Ageing of polyamide 11 used in the manufacture of flexible piping

Abstract

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.

Structural and Thermo-mechanical Evaluation of Two Engineering Thermoplastic Polymers in Contact with Ethanol Fuel from Sugarcane

“…It can be noted that the first weight loss step of the unaged PA-11 occurred at approximately 232 °C with a 6.7% mass loss. Based on the literature 25,40,41 , this decomposition temperature is compatible with the N-butyl-benzenesulfonamide (BBSA) plasticizer usually found in the composition of the PA-11. After the ageing in ethanol at 60 °C, the peaks decomposition temperature of the supposed plasticizer decreases to 182 °C (mass loss of 3.5% after 1 month in anhydrous ethanol), 189 °C (mass loss of 5.8% after 1 month in hydrated ethanol), 192 °C (mass loss of 5.3% after 3 months in anhydrous ethanol) and 189 °C (mass loss of 2.9% after 3 months in hydrated ethanol).…”

“…The choice of the PA-11 at comparison to PEEK was made purposely because of its known and related loss of chemical resistance in environments such as pure water 23,24 or oilfield water 25 , under the effect of temperature. In addition, some samples were aged for the same time at 60 °C (annealing with no ethanol), whereas others were aged in ethanol at room temperature (23 °C) for comparison.…”

“…Unaged PA-11 presented a low crystallinity value (approximately 16%, as measured by DSC) ( Table 1), which is related to the presence of plasticizers in its polymer chain and the employed processing technique (compression molding) 23,25 . In the unaged condition, the complete fusion of the PA-11 occurred at T m = 180.8 °C.…”

“…Because the grade of PA-11 used in the present study contains plasticizers 23,25 , two simultaneous processes with different kinetics seem to be operating during ageing, the removal of the plasticizer to the environment and anhydrous and hydrated ethanol absorption by the polymer. The removal of the plasticizer was confirmed by thermogravimetric analyses, shown below, and the absorption of fluid was confirmed by a volume variation evaluation (see subsection 3.4).…”

Mechanical properties of polyamide 12 after exposed to biodiesel

“…PA12 is the most non-metallic material used for automotive fuel hoses systems due to its relative low cost and good mechanical properties [2]. Some works have been done to characterize the behavior of the PA12 and PA11 immersed in gasoline, ethanol, gasoline containing different concentrations of ethanol and petroleum [3][4][5][6]. Nevertheless, no studies have been conducted to evaluate the mechanical behavior of PA12 when immersed in pure biodiesel.…”