Bill MacNaughtan

Reduction of enthalpy relaxation in gelatine films by addition of polyols

The aim of this study was to evaluate the effect of plasticisers with different molecular weights (glycerol and sorbitol) on the structural relaxation kinetics of bovine gelatine films stored under the glass transition temperature (Tg). Plasticisers were tested at weight fractions of 0.0, 0.06 and 0.10. Films conditioned in environments under ∼44% relative humidity gave moisture contents (w/w) in the range 0.14-0.18. The enthalpy relaxation (ΔH) was determined using differential scanning calorimetry (DSC). Samples used had Tg values in the range 24-49 °C. After removing the thermal history (30 °C above Tg, 15 min), samples were isothermally stored at 10 °C below Tg for between 2 and 80 h. The addition of plasticisers induced a significant reduction in the rate of structural relaxation. The linearisation of ΔH by plotting against the logarithm of ageing time showed a reduction in the slope of samples plasticised with both polyols. The reduction in relaxation kinetics may be related to the ability of polyols to act as enhancers of molecular packing, as recently reported using positron spectroscopy (PALS). However, a direct correlation between the relaxation kinetics and the plasticisers molecular weight could not be established, suggesting that this phenomenon may be governed by complex molecular gelatin-plasticiser-water interactions.

Effects of tetramethylammonium hydroxide (TMAH) treatment on interfibrillar structure of lyocell (TENCEL) fibres

Abstract Lyocell fibres were treated with tetramethylammonium hydroxide (TMAH) up to 1·5M, which was demonstrated to be more effective than LiOH, NaOH and KOH treatments at the same concentration in the sole interfibrillar swelling region. The porous structure of fibres was studied by inverse size exclusion chromatography to identify mean pore diameter, total pore area and accessible pore volume. The mean pore diameter of fibres was not affected by TMAH treatments, which was analogous to the effects of NaOH treatment. The degree of swelling, carboxyl content using methylene blue sorption method, depth of colour measured after dyeing with C.I. Direct Red 81 and weight loss changed gradually up to 1·5M. Wide angle X-ray diffraction analyses were applied to identify the crystallinity index and crystallite size normal to the 110, 110 and 020 planes. Treatment using TMAH suggests new possibilities for the pretreatment of lyocell fibres owing to the usage of lower concentration to gain comparable results with the conventional NaOH treatment without loss in tensile properties and with less decrease in carboxyl content and weight loss.