Surface Temperatures in Photodegradation and Weathering
Surface temperature is a critical factor for the rate of photochemical reactions in weathering:
• According to Arrhenius, increasing temperature accelerates the rates of chemical reactions.
• Weathering is a “surface effect”. The surface temperature is key for the degradation rate.
• Specimen properties (color, IR absorbance, material density, thickness, sample backing) influence the surface temperature and the degradation behavior.
The measurement of individual surface temperatures with thermocouples is complex and not feasible for multiple samples especially in laboratory weathering instruments. Therefore, surface temperatures are usually neglected or only roughly estimated based on black and white standard or panel reference temperatures.
Specific Specimen Surface Temperature Measurement with Atlas S3T
Atlas S3T system measures the actual surface temperature through contactless pyrometer technology. It helps to optimize test parameters and provides:
• Better reproduction of natural conditions (heat uptake, color distribution)
• Better control of test parameters to avoid overheating of specimens
• Continuous tracing of the specific sample temperature allowing for the immediate detection of property changes such as darkening without disruption of the test
• Investigation of specific sample characteristics e.g. cool pigments, IR-reflective coatings or effectiveness of heat and light stabilizers
S3T contactless sensor inside a Ci5000
Benefits of Knowing the Actual Surface Temperature of a Material
S3T assists experimenters in analyzing and investigating weathering processes and results and provides opportunities and benefits:
• Comparison between different exposures
• Estimation of theoretical acceleration factors (based on Arrhenius)
• Determination of activation energies of photochemical degradation reactions
• Reproducibility of weathering data
• Planning and evaluation of correlation studies
• Exact data for modelling
Validation of S3T against thermocouples for many standards
S3T Technical Details
The core of the S³T system is an integrated stationary IR pyrometer which measures and assigns the surface temperature of each specimen in the middle specimen tier. S³T system calibration is traceable to a recognized standards body.
The accuracy has been validated for various basic standards using thermocouples.
The S³T system can operate continuously during the complete exposure.
S3T technology is available in Atlas Ci5000 Weather-Ometer.
Ci5000 Weather-Ometer
More Information
Download a free Technical Note on Specific Specimen Surface Temperature Measurement (S3T) technology.
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