Phase densities and lamellar morphologies of semicrystalline polyethylenes via absolute small-angle X-ray scattering measurements

• Published in: Journal of applied crystallography 2015-10, Vol.48 (5), p.1498-1506
• Main Authors: Basiura-Cembala, Monika, Erlacher, Kurt, Pedersen, Jan Skov, Goderis, Bart
• Format: Article
• Language: English
• Subjects: absolute invariant; amorphous phases; Crystallography; Morphology; Polyethylene; Scattering; small-angle X-ray scattering; Solar energy
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S1600576715014752

With the crystalline volume fraction from small‐angle X‐ray scattering (SAXS) and the density of the crystalline phase from wide‐angle X‐ray diffraction, the amorphous phase density of two representative polyethylenes was calculated as a function of temperature using the absolute total SAXS scattering power or invariant. The density of the amorphous phase in semicrystalline polyethylene is crystallinity independent and is lower than melt‐extrapolated values reported in the literature. Model‐independent SAXS‐based crystallinity values can be calculated with the aid of the densities of the crystalline and amorphous phase and the absolute SAXS invariant. Such model‐independent crystallinity values can be used in SAXS curve‐shape analysis procedures to obtain the average thickness of the crystalline and amorphous layers also in the case of non‐ideal lamellar semicrystalline polymer morphologies for which the number‐average long period cannot be retrieved from the maxima in correlation functions or interface distribution functions.