adhesives
adhesives are used to stick objects together.they can be made from natural materials such as bones horns and animals skin which can be boiled to make glue. plants with a lot of starch such as potatoes can also be used to make glue. liquid rubber is another example of a good natural adhesive or glue.
adhesives can also be made artificially.synthetic adhesives are stronger than natural ones.some called thermoplastics get soft when heated and hard again when cold.for example synthetic resins are used to stick together the layers of glass that make the safety glass of car windscreens. other thermosetting adhesives become very hard when heated.they are usually made by mixing two chemicals and heating the mixture to make a very strong bond.some thermosetting adhesives are used to stick the layers of plywood together.among the strongest adhesives of all are EPOXY RESINS see also PLASTICS.