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.“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.