Specifications - Types of Adhesives

Adhesives for Automatic Machine Labelling of Glass Bottles (Intent to Withdraw). 

ASTM D 1874-62 (1986) Specification for Water- or Solvent-Soluble Liquid Adhesives for Automatic Machine Scaling of Top Flaps of Fiberboard Shipping Cases. 

ASTM D 4317-88 Specification for Polyvinyl Acetate-Based Emulsion Adhesives. 

ASTM D 4690-90 Specification for Urea-Formaldehyde Resin Adhesives. 

BS 1000[665] 1979 Universal Decimal Classification. Second English full edition. Oils. Fats. Waxes. Adhesives. Gums. Resins. 

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A specific type of adhesive failure is lift which is a very slow low-angle peel of a tape at its edges. The optimal physical properties to resist lift often differ from those necessary to provide high short-term peel adhesion. Longer time (low frequency) material properties become important, and the ability of the adhesive or backing to relax stress over time also becomes important, since stresses imparted to the tape during application can lead to long-term failure if they cannot be dissipated. 

The required service properties frequently can be obtained by using different basic raw materials or different kinds of formulations. Accordingly, the raw materials often cannot be assigned unequivocally to specific types of adhesive. Because almost every polymer and resin and also many other substances in principle may be used for the production of adhesives, it is not possible to provide a complete list of every possible raw material. For this reason, only the most important are listed in the following. 

Application consideration. There are, of course, certain applications that require specific types of adhesive. Again, available equipment may limit adhesive choice, and special adhesives can be very expensive. Generally speaking, however, the performance requirements are much more rigid than application requirements. 

But these books usually focus either on the science and chemistry of adhesion and adhesives, on specific types of adhesives (such as pressure-sensitive adhesives, structural adhesives) or on industries that use adhesives and sealants, such as packaging, construction, metal bonding, etc. 

The problem of adhesion between a polymer and a metal is strongly dependent on the specific type of polymer and metal involved, as well as on the deposition process under which the interface between the two is formed. In order to improve adhesion, different pretreatment methods can be used, but the development of such techniques requires detailed information about metal-polymer interfaces. Particularly, in the case of thin metal films deposited by physical vapor deposition (PVD) in ultra high vaccum (UHV), X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) have been used to obtain chemical information about initial film growth modes,... 

The many different types of adhesives and the wide variety of ways in which they can be used influence the potential for migration of chemicals into the packaged food. This then helps to provide a framework for subsequent considerations of specific applications. The two main parameters considered are the surface area of adhesive used and the residual content of low molecular weight substances. Taking surface area first, there clearly is a quantitative difference between small spots or strips of adhesive used at ends and seams to fabricate cartons and pouches or used to attach small sticky labels, compared to an adhesive used to glue whole sheets of materials together to make a laminate. As regards composition, for solvent-based, water-based heatseal... 

In the foUowing sections, we will describe methods to prepare vascular and organ-specific microvascular EC, methods for phenotypic modulation of EC in vitro (organ-specific modulation by subendothelial matrix, and activation by cytokines), and different types of adhesion assay of tumor cells on cultured EC. 

One typical concern with acrylic adhesives, specifically those containing methyl methacrylate as a component, is the characteristic odor of the methyl methacrylate monomer. This odor may be objectionable to some people and may result in the use of other types of adhesives instead. Later in this chapter some of the new low odor formulations will be briefly discussed as alternative adhesives where odor has been an issue. This new technology offers performance characteristics equal to methyl methacrylate-containing products, albeit at a higher price. 

Another method to combine materials is to join them with an adhesive such as glue (Figure 16-27). Each type of adhesive is designed to be used with specific materials. Wood glue is used when building a prototype with lumber. It bonds quickly and is not toxic. 

With single-component adhesives, the adhesive components are premixed in their final proportions. They are however chemically blocked. As long as they are not subjected to the specific conditions which activate the hardener, they will not bond. They require either high temperature or substances or media (light and humidity) from their surroundings to initiate the curing mechanism. The containers in which this type of adhesive is stored are carefully chosen to prevent any undesirable reaction. 

A cream for use on the skin to protect against injury (e.g., dermatitis, inflammation, etc.) from contact with specific types of harmful substances (e.g., adhesives, oils, solvents, resins, fiberglass, dyes, etc.). 

As mentioned earlier, joints should be specifically designed for adhesive bonding. Figure 7.2 illustrates various types of adhesive joints used for flat adherends. Adhesive bonds designed to follow the following general principles will result in maximum effectiveness... 

For the best possible performance, joints should be specifically designed for adhesive bonding. In a few cases only can an adhesive be used on a joint not specifically designed for adhesives - mainly cylindrical joints. Bond stresses, materials, type of adhesive, surface preparation, methods of application and production requirements can then all be considered in relation to each other at the outset. The designer should consider especially the effect of shear, tension, cleavage and peel stresses upon the joint (Fig. 1) (see Joint design strength and fracture perspectives). 

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