Shrinkage inspection

Although the scale of typical liquid-gas interfaces is large compared to the resolution of many modern characterisation techniques, they are difficult to observe because the surface of interest is situated beneath the drop of the liquid. The method presented here bypasses this difficulty by solidifying the drop and inspecting the surface directly. Slight shrinkage of the drop when it is subjected to the laser beam of the confocal microscope may cause a problem. Earlier works have used a plasticising drop where this is not a problem [15]. However, the benefit of the present method is that it uses a water-based system with a surface tension similar to that of water. 

An inspection of Fig. 1 indicates that the densities of the monomeric spiro ortho carbonate and the polymer appear to cross above 200 . At that point, one would expect no change in volume during polymerization since the two materials have the same density. Above this critical temperature, one would expect to get shrinkage during the polymerization. Unfortunately, the polymerization cannot be carried out conveniently in this temperature range with the catalysts now available since carbon dioxide is liberated and the polycarbonate is not obtained in a pure form. At the lower end of the temperature scale the two lines appear to Intersect again, but one would expect below the glass transition of the polymer that the density line would become more nearly horizontal and become essentially parallel to the line of the density of the monomer. 

At first inspection Eq. 1 seems well suited to densification by hot pressing, in which case the creep strain rate would be replaced by the rate of densification. However, it leaves something to be desired in that the effect of porosity on the rate of densification is ignored in addition, this equation would predict a finite shrinkage rate at the end point condition of zero porosity, where shrinkage must obviously cease. 

Inspection tests before shipments of adhesive products are as follows adhesion strength, tackiness, hardness, viscosity, density, volume shrinkage, thermal expansion, shelf life, pot life, gelation time, water resistance, chemical resistance, weather resistance, flame retardance, electric conductivity, color, optical properties, amount of volatile organic compounds (VOC) emergence, etc. Some of these tests are the same as those tests for acceptance. Before shipment, strength tests of joints are very important for adhesives in terms of performance proof (see Chap. 19). In contrast, for PSAs, tackiness is important (see Chap. 15). Other important properties that should he tested are shown below. 

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