Because of its high stiffness, chemical resistance, and low viscosity, Poly (oxymethylene) (POM) is of high relevance for technical applications. The thermal degradation of POM during processing affects its final properties and decreases the long-term stability. The degradation is indicated by the emission of formaldehyde (FA) gas. The aim of this study is to monitor the thermal degradation of POM online, during the melt extrusion in a co-rotating twin screw extruder (TSE). The effect of the processing conditions on the thermal stabilisation of the POM is observed by FA emission and online viscosity measurements. The effect of processing conditions on the compounding of POM with two different FA scavengers is also studied. Fourier transform infrared (FTIR) spectroscopy is used for the online measurement of FA gas and acetyl acetone colour measurement for the offline characterisation. The online viscosity is measured by passing the melt through a slit die at constant volume flow rate. An enhanced thermal degradation is found with decreasing throughput and increasing screw speed. A good correlation between the online viscosity and offline FA measurement is observed.

When polycarbonate (PC)/poly(acrylonitrile-butadiene-styrene) (ABS) blends are exposed to outdoor conditions, they are mainly degraded by sunlight; this is known as photodegradation. It is the ultraviolet radiation in the sunlight that is responsible for the degradation of the blend. To stabilize the blend against the harmful ultraviolet radiation, ultraviolet absorbers (UVAs) are used. In this study, three different UVAs-Tinuvin 1577 (a hydroxyphenyl triazine type), Cyasorb 5411 (a benzotriazole type), and Uvinul 3030 (a cyanoacrylate type)-were compounded with a PC/ABS blend at 240 C with a twin-screw extruder. Accelerated aging of the compounded sample was done by an Atlas Suntest containing xenon lamp. The degradation studies were performed with ultraviolet-visible spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and yellowing index measurements. The molecular weight of the compounded sample was determined by gel permeation chromatography. It was found that hydroxyphenyl triazine type UVA showed the best results for decreasing the degradation products, oxidation rate, and yellowing of the PC/ABS blend.

Temperature dependence of dye diffusion in poly(ethylene terephthalate) (PET) fibers heat set under slack and taut conditions at various temperatures (in the range 100-240°C) was investigated. The observed temperature dependence of diffusion coefficient was more appropriately represented by the Williams-Landel-Ferry approach rather than the Arrhenius equation. Values of the parameter Bd were determined.

ABSTRACT:The polycarbonate/poly(acrylonitrile butadiene styrene) blends, (PC/ABS), are mainly degraded by sunlight known as photodegradation when exposed to outdoor conditions. It is the ultraviolet (UV) radiation that is responsible for the degradation of the blend. To stabilize against the harmful UV radiation and to scavenge the radical species which arise from UV or thermally induced degradation of the PC or the ABS, UV absorbers, and UV stabilizers are used. In this article three different UV absorbers namely, Tinuvin 1577-hydroxyphenyl triazine type, Cyasorb 5411-benzotriazole type, Uvinul 3030-cyanoacrylate type, and two different UV stabilizers, Tinuvin 765-monomeric hindered amine type, Tinuvin 622-oligomeric hindered amine were compounded in different combinations with PC/ABS blend at 240 C using a twin screw extruder. Accelerated aging of the compounded sample was done by Atlas Suntest apparatus. The photodegradation studies were done using UV-vis, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and Yellowing index measurement. The molecular weight of the compounded sample before aging was determined by gel permeation chromatography (GPC). It was found that samples protected with hydroxyphenyl triazine type UV absorber and oligomeric hindered amine show the best result for decreasing the degradation products, oxidation rate, and yellowing of the PC/ABS blend.