No abstract

Photodegradation of PCL was performed exposing injected specimens to ultraviolet radiation (UV-B) up to 9 weeks. Photodegradated PCL specimens were tested by Differential Scanning Calorimetry (DSC), Infrared Spectroscopy (FTIR), mechanical properties, Optical Microscopy (MO) and Scanning Electron Microscopy (SEM).Upon exposure decrease in elongation at break and increase of elastic modulus were verified, higher degree of crystallinity was observed for longer exposure what can be due to the chemi-crystallization mechanism. From IR spectra new carbonyl group (C=O) peaks were observed. Presence of micro cracks on specimens' surface was identified by MO. From morphological analyses is suggested that the photodegradation in PCL takes place by bulk erosion mechanism.

No abstract

No abstract

RESUMOO reômetro de torque é um equipamento que reproduz em escala laboratorial o processamento de polímeros. Neste equipamento, a velocidade de rotação dos rotores, temperatura e tempo de processamento são parâme-tros predeterminados e impostos ao sistema investigado; avalia-se o torque necessário para a fusão, mistura e homogeneização da amostra. Através do gráfico do torque em função do tempo e do gráfico da temperatura em função do tempo de processamento, cujos valores estão relacionados com as propriedades reológicas, estrutura e massa molar das amostras, é possível obter informações sobre o comportamento dos polímeros em fluxo, ou seja, durante o processamento. Neste trabalho, foi investigado o efeito do polietileno graftizado com ácido acrílico (PEgAA) e do polietileno graftizado com anidrido maléico (PEgMA) no biopolietileno (Bio-PE) e no poli(ε-caprolactona) (PCL) por reometria de torque. Foi verificado que o PEgAA e o PEgMA promoveram aumento no torque dos sistemas Bio-PE/PEgAA, Bio-PE/PEgMA, PCL/PEgAA e PCL/PEgMA, possivelmente resultante de interações e/ou reações químicas ocorridas nesses sistemas poliméricos. Espectros de FTIR evidenciaram possíveis interações e/ou reações químicas entre os grupos funcionais dos políme-ros grafitizados e o Bio-PE e o PCL. Valores de torque mais altos foram observados nos sistemas com parâ-metros de solubilidade (δ) mais próximos, corroborando com os cálculos propostos por Hansen. Palavras-chave:Bio-PE, PCL, PEgAA, PEgMA, reometria de torque, parâmetro de solubilidade. ABSTRACTThe torque rheometer is equipment that enables to simulate the polymer processing in a laboratory scale. A set of parameters, i.e., rotor speed, temperature and processing time are predefined and imposed to the compounds under analysis. The necessary torque for melting and mixing the compound is measured. Through the plots of torque as a function of time and temperature, which are linked to the rheological properties, microstructure and molar weight of the samples, it is possible to acquire information regarding the flow behavior of polymers, meaning during processing. In this work, the effect of acrylic acid-grafted polyethylene (PEgAA) and maleic anhydride-grafted polyethylene (PEgMA) in bio-polyethylene (Bio-PE) and in poly(ε-caprolactone) (PCL) was performed by torque rheometry. PEgAA and PEgMA increased the torque rheometry values of the polymeric systems under investigation, i.e, Bio-PE/PEgAA, Bio-PE/PEgMA, PCL/PEgAA and PCL/PEgMA, possibly due to chemical interaction and/or reactions occurred during the processing. FTIR spectra presented possible interactions and/or chemical reactions between the functional groups of grafted polymers and Bio-PE and PCL. Higher torques were observed for the systems with similar solubility parameters agreeing with the mathematical calculations provided by Hansen.