Meaning
A thermal analysis technique that measures the inherent crystallization and melting behavior of a polymer sample after erasing its thermal history through a controlled cooling cycle provides unbiased material identification. In raw material procurement and quality assurance contracts, the second heat scan is the standard method used to verify the baseline resin grade without the influence of previous molding conditions. This analysis ensures that the material supplied matches the specified polymer grade.
Thermal Reset
The first heating run in differential scanning calorimetry melts the polymer, erasing the effects of rapid cooling or orientation from previous extrusion or molding. After a controlled cooling step, the sample is reheated to obtain the clean baseline data. This process ensures that the thermal properties measured reflect only the polymer chemistry.
Grade Verification
By analyzing the peak melting temperature and enthalpy of fusion, technicians can determine the degree of crystallinity and identify the specific polymer blend. This verification is required when evaluating recycled content or checking for the presence of blended copolymers. Any deviation from the expected melting profile indicates the presence of an incorrect resin grade.
Specification Compliance
Purchasing agreements for high-performance plastics reference the second heat scan to define the acceptable ranges for glass transition and melting temperatures. When a batch of molded parts exhibits premature failure, this testing helps determine if the resin supplier provided the correct material or if the molder processed it incorrectly. If the second heating run shows the polymer meets the raw material specifications, the failure is attributed to processing parameters, shifting the liability to the molder.
These test results act as definitive evidence in resolve-of-dispute procedures between resin manufacturers and plastic converters.
