Adhesive underwater curing

Extensive adhesive testing has been reported for a variety of systems aimed at widely different bonding applications. Aircraft is represented with numerous studies of which selected references are representative for nitrile rubber modified adhesive systems (54-56). Underwater curing adhesives (57), construction adhesives (58), intumescent adhesives (59) and materials related to improved adhesion or adhesives in electrical/electronic circuitry fabrication (60-62) serve to show the wide latitude of nitrile rubber modified adhesive proliferation. ... 

Composite overwrap repairs can provide both strengthening and leak reinforcements to the pipe. Specially formulated resins are required for underwater applications where there are limitations with adhesion and curing. These repairs can be applied in situ without hot work, to partially or completely restore the pressure capacity of a corroded or mptured pipe, with the added corrosion protection benefit. Composite overwraps are primarily suited to onshore or offshore shallow water applications, due to the reliance on personnel to manually apply the composite onto the defect area. In addition, the overwraps require stringent surface preparation to ensure optimum adhesion and effectiveness of the repair, which is not always practical under field conditions. 

As a family of curing agents for epoxy resins, the amidoamines are lower in viscosity than the polyamides. They exhibit very good adhesive properties due to their chemical structure and easy penetration. Amidoamine cured epoxy adhesives have shown very good properties on concrete and other porous substrates. They cure extremely well under humid conditions. In fact amidoamine cured epoxy formulations have been used to cure underwater in certain applications. A typical general-purpose room temperature curing epoxy-amidoamine system is described in Table 11.7. This adhesive is used as a general-purpose metal-to-metal adhesive and body solder in the automotive industry. 

Perhaps, the earlier materials found to have a useful capacity for adhesive bonding underwater depended upon the use of a stoichiometric excess of water-scavenging polyamide hardener in an epoxide-based adhesive. This approach can lead to the production of effective joints in the short term, but formulations of this type, which are hydrophilic in the uncured state, are also likely to absorb significant amounts of water in the cured condition. It is a widely accepted view that the extent of joint weakening in susceptible joints, quite apart from the consequences of plasticization, is a function of the water-uptake characteristics of the adhesive (see Glass transition temperature). The consequence is therefore likely to be that such joints will show poor durability in the presence of water, when rapid uptake of water may lead to equally rapid degradation of both cohesive and interfacial properties (see Durability fundamentals). 

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