Quantitative Analysis for Polymer Degradation in the Extrusion Process

Abstract

Polymer degradation in the extrusion process decreases quality and productivity. For this reason, it is necessary to prevent polymer degradation. In the extrusion process, polymer degradation is caused by oxidation. It depends on the processing temperature and the amount of dissolved oxygen in the molten polymer. Therefore, a quantitative analysis of these factors is required.As for the degradation characteristics of the material used in this study, temperature and oxygen concentration dependency of the oxidation rate could be quantitatively characterized with an apparatus to evaluate polymer degradation which utilized chemiluminescence generated by an oxidation reaction.Moreover, an online measuring apparatus to analyze dissolved gas in the extruded molten polymer was developed. With this apparatus, the volume ratio of dissolved gases (N 2, O 2 etc.) to the extruded molten polymer could be quantitatively analyzed and the quality of the extruded molten polymer evaluated.With this apparatus, dissolved nitrogen (an index of entrained air) was analyzed with a full-flight screw and a barrier screw. Furthermore, observation of cross sectional views in the screw channel obtained from the cooling experiment under the operating conditions was carried out for the full-flight screw and the barrier screw. With the full-flight screw, break up phenomenon (collapse of solid polymer) occurred in the screw channel and the amount of nitrogen increased. With the barrier screw, the amount of nitrogen decreased because of prevention of the break up phenomenon in the screw channel.Consequently, it is shown that the use of the barrier screw is suitable for oxygen reduction in the molten polymer, which is a factor in causing polymer degradation.

Dissolution, bioactivity and osteogenic properties of composites based on polymer and silicate or borosilicate bioactive glass

“…The decrease in molecular weight could not only be assigned to the processing temperature but also to the presence of the BAG particles [18]. The mechanical properties of the scaffold were also found to decrease drastically over the short immersion time in vitro.…”

Mechanical recycling of polylactide, upgrading trends and combination of valorization techniques

“…The degradation makes physical properties and functional quality of a polymer worse, hence reprocessed products of high confidence are difficult to obtain. In particular, top quality is crucial in the case of thin films, for which optical and barrier properties, among other issues, play an important role [22]. These degradation processes may modify the structure and composition of the polymers and consequently change the thermal, viscoelastic and mechanical performance of the recyclates [21].…”

Relationship between processing method and microstructural and mechanical properties of poly(ethylene terephthalate)/short glass fiber composites

“…Therefore, for the PET/GF composites under study, the barrier melting section of the SSE is believed to increase the residence time in which glass fibers remain in contact with melted PET chains, thus maximizing the glass fiber dispersion and distribution throughout the PET. Moreover, although not measured here, some studies have shown that barrier screws are suitable for oxygen reduction in the molten polymer20 and this could help to minimize the PET degradation during extrusion, which is an additional benefit.…”