Reduction shrinkage during

Shrinkage during solidification always tends to reduce the dimensions to values lower than those of the mold. The magnitude of this shrinkage is shown in Figure 23.12. It appears that for amorphous polymers a reduction in volume of circa 10% occurs when the polymer is cooled from the processing temperature to the ambient for crystalline polymers, this reduction may amount to 20-25% (Fig. 23.12). 

Cellulose reinforcing fibers are commonly manufactured from softwood logs. Use of cellulose libers in moldings results in a reduction of shrinkage during cure, and an improvement of impact strength. The products obtained are light colored materials. 

Shrinkage—The volume reduction occurring during adhesive curing, sometimes expressed as a percentage volume or linear shrinkage size reduction of adhesive layer due to solvent loss or catalytic reaction. 

Bond coat phase transformation Most of the bond coats, either MCrAlY or (Ni,Pt)Al, used in TBCs are based on the P-NiAl phase. As shown in Fig. 10, the major change in the bond coat microstructure during oxidation is the formation of the y -NisAl phase. This is attributed to aluminium depletion caused by the formation of AI2O3 on the surface and by inward diffusion of aluminium into the superalloy. Since the density of P-NiAl (5.9 g/cm ) is smaller than that of y -Ni3Al (7.5g/cm), there is a volume shrinkage during this transformation [68]. If the decomposition of the P-NiAl takes place locally or at a different time in different places, then the volume reduction will also be localised. This may cause the bond coat surface to distort from its original shape or cavities to form inside the bond coat. 

FIGURE 13.10 Bilayer artificial muscle with (a) clockwise movement caused by PPy shrinkage during oxidative processes, (b) neutral state of PPy and angle described, and (c) counterclockwise movement caused by PPy expansion during reductive processes. Reprinted with permission from [97]. Copyright 2011 Elsevier. 

During the process, the solute diffuses into the intercellular space and, depending on the characteristics of the solute, it may pass through the membrane and enter the intracellular space. Differences in chemical potentials of water and solutes in the system result in fluxes of several components of the material and solution water drain and solute uptake are the two main simultaneous flows. Together with the changes in chemical composition of the food material, structural changes such as shrinkage, porosity reduction, and cell collapse take place and influence mass transfer behavior in the tissue. 

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