Hygroscopic expansion coefficient

Each of the components, polymer and metal, has both thermal and hygroscopic expansion coefficients which may differ between components by orders of magnitude. Thus, the very act of fabrication introduces internal stresses into the device. If permitted to act, these stresses are capable of ripping apart the device, destroying it Such destruction is prevented by strong interfacial adhesion, maintained at every step during manufacture, as well as throughout the use life of the device. 

BiaxiaHy orieated PPS film is transpareat and nearly colorless. It has low permeability to water vapor, carbon dioxide, and oxygen. PPS film has a low coefficient of hygroscopic expansion and a low dissipation factor, making it a candidate material for information storage devices and for thin-film capacitors. Chemical and thermal stability of PPS film derives from inherent resia properties. PPS films exposed to tolueae or chloroform for 8 weeks retaia 75% of theh original streagth. The UL temperature iadex rating of PPS film is 160°C for mechanical appHcatioas and 180°C for electrical appHcations. Table 9 summarizes the properties of PPS film. 

The vitreous B2O3 is colourless, transparent and hygroscopic. It can be prepared by dehydration of H3BO3 at 266 °C —270 C under a reduced pressure of 130 — 260 Pa. The removal of water by heating H3BO3 in air is quite difficult and even the melt contains considerable amounts of residual water.The final H2O content after fusion at 700,1100 and 1200 °C is 0.25, 0.17 and 0.14% respectively (Poch, 1964). As a result of the H2O content, the data on the basic properties (e.g. those on viscosity and thermal expansion coefficient) exhibit some differences. The viscosity curve shown in Fig. 7 should serve for rough orientation only. More detailed data are reported by Bruckner (1964), for example. 

Hygroscopic (moisture) effects arise for polymer materials such as some epoxies that absorb moisture chemically after curing and therefore expand. These effects are directly analogous to thermal effects and are characterized by coefficients of moisture expansion and p2 in principal material coordinates in direct analogy to a.( and 02 for coefficients of thermal expansion. All calculations for thermal effects with the a can be replaced by or supplemented with analogous terms for moisture expansion. 

Thoulefs and Sondstadfs liquor Potassium iodomercurate (i.e., aqueous solution of potassium and mercuric iodides) 3250 Introduced by Thoulet and subsequently investigated by V. Goldschmidt. Dense viscous and colorless liquid with a small coefficient of cubic expansion. It is hygroscopic and its action on the skin militates against its use. 

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