Poly(vinyl chloride) (PVC) is an economical and versatile thermoplastic polymer used in many common consumer products. It is the third most widely used synthetic plastic polymer in the world after polyethylene and polypropylene. However, PVC itself is not a particularly useful substance, which means that its many variants require different additives to acquire certain properties. Essential additives for all PVC materials are stabilizers and lubricants, and in the case of flexible PVC, plasticizers are also incorporated. These additives are mostly based on various metal compounds, which, in excessive concentrations, can have a detrimental effect on the properties of the material, and can also harm the environment. In my master's research, I investigated the origin and importance of metals in PVC and determined their role in the breakdown of the material. I also researched methods for determining metals in PVC and compared them. During the experimental work, I optimized the microwave decomposition of PVC and subsequently determined the metals in 49 samples using ICP-OES. Most of the samples were PVC folders or foils that differed in age, translucency and coloration.
When reviewing the results, I found that the metals aluminum, barium, potassium, magnesium, sodium, tin and zinc appeared most often in the samples. Based on certain mass proportions of metals, I also determined stabilizers for all samples, and I noticed that stabilizers containing zinc appear most often. I then first compared the samples with the results of two standards, and found that the standards contained very few metals. This means that pure PVC does not contain significant metal contents and that most of the metals are added to the material during the industrial process. I then compared the samples in terms of transparency or colouration, according to age and according to the stabilizers present. In addition, I also compared the mass proportions of metals in three toy samples with the limit values set by the Toy Safety Directive. I have found that the colored samples contain more metals than the clear samples due to the added fillers. When comparing older samples with newer ones, it turned out that the newer samples mostly do not contain cadmium and lead, but contain a combination of barium – zinc, which indicates a more frequent use of barium – zinc stabilizers. When comparing the effectiveness of barium – zinc and tin stabilizers, barium – zinc stabilizers proved to be more effective.
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