Supplier of equipment, finance and project management Poly-Test Instruments reports that, although the standard of the rubber tested in South Africa is relatively good, companies often buy cheap imported rubber without the correct specifications and quality assurance.
Poly-Test Instruments rubber consultant Peter O'Hare says that the multi-national tyre and conveyor belt manufacturers have to meet stringent international specifications owing to critical safety issues. However, in the wider industry, where price is more important than quality, standards are often sacrificed.
He adds that locally manufactured rubber tyres are on par with global standards, but other rubber products' standards depend on customer demand, in which price playing a significant role. Because profit margins in the rubber industry are estimated to be between 5% to 10%, companies often choose to trade good standards for lower prices, he says.
Further, companies often choose to buy cheaper rubber that is not suitable for a specific application. Rubber products used in the wrong applications often fail, resulting in significant safety and financial consequences.
"The many different types of rubber must be considered when choosing rubber for a specific application. Rubber used for shoe soles and for hoses has different specifications. Therefore, it is important that each type of rubber is tested according to its specific application," O'Hare explains.
Meanwhile, the testing of rubber also plays an important role in ensuring good quality products. There are two types of rubber manufacturers, namely companies that manufacture rubber compound and companies that convert it to rubber. A compounder puts various chemicals into an industrial mixer in batches of 50 kg to150 kg and then prepare a small sample of this mixed batch for testing. To check that the mixing is thorough, it is essential that the rubber compounder has a quality control laboratory, which requires an investment of about R1-million, he says.
"Most manufacturing plants these days are run by accountants who have little understanding of the technicalities and are driven by bottom line profit. An easy way of cost saving is to dispense with a quality control laboratory altogether, as it is seen as an expense as opposed to an asset," O'Hare points out.
He adds that the most significant outlay in the laboratory would be for a rheometer, which can be bought new at an expense of about R700 000. This instrument takes the uncured rubber compound, cures it and provides graphs and statistical data on the sample. In quality control applications, sensitivity is critical as it allows the laboratory technician to detect small variations in rubber compound ingredients between batches, and thus produces a consistent product.
This resultant information is then compared with the clients' requirement and a compliance certificate is issued. O'Hare believes that only in this way can batch-to-batch variations be detected and quality control maintained. Various other tests should be performed on the cured rubber sample, such as hardness, density, abrasion, elasticity and tensile strength, to provide a comprehensive picture of the material and its performance.