Ether polymers epoxy resins

Other phenol derivatives that are used to form the backbone of an epoxy resin include bisphenol E, bisphenol F, resorcinol, brominated bisphenols, and more highly functionalized molecules such as tetrakisphenylolethane. Alcohols, amines, and carboxylic acids may be combined with epichlorohydrin to give a range of diglycidyl ether based epoxy resins. Non-aromatic, commercially available epoxides are produced by peracid epoxidation of alkenes and dienes, such as vinyl cyclohexene and esters of cyclohexane carboxylic acids [23]. The chemical formulas for two common uncured polymers are shown below ... 

Synonyms Condensation prods., epoxy Epoxides, polymers, epoxy resins Epoxy compds. Ethers, cyclic, epoxides, polymers Plastics, epoxy Polyethers, epoxy resins Classification Polymer... 

Synonyms Condensation prods., epoxy Epoxides, polymers, epoxy resins Epoxy compds. Ethers, cyclic, epoxides, polymers Plastics, epoxy Polyethers, epoxy resins Classification Polymer Definition A thermosetting resin based on the reactivity of the epoxide group Toxicology LD50 (oral, rat) 2200 mg/kg strong skin irritant in uncured state poison by inhalation moderately toxic by ingestion little or no toxicity in cured state Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of Cr... 

EPA. See Propylene glycol ethyl ether acetate Eicosapentaenoic acid Epihydrin alcohol. See Glycidol Epoxides, polymers, epoxy resins. See Epoxy resin Epoxidized butyl esters of linseed oil fatty acids. See Epoxidized linseed oil, butyl ester... 

Reactive (unsaturated) epoxy resins (qv) are reaction products of multiple glycidyl ethers of phenoHc base polymer substrates with methacrylic, acryhc, or fumaric acids. Reactive (unsaturated) polyester resins are reaction products of glycols and diacids (aromatic, aUphatic, unsaturated) esterified with acryhc or methacrylic acids (see POLYESTERS,unsaturated). Reactive polyether resins are typically poly(ethylene glycol (600) dimethacrylate) or poly(ethylene glycol (400) diacrylate) (see PoLYETPiERs). 

Gel-permeation chromatography studies of epoxy resins prepared by the taffy process shown n values = 0, 1, 2, 3, etc, whereas only even-numbered repeat units are observed for resins prepared by the advancement process. This is a consequence of adding a difunctional phenol to a diglycidyl ether derivative of a difunctional phenol in the polymer-forming step. 

As is usually characteristic of crosslinked polymers of commercial importance, epoxy resins are prepared in two stages, with the initial reaction leading to a linear prepolymer and the subsequent reaction introducing the crosslinks between the molecules. The prepolymers from which epoxy resins are prepared are diglycidyl ethers with the structure shown in Figure 4.2. 

The epoxy polymers are basically poly ethers. One type of epoxy polymer (or epoxy resins) are prepared from epichlorohydrin and bisphenol-A. The reaction is carried out with excess of epichlorohydrin. The various reactions for the preparation of an epoxy polymer are given in the following discussion. 

Allyl chloride is used to make intermediates for downstream derivatives such as resins and polymers. Approximately 90% of allyl chloride production is used to synthesize epichlorohydrin, which is used as a basic building block for epoxy resins and in glycerol synthesis. Allyl chloride is also a starting material for allyl ethers of phenols, bisphenol A and phenolic resins, and for some allyl esters. Other compounds made from allyl chloride are quaternary amines used in chelating agents and quaternary ammonium salts, which are used in water clarification and sewage sludge flocculation (Kneupper Saathoff, 1993). 

Tetraglycidyl ether of tetraphenolethane is an epoxy resin that is noted for high-temperature and high-humidity resistance. It has a functionality of 3.5 and thus exhibits a very dense crosslink structure. It is useful in the preparation of high-temperature adhesives. The resin is commercially available as a solid (e.g., EPON Resin 1031, Resolution Performance Polymers). It can be crosslinked with an aromatic amine or a catalytic curing agent to induce epoxy-to-epoxy homopolymerization. High temperatures are required for these reactions to occur. 

Epoxy resins and other polymers (tetrahydrofuran, vinyl ethers, styrene, etc.) can be cured when exposed to an acid or cation intermediate species. The photoactive catalyst system commonly used to cure epoxy resins and multifunctional vinyl ether materials is composed of salts of aryldiazonium, triarylsulfonium, and diaryliodonium. These systems are commonly employed in coatings and adhesives for electronic products. The acid initiator generated from the photoinitiator continues to be active even after uv curing, and so conversion of reactants and crosslinking continue even in the absence of uv light. This phenomenon is typically referred to as dark cure. 

In Table 15.3 are shown the chemical structures and Tg and of some representative thermoplastic polymers for use at high temperature (3,9). These matrices have high continuous service temperatures (120-200° C) even under wet environmental conditions. Advantages of thermoplastic over thermoset matrices are their shorter fabrication cycle (generally controlled environment storage is not required) and the possibility to be reprocessed and reconsolidated after manufacture. Poly(ether ether ketone) is a strong contender with epoxy resins for use as a matrix in composite prepregs with carbon fibers to be utilized in structural aircraft components. 

The lower molecular weight LP-3, LP-33 and ZL-1400 C polymers are used as elastomeric modifiers, particularly for epoxy coatings and adhesives. Owing to their low molecular weight these polymers have the lowest viscosities of commercially available LPs. This low viscosity is particularly beneficial under cold conditions. Even at 4°C the polymers have viscosities which are considerably lower than those associated with standard unmodified bisphenol A [diglycidyl ether of bisphenol A (DGEBA)] epoxy resins at 25°C. 

Before going into the methods for radical reactions it most be said tlmt polycondensation or polyaddition have led to more industrial preparation. In this connection epoxy resins, the polyurethanes obtained from prepolymers and, more recently, more specialized polymers such as the PEB AC (ATOCHEM), amid-ether or polyimids (KHERIMIDE from RHONE POULENC must be mentioned). Moreover, it is interesting to note that the ionic methods (cationic or anionic ones) have not produced industrial products (except dihydroxy poly (dimethyl siloxanes), poly (tetrahydro-furanes)) but they have facilitated theoretical studies both on the analytical aspects and the materials we can obtain. 

Polymers containing ether groups in the backbone include two subclasses, namely true polyethers and polyacetals. Polyethers such as polyethylene glycol [-0-CH2-CH2-]n having higher polarity compared to polyhydrocarbons are used for many practical applications where some hydrophilic character is necessary. Epoxy resins are also polyethers. 

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