Methods of adhesive application

When large, flat surfaces and webs of materials are to be coated and when production reaches rates of 200 to 300 pieces per day, machine methods of application should be considered over the manual methods described above. Mechanical-roller methods are commonly used to apply a uniform layer of adhesive via a continuous roll. Such automated systems are used with adhesives that have a long working life and low viscosity. Various machine methods of adhesive application are illustrated in Fig. 17.8, and several are described below. 

The large standard deviation observed (compared with untreated papers) reflects nonuniformity in sample thickness produced by the above methods of adhesive application. Generally, it was observed that the treated paper ruptured before the adhesive. The double folds to rupture the paper and the double folds to complete rupture of the system are reported. 

Methods of adhesive application Adhesives may be applied in several ways, as follows. 

Manufacturing facilities, e.g. methods of adhesive application, cure rate, health and safety issues (when solvents are involved). 

Figure 1. The use of adhesive pellets as a self-metering method of adhesive application.

Film adhesives offer the simplest method of adhesive application to the substrate to be bonded. This is particularly so when the tack of the film is highly controlled enough tack to ensure the film stays where it is put but not so high as to prevent repositioning. 

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

In this paper, we have presented test results of two methods of adhesion improvement on a specific aluminum alloy and a stainless steel. The methods are based on flame pyrolysis of silane precursors and a laser pretreatment in connection with a primer. While the first method seems to be most favorable for steel surfaces, the latter gives good results on both aluminum and steel. Both methods are well suited for application in the railroad industry since they are effective under atmospheric conditions and are therefore promising for integration in an automated production line. 

Adhesives may be classified by various methods such as function, chemical composition, mode of application and setting, physical form, cost, and end use. The most common methods of adhesive classification are summarized in Table 7.6 (p. 7.22). 

Similar relationships for the variation of adhesion, depending on the method of dust application, were obtained not only for water, but also for aqueous solutions of sodium dodecyl sulfate and a dodecyl octaglycol ether [165]. 

Screen printing is not suitable for use with low-viscosity products. These fluid materials can, sometimes, be applied by transfer printing methods. One such system utilizes a printing pad of the proper shape immersed in a reservoir of adhesive. Application takes place when the pad is raised up through the liquid and then contacts the substrate positioned above the reservoir. 

An adhesive is a material that is used to join two objects through nonmechanical means. It is placed between the objects, which usually are called adherends when part of a test piece or substrates when part of an assembly, to create an adhesive joint. Although some adhesives form joints that nearly immediately are as strong as they will be in actual use, other adhesives require further operations for the adhesive joint to reach its full strength. Adhesives can be made in several different physical forms, and the form of a given adhesive will define the possible methods of its application to the substrate. 

Metering/Dispensing/Application methods is a big and important chapter of this Volume 2, where we have reviewed all the methods of dispensing/application for every type of adhesive and sealant, in all industries,... 

A number of other specialized adhesion testing methods have been tried, but most apply only to a very limited class of materials. These other methods use many other techniques, such as surface indentation probes or acoustic or thermal shock of the coating to get an idea of the film adhesion. In addition to being applicable only to a small class of materials, all of these techniques are plagued by the lack of a direct relation to adhesive strength and limited use and experience with the technique. Reference 16 reviews a few of the more common methods of adhesion testing. 

Generally, this adhesion is obtained by prior treatment of the fabric, although there are other ways by which adequate adhesion can be obtained. Needless to say, the methods used are largely dictated by the type of fibre being used, the polymer to which it is to be bonded and final application of the composite product. The various methods of adhesion are discussed in this chapter, together with other factors which can affect adhesion. Finally, the environmental aspects of the various treatments are considered. 

There are many non-destructive methods of adhesion strength evalua-tion. These methods give indirect evaluation of adhesion interaction based on the change of the interphase layer properties. The analysis of propagation of ultrasound waves is one of the most widely used methods.The application of the surface ultrasound waves was described for evaluation of adhesion. The principle of the method is based on the observation that the surface waves formed in the support are transformed into the interfacial waves which provoke the shear stresses near the interface. Their magnitude strongly depends on the... 

The adhesive and the method of its application can be very critical in gaining a satisfactory bond. In most bonding experiments the adhesive bond would fail when the specimens were plunged in liquid nitrogen. The method used (Table I) may... 

The poly(vinyl ethers), whieh were first made available in Germany before 1940, are not of importance in the plastics industry but have applications in adhesives, surfaee coatings and rubber technology. Of the many vinyl ether polymers prepared, only those from the vinyl alkyl ethers and some halogenated variants are of interest. Two methods of monomer preparations may be used. 

Because of their ease of use and their cost-effectiveness relative to other methods of assembly, pressure sensitive adhesives continue to penetrate all kinds of industrial applications. Some of the main reasons PSAs and PSA coated articles are prime candidates for industrial applications include the following ... 

The viscosity of elastomeric adhesives determines their method of application. Typically, solvent-borne rubber compounds require low viscosities for application. Thus, viscosities lower than 0.6 Pas for spray, curtain or dip applications are required, whereas for brush application viscosities lower than 5 Pa s are generally used. Roll- coating technology requires viscosities between 5 and 15 Pa s. 

Each of these product types will be discussed, including the method of application, the type of substrates that are bonded by each approach, and one or more typical adhesive formulations. In order to understand the adhesive cure mechanism, a brief review of the common urethane reactions is needed. 

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