The first heating scan

Differential scanning calorimetry records heat flow as a small specimen follows a temperature program. The first heating scan can reflect the condition of the molded sample as received. Depending on the polymer, the curve may show a glass transition, a relaxation feature, cold crystallization or melting. The cooling and storage history of the part can affect which features appear and how they look.

Packaging sample showroom of SamBound New Material Technology Company Ltd. (sambound.com).

The controlled cooling and second scan

A common comparison heats the specimen through the relevant transitions, cools it at a defined rate and then heats it again. The second scan describes the same material after that laboratory history. Its shape still depends on the chosen cooling and heating rates. Where the first and second curves differ, check whether the difference is consistent with thermal history or with a change during the first scan, such as degradation.

To compare two molded packaging lots, sample equivalent locations and record the rates, temperature range, atmosphere and specimen mass. A difference between curves can justify further investigation, but the scans do not reconstruct exact molding settings or establish whether a finished closure will hold its dimensions.

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