Shrinkage problems

One of the principal reasons for the use of mineral fillers in these polymers is to reduce this shrinkage problem. Platy fillers have generally been found to be the most effective in this respect, giving the highest levels of shrinkage reduction consistent with maintaining adequate properties in other areas. 

Numerical simulation results of batch and continuous drying models for slices of peppers in packed beds were presented in this work. The reported models were based on differential mass and energy balances in the dryer along with kinetic equations describing transport phenomena in individual particles and product quality deterioration. The shrinkage problem was... 

This new synthesis method provides an improved means of preparing monolithic media compatible with stationary-phase synthesis techniques developed for particulate media. The new technique is compatible with polymeric column hardware and does not require covalent bonding of the monolith to the inner column wall. The use of prepolymerized particles circumvents issues associated with shrinkage problems that are characteristic of conventional monolith syntheses (see Section 3.4.1.6) while providing excellent efficiency for small-molecular weight anions, even under isocratic conditions. 

Shrinkage problems can be much more acute in cast materials such as acrylic where the polymerization shrinkage is close to 30%. An object made by casting is unlikely to be stress relieved by annealing, residual stresses can be very large and the part may craze (forming a network of microscopic cracks) or fracture over a period of a year or two. One area where annealing is carefully carried out is in plastic optical components where residual stresses can cause optical distortions. 

David Brown, Bridges Three Thousand Years of Defying Nature, 2001, pp. 122-123. Low-quality cement in early reinforced concrete projects would have aggravated the shrinkage problem. Freysinnet s designs always made much of the problem. 

The concept of caibon membrane for gas separation can be found in the early nineteen seventies. Barrer et al. compressed non-porous graphite caibon into a plug, called caibon membrane [8]. Bird and Trimm used poly(fuifuiyl alcohol) (PFA) to prepare unsupported and supported caibon molecular sieve membranes. During carbonization, they encountered shrinkage problems, which lead to cracking and deformation of the membrane. Hence, they failed to obtain a continuous membrane [9]. 

The use of excessive solvent may cause a shrinkage problem when the sealant cures. Volume shrinkage will always be greater than the weight percent of solvent due to its much lower density than other components in the sealant. Toluene, xylene, petroleum spirits, water, and others are used as solvents in sealant formulations. In case of solvent mixtures, the balance of volatility between solvents is very important to avoid a trouble such as the sealant s skin drying problem. 

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