Online monitoring of the thermal degradation of POM during melt extrusion

Abstract

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.

Process monitoring and visualization solutions for hot-melt extrusion: a review

“…Rajan et al [94] monitored the thermal degradation of polyoxymethylene (POM) during extrusion on a corotating twin-screw extruder. The degradation is indicated by the emission of formaldehyde (FA) gas, which was monitored off-line with acetyl acetone colour measurements and by a reduction of viscosity.…”

Enhancement of POM thermooxidation resistance through POSS nanoparticles

“…The weight loss of POM took place in a single step in the temperature ranges of 250-3508C, with an abrupt drop at 2708C (T 5% ). The thermal degradation of POM is basically due to the chain scission of the CÀ ÀOÀ ÀC bonds [6][7][8][9][10].…”

“…Particularly, Polyhedral Oligomeric Silsesquioxanes (POSS) are nanosized cage structures that are generally represented by (RSiO 1.5 ) 8 , and can be easily incorporated into thermoplastics or thermosetting polymers [3,4]. These nanostructured skeletons use silicon atoms with covalent bonds to link to a broad range of organic groups providing different functionality, solubility, polarity, and reactivity depending on the group chosen.…”

“…Whereas there is plenty of literature on thermal degradation and oxidation of polyoxymethylene up to the melting temperature [6][7][8][11][12][13][14][15][16], and a fair deal of attention is being paid currently on POSS nanocomposites [1][2][3][4][5], the degradation characterization of POM/POSS in particular demands thorough analysis and reporting. This article is focused on evaluating and quantifying the degradation development of polyoxymethylene enhanced with four different POSS molten mixtures, being Glycidyl, Glycidy-lIsobutyl, Aminopropylisobutyl, and Poly(ethylene glycol).…”

“…Although POM is an attractive engineering material due to its properties of high stiffness, fatigue endurance, resistance to creep, and low friction coefficient, it has a low thermal resistance even in stabilized copolymers, which leads to quick degradation through random chain scission induced by hydroperoxides (POOH), as well as depolymerization from POOH decomposition [6][7][8][9][10].…”