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An investigation into the crystalline morphology transitions in poly-L- lactic acid (PLLA) under uniaxial deformation in the quasi-solid-state regime
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Billimoria, Kharmen, Heeley, Ellen L., Parsons, Nathan and Figiel, Lukasz (2018) An investigation into the crystalline morphology transitions in poly-L- lactic acid (PLLA) under uniaxial deformation in the quasi-solid-state regime. European Polymer Journal, 101 . pp. 127-139. doi:10.1016/j.eurpolymj.2018.01.031 ISSN 0014-3057.
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Official URL: https://doi.org/10.1016/j.eurpolymj.2018.01.031
Abstract
The mechanical behaviour, crystalline and macromorphology structure development during uniaxial deformation and annealing of poly-L- lactic acid (PLLA), with varying strain rate and draw temperatures (Td) above Tg, have been investigated using small- and wide-angle X-ray scattering (SAXS/WAXS), microscopy, thermal and mechanical techniques. The mechanical behaviour of PLLA, was strongly dependent on Td where embrittlement and eventual failure were observed as Td was increased, during uniaxial drawing of the amorphous polymer. This was mirrored in the bulk surface morphology where crazing, microvoiding and cavitation occurred with increasing Td. SAXS/WAXS data showed that strain-induced crystallization occurs on drawing, but crystallite orientation decreased with increasing Td, due to chain relaxation at temperatures ≥30 oC above Tg. However, no long-range oriented lamellar macromorphology was observed post-draw directly and only developed in the samples that were step annealed at temperatures above Td. Also, the disordered α’ crystal form was observed post-draw at Td between 60 – 80 oC, whereas Td ≥ 90 oC, resulted in the ordered α crystal form directly. However, on annealing at temperatures of ≥110 oC, the α’- α crystal transition ensued and in all samples, an oriented lamellar macromorphology developed. Therefore, Td and post-draw annealing, have a significant influence on the mechanical properties, crystallinity and crystalline phase transformation in PLLA, which in-turn, affects the polymers medical and industrial applications.
Item Type: | Journal Article | |||||||||
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Subjects: | T Technology > TP Chemical technology | |||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Engineering > WMG (Formerly the Warwick Manufacturing Group) | |||||||||
Library of Congress Subject Headings (LCSH): | Polylactic acid, Polymers -- Industrial applications | |||||||||
Journal or Publication Title: | European Polymer Journal | |||||||||
Publisher: | Pergamon | |||||||||
ISSN: | 0014-3057 | |||||||||
Official Date: | April 2018 | |||||||||
Dates: |
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Volume: | 101 | |||||||||
Page Range: | pp. 127-139 | |||||||||
DOI: | 10.1016/j.eurpolymj.2018.01.031 | |||||||||
Status: | Peer Reviewed | |||||||||
Publication Status: | Published | |||||||||
Access rights to Published version: | Restricted or Subscription Access | |||||||||
Date of first compliant deposit: | 14 February 2018 | |||||||||
Date of first compliant Open Access: | 9 August 2019 | |||||||||
RIOXX Funder/Project Grant: |
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