Silarilenos-siloxanos : sintese, correlação estrutura-propriedades e blendas com polimeros organicos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

The development and use of silicon based polymers has been intensified in the last few years, mainly due to the differentiated properties shown by this class of polymers. Particularly, with regards the use of poly(dimethylsiloxane), PDMS, which shows a set of properties not common to organic polymers, such as: high flexibility at low temperatures, chemical inertness, biocompatibility, hydrofobicity and high permeability to gases, has been emphasized. However, this polymer does not show excellent thermal stability. The insertion of rigid groups in the polymer chain can be used to improve this last property, minimizing the occurence of cyclization reactions, responsible for the polymer degradation, affecting, consequently, others properties of these materials. In this work the relationships between structure and properties of a series of polysilarylenes and poly(silarylenes-siloxanes) were studied, specially the effects promoted on the glass transition temperature, on the crystallinity behavior and on the thermal stability of these polymers. The influence of the molecular weight and of the presence of blockade group in the polymer chain, over the properties of these materials, were considered. In addition, the miscibility of some silicon based polymers with PPE or PS was analysed. In these mixtures, the former could act as an impact absorber, due to it low Tg value. The presence of rigid segments in the poly(silarylenes-siloxanes) caused a strong effect in the Tg value, by increasing it in relation to PDMS. Variations in the crystallinity and in the thermal stability of these polymers were also observed. The distribution and sequence of the siloxanes and silarylenes groups, in the polymer chains, and the presence or not of blockade groups, caused marked changes in their properties. In the study of the polymer blends, a tendency for immiscibility was found between the silicon polymer and PS or PPE. However, the morphology of the blends was strongly dependent on the preparation methods of the mixtures.

ASSUNTO(S)

siloxanos polimeros de silicio

ACESSO AO ARTIGO

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