Professional Polymer Technology
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Introduction Do you remember using pur hot melt adhesiv […]
Do you remember using pur hot melt adhesive to paste your drawings on the wall when you were a kid in elementary school? The glue that you used is actually a type of adhesive. An adhesive, in simple terms is basically a material that usually comes in liquid or semi-liquid state and sticks at least two items together. A disadvantage that adhesives posses is that unlike other joint making processes, they do not make joint instantaneously as they require some time to harden and stick the two materials together. They are used very vastly around us due to the fact that they are easy to use and portable. Their uses extend from fixing the soles of shoes to repairing of wooden furniture. Although we may be oblivious to the fact, if we actually take notice, the use of adhesive is very important to us.
Adhesives were first extracted from plants but now can be manufactured synthetically. The first known adhesive to man dates back to around the 200 000 BC. From the 5th to the 15th century, egg white was used in Europe as glue for decorative purposes. Ever since their discovery, adhesives have been continuously developed to meet the needs of people. Adhesive can be classified according to the way they are able to stick and join two things together. Its two main groups are reactive and non-reactive which have a number of sub-categories under them.
Solvent based and emulsion adhesives harden by drying. A solvent based adhesive is one that had mixtures combined to a solvent. They harden as the solvent evaporates and the strength of the bond they form between the two materials being joined depends on the properties of those two materials. Some examples of such can be white glue and contact cements.
These are another category of non-reactive adhesives that form bonds which have very high shear resistance. These adhesives are used in joining the soles of shoes as the bonds between the sole and the shoe need to be strong and shear resistant. They also need to be applied to both surfaces in order to create a strong bond.
This type form bonds through a chemical reaction with an external source that can be heat or moisture. Light curing adhesives (LCM) are amongst the popular adhesives between manufacturers since they can cure very quickly and form very strong bond. With qualities like being able to withstand high temperature, these adhesives have become an ideal choice for industries such as electronics, medical and telecommunications.