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Physical Aging as the Driving Force for Brittle–Ductile Transition of Polylactic Acid
Author(s) -
Zhao Guoqing,
Gomes Felipe P. C.,
Marway Heera,
Thompson Michael R.,
Zhu Zhirong
Publication year - 2020
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201900475
Subject(s) - polylactic acid , elongation , brittleness , modulus , ductility (earth science) , materials science , rheology , polymer , composite material , dynamic mechanical analysis , yield (engineering) , ultraviolet , irradiation , ultimate tensile strength , creep , physics , nuclear physics , optoelectronics
Polylactic acid (PLA) is an inherently brittle polymer, exhibiting a high Young's modulus and minimal elongation‐at‐break. To transition its failure mode to one that is much more ductile without loss in strength is challenging. A new strategy combining physical aging with ultraviolet (UV) radiation is carried out to reach the desired mechanical properties of PLA. Characterization of the modified resin is done by mechanical, rheological, and acoustic analysis. With the new processing strategy, the elongation‐at‐break of PLA increases from below 5% up to 18% by conditioning at −40 °C for 48 h followed by UV irradiation for 30 h. Correspondingly, results demonstrate that the yield strength and Young's modulus remain statistically unchanged. The interlocked entanglements inhibit the formation and evolution of subordered structures, which are attributed to the gained ductility. The high entanglement density and few subordered structures in the modified polymer system contribute to the unusual elongation‐at‐break without alteration of the modulus.