Saturday, 19 May 2012

How does Glue acts as An adhesive?

Every one of us knows that glue joins things together. Glue makes things adhere, or stick together. Some sticky substances like honey, syrup and chewing gum can also act like glue. However, they take long time to harden and thus are not good adhesives. A good adhesive is the one that changes from a soft liquid to a hard solid within a short time period.

Ordinary white glue is made from various synthetic chemicals in which the chemical molecules are in the form of polymers or long strands. Some of them are sticky and others are stretchy. By combining these polymers properly with water, can make good glue.

The water present in glue gets evaporated when it is exposed to air and the glue changes itself from a fluid (liquid like) substance into a solid one. As it dries up, it gets hardened. The evaporated of water allows the bond to hold. Once it becomes dry, it acts like a solid grabbing hold to the object on either side to keep it together.

How it holds on the surface?

When we observe any solid substance under a microscope, we can see lots and lots of tiny ridges and bumps on their surface even in perfectly smooth substance like paper etc.

When glue is applies on the surface of these substances, it fills in all of those little spaces on the surface of the things to be joined. It then forms a layer between the two surfaces. Once this layer gets dries and hardens, it holds the two surfaces on either side of it together. Thus, the glue sticks to the surface of each of the material that we want to join and keeps them together.


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