Modification of Poly(Lactic Acid) Rheological Properties Using Ethylene–Vinyl Acetate Copolymer

• Published in: Journal of polymers and the environment Vol. 29; no. 1; pp. 121 - 129
• Main Authors: Kugimoto, Daisuke, Kouda, Shingo, Yamaguchi, Masayuki
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.01.2021; Springer Nature B.V
• Subjects: Acetic acid; Chain branching; Chemistry; Chemistry and Materials Science; Copolymers; Deformation; Dispersion hardening; Droplets; Elongated structure; Environmental Chemistry; Environmental Engineering/Biotechnology; Ethylene; Ethylene vinyl acetates; Industrial Chemistry/Chemical Engineering; Materials Science; Original Paper; Polylactic acid; Polymer blends; Polymer Sciences; Rheological properties; Rheology; Strain hardening; Vinyl acetate; Viscosity; Poly(lactic acid); Polymer blends; Elongational viscosity; Rheological properties
• ISSN: 1566-2543; 1572-8919
• DOI: 10.1007/s10924-020-01856-y

The effect of ethylene–vinyl acetate copolymer (EVA) addition on the rheological properties of poly(lactic acid) (PLA) was studied. EVA exhibited strain-hardening behavior in the transient elongational viscosity due to its long-chain branch structure, whereas PLA did not show any strain-hardening. The blends showed sea-island structure, in which the size of EVA droplets decreased with the vinyl acetate content in EVA. It should be noted that the blends showed strain-hardening behavior even though EVA is not in the continuous phase. During elongational flow, EVA droplets deform to the fibrous shape owing to hydrodynamic force applied by the matrix PLA, and eventually their deformation is greatly reduced as a result of the strain-hardening. Consequently, the blend system behaved like a rigid-fiber dispersion, which are known to show enhanced elongational viscosity. Finally, the processability of a tubular-blown film was improved by the EVA addition because of the strain-hardening.