14244 IUPAC Gold Book - fold period 10.1351/goldbook.14244 14244 current synonym: fold length 1 Thickness of a lamellar parallel-chain crystal in the direction of its stems. The fold period corresponds to the long period in the case of solution crystallized stacked lamellar crystals with the chain axis perpendicular to the lamellar surface. In melt-crystallized polymers, consisting of lamellar crystals with the chain axis perpendicular to the lamellar surface, the fold period is shorter than the long period because the amorphous layer includes not only the folds but other non-crystallized components. For lamellar crystals with chains whose axes are not normal to the lamellar surface, the fold period is longer than the long period. The fold period is controlled by the crystallization temperature. long period https://goldbook.iupac.org//terms/view/14251 PAC, 2011, 83, 1831. 'Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)' on page 1852 (https://doi.org/10.1351/PAC-REC-10-11-13) https://goldbook.iupac.org/terms/view/14244/html https://goldbook.iupac.org/terms/view/14244/json https://goldbook.iupac.org/terms/view/14244/plain Citation: 'fold period' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14244 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-06-29T00:18:27+00:00