Structure shrinkage problem

The problem of structure shrinkage can be solved, when pre-formed nanocrystalline particles are used as the starting structural elements. This was successfully demonstrated for Sn0262 and Ce0263 nanoparticles, which were assembled in highly periodic cubic crystalline structures using KLE as a... 

There are certain basic rib-design guidelines that should be followed (Fig. 3-9). The most general is to make the rib thickness at its base equal to one-half the adjacent wall s thickness. With ribs opposite appearance areas, the width should be kept as thin as possible. In areas where structure is more important than appearance, or with very low shrinkage materials, ribs are often 75 or even 100 percent of the outside wall s thickness. As can be seen in Fig. 3-10, a goal in rib design is to prevent the formation of a heavy mass of material that can result in a sink, void, distortion, long cycle time, or any combination of these problems. 

The result is a fiber that is less crystalline and dyes more readily. The downside is an unavoidable reduction in transition temperatures, a less stable structure more prone to shrinkage, and the easier escape of dye molecules and oligomers which can deposit onto the surfaces of textile processing equipment. Depending on the level and type of comonomer used, increased problems with lightfastness or polymer degradation can also occur. 

One of the most exasperating problems when building with concrete is its normal shrinkage cracking. Some of the structures where cracks due to... 

The insolubility of peptides is not limited to the solution phase and can occur during peptide synthesis on the solid phase where it manifests itself as the difficult sequence problem. On-resin peptide aggregation and poor peptide segment solubility are due to the formation of (3-sheet-like structures. Difficult sequences contain predominantly hydrophobic residues that consistently show incomplete acylation and a characteristic shrinkage of the peptide-resin during synthesis.111 Reversible backbone protection was introduced into Fmoc/ tBu SPPS after the study of synthesis failure during the assembly of difficult sequences1121 and is now routinely used to circumvent synthesis failure in SPPS. 

Lack of adhesion of a dental restoration to tooth structure results in microleakage at tooth-restoration interface. This occurrence can result in discoloration at the margin of the restoration, or in the formation of caries. Occlusal forces on the restoration and differences between the coeffidents of thermal expansion of the cement and tooth material can lead to leakage. In addition, oral fluids and moisture may affect the adhesion. Microleakage of composite resin restorations has been reviewed by Ben-Amar [233]. Microleakage is not as serious a problem with glass-ionomer cements as it is with resin-based restorative materials, due to reduced polymerization shrinkage [234]. 

Finishing of Wool. Wool (qv) competes for markets where warmth, wrinkle recovery, and ability to set in creases are important. Wool problems relate to shrinkage, particularly to its tendency to felt. This is caused by scaly structure, which tends toward fiber entanglement when wet and subjected to mechanical action. In order to compensate for this tendency, wool needs to be set and also made shrinkproof if it is to be laundered. 

Amorphous nylons are transparent. Heat-deflection temperatures are lower than those of filled crystalline nylon resins, and melt flow is stiffer hence, they are more difficult to process. Mold shrinkage is lower and they absorb less water. Warpage is reduced and dimensional stability less of a problem than with crystalline products. Chemical and hydrolytic stability are excellent. Amorphous nylons can be made by using monomer combinations that result in highly asymmetric structures which crystallize with difficulty or by adding crystallization inhibitors to crystalline resins such as nylon-6 (61). 

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