Memory effect of the molecular topology of lamellar polyethylene on the strain-induced fibrillar structure

• Published in: European polymer journal Vol. 48; no. 6; pp. 1093 - 1100
• Main Authors: Humbert, S., Lame, O., Chenal, J.-M., Seguela, R., Vigier, G.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.06.2012; Elsevier
• Subjects: antagonists; Applied sciences; Chain topology; composite polymers; Engineering Sciences; ethylene; Exact sciences and technology; Fibrillar transformation; Fibrous structure; Fragmentation; heat treatment; Lamellar structure; Materials; Mechanical properties; Microstructure; Organic polymers; Physicochemistry of polymers; Polyethylene; Polyethylenes; Properties and characterization; Reconstruction; SAXS; temperature; Tempering; Topology; Polyethylene; Fibrillar transformation; Chain topology; SAXS; Olefin copolymer; Hexene copolymer; Cold drawing; Fibrillar structure; Experimental study; Semicrystalline copolymer; Ethylene copolymer; Structure modification; Memory effect
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2012.03.010

[Display omitted] ► The fibril long period in drawn polyethylene was shown to be independent of crystallization conditions. ► The microfibril diameter proved to be correlated with the initial morphogenesis. ► This structural feature is directly issued from the fragmentation of the crystal lamellae. ► We have demonstrated a memory effect of the chain topology on the fibril microstructure. ► The amorphous-crystal interphase is the key factor that governs the fragmentation process. The fibrillar structure that develops upon drawing of semi-crystalline polymers has been investigated at room temperature by means of in situ SAXS for a series of ethylene copolymers crystallized through various thermal treatments. The long period of the microfibrils for any given material proved to be only dependent on the experimental conditions of the drawing. This suggested the occurrence of a destruction and reconstruction of the semi-crystalline structure via fragmentation accompanied with melting–recrystallization. However, the diameter of the microfibrils proved to keep the memory of the lamellar microstructure via a correlation with the content of interphase at the crystal-amorphous boundary. A physical explanation is proposed for these apparently antagonist findings. The memory of the lamellar semi-crystalline microstructure is completely erased in the microfibrils owing to the melting–recrystallization process. In contrast, the diameter of the fibrils keeps the memory of the chain topology to which a major role is ascribed in the strain-induced fragmentation of the crystalline lamellae.