The authority on Polymer Sheeting & Rubber Products
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Polymer Content - Busting the Misrepresentation and Myth

23 Oct 2019 | Posted by Andrew Onions

Polymer Content – Busting the Misrepresentation and Myth

We are often asked about the Polymer Content of our materials compared to other options available on the market, and find customers making decisions about supply based on misrepresentation and myth.  Below we have tried to explain what you should believe and what you shouldn’t.

Misrepresentation – Rubber cannot be 100% polymer

This would be like a cake being  100% Flour, 100% Egg or even 100% chocolate, it simply wouldn`t be cake.

The base polymer is the starting block for a Rubber compound, this is essentially a chewing gum like compound of either pure gum rubber or the synthetic equivalent and is basically useless in its raw format.

Depending upon the quality and the technical requirements the percentage of actual Polymer within the finished volume may be as low as 5% for poor quality non European materials and as high as 40% for premium quality European materials.

In order to achieve a fully vulcanised material with specific technical characteristics the base compound needs to be mixed with a wide variety of accelerators, activators, vulcanising agents, softeners, processing aids and fillers.

Therefore, the polymer may be 100% Natural, Neoprene, Nitrile etc, but the relevant question is what percentage of the mix is actually polymer – if you cant get an answer then its probably not going to be good.

MacLellan Rubber materials are all 100% Genuine Polymer but the percentage of the total mix will vary depending on the grade.

Misrepresentation – Mixing SBR with another Rubber grades reduces the performance

SBR is a synthetic rubber compound that is widely mixed in the production of rubber materials, especially but not exclusively standard materials from outside the EU.

It was originally developed as a replacement for Natural Rubber when shortages of pure gum rubber were prevalent and has exceptional abrasion and good tensile characteristics.  It has been adopted as a complimentary mix within standard grades of material in order to meet market expectations on cost reduction, without diminishing the general performance, and therefore is more likely to have improved the overall quality of the material supplied.

Higher Technical Grades of Rubber will always have better physical characteristics and chemical resistance simply because they have more of the main polymer in their mix.

You should also be conscious that chemical resistance advice is typically based on European materials rather than imported blends.

Myth -  A high percentage of Rubber Regrind means the material is a lower quality

Rubber Regrind is a broad definition for all sorts of reprocessed rubber materials.  In some cases this can be a very generic and unsorted composition of whatever goes through the mill.  At the other end of the spectrum this will be recycled tyres which are produced from extremely high-quality rubber, and in some cases, this will actually improve the performance of the base material mix.

Issues with tyre regrind in the early years of its use were around the poor filtering for contaminants, specifically wire, which was could easily find its way into the mix and be vulcanised in the finished sheet.

Processing improvements and inline second stage filtering have all but eliminated the incidence of metal contamination within MacLellan’s standard materials, although we still hear of issues relating to poor quality imports from other distributors.   

Myth – The use of Regrind means that the material is not REACH compliant

As already highlighted any regrind used in the manufacture of MacLellan’s standard grade materials is sourced from qualified sources as will typically be tyre regrind.  Given that the tyre polymer already meets the highest REACH standards we can be confident that we are not compromising the compound mix in this way.

We cannot comment on other manufacturers sourcing procedures or use of regrind.  However indicative features of poor quality regrind being used would be high compression set (50% or above) combined with apparent high elongation and tensile strength.  This contradiction in performance characteristics would suggest poor cross vulcanisation due to poor quality materials being used and potentially under cured material.   

At MacLellan’s we consistently evaluate and review our materials and supply chain to ensure we are delivering the best quality at competitive prices. 

We recognise that there will always be something cheaper available from companies with little technical aptitude, who are simply chasing turnover, but urge our customers to consider what it is they are buying – if you order a pizza and get an under cooked lump of dough or a pancake delivered, you would reject it and complain.  Why would you accept something that is not rubber?