Single Filler Research Articles

Space Frames of Variable Geometry

Space frames are generally studied as stable, rigid structures. However, the addition of transformation systems offers a new dimension in theoretical research. In this paper an approach to the transformation of polyhedral and spherical space frames is introduced, resulting in a uniform, rigid ‘impansion’, whereby all the edges are cut into three parts held together by two hinges. Geometrical description reveals a whole new family of such structures, presented here as being made transformable by the simple vertical motion of a central rod, going up and down, and ex/impanding the structure in a uniform symmetric and rigid way. Motorized scale models illustrate the process throughout the paper. Within this family two structures occur of particular interest, since they can be used as single space fillers: the cube and the rhombic dodecahedron. Used as impandable space frame elements, they can fill up a single- or multiple-layer grid, which is impandable and rigid.

Behavior of Unfilled and Filled Rubbers in Shear in the Glass Transition Region

Abstract Rubbers filled with high amounts of a hard inorganic filler still show typical mechanical properties of a high polymer, viz., a glass transition region, a glassy state and a rubbery state. Effects of filler characteristics on the glass transition are discussed, chiefly on the basis of the course of shear modulus at constant frequency as a function of temperature. Effect of volume content of filler on the glass transition of composite materials consists chiefly in a change of the levels of shear modulus in the glassy and in the rubbery state. This change may be described by a simple macroscopic model due to van der Poel. Predictions by this theory could be confirmed for rubbers filled with single filler fractions in the filler size range 30 to 500 µm, and in the range of filler content 0 to 50 vol%. At smaller particle sizes, an effect of filler size was observed, which points to increase in the transition temperature and to increase in the level of modulus in the rubbery state with decreasing filler size. Preparation of composite materials with high filler contents (>55 vol%) is only possible by using a filler with a bimodal size distribution. In this case, moduli depend on filler content and mixing ratio of coarse to fine filler fraction; the van der Poel theory then gives predictions which are too high in comparison with experimental results.

Factors Affecting Tablet Disintegration

A 4 x 4 x 3 x 2 factorial experiment was run to determine the effects of disintegrating agents, lubricants, binders, and hardness on tablet disintegration. A single tablet filler, starch-lactose equal parts, was used. Tablets were found to disintegrate equally rapidly with or without disintegrating agent, thus allowing no comparison between disintegrating agents. Binders, lubricants, and hardness were found to differ in their effects on disintegration, and these factors are discussed. One two-factor interaction was found and shown to be due to a greater effect of hardness on tablets made with gelatin binder.