Applications of Adhesives

In joining reinforced thermosetting pipe it is particularly important that the pipe be cut without chipping or cracking it. It is also important to sand, file, or grind any mold-release agent from the surfaces to be cemented. Joints are built up layer by layer of adhesive-saturated reinforcement by following the manufacturer s recommended procedure. Application of adhesive to the surfaces to be joined and assembly of these surfaces shall produce a continuous bond and provide an adhesive seal to protect the reinforcement from attack by the contents of the pipe. Unfilled or unbonded areas of the joint are considered defects and must be repaired. 

In many instances, vibration problems in turbomachinery can be attributed to faulty support. Once the problem areas have been identified, correcting defects can be a logical procedure. What is novel is that this result can often be accomplished through the proper selection and application of adhesives. 

The primary challenge facing adhesive bonding of metals is to obtain sufficient durability of a bonded structure. Initial bond strength in metal-polymer adhesive joints is almost invariably excellent. Challenging the application of adhesives in polymer-polymer joining, however, is the problem of obtaining a joint that is... 

Application of adhesive primer presents another challenge. Most adhesive primers require a high-temperature cure, which presents the potential for damaging existing bondlines. Infrared curing can be used to reduce the likelihood of problems. 

Adhesives are not used Just for structural applications on modern aircraft. In fact, the number of non-structural applications of adhesives vastly outnumbers the structural applications. Adhesives are used for everything from assembling lavatory walls to attaching the No Smoking sign to cabin partitions. Just a sampling of adhesive types and applications are discussed below. 

The military has historically led the way in the development and application of adhesive bonding on aircraft. This practice continues today, primarily with bombers, fighter and attack aircraft where weight is a critical consideration, but also with support craft such as reconnaissance aircraft and freighters. 

Volume I of Adhesion Science and Engineering dealt with the mechanics of adhesive bonds and the rheology of adhesives. Volume II deals with the other two disciplines that make up adhesion science, surfaces and chemistry. In addition, this volume describes several applications of adhesion science and engineering. 

The final section in this volume deals with applications of adhesion science. The applications described include methods by which durable adhesive bonds can be manufactured by the use of appropriate surface preparation (Davis and Venables) to unique methods for composite repair (Lopata et al.) Adhesive applications find their way into the generation of wood products (Dunky and Pizzi) and also find their way into the construction of commercial and military aircraft (Pate). The chapter by Spotnitz et al. shows that adhesion science finds its way into the life sciences in their discussion of tissue adhesives. 

This means that ys for Teflon arises only from dispersion (SD) forces. On the other hand, a glass surface shows ys that will be composed of both SD and SP. Hence, the main difference between Teflon and glass surface will arise from the SP component of glass. These criteria have been found to be of importance in the case of the application of adhesives. The adhesive used for glass will need to bind to solid with both polar and apolar forces. 

The criteria for sutureless adhesives are still being developed. Although the criteria are not well defined, the following Table 3.2 embodies certain essential properties that will continue to apply until in vivo testing is complete. These criteria are offered as a template for collecting data after application of adhesives in animals, and the data listed in Table 3.3 are indications of the stress-strain relationships to be expected in humans. 

Brushes, simple rollers, syringes, squeeze bottles, and pressurized glue guns are manual methods that provide simplicity, low cost, and versatility. These methods are probably the most widely used because of their simplicity. Manual dispensing methods allow application of adhesive to only a small segment of a surface and are particularly effective for small or irregular parts or low-volume production. 

Robots are fast gaining prominence in the field of material dispensing, especially in the application of adhesives and sealants. The use of robots provides the end user with the following benefits ... 

FIGURE 17.8 Methods of machine application of adhesive coatings.11... 

Procedures for cleaning, etching, and drying the surfaces of the substrates prior to application of adhesive. 

The time between surface preparation and application of adhesive and the environmental conditions present during this period. This includes the temperature and percent of relative humidity. Usually standard atmospheric conditions are specified (25°C and 50 + 4 percent relative humidity). 

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