Layered silicate nanocomposites based on various high-functionality epoxy resins: The influence of an organoclay on resin cure

The influence of an organically modified clay on the curing behavior of three epoxy systems widely used in the aerospace industry and of different structures and functionalities, was studied. Diglycidyl ether of bisphenol A (DGEBA), triglycidyl p-amino phenol (TGAP) and tetraglycidyl diamino diphenylmethane (TGDDM) were mixed with an octadecyl ammonium ion modified organoclay and cured with diethyltoluene diamine (DETDA). The techniques of dynamic mechanical thermal analysis (DMTA), chemorheology and differential scanning calorimetry (DSC) were applied to investigate gelation and vitrification behavior, as well as catalytic effects of the clay on resin cure. While the formation of layered silicate nanocomposite based on the bifunctional DGEBA resin has been previously investigated to some extent, this paper represents the first detailed study of the cure behavior of different high performance, epoxy nanocomposite systems.

Morphology and properties of thermoplastic polyurethane nancomposites incorporating hydrophilic layered silicates

Hydrophilic layered silicate/polyurethane nanocomposites were prepared via twin screw extrusion and solvent casting. Good dispersion and delamination was achieved-regardless of processing route, illustrating that the need for optimised processing conditions diminishes when there is a strong driving for de for intercalation between the polymer and organosilicate. Evidence for altered polyurethane microphase morphology in the nanocomposites was provided by DMTA and DSC. WAXD results suggested that the appearance of an additional high temperature melting endotherm in some melt-compounded nanocomposites was not due to the formation of a second crystal polymorph, but rather due to more well-ordered hard microdomains. Solvent casting was found to be the preferred processing route due to the avoidance of polyurethane and surfactant degradation associated with melt processing. While tensile strength and elongation were not improved on organosilicate addition, large increases in stiffness were observed. At a 7 wt% organosilicate loading, a 3.2-fold increase in Young's modulus was achieved by solvent casting. The nanocomposites also displayed higher hysteresis and permanent set. (C) 2004 Elsevier Ltd. All rights reserved.

Compatibilization of starch-polyester blends using reactive extrusion

Maleic anhydride (MA) and dicumyl peroxide (DCP) were used as crosslinking agent and initiator respectively for blending starch and a biodegradable synthetic aliphatic polyester using reactive extrusion. Blends were characterized using dynamic mechanical and thermal analysis (DMTA). Optical micrographs of the blends revealed that in the optimized blend, starch was evenly dispersed in the polymer matrix. Optimized blends exhibited better tensile properties than the uncompatibilized blends. Xray photoelectron spectroscopy supported the proposed structure for the starch-polyester complex. Variation in the compositions of crosslinking agent and initiator had an impact on the properties and color of the blends.

Applications of Thermal Mechanical Compression Tests in food powder analysis

A new Thermal Mechanical Compression Test (TMCT) was applied for glass-rubber transition and melting analyses of food powders and crystals. The TMCT technique measures the phase change of a material based on mechanical changes during the transition. Whey, honey, and apple juice powders were analyzed for their glass-rubber transition temperatures. Sucrose and glucose monohydrate crystals were analyzed for their melting temperatures. The results were compared to the values obtained by conventional DSC and TMA techniques. The new TMCT technique provided the results that were very close to the conventional techniques. This technique can be an alternative to analyze glass-rubber transition of food, pharmaceutical, and chemical dry products.