Short Aramid Research Articles

Evaluation of various reinforcements for maxillofacial silicone elastomers.

Various reinforcements have been evaluated according to their effect on the mechanical properties of a silicone elastomer used for the preparation of maxillofacial prosthetic compositions. Emphasis was given to silica reinforcing fillers since fibrillar reinforcements [e.g., short aramid, glass or high modulus polyethylene (UHMPE)] seemed not to improve mechanical properties. An optimal behaviour at filler concentration 35% was determined. As a measure of the crosslinking density, the swelling of specimens immersed in various solvents, at 25 degrees C, was also investigated.

Stress-transfer characteristics in model composites

The stress-transfer characteristics in single fibre polymer-based composites have been investigated. Two distinct classes of specimen geometries were examined involving short-fibre (SFMC) as well as continuous-fibre model composites (CFMC). In all cases, the point-by-point strain in the fibre was measured through the fibre Raman spectrum and its strain dependence. The SFMCs were loaded incrementally to levels of stresses of sufficient magnitude to cause interfacial failure while the fibre strain profiles were monitored closely. The CFMCs were loaded to high enough levels to ensure fibre fracture and then the strain built up in each fragment was carefully mapped. In addition to fibre strain measurements, the interfacial shear stress distribution was derived at each increment of applied strain by means of a balance-of-forces argument. The strain-transfer profiles in the case of short aramid fibre/epoxy SFMCs indicate the presence of two regimes: a perfectly elastic case up to approximately 1.5% of applied s...

Cytotoxic effects of aramid fibres on rat pulmonary macrophages: Comparison with chrysotile asbestos

Aramid fibres have been proposed as a substitute for many asbestos uses. Although dimensional characteristics of aramid fibres vary with the type of application, some of the commercial grades proposed contain fibres whose geometry is clearly in a range where biological reactivities have been reported for other natural or man-made fibres. We wish to report that short aramid fibres, when tested on cultures of rat pulmonary alveolar macrophages (PAMs), induce the commonly recognized signs of a cytotoxic effect, that is: leakage of cytoplasmic and lysosomal marker enzymes, concomittant with a decreased ATP cell content.