Structural adhesives nature

The inner liner forms the vital internal membrane which holds the inflation medium at an elevated pressure within the structure of the tire. In early days the liner was a separate tube of natural or butyl, or more particularly, XIIR compound as an integral part of the tire structure. Adhesion levels of butyl compounds can be critically low requiring an insulating or barrier layer of an NR compound to act as an interface between the liner and the casing. 

Natural-product-based structural adhesives include protein-based adhesives, starch-based adhesives, and cellulosics. 

Of the two groups, the reactive diluents are generally preferred for structural adhesives applications because they do not degrade end properties as much as the unreactive diluents do. Note that diluents, either reactive or unreactive, do not necessarily result in an increase in elongation of the cured epoxy. They may only reduce modulus and hardness. Their enhancement regarding flexibility will depend on the component s functionality and molecular nature. 

With regard to their chemical structure, adhesives are to be assigned to the organic compounds. In contrast to inorganic chemistry, which treats matters of the inanimate nature (e.g., minerals, metals), organic chemistry deals with compounds of carbon as the central element of diverse matters that make up the animate nature (e.g., plant and animal products such as wood, proteins, resins, fats, petroleum). 

The automotive industry is committed to plastic recovery and re-use programs. Problems often arise regarding the incompatibility of the structural adhesive with the plastic recycle recovery process. The intrinsic nature of most structural adhesives poses a serious regrind problem, and therefore the adhesive must be cut out of... 

Plastic products are based on polymers, materials which are omnipresent in nature (cellulose, proteins) or in synthetic form (textiles, adhesives). In contrast to metals and other construction materials, polymers are organic materials with properties that depend strongly upon the environment in which they exist. A prerequisite to fully understand the life cycle of a plastic product is to examine the structure and nature of polymers. 

The problem with high-energy adherend surfaces is that atmospheric contaminants are readily adsorbed on them, so reducing the surface free energy of attraction for the adhesive. Kinloch(2) suggests that the polar nature of structural adhesives will lead to displacement of the less polar, often hydrocarbon, contaminants. Polar water molecules, on the other hand, seem less likely to be readily displaced and, in view of their very small size in relation to an adhesive macromolecule, are able to adsorb in vast numbers on the surface. 

L. H. Lee (Xerox Corporation) What is the nature of the primer for polyurethane structural adhesives ... 

It will often be necessary to undertake very complex testing to yield detailed results before an adhesive joint is used in service. Once this has been done, it may be adequate for quality control purposes to use a relatively simple test, if its results are sensitive to critical factors affecting performance of the joint When a test procedure is chosen, it is necessary to consider the nature of the adhesive a test suitable for a rigid structural adhesive is unlikely to be useM for an elastomeric system such as an adhesive tape. 

The markets for structural adhesives have been indicated in the preceding section. Some applications will be discussed in the chapters dealing with the different classes. As might be expected, many examples are available illustrating the very diverse nature of structural adhesive bonding. A number of references are included here to provide some indication of typical end uses in such markets as transportation, construction, machinery, electronics, and general product assembly. ... 

If we consider the load bearing capabilities of a high strength structural adhesive under all these conditions, it is clear that the nature of the joint is fundamental in achieving satisfactory performance (Fig. 4). 

Sticky tapes and labels are obvious uses of adhesives that cover a wide range of everyday applications. A relatively new type of adhesive has apparently been used in the manufacture of Post-it (trademark, 3M) products, small slips of paper with a reusable adhesive strip at one edge. SEM images show the adhesive partly coating the paper fibers (Fig. 5.83) [396]. Rounded domains of about 5-50 /xm form a contact on the applied surface (Fig. 5.83A). Regions between these rounded domains have a fine particulate structure which does not adhere, permitting the label to be removed easily. In order to image the adhesive nature of these materials, two adhesive strips were attached and then peeled back and exanuned in the SEM. (The adhesive strip and a piece of paper peel away from each other too... 

Over the past thirty years, new analytical techniques have been developed which allow the scientific study of adhesives. Our Symposium this week concerns the science of adhesives and this session focuses on Natural and Structural Adhesives. The papers today exemplify recently developed techniques and show the high science approach being applied to the adhesive bond. These studies replace historically empirical ones and begin to elucidate and separate the adhesive and cohesive factors. 

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