Curing cross linked

Table 10 compares the values of different experimental uv-curable cross-linked polymers with those of BPA-PC for the most important properties of substrate materials (220). In spite of this remarkable progress in the development of fast curing cross-linked polymers, BPA-PC and, to a small extent, glass are still the materials of choice for substrates for optical data storage. 

Etee-tadical reactions ate accompHshed using a variety of processes with different temperature requirements, eg, vinyl monomer polymerization and polymer modifications such as curing, cross-linking, and vis-breaking. Thus, the polymer industries ate offered many different, commercial, organic peroxides representing a broad range of decomposition temperatures, as shown in Table 17 (19,22,31). 

Oxidation has also been cited as occurring in the cure of polymethyUiydrosiloxane [9004-73-3] (PMHS) on cellulose acetate fibers. Investigation of the cured, cross-linked siUcone shows no evidence of the Si—H bond. The same compound under an atmosphere of nitrogen does not cure and retains the Si—H bonds (99). 

This chapter describes many of the important reactions of polymers. Synthesis and curing (cross-linking) of polymers and telomerization are chemical reactions of polymers that have been discussed in previous chapters. 

Another factor affecting thermal stability of componnds based on fluorocarbon elastomers is the curing (cross-linking) system nsed. This snbject is discussed at some length in the section on compounding. 

Typically, spinning is carried out by melt-spinning extrusion through a spinneret to obtain polymer fibers with a diameter of 10-20 (xm. However, solvent spinning has been reported (19). The fragile polymer fibers need to be cured (cross-linked) below their melting point to prevent coalescence... 

A thermosetting plastic is a polymer that can be caused to undergo cross-linking to produce a network polymer, called a thermoset polymer. Quite commonly, thermosetting resins are prepared, by intent, in only partially polymerized states (prepolymers), so that they can be deformed in a heated mold and then hardened by curing (cross-linking). 

Figure 2. Idealized polymer curing (cross-linking) reactions.

Many of the silicone elastomers that are used in biomedical applications are produced by Dow Chemical Corp., under the trade name SILASTIC . For example, a typical medical-grade silicone (like SILASTIC MDX4-4210 Medical grade elastomer) contains, after curing, cross-linked drmethylsiloxane polymer and silica for reinforcement. Silcones are also reinforced with PET (Dacron) fiber meshes for certain biomedical applications. For implantable medical devices, it is important to realize that the cured polymer contains residual catalysts and silicone cross-linkers, which are necessary for the polymerization. 

The matrix in reinforced plastics may be either a thermosetting or thermoplastic resin. The major thermosetting resins used in conjunction with glass-fiber reinforcement are unsaturated polyester resins and, to a lesser extent, epoxy resins. These resins have the advantage that they can be cured (cross-linked) at room temperature, and no volatiles are liberated during curing. 

Heat-curing of silicone rubbers usually involve free-radical initiators such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and f-butyl per-benzoate, used in quantities of 0.5—3%. These materials are stable in the compounds at room temperature for several months but will start to cure at about 70°C. The curing (cross-linking) is believed to take place by the sequence of reactions shown in Figure 4.37. The process involves the formation of polymer radicals via hydrogen abstraction by the peroxy radicals formed from the thermal decomposition of the peroxide and subsequent cross-linking by coupling of the polymer radicals. 

Fully alkylated amino resins require strong acid catalysis for fast and/or low-temperature cross-linking. Their catalysis mechanism is different from that of partially alkylated resins which respond to weak acid catalysts or general acid catalysis. A fully alkylated melamine resin catalyzed by a strong acid catalyst is a faster curing (cross-linking) agent than a partially butylated amino resin. 

Two Types of Fractal Reactions at Curing Cross-linked Polymers 232... 

A duplicate comonomer mixture, pre-cured at 150 C, demonstrated no exotherm with the DSC but rather a smooth baseline indicating an already apparently fully cured, cross-linked system (Fig. 5). Confirmation of the DSC data was essentially provided by Thermomechanical Analysis instrumentation and actual adhesive strength tests. 

Cure—To change the properties of a thermosetting resin irreversibly by chemical reaction, i.e. condensation, ring-closure, or addition. Cure may be accomplished by addition of curing (cross-linking) agents, with or without catalyst, and with or without... 

Epoxide adhesives , then, comprise a very wide and important range of materials. They may be cured (cross-linked) in a variety of ways and their mechanical properties may be markedly changed by toughening . This article is concerned principally with the epoxy polymers as such Epoxide adhesives curatives is concerned with cross-linking reactions. Toughened epoxide adhesives is the subject of further articles. 

Epoxide resins comprise a broad and important class of adhesives. In the article Epoxide adhesives, an introduction was given to some of the molecules to which the epoxy groups in these materials may be attached. The cure (cross-linking) of epoxies may be achieved... 

Self-curing adj. Undergoing cure (cross-linking) without the application of heat. See self-vulcanizing and ambient cure. 

De Buyl, F. Comyn, J. Shephard, N. E. Subramaniam, N. P., Kinetics of Cure, Cross Link Density and Adhesion of Water-Reactive Alkoxysilicone Sealants. Adhesion Sci. Technol. 2002,16,1055-1071. 

Charles Goodyear was an uneducated inventor and not a polymer technologist. Nevertheless, his serendipitous discovery of a process for curing (cross-linking) rubber, which is still in use today, has had a profoimd influence on polymer science and technology. If not engraved in stone, his name was molded in rubber when the Seiberling Brothers used his name for their rubber plant in Akron, OH. 

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