Monitoring the polyamide 11 degradation by thermal properties and X‐ray fluorescence spectrometry allied to chemometric methods

Abstract

The influence of temperature (110 and 120 °C) on the ageing of piping made from polyamide 11 (PA‐11) containing 10–12% of plasticizer was studied using deionized water (pH ≈ 7.0). A clean analytical methodology has been employed for quality control of polymeric materials: energy‐dispersive X‐ray fluorescence spectrometry (ED‐XRF). It provides a fast and suitable technique to characterize chemical elements because of its multielemental capability, good sensitivity, high precision, short analytical time, and nondestructive nature. Herein, the content of additive in PA‐11 was monitored from ED‐XRF measurements where the abundance of the S line is directly related to the ageing time, agreeing with the thermogravimetric analysis. The XRF data were allied to chemometric treatment to classify PA‐11 samples according to the amount of additive and weight average molar mass change, predicting the ageing time, and viscosity values of PA‐11. Therefore, the XRF can be used as a clean analytical methodology to monitor the PA‐11 degradation, thus eliminating the use of toxic organic solvents (necessary to viscosity measurements) and reducing the working time. Also, the effect of hydrolysis on the structure over time and the material morphology were monitored through measurements of dynamic mechanical analysis and differential scanning calorimetry. Copyright © 2012 John Wiley & Sons, Ltd.

Aging of polyamide 11. Part 1: Evaluating degradation by thermal, mechanical, and viscometric analysis

“…Accelerated aging tests were performed in oxygen depleted water at 90°C and 120°C. Contrary to many of the previous publications full evolution of each property up to 10 weeks of aging was reported, which is of particular importance for comparing experiments with degradation model predictions—the second part of our “Aging of Polyamide 11” study …”

“…These two last processes cause structural changes that are not detectable by molecular weight measurements, but may drastically affect the mechanical properties of the polyamide. Some investigations go a step further reporting additional morphological parameters and final properties such as degree of crystallinity, glass transition temperature, modulus, or plasticizer content . None of them however treat all these effects simultaneously and they don't consider additional quantities reported in this work such as density, water uptake, tangential modulus, tensile strength, and damping efficiency.…”

Morphological changes of polyamide 11 through the corrected inherent viscosity plateau

“…However, API 17TR2 16 also defines that this is not the only way to assess the aging of PA11 17 . It has been demonstrated in the literature that in controlled water environments, the CIV decreases exponentially over time and reaches a plateau, where the hydrolysis and the polycondensation reaction rate become equal 1,4,18,19 . The CIV plateau value can be affected by the temperature and pH, decreasing with the increase of the aging temperature and with a more acidic pH 4,18,20 .…”

Aging of polyamide 11. Part 2: General multiscale model of the hydrolytic degradation applied to predict the morphology evolution

“…Sample‐dependent parameters such as initial molecular weight M n 0 and initial degree of crystallinity χ c0 may also, in the first approach, be taken from the literature for a “typical sample” or ideally be obtained experimentally for the studied specimen. This can be done with viscometric and spectrometric measurements for M n 0 or by XRD, DSC, FTIR, and density tests for. χ c0 .…”