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How to compare rubber compounds for slurry applications.

evaluation

Rubber specifications are confusing and some of the properties described in some specification sheet do not help evaluate the wear characteristics of the compound.

In fact most of the time the important lab tests, which tell you how well a rubber will perform in a slurry application are left out.

Specification sheets contain many characteristics which are elemental by definition. In other words the fact that the rubber is tan in color has no relevance to the actual wear “the undesirable mechanical removal of material in fine particle from from the surface.”

Here are some of the common specification criteria and their relevance.

Durometer: (Elemental Property)

In a slurry wear application the fact that a rubber is softter than another may indicate that it may be perfom better or worst but that would be opinion. Harder compounds generally perform better under cut and chip situations but there is a lab test for cut and chip as well as wet sliding abrasion. Durometer is not really the deciding factor. This rubber just happens to be a given duro shore A.

Tensile Strength: (Elemental Property)

Tensile strength is very useful when comparing rubberized tracks and track pads for tanks. As the ability not to rip apart is important. When comparing an elastomeric lining which is adhered to a steel sub-straight it’s tensile strengthen is not relevant factor in this application.

Ultimate Elongation: (Elemental Property)

Going back to my previous example when a snowmobile takes off  the ultimate elongation is very important so that engineers and designers can calculate if this track will perform correctly. In a rubber lined wear application this factor is not relevant. It will never achieve it’s ultimate elongation adhered to a metal sub-straight.

Specific Gravity: (Elemental Property)

This is the actual density of the product. In the olden days the buoyancy of rubber was a good indicator of how many rubber fillers were in the product. Floating rubber was regarded as good rubber. Dense rubber was thought to have more clay which would adversely affected it’s wear performance. This day and age with material sciences helping to improve material quality, adders like carbon is common. Carbon increases wear characteristics in some cases. Therefore the specific gravity is simply that, what it’s density is. Not a good wear performance indicator.

 

Performance properties are “Real factors which can be tested and directly speak to the wear performance in a slurry application.”

 

Cut and Chip: (Wear Performance Property)

Cut and chip is a test performed in a lab where you can accurately compare compounds and find which is the best in a cut and chip application. This is completely relevant when you are trying to increase the longevity of a liner in a slurry application. This was a test devised by BF Goodrich in order to evaluate how good the tires would perform on the road. A very good indicator of wear life.

Wet Abrasion: (Wear Performance Property)

A test to determine the exact resistance in wet abrasion. It’s a sliding plate that cycles on the rubber in a container of a known wear slurry and the removal of the material is then measured to determine is wear performance characteristics. This is very relevant to wet sliding abrasion test to determine the rubber wear.

Water Resistance: (Wear Performance Property)

Also known as the percentage of swell. The reason this is important is the amount of swell will adversely affect wear within certain services such as acid. The more a rubber will swell the less it will perform in that situation.

Resilience:(Wear Performance Property)

The ability to return to it’s original shape is a huge factor in determining if this rubber will be suitable for wear. The more resilient the better the rubber will perform in a slurry application.

Tear (Die C):(Wear Performance Property)

This is another important performance criteria as the ability for the rubber to hang on to the straightaway is important. This is a relevant value when considering rubber for slurry wear applications.

Conclusion

Rubbers with high Cut an Chip resistance and Wet Abrasion resistance will perform better in wet slurry application. Elemental properties such as density are interesting and mater of fact but should not be deciding factors when choosing rubber compounds for wear applications.

 

 

 

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Shelf Life Of Uncured Protective Rubber Linings

Commercial-Grade-Rubber-Sheet

In determining the shelf life of uncured rubber linings, several instances but be understood:

  1. The level of heat memory built into a compound (ex. Synthetic Rubber takes more heat to break down than a Natural Rubber)
  2.  The lower the storage temperature, the longer the rubber lining will be useable.

As a rule of thumb the average uncured rubber linings (NR, IIR) will have a shelf life of approximate shelf life of 9 to 12 months if stored at a temperature of 10°C (also out of sunlight).  If the linings are stored at a lower temperature the rubber lining will much longer the 12 month period.  Please note that Neoprene (CR) and Nitrile (NBR) compounds have a typical shorter shelf life than the above mentioned compounds.  In dealing with these compounds a great of caution is to be used as they can cure much faster.  If storing rubber at a lower temperature that the recommended 10°C  the rubber may become frozen, if this was to happen the roll will need to be unrolled and left at an ambient temperature for 2 weeks to thaw the rubber.  After the 2 week interval the rubber will need to go on a hot table to help facilitate any shrink that might of occurred during the freezing process.

Any Questions please contact RubberSource @ 519-830-0546.

Rubebrsource

 

Buck Meadows / Rubber Technologist

Technical Sales Manager

RubberSource