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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Calcium carbonate (CaCO 3 )/high density polyethylene (HDPE) composites were prepared in a HAAKE twin screw extruder, using the experimental conditions defined by the factorial experimental design presented in a prior study. In this study, the effect of different grades (Ca 1 and Ca 2 ) and CaCO 3 content (varying from 0 to 15 wt %) on the mechanical, rheological, thermal, and morphological properties was evaluated. The results showed that the addition of the filler provoked a decrease on the impact strength, stress at break, and yield stress properties in relation to the pure HDPE. A consequent increase on the modulus of elasticity, indicating an increase on the rigidity of the composite, was observed. It was also verified a tendency to increase the toughness and the viscosity of the composites as CaCO 3 was added. Scanning electron micrographs showed that as the filler was incorporated to HDPE matrix, CaCO 3 particles tended to agglomerate, especially that grade constituted of particles of smaller size. The thermal analysis showed that the addition of mineral filler caused a decrease on the crystallinity degree.