Epoxy resins flexibilizing

Properties Vise, liqs. m.w. 3000-4000 dens. 0.95-0.96 kg/l 11 -26%ACN Uses Epoxy resin flexibilizer Trade Names Tylac 68073-00 Tylac 68074-00 Trade Names Containing Epotuf 98-411 Kelpoxy G272-100 Kelpoxy G293-100... 

Poly-a,p-DL-aspartic acid, sodium salt. See Sodium polyaspartate Polyavin PEN. See polyethylene Polyazelaic polyanhydride Synonyms PAPA Formula H[OCO(CH2)7CO]nOH Uses Epoxy resin flexibilizer specialty PU polyol... 

The lower molecular weight LP-3 and LP-33 are used as epoxy resin flexibilizers for adhesives, coatings, potting compounds, and plastic tooling compounds. 

Flexibilized epoxy resins are important structural adhesives [69]. Liquid functionally terminated nitrile rubbers are excellent flexibilizing agents for epoxy resins. This liquid nitrile rubber can be reacted into the epoxy matrix if it contains carboxylated terminated functionalities or by adding an amine terminated rubber. The main effects produced by addition of liquid nitrile rubber in epoxy formulations is the increase in T-peel strength and in low-temperature lap shear strength, without reducing the elevated temperature lap shear. 

Liquid polymers with terminal mercapto groups (LP-2) are obtained when solid polyolefin poiysulfides are reduced. These liquid polymers may be oxidized to solid polymers in the presence of oxidizing agents, such as lead oxides. The liquid polymers are used in caulking compositions and as reactive flexibilizing agents in epoxy resins. 

Novolac epoxy flexibilizers Improve low and high temperature characteristics of novolac epoxy resins for inhibition of composite rocket propellants [164]. 

Similar to composite propellants, flexibilized epoxy or novolac epoxy resins reinforced with fillers or fibers are used for inhibition of fuel-rich propellants. 

Tpo maximize the utility of crosslinked cycloaliphatic epoxy resins in some of the more critical application areas, improved toughness is required. Such improvements can often be made through modification with various flexibilizing agents, but as a rule this improvement is accompanied by a severe degradation of the strength and heat distortion temperature of the cured system. 

Tougheners Tougheners eliminate brittleness from epoxy resin to prevent cracks and decrease distortion. Unlike flexibilizers, they do not reduce crosslink density. 

The aliphatic epoxy resins formed from reaction with hydrogen peroxide or peracetic acid include epoxidized polybutadiene, epoxidized soya or linseed oil, and epoxidized polyglycols. The resulting products have too low a functionality for use as base polymers. They are almost always used in combination with other epoxy resins to improve properties such as cure rate, flexibility, and heat deflection temperature. Therefore, these resins are often considered to be reactive diluents and flexibilizers. 

The catalyst does not make up part of the final epoxy network structure or have a significant effect on the final properties of the cured resin. Thus, the final cured properties of the epoxy system are primarily due to the nature of the epoxy resin alone. Homopolymerization normally provides better heat and environmental resistance than polyaddition reactions. However, it also provides a more rigidly cured system, so that toughening agents or flexibilizers must often be used. In adhesive systems, homopolymerization reactions are generally utilized for heat cured, one-component formulations. 

It should also be emphasized that the epoxy resins are only building blocks in the development of epoxy-based adhesives. The formulation will ultimately involve one or more epoxy resins curing agents modifiers, such as plasticizers, flexibilizers, accelerators, stabilizers, and flow control agents and fillers. In general, flexibility can be controlled by the parameters shown in Table 3.8. 

TABLE 4.4 Properties of an Epoxy Resin Formulation Based on a Blend of Polyglycol Diepoxy Flexibilized Resin and Standard DGEBA Resin, Cured with Methylene Dianiline5... 

Diluents are higher-MW components than solvents that are also added to the epoxy adhesive formulation to lower the viscosity and modify processing conditions. The primary function of a diluent in an epoxy resin formulation is to reduce its viscosity to make it easier to compound with fillers, to improve filler loading capacity, or to improve application properties. Solvents, certain curing agents, and flexibilized epoxy resins can also lower the viscosity of epoxy adhesive formulations, but this is not their primary function. The effect of various diluents on the initial viscosity of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin is illustrated in Fig. 6.3. 

Functionalized, liquid polybutadiene derivatives have also been developed as hybrid flexiblizers for epoxy resins. Carboxyl-terminated butadiene/acrylonitrile polymers, butadiene homopolymers, and maleic anhydride-amino acid grafted butadiene homopolymers have been used as flexibilizers to impart good low-temperature strength and water resistance to DGEBA-based epoxy adhesives. An epoxy system toughened by polybutadiene with maleic anhydride is claimed to provide a hydrophobic backbone, low viscosity, softness, and high tensile strength and adhesion (Table 7.10). 

Flexibility is primarily characterized by a material s elongation. Flexibilizers in epoxy systems work by allowing the material to deform under stress. In this way stresses on the joint are distributed over a larger area. The flexibilized epoxy resin has the capability of compensating for differences in thermal expansion or elastic moduli of the substrates. 

Another common method of flexibilizing epoxy adhesives is by blending the primary epoxy resin with other, more elastic polymers. Epoxy-nylon, epoxy-polysulfide, and to a certain extent epoxy-urethane hybrids use such a mechanism to provide flexibility. These flexibilizers are important additives for epoxy adhesives even though they may reduce certain... 

Di- or polyfunctional epoxy resins may be considered reactive diluents that provide a degree of resiliency, yet most preserve the inherent properties of the base epoxy resin. When added to an epoxy formulation, they will not reduce functionality, and in some cases an actual increase in crosslink density is noticed. Typical resins of these types are shown in Fig. 8.4. As flexibilizers, these diluents are often blended with the more reactive epoxy resins. They, of course, can also be used as epoxy resins in themselves. 

The commercial flexibilizing reactive diluents are predominantly glycidyl derivatives of glycols, dimerized acids, or reaction products of dicarboxylic acids with epoxy resins. The properties of certain polyepoxy diluents are summarized in Table 8.3. Some of, but not all, these materials provide good reactivity with aliphatic primary amines at room temperature. 

Chapters 4 through 10 describe the basic raw materials that are commonly employed in formulating epoxy adhesives. These include the epoxy resins, curing agents and catalysts, solvents and diluents, resinous modifiers, flexibilizers and tougheners, fillers, and adhesion promoters. 

Ancarez / [Pacific Anchex ] Epoxy resin and flexibilizer. 

Cyracure. [Unbn Carbide] Cycloaliphatic epoxy resins diluents and flexibilizers for uv-cured coatings and adhesives. 

Rubber toughened epoxy resins are the well known examples of impact modified thermosets utilizing reactive rubbery prepolymers. Epoxy resins can be toughened or flexibilized by any one of the following types of oligomeric reactive elastomers ... 

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