Glassy material

Although vitreous siUca is a simple, single-component glass, its properties can vary significantly, depending on thermal history, the type and concentration of defects, and impurities. Vitreous siUca can, however, be one of the purest commercially available glassy materials. In synthetic vitreous sihcas, for example, total metal contamination is typically measured ia the 50—100 ppb range. Even at such a low level of impurities, differences ia properties, such as uv-transmission, are observed for various siUcas. 

Chlorinated paraffins vary in their physical form from free-flowing mobile Hquids to highly viscous glassy materials. Chlorination of paraffin wax (C24—C30) to 70% chlorine and above yields the only soHd grades. Physical properties of some commercially available chlorinated paraffins are Hsted in Table 1. 

The calcium oxide formed reacts with impurities in the iron ore to form a glassy material called slag. The main reaction is with Si02 to form calcium silicate, CaSi03 ... 

There is another result of frozen-in residual stresses that can be equally damaging to the product function and which affects materials that are not in the glassy state. This may affect an impact grade of material or a crystalline plastic even more drastically than a glassy material. The frozen-in stresses are real loads applied to the material and when even slightly elevated temperatures are applied stresses can cause the product to deform severely. 

Molecular hybrids between organic polymers and silica gel are expected to show many possibilities as new composite materials. First, the hybrids may show intermediate properties between plastics and glasses (ceramics). In addition, the composition of the hybrids can be widely varied. In other words, the hybrids can be used to modify the organic polymer materials or to modify the inorganic glassy materials. The hydrophilic modification as described before is a typical example. 

Upon cooling, molten and rubberlike polymers pass the glass transition and solidify as glassy materials. The temperature TB of the glass transition depends on the chemical nature of the polymer as well as on the number of crosslinks between the molecular chains. Two different test methods were used for the determination of the glass transition range ... 

Nevertheless the spectra can give worthwhile evidence ofthe occurence and frequency of particular conformations of crystalline and glassy materials. However, the example of polyethylene shows that the MAS NMR technique does not offer this kind of information always and easily for the amorphous phase. Specific characteristics... 

PMMA is a transparent, glassy material, which is known from A-ray studies to be amorphous at the molecular level. It is clearly polar, as is shown by... 

In order to illustrate the potential applications of rheo-NMR five examples have been chosen. The first example deals with wormlike micelles [22] in which NMR velocim-etry is used to profile anomalous deformational flow and deuterium NMR spectroscopy is used to determine micellar ordering in the flow. The second example concerns flow in a soft glassy material comprising a solution of intermittently jammed star polymers [23], a system in which flow fluctuations are apparent. The third... 

Velocity Field Fluctuations for a Soft Glassy Material... 

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