Dimensional stability INDEX

To be successful, molded optical elements of plastics must be produced with careful control of the fabricating process. In the case of these optical products it is particularly important that the molding conditions be carefully controlled to minimize molded-in stress. In addition to these stresses reducing the dimensional stability of the products leading to distorted images, the stresses themselves affect the quality of the image. This is a result of the fact that the stresses/strained areas have a different refractive index from that of the... 

This method, however, did not result in improved flame retardance because the isocyanurate content was too low. In recent years, however, high-functionality and low-viscosity polyether polyols have become available, and therefore the above method has become less important. Even so, the method was sometimes used to make foams having increased crosslink density to improve dimensional stability or chemical resistance. Therefore, a higher isocyanate index, e.g., 150 to 200, was used to incorporate isocyanurate linkages in rigid urethane foams. 

Optical characteristics of plastics include color, clarity, general appearance, and more directly measurable properties, such as index of refraction [29]. For optical applications, however, other properties, including dimensional stability, scratch resistance, temperature limitation, weatherability, and water absorption, must be considered. 

Chem. Descrip. Calcium carbonate CAS 471-34-1 EINECS/ELINCS 207439-9 Uses Filler for plastics, PVC, polyolefins, polyesters, BMC/SMC, paint, caulks, sealants, adhesives, paper, foam urethane, modified acrylics, filled thermosets/thermoplastics, and rubber Features Improves impact str., dimensional stability Regulatory NSF approved for potable water materials Properties Wh. powd. 2 avg. particle diam. 99.9% finer than 8 0.15% sol. in water sp.gr. 2.70-2.71 dens. 22.57 Ib/gal bulk dens. 38 Ib/tP (loose) oil absorp. 23 01 cc/100 g brightness (Hunter) 95 ref. index 1.6 pH 9.5 (sat.) hardness (Mohs) 3.0 Toxicobgy Nontoxic Camel-TEX [IMERYS]... 

Other parameters requiring consideration in polymer design are wettability, dimensional stability and refractive index. The enhancement of oxygen permeability in siloxane lens systems is associated with high relative proportions of silicon-oxygen and silicon-carbon bonds. These long bonds lead to a free volume element which in the case of polydimethylsiloxane is 5-6 times greater than that for polymethacrylates [3]. 

Max. continuous temperature of use Coefficient of linear thermal expansion Thermal conductivity Oxygen Index Electrical volume resistivity Processing Mold shrinkage Drying temperature Drying time Mold temperature Melt temperature Dimensional stability Trade names... 

Polymethyl methacrylate (PMMA) is a typical transparent amorphous polymer. It has been widely used as an important material in optical devices. It has several advantages, including good flexibility, high strength and excellent dimensional stability however, it suffers from shortcomings such as poor heat resistance, a weak mechanical surface and low refractive index [41, 42]. 

As the number of C atoms increases (higher index numbers), the water absorption capability falls rapidly (increased dimensional stability). Strength and rigidity show a slight tendency to fall. The price rises. (PA 12 is twice as expensive as PA 6). 

Features Rec. in specialty appiics. where readily swellable materials such as soft rubber have poor dimensional stability in contact with other lubricants Properties Vise, liq. sp.gr. 0.96 vise. 150-300 cSt ref. index 1.4061 Hazardous Decomp. Prods. Fleated to decomp., emits SiOj, org. acid vapors, formaldehyde... 

MCM-50, a stabilized lamellar structure, exhibits an x-ray diffraction pattern consisting of several low-angle peaks that can be indexed to (hOO) reflections, that is, the material is pillared-layered consisting of two-dimensional sheets [117]. 

The real part represents a one-dimensional wave that propagates in the direction of the X axis. This wave can grow, attenuate or remain constant with time. The latter case is realized, for example, in the expression (17.50). Let us set CO = a>r + Then at w < 0 the time-dependent index of the exponential in (17.55) is positive and the value of cj> increases with time all the way to infinity. It means that perturbations grow with time and are unstable. For coi > 0, the index of the exponential function is negative and perturbations decrease with time. It means that perturbations are steady. At co = 0 the quantity cj) either does not depend on t (if cOr = 0), or is a periodic function of time t. In this case we talk about neutral stability . 

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