Dimension Dimensional stability

Driers are used in the forest products industry to lower the moisture content of the wood product being processed. Drying of dimension lumber gives it dimensional stability. This type of drying is done in steam kilns and is a batch process. No appreciable pollutants are released. 

The very low water absorption of bis-phenol A polycarbonates contributes to a high order of dimensional stability. Table 20.6 shows how the water absorption of j in thick samples changes with time and environmental conditions and the consequent influence on dimensions. 

The moisture content of a plastic affects such conditions as electrical insulation resistance, dielectric losses, mechanical properties, dimensions, and appearances. The effect on the properties due to moisture content depends largely on the type of exposure (by immersion in water or by exposure to high humidity), the shape of the product, and the inherent behavior properties of the plastic material. The ultimate proof for tolerance of moisture in a product has to be a product test under extreme conditions of usage in which critical dimensions and needed properties are verified. Plastics with very low water-moisture absorption rates tend to have better dimensional stability. 

By the term particulate composites we are referring to composites reinforced with particles having dimensions of the same order of magnitude. Particulate composites are produced from a polymeric matrix, into which a suitable metal powder has been dispersed, and exhibit highly improved mechanical properties, better electrical and thermal conductivity than either phase, lower thermal expansivity, and improved dimensional stability and behaviour at elevated temperatures. 

Factice has a number of uses in rubber compounds where it can stabilise dimensions of products such as hoses and tubing during the early stages of heating of the vulcanisation cycle. It imparts stability to extruded products, a silkiness to calendered products, gives good dimensional stability and overcomes many of the problems of crows feet and blistering. 

The most common dimensional measurements relate to the size of test pieces because this information is required for virtually all physical test methods. There is also sometimes need to measure dimensions of components of the apparatus, such as the thickness of spacers in compression set tests. Other aspects of dimensional measurement that are relevant to rubber testing include extensometry, surface roughness, dimensional stability and dispersion. 

Generally, vulcanised rubber is dimensionally very stable (unless it is strained), which probably explains the lack of standard test methods for this property. In this context, thermal expansion and swelling in liquids are properties considered in their own right and not normally thought of as being measures of dimensional stability. This is a different situation to that which exists with plastics where a number of dimensional stability tests are in existence. If a measure of dimensional change is required, the appropriate dimensions of a suitable sized test piece can be measured by any of the methods mentioned in this chapter before and after an ageing treatment. 

Dimensional stability of polystyrene resins is excellent, Mold shrinkage is small. The low moisture absorption (about 0.02%) allows fabricated parts to maintain dimensions and strength in humid environments. 

Ultem PEI resins are amber and amorphous, with heat-distortion temperatures similar to polyethersulfone resins. Ultem resins exhibit high modulus and are stiff yet ductile. Light transmission is low. In spite of the high use temperature, they are processible by injection molding, structural foam molding, or extrusion techniques at moderate pressures between 340 and 425°C. They are inherently flame retardant and generate little smoke dimensional stabilities are excellent. Large flat parts such as circuit boards or hard disks for computers can be injection-molded to maintain critical dimensions. 

An unstable periodic orbit is one-dimensional, being of dimension two less than the energy surface in systems with two DOFs. In an n-DOF system the energy surface is of dimension 2n — 1. In such systems, Wiggins showed that the analog of unstable periodic orbits is the so-called normally hyperbolic invariant manifold (NHIM) of dimension 2n — 3 [20,21]. Trajectories slightly displaced from an NHIM can be analyzed using a many-dimensional stability analysis. The... 

Method 1 - Dimensions Method 2 - Apparent density Method 3 - Compression Method 4 - Cross-breaking strength Method 5 - Dimensional stability... 

The taking of tooth impressions to assess wear in vivo has become popular in recent years, as silicone impression materials are available with excellent detail reproduction and good dimensional stability. Several authors [35-38] have reported the use of these materials to capture the dimensions of selected teeth (or teeth surfaces) over a period of time. The silicone impressions are scanned using a profilometry system, typically a laser profilometer, to build an electronic image of the tooth surface. Several scans of the same tooth or surface, taken over a period of time, can then be electronically overlaid and subtracted, to calculate the change in surface contour, or the volume of material removed. This technique can only work if the two scans are precisely overlaid. To avoid... 

These prefabricated I-joists are popular with builders because of their lightweight, dimensional stability, and ease of construction. Their accurate and consistent dimensions, as well as uniform depth, allow the rapid creation of a level floor. Utility lines pass easily through openings in the webs. 

PPE-MA with bis-2-hydroxy ethyl fumaramide, PA, and functionalized ethylene-a-olefin elastomer Dimension commercial blends with high elongation, impact strength, HDT, and dimensional stability Akkapeddi etal., 1988, 1992... 

PEGs have a plasticizing effect on lacquers and some paint-binding media. This effect makes it inadvisable to brush or spray PEG solutions on a painted surface. Even treatment with PEG of unpainted surfaces of the object may endanger paint layers because the PEG may move inside the wood structure and eventually reach the painted surface. Such a one-sided treatment may not be totally satisfactory as dimensional stabilization. Thus, painted objects need another type of dimension-stabilizing agent. 

Dimensional stability - The ability to maintain the molded dimensions after exposure to a broad range of temperatures and environments... 

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