Applicability of the WLF equation to correlation between different evaluating test methods of scratch resistance of automotive coatings

There are many different methods to assess the scratch resistance of automotive coatings but there is no often a good correlation between them. A reason for this non-correlations could be resulted the difference between the strain rate and the operation temperature of different test methods. This paper focuses on investigating the relationships between scratch resistance determined by carwash and other evaluating methods by using of Williams Landel Ferry (WLF) equation. The apparent activation energy of an automotive clearcoat was determined and also strain rates and the operation temperature of laboratory carwash, tensile stress-strain, nano indentation and nano scratch tests were calculated. In The calculated operation temperatures of different test methods show that they are practical and their operation conditions are not difficult.

Keywords:

Scratch resistance , WLF equation , strain rate , apparent activation energy