NR/SR substitution

The Rubber Economist Ltd

NR/SR substitution

It should be understood that SR and NR are to some degree substitutes as well as complimentary products to each other. Their relationship is through both their similarities and their differences. The choice of using one or the other depends not on cost consideration but also on the properties and performance required for the end use; as well as other factors including processability in the manufacturer’s factory and strategic reasons.

The trend of NR/SR shares in the tyre and general rubber product sectors are different. In the tyre sector, this depends on whether the tyre is for passenger car or for commercial vehicle. The former weight is about 4-5 kg/tyre and for the latter the average is about 20 kg/tyre. Furthermore, rubber weight per tyre tends to be higher for radial tyre than for a cross-ply tyres. NR is more important in radial and commercial vehicle (CV) tyres than cross-ply or passenger car (PC) tyres. The amount of rubber used in general rubber products varies not only from one product to another but also from the same product produced by different producers. NR latex is important in producing dipped goods and speciality rubbers are mainly used in the general rubber products.

Trends of NR/SR price ratio and SR/NR share, 1990-2007

The changes in input mix of NR/SR need time to happen since quite often manufacturers have long-term contracts for the supply of raw materials and the substitution will involve high extra costs. Therefore substitution will take place only when manufacturers expect the change in relative prices to continue for some period of time. Furthermore the manufacturers have to consider whether the substitution will have any effect on marketability of their product. They also have to consider the expenses involved including developing and testing new compounds, new capital equipment, etc. Substitution because of price criteria is important for those products which are not technically determined.

The choice of a particular type of rubber is determined by the requirement that end-products meet certain specifications. For example, the properties required of elastomers use for hose and tubing are flexibility, abrasion resistance and chemical resistance.

Another important advance of SR over NR is its processability. While many steps are required for NR before it can be used in the Banburry Mixer where lending takes place before vulcanisation, SR can be used immediately. In compounding NR tends to perform better than SR because of its green strength, i.e. the strength of the mix rubber before cross-linking has taken place, and its tack, i.e. the ability to amalgamate.

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