Biodegradable Poly(lactic acid) Blends with Chemically Modified Polyhydroxyoctanoate Through Chain Extension

• Published in: Journal of polymers and the environment Vol. 17; no. 4; pp. 240 - 247
• Main Authors: Lee, Jinkoo, McCarthy, Stephen
• Format: Journal Article
• Language: English
• Published: Boston Boston : Springer US 01.12.2009; Springer US; Springer Nature B.V
• Subjects: Biodegradable materials; Biodegradation; Chemistry; Chemistry and Materials Science; Composite materials; Environmental Chemistry; Environmental Engineering/Biotechnology; Industrial Chemistry/Chemical Engineering; Materials Science; Mechanical engineering; Original Paper; Polymer Sciences; Polymers; Shear stress; Viscosity; Poly(lactic acid); Polyhydroxyoctanoate; Polymer blends
• ISSN: 1566-2543; 1572-8919; 1572-8900
• DOI: 10.1007/s10924-009-0144-9

Poly(lactic acid) (PLA) was blended with chemically modified Polyhydroxyoctanoate (mPHO) using a Haake twin-screw mixer. Due to the melt viscosity disparity between the two components, PHO was reacted with Hexamethylene diisocyanate (HDI) used as a chain extender to produce high molecular weight for improving compatibility and processability with PLA. The number average and weight average molecular weight of the PHO, reacted with 0.55 wt% HDI, were increased 314 and 275%, respectively, compared with those of the unmodified PHO. The blends were characterized for rheological, thermal, and mechanical properties. Infrared spectra confirmed the formation of the urethane linkages in mPHO. The shear viscosity, as a function of shear rate or shear stress, decreased with an increase in mPHO content, indicating that the PLA/mPHO blends show shear-thinning behavior along with the power-law model. DSC thermograms showed that the two components in the blends were found with two crystalline phases and two amorphous phases confirming the coexistence of two immiscible components. Tensile results indicated that tensile strength for blends decreased with increasing mPHO content up to 80%. A decrease in elastic modulus, as well as an increase in elongation at break, was seen as a function of mPHO content. Results of aging tests showed that the mechanical properties of the blends also dropped more at a higher PLA level when compared with those of the unaged samples.