Formation of shish-like fibril crystals from the melt of blends of cyclic and linear polyethylene under shear flow

• Published in: Polymer journal Vol. 54; no. 7; pp. 913 - 920
• Main Authors: Kobayashi, Keiko, Yamazaki, Shinichi, Kimura, Kunio
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.07.2022; Nature Publishing Group
• Subjects: 639/638/440; 639/638/455; Biomaterials; Bioorganic Chemistry; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Crystallization; Crystals; Density; Entanglement; Mathematical analysis; Molecular weight; Original Article; Polyethylene; Polyethylenes; Polymer blends; Polymer Sciences; Shear flow; Surfaces and Interfaces; Thin Films
• ISSN: 0032-3896; 1349-0540
• DOI: 10.1038/s41428-022-00643-x

The role of chain entanglements in shear-induced crystallization is one of the most important unsolved problems. The entanglements formed by topologically distinct cyclic and linear polymers are particularly notable. The shear-induced crystallization behavior of a blend of cyclic polyethylene (C-PE) and linear polyethylene (L-PE) was investigated. Using C-PE as a matrix and L-PE as an additive, we changed the molecular weight and blend ratio of C-PE and L-PE and measured the formation rate of shish-like fibril crystals, I . In both blend systems of C-PE(230k)/L-PE(42k) and C-PE(230k)/L-PE(104k), where the values in parentheses represent the molecular weight, I reached a maximum at a certain weight fraction of L-PE, Φ L-PE . As the Φ L-PE was increased, that is, the entanglement density was increased, the formation of the oriented melt was promoted while crystallization was simultaneously suppressed by entanglements. The maximum value of I was observed owing to these two competing factors. Similar behavior was observed in the blend systems of C-PE(230k)/L-PE(42k), C-PE(130k)/L-PE(42k), and C-PE(86k)/L-PE(42k). The shear-induced crystallization behavior of the blends of cyclic polyethylene (C-PE) and linear polyethylene (L-PE) was investigated. This figure shows the formation rate of shish-like fibril crystals ( I ) in the blend systems of C-PE(230k)/L-PE(42k) and C-PE(230k)/L-PE(104k) against the weight fraction of L-PE, Φ L-PE . I reached a maximum at a certain Φ L-PE . As Φ L-PE increased, that is, as the entanglement density increased, the formation of the oriented melt was promoted. Crystallization was also suppressed by the entanglements. The maximum value of I was observed owing to these two competing factors.