RESUMO
Nanocomposite films of thermoplastic corn starch (TPS) with talc particles were obtained by thermo-compression in order to study the effect of filler on structure, optical, and thermal properties. Talc increased the films rigid phase, thus their cross-sections resulted more irregular. Talc preferential orientation within matrix and good compatibility between particles and TPS was observed by SEM. Slight crystalline structure changes in TPS matrix were measured by XRD and DSC, due to talc nucleating effect. Randomly dispersed talc nanoagglomerates and individual platelets were assessed by TEM. Laminar morphology and nano-sized particles allowed that nanocomposite films were optically transparent. TPS-talc films resulted heterogeneous materials, presenting domains rich in glycerol and others rich in starch. Talc incorporation higher than 3%, w/w increased softening resistance of the nanocomposites as stated by DMA. Relaxation temperatures of glycerol-rich phase shifted to higher values since talc reduces the mobility of starch chains.
Assuntos
Nanopartículas/química , Amido/química , Talco/química , Cristalização , Glicerol/química , Plásticos/síntese química , Plásticos/químicaRESUMO
In this work, the influence of processing methods on the properties of starch/gelatin films plasticized with glycerol and sorbitol is reported. Four different processing techniques: casting; pressing; pressing followed by blowing and extrusion followed by blowing were evaluated. Bioplastics prepared by casting were homogeneous and transparent with lower opacity and water vapor permeability (WVP) values when compared to films prepared by other techniques. Among the cast films studied, those with 3% lipophilic starch, in 1:1 proportions and plasticized with sorbitol, showed lower WVP values and higher tensile strength (TS). Films obtained by pressing and blowing showed little expansion during blow, had cracks in the surface, low TS and higher WVP. These films were the only samples to show crystallinity as determined by thermal analysis and X-ray diffraction. In conclusion, different processing techniques have significantly affected the properties of these films.
Assuntos
Gelatina/química , Amido/química , Glicerol/química , Teste de Materiais/métodos , Permeabilidade , Plásticos/síntese química , Plásticos/química , Solubilidade , Sorbitol/químicaRESUMO
Different Andean crops were used to obtain starches not previously reported in literature as raw material for the production of biodegradable polymers. The twelve starches obtained were used to prepare biodegradable films by casting. Water and glycerol were used as plasticizers. The mechanical properties of the starch based films were assessed by means of tensile tests. Compost tests and FTIR tests were carried out to assess biodegradability of films. The results show that the mechanical properties (UTS, Young's modulus and elongation at break) of starch based films strongly depend on the starch source used for their production. We found that all the starch films prepared biodegrade following a three stage process and that the weight loss rate of all the starch based films tested was higher than the weight loss rate of the cellulose film used as control.
Assuntos
Produtos Agrícolas/química , Plásticos/síntese química , Amido/isolamento & purificação , Biodegradação Ambiental , Teste de Materiais , Peru , Plásticos/química , Espectroscopia de Infravermelho com Transformada de Fourier , Amido/química , Resistência à TraçãoRESUMO
Mediante la selección de 8 compuestos plásticos utilizados en el mercado, adquiridos a la firma Aldrich Química SRL (Alemania), se valoró su capacidad de ser asimiladas como única fuente de carbono in vitro, por 2 grupos de microhongos pertenecientes a los asco-deuteromycetes. Estos compuestos fueron: poliestireno, polivinilacetato, poliacrilonitrito, policaprolactona, polimetacrilato de metilo, polivinilcloruro, acetato de celulosa y polietileno. Solo la policaprolactona y el polivinilacetato fueron utilizados por los 2 grupos de hongos en estudio, en especial por cepas de aspergillus, chaetomiun, cladosporium, fusarium, penicillium y scopulariopsis. La policaprolactona fue el polímero más utilizado entre ph 6.5 a 8. Las diferentes especies pertenecientes a los géneros aspergillus y fusarium, presentaron la mayor actividad en la utilización de estos compusetos
Assuntos
Aspergillus/patogenicidade , Biodegradação Ambiental , Chaetomium/patogenicidade , Cladosporium/patogenicidade , Fungos/patogenicidade , Fusarium/patogenicidade , Técnicas In Vitro , Fungos Mitospóricos/patogenicidade , Penicillium/patogenicidade , Plásticos/síntese químicaRESUMO
La conservabilidad de la solución de ácido ascórbico a temperaturas elevadas y a temperatura ambiental, brindada por los diferentes tipos de envases evaluados, ha sido del orden siguiente: II>PVC>I>PE, en tanto que frente a la radiación luminoso artificial fue: PVC>II>I>PE. El efecto producido por la radiación luminosa artificial, sobre las muestras, fue cercano al ocasionado a temperaturas de 30 `C y 50 `C en los envases de polietileno. La solución envasada. en los cuatro tipos de envases, no evidenció alteración significativo en PH, ni peso específico. El envase de polietileno, fue el menos apropiado por ser el menos resistente a la radiación luminosa artificial y permitir una rápida degradación de la solución de la solución de ácido ascórbico, en tanto que el envase de cloruro de polivinilo demostró ser el más apropiado para conservar la fórmula evaluada.