Adhesion or Bond Strength

Incorporating lime in mortar is reported to improve adhesion (or bond strength) and reduce rain penetration [26.24]. 

Avery useful aspectof latex-modified mortars and concretes is their improved adhesion or bond strength to various substrates compared to conventional mortar and concrete. The development of adhesion is attributed to the high adhesion of polymers. The adhesion is usually affected by polymer-cement ratio and the properties of substrates used. The data on adhesion often show considerable scatter, and may vary depending on the testing methods, service conditions or porosity of substrates. 

A common procedure used to assess adhesion or bond strength in laminated materials is the Peel test. 

Substrate adhesion, or bond strength, is dependent on die materials and dieir prop es and generally is characterized as a mechanical bond between the coating and the substrate, unlike the metallurgical bond found in weld-overlay coatings. 

ASTM C-1135 can be used to determine the tensile adhesion strength of a sealant bond. Although no ASTM standards that specifically address the measurement of the adhesion or bond strength of sealants loaded in shear, the standards in place for adhesive bonds can be used (single lap shear - ASTM D-1002, notched lap shear - ASTM D-3165, and double lap shear - ASTM D-3528). Much of the adhesion testing that is performed in the industry is testing to determine the effects of environmental and chemical exposure on sealant adhesion. This exposure can be either static or cyclic (Gutowski and Cerra 2009). 

Reacts by accelerating or retarding adhesive cure Properties of modified adhesive affect bond strength ... 

Tile adhesives High bond strength Chemical resistance Bonding ceramic tiles to concrete or steel... 

It is shown that the composite adhesion or bond quality is dependent on the PA-6 modification as examined by tensile test. The processing parameters are not optimised to obtain the highest values for the tensile strength. The aim of this investigation was the determination of the influence of the increase of carboxylic acid... 

The adhesion or bond of latex-modified mortars to reinforcing bars is found to be very important for their use in repair work for damaged reinforced concrete structures. Figure 4.54l l illustrates the bond strength of the latex-modified mortars to the reinforcing bars, determined under direct tension by pull-out method. In general, the bond strength of the latex-... 

Tapes with a pressure-sensitive adhesive (such as standard office tape) are called pressure-sensitive tapes. The adhesives all deteriorate with storage. The deterioration is marked by loss of tack or bond strength and can be inhibited by storage at low temperature. 

A fast-set, smooth workable paste system for use in composite aerospace, aircraft, automotive and general GRP tooling, and final fabrication where potential exposure to elevated temperatures up to 230 C has to be tolerated for short-term or continuous periods. Has excellent adhesion and bond strength to GRP, SMC, BMC, RIM, epoxy, graphite and Kevlar as well as aluminium, plaster and other substrates. 

Satisfactory tensile shear stresses may be achieved in the bonding of glass-filled Noryl or PPO parts with a variety of epoxy, rubber-based, or silicone adhesives. Excellent bond strengths of greater than 5,500 psi have been obtained with Allaco M-2 adhesive (Allaco Products). None of the adhesives listed in Table 5-2 show any evidence of attack on glass-filled PPO or Noryl. 

Elastomer epoxies generally contain nitrile rubber as the elastomeric component. This system is also referred to as a modified or toughened epoxy. One of the applications of widest use is in films and tapes. Elastomer epoxies cure at low pressures and low temperatures over a short time interval. This is achieved by adding a catalyst to the adhesive formulation. Bond strengths of elastomer epoxies are lower than those of nylon epoxies. However, the major advantage of elastomer epoxies is their sub-zero peel strengths, which do not decrease as fast as those of nylon epoxies. In addition, the moisture resistance of elastomer epoxies is better than that of nylon epoxies but not as good as that of vinyl-phenolics or nitrile-phenolics. Limitations to the use of elastomer epoxies include poor water immersion resistance and poor properties when exposed to marine conditions. 

Eor maximum strength, prime with nitrile-phenolic adhesive or bond immediately... 

Adhesives. Acryhc emulsion and solution polymers form the basis of a variety of adhesive types. The principal use is in pressure-sensitive adhesives, where a film of a very low T (<—20 " C) acrylic polymer or copolymer is used on the adherent side of tapes, decals, and labels. Acrylics provide a good balance of tack and bond strength with exceptional color stabiUty and resistance to aging (201,202). AcryUcs also find use in numerous types of constmction adhesive formulations and as film-to-film laminating adhesives (qv). 

Pentaerythritol in rosin ester form is used in hot-melt adhesive formulations, especially ethylene—vinyl acetate (EVA) copolymers, as a tackifier. Polyethers of pentaerythritol or trim ethyl ol eth an e are also used in EVA and polyurethane adhesives, which exhibit excellent bond strength and water resistance. The adhesives maybe available as EVA melts or dispersions (90,91) or as thixotropic, one-package, curable polyurethanes (92). Pentaerythritol spko ortho esters have been used in epoxy resin adhesives (93). The EVA adhesives are especially suitable for cellulose (paper, etc) bonding. 

Adhesives. Contact adhesives are blends of mbber, phenoHc resin, and additives suppHed in solvent or aqueous dispersion form they are typically appHed to both surfaces to be joined (80). Evaporation of the solvent leaves an adhesive film that forms a strong, peel-resistant bond. Contact adhesives are used widely in the furniture and constmction industries and also in the automotive and footwear industries. The phenoHc resins promote adhesion and act as tackifiers, usually at a concentration of 20—40%. In solvent-based contact adhesives, neoprene is preferred, whereas nitrile is used in specialty appHcations. The type and grade of phenoHc resin selected control tack time, bond strength, and durabiHty. 

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