Drying methods dimensional change

Several methods have been developed for getting PEG into artifacts. Most small artifacts and a few whole ships are being treated by immersion in appropriately sized and configured tanks in which a controlled sequence of concentrations and, recently, molecular weights of PEG are added to an aqueous solution. The PEG enters the wood by diffusion. When a desired concentration is reached, the objects are removed and dried slowly while maintaining a low moisture gradient within the artifacts to control dimensional changes. 

When it comes to textiles, dimensional stability has attracted a lot of standards attention, and there are at least five international methods as well as national equivalents. The ISO methods cover washing and drying [65], free steam [66], cold water immersion [67], and dry heat [68], The fifth standard covers the preparation, marking, and measuring of specimens and garments for dimensional change tests [69]. 

Thermal dilatometric curves obtained for six bricks extruded from different raw materials are shown in Fig. Curves for those manufactured from similar raw materials, but made by different forming methods, i.e., soft mud, dry press, and stiff extrusion, are shown in Fig. 23. From room temperature up to 500°C, the dimensional change is approximately linear and is due to thermal expansion. The abrupt increase in expansion (500-800°C) is due to phenomena such as quartz inversion, exfoliation of the illitic, and chloritic minerals due to dehydroxylation, and, possibly, the escape of CO2 under pressure. 

Freeze drying is one of the crystallization methods however, denaturation, deactivation, or a slight change in the three-dimensional structure of a protein is sometimes observed. It is necessary to check the stability before freeze drying. 

In Eulerian coordinates, shrinking causes an advective mass flux, which is difficult to handle. By changing the coordinate system to Lagrangian, i.e., the one connected with dry mass basis, it is possible to eliminate this flux. This is the principle of a method proposed by Kechaou and Roques (1990). In Lagrangian coordinates Equation 3.91 for one-dimensional shrinkage of an infinite plate becomes ... 

Zinc electrodes can also be manufactured by the plastic-bonded method, similar to that of the nickel electrode described above. The zinc oxide dry powder, PTFE binder and other additives are blended with an organic solvent and then the mixture is passed through a calendaring process similar to that in Fig. 31.1. The PTFE fibriUates into a nano-structured three-dimensional fiber matrix. This electrode structure for the calcium zincate electrode is shown in Fig. 31.3 for a freshly prepared electrode. The active materials are locked into the electrode structural matrix which helps to reduce the tendency towards shape change and dendritic growth. 

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