Chain slip

For density values g > 0.92 g/cm3 the deformation modes of the crystals predominate. The hard elements are the lamellae. The mechanical properties are primarily determined by the large anisotropy of molecular forces. The mosaic structure of blocks introduces a specific weakness element which permits chain slip to proceed faster at the block boundaries than inside the blocks. The weakest element of the solid is the surface layer between adjacent lamellae, containing chain folds, free chain ends, tie molecules, etc. 

Cations can be seen as acting as ionic crosslinks between polyanion chains. Although this may appear a naive concept, crosslinking can be seen as equivalent to attractions between polyions resulting from the fluctuation of the counterion distribution (Section 4.2.13). Moreover, it relates to the classical theory of gelation associated with Flory (1953). Divalent cations (Zn and Ca +) have the potential to link two polyanion chains. Of course, unlike covalent crosslinks, ionic links are easily broken and re-formed under stress there could therefore be chain slipping and this may explain the plastic nature of zinc polycarboxylate cement. 

In a uniform magnetic field, the iron particles interact with each other, but the particles do not interact with the polymer network. The polymer network can immobilize the ordered structure, but it cannot prevent the break-up of the ordered structure under compression. The iron particles in the chains slip out from the columnar structure, breaking the ordered structure and resulting in hysteresis, as shown in Fig. 15. 

Polyethylenes undergo interlaminar deformation during tensile elongation. This can give rise to a double yield phenomenon. At the onset of the hrst tensile yield, chain slip and lamella rotation occur and this process is reversible. The second tensile yield is irreversible and coinsides with lamella fragmentation (36). These mechanically induced morphological changes and the observation of any double yield phenomena are dependent on several structural factors that can be controlled by... 

The keratin of hair is essentially a bundle of long protein strands joined together by disulfide bonds. If these bonds are broken (reduced) by the addition of a thiol and the hair curled, the keratin chains slip past each other into a new configuration. When an oxidizing agent is added, new disulfide bonds are formed, thus stabilizing the new curled state. 

Figure 8.3 Chain-slip in lamellar crystals, seen edge-on. The slip direction is parallel to the c axis and occurs on many parallel slip planes.

Asa result of molecular chain slipping processes, solid properties also depend to a greater or lesser degree (depending on constitution and configuration) on the mean molar mass. 

Macromolecules (state) Chain slipping Mechanical damping internal friction ... 

The primary forming of plastics is generally a flow process. The individual macromolecules of thermoplastics, duroplastics, and elastomers must be mobile and capable of chain slipping. The duroplastics and elastomers do not crosslink or vulcanize until after forming, when they develop their characteristic crosslinked structure. 

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