Deconvolution Protocols for Melt Crystallization Peaks in Recyclate Blends
Deconvolution of DSC melt crystallization peaks isolates PE and PP fractions in recyclates to verify composition before compounding.
Thermal History Erasure
Meaning
Pre-processing step in thermal analysis heats a sample above its melting point to remove the influence of previous processing conditions. Thermal history erasure ensures that a resin test reflects the inherent properties of the material rather than the effects of extrusion or moulding. Without this step, differential scanning calorimetry results would be biased by the cooling rate and shear stress the polymer experienced during pelletization.
This is particularly important when comparing a virgin resin to a regrind sample that has undergone multiple heat cycles.
Standard Procedure
Heating the specimen to at least 30 degrees Celsius above its peak melting temperature is usually sufficient to randomize the polymer chains. Once the melt is held at this temperature, thermal history erasure is complete, and the sample can be cooled at a controlled rate to establish a known baseline. This allows for an objective measurement of the glass transition and crystallization temperatures.
Testing Accuracy
Quality control labs use this method to detect contaminants that change the crystallization behavior. Even small amounts of foreign polymer can be identified by looking for unexpected peaks in the cooling curve.
Material Evaluation
Comparison between the first and second heating scans reveals how much the processing history affected the part. This data helps the moulder understand the level of internal stress present in the original component.