The retardation effects of lamellar slip or/and chain slip on void initiation during uniaxial stretching of oriented iPP

POLYMER

卷:215

Article

Chang, Baobao¹  Shi, Honghui¹  He, Man¹  Schneider, Konrad²  Heinrich, Gert^2,3  Liu, Chuntai¹  Shen, Changyu¹ 

[1] Zhengzhou Univ, Key Lab Mat Proc & Mold, Natl Engn Res Ctr Adv Polymer Proc Technol, Minist Educ, Zhengzhou 450002, Peoples R China

[2] Leibniz Inst Polymer Res Dresden, D-01069 Dresden, Germany

[3] Tech Univ Dresden, Inst Text Maschinen & Text Hochleistungswerkstoff, D-01069 Dresden, Germany

关键词: Cavitation;    Lamellae slip;    Chain slip;    Isotactic polypropylene;   

DOI  :  10.1016/j.polymer.2020.123342

来源: Elsevier

【 摘 要 】

Cavitation is frequently encountered during the deformation of semi-crystalline polymers. Although abundant works have been performed to reveal the cavitation behavior in detail, the relationship between void formation and the plastic deformation of crystalline phase is still unclear. In this work, by in-situ synchrotron X-ray scattering, the void formation and the slip process in crystalline phase during uniaxial stretching of oriented isotactic polypropylene (iPP) were investigated. Results proved clearly that lamellae slip or/and chain slip presents a retardation effect on void formation. As the Deviation Angle (DA, defined as the angle between stretching direction and lamellae normal) was 0 degrees, voids were initiated at a Hencky strain (epsilon(H)) of 0.04 and the longitude direction of voids was perpendicular to lamellae normal. Meanwhile, no slip process happened when voids were induced. As DA was 15 degrees, lamellae slip took place once the stretching was started and voids were formed at epsilon(H) of 0.09. When DA was further enlarged to 30 degrees and 45 degrees, both lamellae slip and chain slip could be found as voids were induced. The epsilon(H) of voids formation were 0.29 and 0.31, respectively. Interestingly, it is worth noting that as DA was increased from 0 degrees to 45 degrees, although the orientation degree of voids was decreased, the longitude direction of voids stayed perpendicular to the normal of lamellae. When DA was enlarged further to 90 degrees, voids were formed at epsilon(H) of 0.1 and the longitude direction of voids coincided with lamellae normal. Additionally, neither lamellae slip nor chain slip existed once voids appeared. Combining the value of micro-strain of lamellae stacks and crystal lattice, it is proposed that voids were formed either in the amorphous phase on the normal side of lamellae (0 degrees <= DA <= 451 or in the amorphous phase on the lateral side of lamellae (DA = 90 degrees).

【 授权许可】

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