Cross-link effects

These materials have characteristics of both rubbers and thermoplastics. At room temperature they behave like cross-linked rubbers, but at elevated temperatures the cross-links effectively disappear (they are said to be heat fugitive) and the material may be processed as a thermoplastic. Unlike truly cross-linked (vulcanised) rubbers, these materials may be capable of disolution in solvents, although not necessarily at room temperature. 

Santora BP, Gagne MR, Moloy KG, Radu NS. Porogen and cross-linking effects on the surface area, pore volume distribution, and morphology of macroporous polymers obtained by bulk polymerization. Macromolecules 2001 34 658-661. 

Stability of the Cross-Linked Tropomyosin Dimer Cross-Link Effect on the Cooperatlvity of the Ordering Process and on the Maximum in the Helix Probability Profile" Mattice, W. L. Skolnick, J. Macromolecules 1982, IB, 1088. 

An area of chemical modification that is very important to the medical support industry is concerned with the modifications for altering biological properties. An application of glutaraldehyde s cross-linking effect on proteins is in the preparation of prostheses for internal organs, e.g. heart valves (125). 

Cross-linking effects are more important in the plateau and terminal zones. For moderately cross-linked polymers, such as soft vulcanized rubbers, the equilibrium modulus is similar in magnitude to the entanglement network modulus before vulcanization. In some cases, however, the former modulus may be higher by as much as a factor of 2 than the latter one, thus... 

Cross-linking Effect on Polymerization. The general cross-linking reaction that occurs during polymerization and involves components with a functionality greater than one (two or more double bonds, divinyl monomer) has been studied extensively. The statistical analysis of molecular distributions in such reactions is due to Flory (36). 

A plot of the melt viscosity of a typical SPSNa. (1.78 mol% sulfonate) against its Tg value is shown in Figure 6. The viscosity collapse on addition of glycerol causes a sudden drop in Tg, practically eliminating the quasi-cross-linking effect of the ionic clusters. The decrease in Tg upon addition of DOP reflects a classical plasticizing effect on the hydrophobic domains that form the bulk of the polymer41. 

In narrow pore silicas water is eliminated by reaction between hydroxyl groups on adjacent sites (Figure 6.34). No reverse reaction is possible and there is an effective loss of surface area due to the cross-linking effect. 

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