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Is it true that good quality rubber = high duro?
Last July, we talked about components that had a direct impact on rubber properties. I pointed out that it wasn’t easy to affirm that cheap rubber was made of synthetic material. Sometimes I hear that good rubber = high duro… Nothing could be further from the truth!!! Now we’ll explain how rubber is being tested here at LanOTR:
The duro is a measure used to determine the hardness of a semi-solid material. Therefore, steel or glass will have a duro of 100% while liquids will have a duro of 0%. Generally speaking I have observed duros of between 55 and 75 regardless of the brand and application of the tires. Consequently, if the duro is not the measure, what are the most important properties to look for?:
1. Capacity of material to stretch without tearing: Particularly for tires, we need a rubber that can stretch to the extreme before it tears to avoid puncture. Therefore, standard tests are being performed to compare compounds between themselves. This value needs to be maximized to obtain the strength required to avoid puncture and also that the material is able to stretch to the extreme before tearing occurs.
2. Material capacity to dissipate heat : We know that for rubber, heat = vulcanization.. Therefore, an overheated tire will reach the point where rubber will start to vulcanize… Consequently, rubber will degrade and decompose; this will lead to premature wear but more precisely to separations. There are some standard tests that measure the energy stored in a particular material. The concept is to drop a standard sledgehammer on the material (from a reasonable height). Thus, if the sledgehammer bounces up to the original height, it means that the least energy has been stored in the material itself and less it will tend to heat. This property depends on the chemical structure, therefore on the ingredients used.
3. Abrasion test: One of the main property of a tire is to wear slowly. Consequently, the use of standard tests is a must to wear rubber samples. They must be tested from different angles because rubber has long molecules and according to its compounding and production, these molecules will tend to be misaligned. This could significantly affect the abrasion resistance in some ways.
In our case, we perform one-off tests on a regular basis such as : change of properties caused by outside temperature variations (from -40 to +40 Celcius), hydrocarbon resistance such as oil, gasoline or in case of spill (ex : wheel bearing) and others…
Frankly, I would love to say that the duro tells everything… It would be so easy! But unfortunately no, we need to be systematic and it’s just the beginning!
Daniel Marleau – PDG LanOTR