Thermal Desorption Oven Calibration Standards for Recycled Engineering Thermoplastics
Calibrating thermal desorption ovens with matrix-matched gas-phase standards prevents outgassing underestimates in post-consumer engineering resin qualification.
Hexadecane Equivalents
Meaning
Calibration metric representing the concentration of high-boiling volatile organic compounds relative to a hexadecane reference is used to evaluate plastic outgassing. Thermal desorption analyses of automotive plastics employ hexadecane equivalents to quantify the condensable fogging residue.
Emission Quantification
High-temperature emissions from molded components are evaluated by comparing the chromatographic peak areas of the sample against those of a known hexadecane standard. This comparison relates to the FOG value under the vda 278 standard, which dictates emission limits for interior cabin parts. Expressing the results in hexadecane equivalents provides a uniform baseline for comparing the outgassing tendencies of different thermoplastic grades.
Molding Parameters
Melt temperatures that exceed the recommended limits of the resin datasheet accelerate the thermal degradation of the polymer chain. This decomposition increases the volume of semi-volatile compounds that can be measured as hexadecane equivalents in the finished part. Molders utilize these values to modify screw speed and back pressure, seeking to reduce shear heating and subsequent outgassing defects.
Material Qualification
Automotive OEMs establish strict thresholds for condensable organic emissions to prevent windshield fogging and passenger cabin odors. Using recycled resins often results in higher hexadecane equivalents than virgin resins due to residual contaminants from previous life cycles. Testing material batches ensures that the molders select polymers that comply with vehicle safety and environmental standards.