Processing window for extrusion foaming of hydroxypropyl methylcellulose

Abstract

Foamed materials are gaining an increased interest due to their good mechanical properties in relation to their low densities and an increased industrial demand can be expected. A few less attractive issues can however be associated with commodity foamed products. For instance the rawmaterial often originates from non-renewable, fossilbased, sources. Furthermore, degradation in nature is slow, therefor the disposed product is burned or end up in landfills. One possibility to reduce the impact on nature could be to produce foams from natural polymers such as starch or cellulose. In this study the possibility to produce foams from hydroxypropyl methylcellulose (HPMC) with water as blowing agent, by continuous extrusion, was investigated. A prestudy using a capillary viscometer, batch-extruder, was conducted to evaluate the foamability of HPMC. Due to promising results further experiments were conducted with a single-screw extruder. The goal was to find an adequate processing window for foaming. It was concluded that HPMC could successfully be foamed by continuous extrusion, although a careful tailoring of the processing parameters was required. Crucial parameters were here the temperature, pressure and residence time distribution in the extruder. Regions of the extruded foams were examined using optical and scanning electron microscopy and HPMC foams with a density in the range of that of fossil-based polymeric foams could be produced.

Chain-Length Shortening of Methyl Ethyl Hydroxyethyl Cellulose: An Evaluation of the Material Properties and Effect on Foaming Ability

“…The measured T g (being mainly between 170 and 180 °C) are also in accordance with previously reported values for similar cellulose derivatives. Sakellariou et al reported T g -values of HPMC in the range of 169-180 °C depending on experimental conditions and technique used [16] and Karlsson et al measured the T g by DMTA to be in the region 160-170 °C, also for HPMCgrades [17].…”

Hot-mould foaming of modified hemicelluloses and hydroxypropyl methylcellulose

“…In addition, methyl cellulose (MC) have been investigated for use in packaging materials [13,14]. It is also known to give foams by using a hot-mould foaming technique [15], as well as by extrusion using water vapour as the blowing agent [16].…”