Meaning
Standardized multi-part testing protocols using differential scanning calorimetry characterize the thermal transitions of polymer materials. The iso 11357 thermal analysis standard defines the methods for determining melting and crystallization temperatures, glass transition behavior, and enthalpy changes in plastics. It provides molders with a consistent methodology for analyzing the thermal fingerprint of incoming resins and molded parts, helping them optimize processing temperatures and identify material inconsistencies before molding.
DSC Testing
Temperature scan runs are performed by heating or cooling the sample at a controlled rate, typically ten degrees Celsius per minute, in a controlled atmosphere. The instrument measures the heat flow required to maintain this temperature program, recording endothermic and exothermic events. These thermal profiles are used to verify the purity and grade of the polymer resin.
Crystallinity Assessment
Fusion enthalpy values obtained from the melting peak are compared to the theoretical value for a fully crystalline polymer to calculate the percentage of crystallinity. This percentage is a critical factor in determining the stiffness, shrinkage, and chemical resistance of semi-crystalline molded parts. Molders can use this information to adjust cooling times and mold temperatures to achieve the desired crystallinity.
If the cooling rate is too fast, the crystallinity will be too low, resulting in parts that are soft and prone to post-molding shrinkage. Adjusting these parameters based on this thermal analysis ensures that the finished parts meet the required specifications.
Quality Control
Material fingerprinting using this standard allows molders to identify batches that have been processed incorrectly or contaminated with other resins. If the glass transition temperature or melting point deviates from the expected values, the material may have been degraded or contaminated during transport or handling. This screening helps prevent processing issues and product failures caused by incorrect resin grades.
