Toughened epoxide adhesives

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. 

Cured epoxide adhesives form strong bonds to many substrates, but in their unmodified form tend to be brittle Toughened epoxide adhesives are the subject of separate articles. 

Structural adhesives are normally categorized or subdivided into subclasses based on the resin chemistries used in their formulation, which can be in the form of solids, liquids, pastes or films. The most important categories of structural adhesives are the thermoset cured adhesives based on phenolic, epoxy and polyurethane or acrylic resins and include phenolic adhesives. Epoxide adhesives, Toughened epoxide adhesives, Polyurethane adhesives, Acrylic adhesives and Toughened acrylic adhesives. Several of the categories can be further subdivided into both one- and two-component adhesives. The one-component structural adhesives, which can be liquids, pastes or solids (films), usually require the inclusion of added energy for activation or to effect cure in the... 

Other articles of relevance are Toughened adhesives and Toughened epoxide adhesives. In Structural adhesives, properties of epoxide and Polyurethane adhesives are compared with those of toughened acrylics. 

Simple formulation with the epoxy resin is not satisfactory as reactive groups such as amines present in the epoxy hardener compete with the carboxyl groups in reaction with epoxy groups (v. Toughened epoxide adhesives). As a result, very little RLP is incorporated into the matrix because the epoxy group has a much higher reactivity towards... 

The various ways in which epoxies can be toughened by introduction of a secondary phase are discussed in separate articles Toughened epoxide adhesives particle formation prior to cure, Toughened epoxide adhesives precipitation during cure and Toughened epoxide adhesives blend synergy. 

Toughened epoxide adhesives particle formation prior to cure... 

Toughened epoxide adhesives precipitation during cure... 

The reasons for modifying Epoxide adhesives by introducing a toughening secondary phase are considered in Toughened epoxide adhesives. Here, the precipitation of the secondary phase during the curing process is discussed. This is by far the most common approach and the technique around which much research and development effort has... 

Toughened epoxide adhesives J A BISHOPP Basis of toughening... 

Toughened epoxide adhesives blend synergy J A BISHOPP Effects of two types of particles... 

Toughened epoxide adhesives precipitation during cure J A BISHOPP The most widely used method... 

Kilik et al. (1989) have measured thermal conductivities of a toughened epoxide adhesive filled with copper and aluminum powders. The effect of the size and shape of particles is less significant than the amount of filler used. Al-Samhan and Darwish (2005) showed that the thermal conductivity of an adhesive was increased firom 1.06 to 1.81 W m when filled with copper. 

Fay and Maddison (1990) measured times to failure at 100% r.h and 42 8°C for joints in steel with a number of surface treatments, and bonded with a toughened epoxide adhesive. Their results showed that failure was hastened by increasing stress and that time to failure can be much increased by selection of an appropriate surface treatment. 

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