Altered Thermal and Mechanical Properties of Spruce Galactoglucomannan Films Modified with an Etherification Reaction.

Native hemicellulose lacks many of the properties that make fossil fuel-based polymers excellent for use in today's industrial products and processes. The mechanical and thermal properties of the hemicellulose can, however, be modified, and its processability increased. We functionalized galactoglucomannan to lower its glass transition temperature (Tg) and thereby increase its processability. The functionalization was achieved through an etherification reaction with butyl glycidyl ether used at three molar ratios. Films were produced, and their mechanical and thermal properties were evaluated. Thermogravimetric analysis showed that increased substitution increased the degradation temperature and decreased the water content in the sample, implying increased hydrophobicity upon modification. Dynamic mechanical analysis indicated that butyl glycidyl ether functionalization alters the thermal properties of the modified films both in the absolute values of Tg and in the strength of the films. The etherification reaction resulted in a more ductile material than the unmodified galactoglucomannan (GGM).

Microcellular foaming of arabinoxylan and PEGylated arabinoxylan with supercritical CO2.

In this study, arabinoxylan extracted from barley husks was reacted with polyethylene glycol (PEG) of various molecular weights to introduce an internal plasticizer into the polymer matrix. A successful PEGylation reaction was identified using FTIR and elemental analysis. Thermal and mechanical properties were studied using dynamic mechanical analysis, which revealed that the attachment of PEG chains reduced the glass transition temperature by up to 25°C. Foaming experiments were conducted under different test conditions in a batch foaming process with supercritical CO2 in a thermoregulated and pressurized cylinder. The foams were evaluated using SEM by studying the morphology of the samples foamed at different temperatures. The unmodified arabinoxylan sample was found to produce the best foam morphology, though the PEGylated samples could be produced at lower temperatures than could the unmodified arabinoxylan. This was interpreted as due to the decrease in the glass transition temperature.

New insights on the influence of manufacturing conditions and molecular weight on phase-separated films intended for controlled release.

The aim of this work was to investigate how manufacturing conditions influence phase-separated films of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC) with different molecular weights of HPC. Two HPC grades, SSL and M, with weight average molecular weights (Mw) of 30×103g/mol and 365×103g/mol, respectively, were combined with EC 10 cps (70:30w/w EC/HPC) and spray-coated from ethanol solutions onto a rotating drum under well-controlled process conditions. Generally, a low spray rate resulted in a more rapid film drying process and, consequently, in smaller HPC-rich domains in the phase-separated film structure. For EC/HPC films with the low Mw HPC (SSL) the most rapid drying process resulted in a shift from a HPC-discontinuous to a partly bicontinuous structure and an increase in the permeability for water. In contrast, films containing the high Mw HPC (M) all showed bicontinuous structures, which resulted in overall higher water permeabilities and polymer release compared to the low Mw films. Interestingly, a maximum in permeability was observed for the high Mw films at intermediate spray rates. Below this spray rate the permeability decreased due to a lower amount of polymer released and at higher spray rates, the permeability decreased due to a loss of pore connectivity (or increased tortuosity). To conclude, this study shows that different Mw systems of EC/HPC can respond differently to variations in manufacturing conditions.