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. 2022 Dec 9;12(54):35328-35340.
doi: 10.1039/d2ra07132k. eCollection 2022 Dec 6.

Polyester-based polyurethanes derived from alcoholysis of polylactide as toughening agents for blends with shape-memory properties

Chorney Eang  1 , Bunthoeun Nim  1 , Mantana Opaprakasit  2 , Atitsa Petchsuk  3 , Pakorn Opaprakasit  1
Affiliations

Polyester-based polyurethanes derived from alcoholysis of polylactide as toughening agents for blends with shape-memory properties

Chorney Eang et al. RSC Adv. .

Abstract

A process for sizing down and functionalizing commercial polylactide (PLA) resin is developed by alcoholysis with 1,4-butanediol (BDO) and propylene glycol (PG) to medium-sized PLA-based diols, with lower cost than a bottom-up synthesis process. These are subsequently used as polyols in preparing polyurethanes (PU) by reacting with 1,6-diisocyanatohexane (HDI). The PLA-based PU has an excellent elongation at break of 487%. The products are suitable as toughening agents for brittle PLA resin due to their highly elastic properties and high compatibility with PLA. The PU products are blended with PLA resin at various compositions, and their physical and mechanical properties and shape recovery are examined. The tensile tests showed enhancements in elongation at break up to 160% with low modulus. The fracture morphology and FTIR results confirm that the blends show strong interfacial interaction and adhesion between the PLA-based PU disperse phase and the PLA matrix. The PLA/PU blends exhibit a high shape recovery efficiency, and their recovery mechanisms are identified. These flexible PLA/PU blends are promising for various applications where bio-compatibility/degradability and high ductility are required, especially as filaments for 3D bio-printing.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1
Fig. 1. Overview of the synthesis of PLA-based PUs from the products of the sizing down and functionalization of PLA, and utilizing them as a toughening agent for brittle PLA resin.
Fig. 2
Fig. 2. ATR-FTIR spectra of different alcoholized PLA and PLA-based PU samples.
Fig. 3
Fig. 3. The 1st heating and 2nd heating scan DSC thermograms of alcoholized PLA products.
Fig. 4
Fig. 4. The 1st and 2nd heating DSC thermograms of PUs obtained from the reactions between HDI with LBDO61 and LPG61 diols.
Fig. 5
Fig. 5. The stress–strain curves of (a) PLA/PU1, (b) PLA/PU2, and (c) PLA/PUp blends as a function of the blend compositions.
Fig. 6
Fig. 6. ATR-FTIR spectra of PLA/PU1 blends as a function of the blend composition.
Fig. 7
Fig. 7. The cryogenic crack morphology of neat PLA, PLA/PU1 blends at different blend compositions, and PU1 original films.
Fig. 8
Fig. 8. The 1st (a) and 2nd heating (b) DSC thermograms of neat PLA and PLA/PU1 blends as a function of the blend composition.
Fig. 9
Fig. 9. TGA thermograms and 1st derivative TGA (DTGA) curves of PLA/PU1 blends as a function of the blend composition.
Fig. 10
Fig. 10. X-ray diffraction (XRD) patterns of neat PLA and PLA/PU1 blends.
Fig. 11
Fig. 11. (a) Structure changes of PUP-50 film after applied strain and shape recovery cycles, (b) stress–strain curves, and (c) tensile strength and modulus during the shape recovery tests at 10 and 20% strains and testing cycles.
Fig. 12
Fig. 12. The structure recovery (Rr, %) and fixing shape (Rf, %) of PUP-50 films at different applied strains and testing cycles.
Fig. 13
Fig. 13. 2d and 3d plot of stress–strain curves as a function of time and temperature of (a1), (a2) PUP-30 and (b1), (b2) PUP-50 during the structure recovery tests.
Fig. 14
Fig. 14. Stress–strain curves of PUP-30 and PUP-50, as a function of shape recovery cycles.
Fig. 15
Fig. 15. Structure recovery (Rr, %) of (a) PUP-30 and (b) PUP-50 at 60 °C, as a function of time.
Fig. 16
Fig. 16. Proposed shape recovery mechanism of the PLA/PU lend system.
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