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TECHNICAL REPORT
Hardness
Probably this is the most often measured property of tread rubber, using a hardness durometer. Hardness measurements lack in precision since it is very common to find a minimum of 5 points difference in readings measured by various people using different durometers on the same piece of rubber. While ideal hardness is 65 IRHD, many supplies are well
above this level and up to 72. Higher hardness may lead to poor mileage, chunking of tread, bumpy ride etc, as such high hardness is the result of compound formulations of low rubber hydrocarbon with high contents of non-carbonaceous fillers like china clay etc, which are not recommended for use in tread rubber compounds.
Specific Gravity
Specific gravity provides insight on the type and quantum of raw materials used in the manufacture of tread rubber. Higher values may be indicative of usage of large percentage of reclaimed rubber and white fillers, leading to inferior properties and performance. An ideal performing tread normally has a specific gravity around 1.13. Surprisingly most of the samples from Middle East and Africa showed values ranging from 1.16 to 1.19, an indicator of cheapening by unfair means.
While substandard materials bring about disrepute to the concept of retreading itself, the total lack of safety inherent with the use of such unworthy retreads also must be a matter of serious concern. It is to be remembered that when a retread prematurely fails, besides the cost of retreading inputs, and that of utilities, the actual loss is the attainable productive life of a tyre casing too.
One major problem facing the tread and repair material selection is absence of standard specifications for these inputs. Apart from BSAU 144 specifications compiled as early as 1962, which in the present scenario is antiquated, there are no other standards prescribed for tread rubber and retreading inputs which can be bench marked for those making and selling tread rubber and other related retreading inputs.
From the supply sources, it is essential that even when different grades are marketed, ranging from
premium, semi-premium, standard etc., it is essential that such grades are designed considering the requirement of mechanical properties suggested through the graphical representations.
To conclude this short report, it can be suggested that until such time competent authorities come out with standard specifications for tread rubber and tyre repair materials, retreaders by and large, may source their requirements from reputed manufacturers, after assessing the merits on the basis of overall physical properties.
The author, Mr. Joseph Kurian, is a technocrat with five decades of manufacturing experience in retreading materials, embracing modern technology and supplies quality produce worldwide. Currently he is the Managing Director of group of companies with the flagship company M/s United Rubber Pvt. Ltd., located in Western India. For further information, he may be contacted at exports@unirub.com or josephk2642@gmail.com
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