The Language of Rubber – Part 7 (Deterioration of Rubber Products) - By John Woon (Senior Latex Consultant)

Natural Rubber products would undergo a deterioration process when exposed to weathering and sunlight. The deterioration rate is increased in the presence of UV light, namely sunlight. The causative factors are widely accepted to be ozone attack and oxidation.

The following changes would take place when a vulcanised rubber product is exposed to weathering conditions:

1) Surface of the rubber would be oxidised with the formation of a softer and sometimes tackier surface skin. If nothing is done at this stage to address the problem, the rubber hardens into a resinous product which very often lead to cracking.

2) Cracking on the surface due to ozone attack especially when the rubber is under stress such as being stretched or compressed.

3) A general drop in physical strength such as tensile strength, along with modulus and elongation.

The resistance to deterioration could be controlled to a certain extent by judicious compound design. Products that could withstand long exposure to sunlight, etc during service life could be produced with the right curatives and antidegradants.