Chemical properties

Chemical properties

Standard Malaysian rubber

There is always a small amount of non-rubber materials in natural rubber (Standard Malaysian Rubber ) , which although the amount of these materials is very small (5 to 8%), but have a profound effect on the properties of rubber. These materials were present in the leachate from the beginning and their amount was closed in dry rubber .It differs in the way it is prepared. However, because the amount of these substances in the leachate also changes in different seasons and different times during the leachate day, the rubbers (Standard Malaysian Rubber ) that are prepared in exactly the same conditions do not have the same properties.

The protein in rubber activates the curing system and changes its properties after curing the rubber. Fatty acids, sterols and esters are less important, however, they have anti-oxidant properties in rubber. The amount of ash in natural rubber (Standard Malaysian Rubber ) is important in that it contains copper and manganese because these two substances have a strong catalytic effect on the oxidation process of rubber and in high quality rubber their amount should be less than 0.001%. The bark of the tree also contains a relatively large amount of manganese, so it should be kept to a minimum in rubber. 

The natural rubber (Standard Malaysian Rubber ) hydrocarbon fraction, as mentioned earlier, is more than 99.99% cis 1 and 4 polyisoprene, which has completely different properties from trans 1 and 4. It has polyisoprene (gutta-percha). The average molecular weight of polyisoprene in natural rubber varies from 200,000 to 400,000. That is, there are about 3,000 to 5,000 isoprene units in each chain. 

It is because of this wide distribution of molecular weight that the processability of natural rubber (Standard Malaysian Rubber ) is excellent  in polyisoprene, there is one double bond per unit of isoprene. This dual bond acts as an open and tends to react with substances that participate in electron-cell reactions. The presence of methyl groups in 1 and 4 polyisoprenes causes an increase It has dual bond activity, which is why natural rubber is more reactive than SBR or polybutadiene to a wider range of chemicals (including curing system materials

Natural rubber due to the presence of double bond

(Unsaturation) Reacts easily with oxidizing agents such as peroxides, peroxyacids, potassium manganate, ozone, chlorine … On the other hand, because NR contains some antioxidants, it can be stored for a long time under normal conditions. However, with increasing temperature or exposure to light, NR is oxidized and hydroperoxides are formed in it. The presence of even a small amount of copper and manganese salts causes these hydroperoxides to become active radicals and the oxidation of the polymer to continue.


Table of Contents