Q. Show the result of vulcanization?
As a result of vulcanization, rubber molecules are cross-linked with sulphur. This cross-linking makes the rubber stronger. It allows the rubber to keep its shape better even when it is stretched over and over again. But there is a drawback of cross-linking also. Vulcanized rubber doesn't flow when it gets hot, therefore one has to mould it into whatever shape one wants before cross linking. Due to the same reason, it can't be recycled - a big environment problem. The tyres of the vehicles also use the same material, and we are not able to recycle the cross-linked rubber used in tyres.
One of the most well known natural rubber is 'Poly-isoprene' which is harvested from the sap of 'Hevea' tree. Natural rubber have all the excellent properties making it extremely suitable to many engineering applications, except for its relatively high reactivity with environment particularly ozone. Ozone causes surface cracking that can rapidly penetrate even at very low tensile stress.