decreased. However, with a further increase in the concentration of ADC to 0.4%, the expansion ratios dropped considerably. The effects of citric acid on radial expansion and other properties were similar to those of ADC. Compared to ADC, citric acid produced foams with higher radial expansion and correspondingly lower densities. Extrudates containing citric acid had large-sized cells, but the cell walls were structurally damaged due to degradation of starch. The spring indices of foams treated with various additives were not significantly different, indicating that spring index may not be a reliable measure of the elasticity. On the other hand, compressibility and modulus of elasticity varied depending on the starch, talc, and blowing agents. Foams extruded with ADC were superior in terms of their cushioning ability and other functional properties. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071049h