Polyester cross-linked amorphous

The less simple polymers (like the epoxies, the polyesters and the formaldehyde-based resins) are networks each chain is cross-linked in many places to other chains, so that, if stretched out, the array would look like a piece of Belgian lace, somehow woven in three dimensions. These are the thermosets if heated, the structure softens but it does not melt the cross-links prevent viscous flow. Thermosets are usually a bit stiffer than amorphous thermoplastics because of the cross-links, but they cannot easily be crystallised or oriented, so there is less scope for changing their properties by processing. 

Photopolymerization of Powder Formulations Powder coatings are very attractive [314]. The powder is applied on the substrate and exposed to an IR source to get the coalescence of the solid particules then, the cross-linking reaction is carried out under UV (or visible) light in a very short time and at a temperature about 100-120°C. Largely encountered systems are based on, for example, polyesters (with maleates or fumarates unsaturations) and polyurethane vinyl ethers that copolymerize according to a radical process, amorphous polyesters and functionalized polyesters (with allyl ethers). 

Total impregnation. The infusion of consolidant becomes necessary when the original fabric is degraded to the point of being dissociated to an amorphic substance. While acrylic and vinyl resins are preferable for their solvency after polymerization, cross-linking epoxides and polyesters may be necessary for their cohesive and gap-filling properties. 

There are two important distinctions to be made between the S—B—S systems considered in the previous section and the poly ether-polyesters. In the first instance the latter materials are prepared by the techniques of condensation polymerization as opposed to the anionic double-bond polymerization used with the S—B—S systems. Secondly, whereas both components of the S—B—S polymer are amorphous one of the components in the industrially important polyether-polyesters is crystalline. The two groups of materials do however have the common feature that there is some separation of the systems into hard and soft (rubbery) regions with the hard zones effectively acting as multiple cross-links. 

Polyesters. Unsaturated polyesters dissolved in styrene or methacrylates are used as reactive adhesives. Hot-melt adhesives can be made from saturated and fusible polyesters based on aliphatic and/or aromatic carboxylic acids, in some cases by using dimerized fatty acids. High molecular mass amorphous polyesters and low molecular mass crystalline polyesters are important raw materials for moisture cross-linking polyurethane adhesives in solution or solvent-free systems. 

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