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The Relaxation Times Blog

A Faster Test for Key Tire Performance Predictors

Rheology Scientists & Engineers

Author

Alpha Technologies

So, there’s good news, then bad news, but then good news, again. 

The good news is you’re thinking of getting a Dynamic Mechanical Analyzer (DMA) to measure cured rubber specimens in tension for tire performance predictors. That will significantly increase your ability to improve the value and quality of your material. The bad news is that you will also need to hire a skilled technician to prepare and run those samples. The other bad news is that DMA test times can be prohibitively long when you’re working in a quality release or production environment. So, quality testing a batch as it comes out of the mixer is not really an option with a DMA.

But fortunately, thanks to our good friend Siméon Denis Poisson and the engineers at Alpha Technologies, it is now possible to make these measurements in torsion – providing 11 key tire performance predictors is about 23 minutes. So, instead of spending a lot of money on a DMA, you can run the same tests on Alpha’s Premier RPA – an instrument that you already have in your quality and R&D labs… or should. Good news, indeed.

Take traction and handling, for example.

Start with a tire tread compound that has proven excellent traction and handling and test the rubber in that tire. The result of your testing becomes the reference data for other compounds. Properties for traction and handling are based on your reference compound and values of elastic module (G’) and Tangent Delta (G”/G’ also known as the viscoelastic ratio) are compared against the reference at various temperatures. For example, in the case of winter traction a lower elastic modulus is desirable meaning the product should be soft enough at lower temperatures to allow for full contact of the tread.

Figure 1. Winter Traction of 5 formulations with increasing (1-5) loading levels of silica.

So, how does an RPA get you to the same measurements for modulus as the more expensive and time-consuming DMA? That brings us back to Poisson and his ratio. Since modulus is defined as stress over strain, regardless of being in tension or shear, Poisson’s ratio tells us that modulus measurement on the Premier RPA should be approximately 1/3rd of their DMA counterpart under similar conditions.Rheology Scientists & Engineers“Similar conditions” is the key phrase here. How do you create a sub-zero environment on an RPA to meet the “similar conditions” criteria and allow wet, ice and winter traction measurements? The answer is Alpha Technologies’ latest innovation for their Premier RPA lineup. Utilizing proprietary cooling technology Premier RPA is now capable of being cooled to -25º C. What’s more, these test conditions can be included at the end of a standard RPA release test that measures uncured processing, cure/scorch, and physicals. You are able to add tests for rolling resistance and wet/ice traction predictors that were previously exclusive to a DMA, utilizing Alpha’s Sub-Zero™ technology.

23-minutes to Tire Predictors Paradise

One test, on one sample, utilizing one really cool (pun intended) instrument can give you eleven or more release criteria in about 23 minutes. And, with the addition of automation, even more rigorous release testing can be performed 24/7 without the need for a trained technician or operator.

Table 1. Sample Tire Performance Predictor Test Method

Removing barriers to low temperature quality control.

Many tire companies and rubber compounders often face barriers of cost and personnel to their ability to do more rigorous and consistent low-temperature quality testing. And yet, being able to make these measurements is essential for the safety of people driving in wet and icy winter conditions. The Premier RPA with Sub-Zero technology gives quality labs an extended portfolio of tests they can run at low temperatures, assuring the winter weather performance of their materials.

There’s a lot riding on our testing.™

For more information, contact Alpha Technologies.

Who is Siméon Denis Poisson?

The Baron Siméon Denis Poisson was a French mathematician, engineer and physicist who is credited with many scientific advances in a wide range of disciplines including electricity and magnetism, optics, mechanics and thermodynamics. He began publishing scientific papers at the age of 19, while still a student at the École Polytechnique in Paris. Poisson’s ratio is used to calculate the correlation between testing with a Dynamic Mechanical Analyzer and testing under similar conditions with Alpha’s Premier RPA. The rheology scientists and engineers at Alpha Technologies are always raising the bar for testing that makes a difference in the rubber and polymer world. And they know stuff.

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