Adhesive joining

Joining Adhesive joining Bonding Cracking tendency Heat zone effect Welding... 

Hot-melt adhesives the molten adhesive wets the surfaces of the plastics to be assembled and interlocks them while solidifying again on cooling. It is necessary for the materials to be assembled to tolerate the temperature of the molten adhesive. Joining is sensitive to the temperature, which involves the melting of the adhesive joint. However, some hot-melt adhesives crosslink after joining and become less sensitive to heat. 

Adhesive Disadvantages. There are some limitations in using adhesives to form assemblies. The major limitation is that the adhesive joint is formed by means of surface attachment and is, therefore, sensitive to the substrate surface condition. Another limitation of adhesive bonding is the lack of a nondestructive quality control procedure. Finally, adhesive joining is still somewhat limited because most designers of assemblies are simply not familiar with the engineering characteristics of adhesives. 

Even if pigments are completely stable to wet treatments, there is the potential for starch adhesive joins and fills adhered with starch to give way. In addition, delaminations between layers may also occur, or increase if already present. It has also been observed that tapa may decrease in strength while wet, and can be stretched and distorted if not carefully supported. 

The successful use of adhesive joining in producing any assembly depends on viewing... 

For an adhesive to be successful it must compete with non-adhesive joining techniques such as welding, nuts and bolts, rivets and staples. Modern adhesive joining can be used to replace or supplement traditional joining methods only when the quality, performance and economics are acceptable. 

The adhesive joining of hybrid constructions can be considered an example of the transition from nonstructural to stmctural adhesive technology. 

Figure 1 shows a highly demanding structural component in terms of structural adhesive joining. Careful selection and placement of the adhesive bond ensure that the telescope mirror dimensions remain virtually uniform, despite the enormous diameter, under the influence of temperature changes. The coefficient of expansion of the entire system is kept at zero for all practical purposes. 

The entire field of adhesive technology is comprised of 15% structural adhesive joining and 85% other fields of application, which is also reflected in the development of basic materials for adhesive technologies ... 

Fig. 1 Radiotelescope with adhesively Joined structures cranprising CFP segments...

Low-cost adhesive joining of both large and small structural components will... 

Pneumatically powered devices fitted with a wide range of dosing needles are available for application of even the tiniest amounts of adhesive. Fig. 8. This means a high level of consistency in the adhesive amounts and surface areas - an important precondition for uniformly reproducible adhesive strength levels. Also, loss and waste of adhesive is minimized in such applications, so that very little waste disposal is required. Boiling in alkaline solutions completely depolymerizes and dissolves the adhesive. This facilitates reprocessing or dismantling of adhesively joined structural components. 

Since wood, leather, and textiles always continue to supply sufficient moisture, these materials are particularly well-suited to adhesive joining with these adhesives. With impermeable adhesives, the moisture can only diffuse through the adhesive film, so that the postpolymerization process is much slower exceptions to this include, for example, polyamides that contain moisture. 

Hotmelt adhesives are suitable for adhesive joining of clips, lamination of films, leather and textiles and bonding of films, foams, textiles, and wood. Resistance to hot water and steam is a problem that arises most particularly in the field of textile bonding. This problem was solved using hotmelt adhesives based on copolyamides. 

Several different properties are united in the PSAs They remain permanently adherent, can in some cases be used repeatedly, and stick when pressed briefly against a surface. The PSAs, are highly viscous liquids usually applied to carrying materials such as paper, textiles, metal strips, or plastic films. To make transfer strips, the PSAs are applied to siliconized paper, from which they are transferred when needed to a component by means of pressure. Then this component can be adhesively joined to another. 

The typical melting temperatures are between 60 and 200°C, so that temperature-sensitive products can be adhesively joined, resulting in bonds that can withstand high thermal load levels. 

On the other hand, the most recent developments have resulted in adhesives capable of adhesive joining of PE, PP, copolymers and PTFE without pretreatment. 

Shah T, Danzinger S, Moores K, Joshi Y. Cyanate Ester Die Attach Material for Radiation Hardened Electronic Packages. Proc. 3rd Inti. Conf. Adhesive Joining and Coating Techniques in Electronic Mfg. Sep. 1998 49-54. 

Zwohnski M, Hickman J, Rubon H, Zaks Y. Electrically conductive adhesives for surface mount solder replacement. In Proc. Second Int. Conf. Adhesive Joining Coating Tech, in Electronics Mfg. Stockholm Sweden 1996 333-340. 

OfflO STATE UNIVERSITY NEMJET Offiee, 190 West 19th Avenue, Columbus OH 43210, (614) 292-1182. Struetural Adhesive Joining. 

Zwolinski, M., Hickman, J., Rubon, H., and Zaks, Y., Electrically Conductive Adhesives for Surface Mount Solder Replacement, Proc. 2 Inti. Conf. on Adhesive Joining Coating Tech. In Electronics Mfg., Stockholm Sweden, pp. 333-340 (1996)... 

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