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The influence of temperature and pH on the ageing of piping made from polyamide 11 (PA-11) was studied using water from an oilfield (pH ¼ 5.5) and deionized water (pH ¼ 7.0) with monitoring by corrected inherent viscosity (CIV) measurements. The hydrolytic degradation was more extensive at high temperatures in oilfield water. When the system reaches equilibrium, the pH affects mainly the CIV plateau values. Thermogravimetry, energydispersive X-ray spectroscopy, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy measurements were also used to investigate aspects involved in the ageing PA-11. The hydrolytic degradation of PA-11 leads to formation of low molar mass compounds, such as oligomers dispersed in the polymeric matrix. This is a process that occurs preferentially in the amorphous domain of PA-11, which leads to an increase in the degree of crystallinity and the formation of a new c-phase.

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ResumoForam investigadas as propriedades térmicas e mecânicas de compósitos de polipropileno reciclado e virgem, reforçados com até 40% em peso de fibras de celulose (FC), bem como a morfologia da matriz polimérica. Para a obtenção dos dados, foram utilizadas as técnicas de Análise Témica Dinâmico-Mecânica (DMTA), Calorimetria Exploratória Diferencial (DSC) e Microscopia Eletrônica de Varredura (MEV). Os resultados mostraram que os compósitos de polipropileno reciclado,com percentagem de 30% FC e os compósitos de polipropileno virgem, com percentagem de 20% FC, tiveram um aumento significativo nos valores de módulo de armazenamento (E') e grau de cristalinidade (χ c ), indicando com isso uma resistência mecânica mais elevada. Já nas amostras com 40% FC, houve uma diminuição na rigidez do material. Estes resultados foram confirmados por MEV, onde observou-se a aglomeração das fibras de celulose na matriz. Não houve alteração nas temperaturas de transição vítrea (T g ) e fusão cristalina (T m ) dos compósitos produzidos. Palavras-chave: compósitos de polipropileno, fibras de celulose, compósitos pós-consumo. AbstractThe thermal and mechanical properties of composite recycled and virgin of polypropylene were investigated, reinforced with up to 40% by weight of cellulose fibers (FC), as well as the morphology of the polymer matrix. To obtain the data, techniques for Dynamic-Mechanical Thermal Analysis (DMTA) were used, Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The results showed that recycled polypropylene composites with a percentage of 30% FC and virgin polypropylene composites with a percentage of 20% FC had a significant increase in storage modulus values (E') and degree of crystallinity (χc), indicating a higher mechanical strength in these composites. Since the samples with 40% FC, there was a decrease in the stiffness of the material. These results were confirmed by the SEM, where noted agglomeration of the cellulose fibers in the matrix. There was no change in the glass transition temperature (Tg) and crystalline melting temperature (Tm) of the produced composite.

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