The Effect of the Method of Transport to the Processing of PVC Granules

The paper is focused on an investigation of the cause of different processing behaviors of the PVC granules of one batch delivered by different transport modes (air, shipping). While airborne transported granules (delivery time approximately 14 days) did not show any production problems, the surface of the final cables produced from granules transported by shipping (delivery time approximately 2 months) contains in some cases a surface defect in the form of swelling. Both samples of granules were analyzed using methods of structural analysis to investigate mutual differences between samples. Simultaneous Thermal Analysis (STA), Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR) were used for the samples comparison. As an additional test, analysis of dissolved gases evolved during thermal decomposition of the sample from shipping transport was recorded. Results of the performed analyses showed different behavior of tested samples. Typical decomposition behavior of PVC corresponds especially to air transport granules while the sample transported by shipping contained an additional weight reduction at around 200 °C. The composition of evolved gases at this temperature contains only water and carbon dioxide, which are probably the decomposition products of hydrotalcite contained in the sample of PVC granule, whose structure could contain up to 12 % of the water of crystallization. The obtained results demonstrated that probable cause of the different processing behavior of samples represents the higher content of the water of crystallization in granules transported by shipping.