fold period

symbol: $L_{\rm{f}}$; unit: $\pu{m}$
synonym: fold length
https://doi.org/10.1351/goldbook.14244
Thickness of a lamellar parallel-chain crystal in the direction of its stems.
Notes:
  1. 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.
  2. 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.
  3. For lamellar crystals with chains whose axes are not normal to the lamellar surface, the fold period is longer than the long period.
  4. The fold period is controlled by the crystallization temperature.
Source:
PAC, 2011, 83, 1831. (Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)) on page 1852 [Terms] [Paper]
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. https://doi.org/10.1351/goldbook.14244 RIS BibTex EndNote
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