Analytical Methods For Determination Of Impurity Elements Residue In High Purity Special Engineering Plastics

Aromatic poly(ether ketone)s(PAEKs) constitute an important family of materials that are currently attracting technical interest on their impressive thermal and mechanical properties and chemical resistance. Determination of impurity element residue in PAEK is crucial, since the residue of impurity element in PAEK can weaken the performance of PAEKs and restrain their application in the areas of modern astronavigation and electronics. Conventional approaches for handling samples cannot meet the testing requirements of atomic absorption spectrometry and ion chromatography because PAEK possesses high chemical resistance. Establishing new methods is necessary for determination of impurity element residue in PAEK. Specific contents are as follows:A new method was developed for fast determination of Al residue in PEKK special polymer material by graphite furnace atomic absorption spectrometry(GF-AAS). Instead of high temperature ashing, sample was dissolved in concentrated sulfuric acid and diluted by tetrahydrofuran, then was directly analyzed by GF-AAS. Sample processing methods were studied systematically including dissolving temperature, dissolving time, sample weight and amount of concentrated sulfuric acid. It was found that for 0.2 g of sample weight, a clear sample solution could be obtained by heating at 220℃ with 2ml of concentrated H2SO4 for 4 min, and the obtained solution was ready for the subsequent mixing with tetrahydrofuran for sample dilution or dispersion before analysis. Redesign of the GF-AAS temperature program was also made, on the basis of the recommended program a pre-ashing step was added, which greatly helped increasing the analytical precision when the temperature was set at 400℃ and the total time was set at 40 s. The detection limits(3σ)was 38.5 ng/g, the RSD for six parallel determination of real samples was 2.18%,and the recoveries for spiked tests were 99% and 105%, respectively. In comparison with the traditional high-temperature ashing technique, the established method was more concise, faster and less exposed to contamination during sample preparation.A new built-in non-contact oxygen flask combustion technology, microwave-induced oxygen flask combustion method was further developed in this work. PEEK solid particles could be ignited by carbon fiber under microwave irradiation to generate heat in a completely closed flask. The RSD for all parallel determination of samples was less than 5%. The detection limit was 0.0254 μg/mL, and the recoveries of chlorine in plant standard sample were more than 90%. Compared with conventional oxygen flask combustion method, the ignition structure of this method was simple, easy operated and could avoid pollution, which could handle multiple samples with high efficiency and low combustion system blank background. In addition, the oxygen flask combustion treatment process produced a large number of CO32-, which interfered seriously for the determination of NO3- and SO42-. In this work, suppressor device was used to eliminate carbonate ions. Preliminary results indicated that the influence of CO32- was basically eliminated and there was no interference for determination of NO3-and SO42-.