Professional Polymer Technology
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Hot Melt Adhesive are used in many different areas. The […]
Hot Melt Adhesive are used in many different areas. They are so inextricably linked to our lives that we become oblivious of their presence. But if we look around, we will find some kind of adhesive used in every sphere of our daily lives, be it furniture, gadgets or toys. Their varied use in food packaging to building construction has forced the manufacturers to research and make different kinds to suit different needs. Some are toxic and strong, they serve industrial purpose. Some are mild and free of any kinds of toxics. They are used in making toys for children, infant products or edibles packaging. Some are water resistant and non toxic. For example, adhesives are used in the packaging of ice creams.
In the early days of manufacturing adhesive compounds, the terms cement, glue, gums, mortars, resins, mucilage, pastes and adhesives and sealants were used in free exchange of one another. It has been within modern times that we have sought to differentiate between sealants and adhesives. It is a difficult task because most sealants can be adhesives, and most adhesives can be sealants. For example, it is common for polyurethane sealants to have similar strength properties to structural adhesives. Adhesive manufacturers have been working towards setting up better definitions for these terms to guide customers as to what they should purchase.
Various forms of adhesive have been used for a quite long time as evidenced by them being found in the Sibudu Cave of South Africa and dating back to that era. Today, adhesives have advanced far beyond the natural glues found in the Sibudu Cave of plant gum and red ochre, and even the more complex adhesives used 6,000 years ago used on ceramics when someone no doubt carelessly dropped on or knocked it off the end table. Funny how times moves forward but things never change. We still have to fix things and adhesives have been there for us for 74,000 years to help us correct our mistakes.
Drying adhesives is the most common glue in industry. They come in two kinds, first is solvent based adhesives, like white glue, contact adhesives, and rubber cements. They all have varying degrees of adherence depending on their chemical composition. The second is polymer dispersion adhesives. These milky white types of glue are often based on polyvinyl acetates. They are mostly only used in the woodworking, packaging, and fabric industry, with loudspeaker cones also being engineered with them being utilized
Pressure sensitive adhesives work by forming a bond with the use of light pressure. The adhesive is soft enough to flow and adhere which leads to the form of bond. The bond strength is due to its resistance to being separated. Temporary sticky notes also fit under this category, their ability to stick and un-stick repeatedly is related to their soft adhesion, which is good for low weight applications that involve repeated use.
Contact adhesives are used for strong bond purposes with high shear-resistance, such as bonding Formica to a wooden counter, sealing artificial turf, and attaching the soles of your shoes to the uppers. The common make up is of natural rubber and polychloroprene. Both of these undergo strain crystallization which needs the glue to be put on both surfaces and allowed time to dry before the two surfaces can be put together.
The last one I want to look at is natural adhesives. These are sourced from organic matter such as vegetables, starch, resins and animal casein. They are commonly used in bookbinding, and wood joining, but are slowly being replaced by synthetic glues. Although animal glue still remains the preferred adhesive of professional musicians. You just can't get a natural sound with an artificial adhesive.