adhesives

Adhesive or glue is a compound in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. Some modern adhesives are extremely strong, and are becoming increasingly important in modern construction and industry. The types of materials that can be bonded using adhesives is virtually limitless, but they are especially useful for bonding thin materials. Adhesives usually require a controlled temperature to cure or set. They can be electrically and thermally conductive or nonconductive
Categories of adhesives
Natural adhesives
Natural adhesives are made from inorganic mineral sources, or biological sources such as vegetable matter, starch (dextrin), natural resins or from animals e.g. casein or animal glue. They are often referred to as bioadhesives. One example is a simple paste, made by mixing flour and water.

Synthetic adhesives
Elastomers, thermoplastic, and thermosetting adhesives are examples of synthetic adhesives.




Hot adhesives


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A glue gun, an example of a hot adhesive
Main article: Hot glue
Hot adhesives, also known as hot melt adhesives, are simply thermoplastics. They are applied hot and harden as they cool. These adhesives have become popular for crafts because of their ease of use and the wide range of common materials to which they can adhere. A glue gun, pictured right, is one method of applying a hot adhesive. The glue gun melts the solid adhesive and then allows the liquid to pass through the "barrel" of the gun onto the material where it solidifies.
Paul E. Cope is reputed to have invented thermoplastic glue around 1940 while working for Procter & Gamble as a chemical and packaging engineer. His invention solved a problem with water-based adhesives that were commonly used in packaging at that time. Water-based adhesives often released in humid climates, causing packages to open and become damaged.



please see also the website
http://en.wikipedia.org/wiki/Adhesives

任何化學物因其獨特bonding arrangement, 使當其表面與令一物体之表面接觸時, 可以緊緊地連接著, 不會脫離. 而此bonding 可以physical or chemical. 有此特性稱為----ADHESIVES.