ISO 11357-3:2025

Overview

ISO 11357-3:2025 - Plastics - Differential scanning calorimetry (DSC) - Part 3: Determination of temperature and enthalpy of melting and crystallization specifies a method for measuring melting and crystallization temperatures and enthalpies of crystalline or partially crystalline plastics using conventional DSC. This fourth-edition standard (May 2025) is part of the ISO 11357 series and applies only to conventional DSC as referenced in ISO 11357-1; it explicitly excludes fast DSC methods (ISO 23976).

Key topics and requirements

The standard defines the essential elements required for reliable DSC thermal analysis of plastics:

• Principle: use of conventional differential scanning calorimetry to record thermal transitions associated with melting and crystallization.
• Apparatus and materials: general requirements for DSC instruments and crucibles as referenced to ISO 11357-1.
• Specimen preparation: guidance on sample size, conditioning and handling of crystalline or partially crystalline specimens.
• Test conditions and conditioning: recommended temperature programs, heating/cooling rates and atmosphere considerations (see standard for specifics).
• Calibration: procedures for instrument calibration to ensure accurate temperature and enthalpy results.
• Operating procedure: stepwise workflow covering instrument start-up, sample loading, placing crucibles and running temperature scans.
• Expression of results: methods for determining transition temperatures and calculating enthalpies of fusion/crystallization from DSC traces (see clauses 10.2 and 10.3).
• Fidelity and reporting: criteria for measurement repeatability/uncertainty and the required content of a test report.

Practical applications

ISO 11357-3:2025 is used to generate quantitative, comparable thermal data for plastics:

• Determining melting points and crystallization temperatures for polymer specification and grade control
• Measuring heats of fusion/crystallization to estimate degree of crystallinity
• Supporting processing parameter development (molding, extrusion, annealing)
• Comparing recyclates, blends and formulations for thermal performance
• Failure analysis and material verification in quality assurance

Who should use it

• Polymer R&D and analytical laboratories
• Quality control and production teams in plastics manufacturing
• Certification and testing bodies providing materials compliance services
• Material suppliers, compounders and recyclers seeking validated thermal data

Related standards

• ISO 11357-1 (general principles and equipment for DSC)
• ISO 23976 (fast DSC - excluded by this part)
• Other parts of the ISO 11357 series covering related thermal analysis methods

Keywords: ISO 11357-3:2025, differential scanning calorimetry, DSC, melting enthalpy, crystallization enthalpy, plastics testing, conventional DSC, thermal analysis standard.