O presente trabalho investigou o efeito da adição de baixas concentrações (0,5 e 1,0%) de poli(3-hidroxibutirato) (PHB) na cristalização isotérmica a frio do poli(tereftalato de etileno) (PET). As curvas de energia foram obtidas por calorimetria exploratória diferencial (DSC) e a cinética de cristalização foi analisada pelo método de Avrami. Dois estágios de cristalização foram observados. Os resultados mostraram que o PHB promove alterações na taxa de cristalização do PET, como verificado por mudanças nos tempos para se atingir 1, 10, 30, 50 e 99% de cristalinidade relativa. As energias de ativação para o primeiro e segundo estágios da cristalização foram determinadas através das curvas de Arrhenius, sendo praticamente independentes da presença de PHB nas misturas PET/PHB. As temperaturas de fusão de equilíbrio foram determinadas de acordo com o procedimento de Hoffman e Weeks; as misturas PET/PHB apresentaram valores mais elevados deste parâmetro sugerindo que o PHB altera a estrutura cristalina do PET.

The present work is concerned with the effect of low concentrations (0.5 e 1.0%) of poly(3-hydroxybutirate) (PHB) on the isothermal cold crystallization of poly(ethylene terephthalate) (PET). Energy curves were obtained by differential scanning calorimetry (DSC) and the kinetics of the crystallization was analyzed using Avrami's method. Two crystallization stages were observed. Results showed that the presence of PHB affects the crystallization rate of PET, as verified by changes in the time needed to reach 1, 10, 30, 50 and 99% of crystallinity. Activation energies for the two crystallization stages were computed using Arrhenius plots; PET/PHB mixtures showed slightly smaller values. The equilibrium melting temperatures were estimated according to the procedure of Hoffman and Weeks; the higher values obtained for the PET/PHB mixtures suggest that PHB affects the crystalline structure of PET.

Photodegradation of LDPE/modified starch blends 80/20 m/m has been examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X ray diffraction (DRX) before and after exposure to ultraviolet radiation (UV). Samples were exposed to UV in the laboratory for periods of 6, 24, 48 and 60 hours. The main alteration in the polymeric material after exposure to the radiation was a decrease in the mechanical properties, tensile strength and elongation. There were also changes in the chemical structure of the blend with an increase in the carbonyl and vinyl indices, 65.58 and 53.29%, respectively. The analysis of the blend crystallinity pointed to the formation of a new crystalline symmetry that did not exist before the irradiation.

O crescimento do consumo de plásticos vem gerando grandes problemas ambientais, pois um polímero, uma vez descartado no ambiente, necessita de mais de cem anos para se degradar. O plástico ideal deve apresentar propriedades industriais desejáveis e, ao mesmo tempo ser degradável num período considerado satisfatório. Busca-se desenvolver plásticos com boas propriedades para embalagens e que possam ser biodegradados quando descartados ao ambiente. Neste trabalho avaliamos a biodegradação da blenda do copolímero poli(β-hidroxibutirato-co-valerato), PHB-HV, que é um termoplástico natural, biodegradável e biocompatível, e do amido anfótero, na proporção de 75 e 25% m/m, respectivamente. Os resultados foram obtidos através do teste de Sturm, uma metodologia para a avaliação da biodegradação na presença de uma cultura mista dos fungos Phanerochaete chrysosporium e Talaromyces wortmannii. Os resultados evidenciam a biodegradação da blenda em função do tempo, de acordo com os resultados do teste de Sturm, com o aparecimento de grupos carboxílicos terminais. Foi detectado também o aparecimento de nova simetria cristalina na estrutura polimérica.

The increasing consumption of plastics has generated environmental problems because it takes more than a hundred years for a discarded polymer to degrade. The ideal plastic should present desirable industrial properties and be degradable within a satisfactory time period. Researches is conducted to plastics with good properties for packaging, but that are biodegradable when discarded to the environment. In this work we evaluated the biodegradation of the blend of the copolymer poly(hydroxybutyrate-hydroxyvalerate, PHB-HV, which is a natural, biodegradable and biocompatible thermoplastic, and of the starch amphiprotic, in the proportion of 75 and 25% m/m, respectively. The results were obtained through the Sturm test, a methodology for the evaluation of biodegradation in the presence of a mixed culture of Phanerochaete chrysosporium and Talaromyces wortmannii fungi. The results pointed to biodegradation of the blend as a function of the time, with the appearance of terminal carboxylic groups. In addition, a new crystalline symmetry was observed in the polymeric structure.

This work deals with the biodegradation of blends of poly(beta-hydroxybutyrate)/starch and poly(beta-hydroxybutyrate-co-hydroxyvalerate)/starch. The blends were obtained by evaporation of the solvent in the mixture of the polymers in chloroform. Tests were carried out in presence of micro-organisms which acted as biodegradation agents. The blends were consumed as carbon substrate and the production of CO2 was evaluated in the process. In addition, the polyesters' mechanical properties were reduced by the incorporation of starch in its structure. (¹H) NMR and infrared spectroscopy detected some characteristic polyester degradation groups in the polyesters' chemical structure, thus confirming the alteration suffered by it.

Dentre as diversas técnicas de caracterização superficial de filmes poliméricos, foram utilizadas nos filmes de PET do presente estudo a refratometria, rugosidade, análises de coeficiente de atrito e ângulo de contato. As amostras de filmes de PET analisadas têm 12mim de espessura e compreendem três tipos de estuturas superficiais: filme de homopolímero PET, filme PET com tratamento corona e filme de poli(tereftalato de etileno-co-ciclohexanodimetanol). O filme com tratamento corona apresentou o maior valor de tensão superficial em função da maior parcela dos grupos polares. Resultados de índice de refração indicam que a superfície do filme com copoliéster é menos cristalina que as superfícies dos demais filmes avaliados. A estruturas amorfa e elevado nível de tensão superficial de filmes tratados deverão favorecer a um aumento dos níveis de adesão a tintas e revestimentos.

The current work is concerned with some techniques which allow the characterization of PET film surface, i.e: refractometry, roughness, friction coefficients analysis and contact angle analysis. The samples analysed were homopolymer, corona-treated and a poly(ethylene terephthalate-co-1,4 ciclohexanedimethanol) films. The corona-treated PET film showed higher surface tension value due to the major contribution on the polar groups. The copolyester film structure showed to be much less crystalline than the others, which have been obtained by refractive index measurements. These amorphous structures and the higher tension level of the treated films should provide a better understanding of the adhesion phenomena.