Ternary PLA–PHB–Limonene blends intended for biodegradable food packaging applications

• Biodegradable PLA–PHB films plasticized with d-limonene were successfully prepared.
• d-limonene improved the processing, interaction and disintegration in composting of PLA–PHB blend.
• PHB act as a reinforcement agent in PLA matrix and d-limonene decreased the Tg.
• PHB produced amber tonality, but films also showed high transparency.
• Crystalline PHB delayed the disintegration of PLA in composting.

In this work poly(lactic acid) PLA, and poly(hydroxybutyrate) PHB, were blended and plasticized with a natural terpene d-limonene (LIM) with the dual objective to increase PLA crystallinity and to obtain flexible films intended for food packaging applications. Materials were melt-blended and processed in transparent films. Structural and surfaces properties were evaluated. Moreover, functional properties were studied by means colorimetric parameters, oxygen permeation and water resistant measurements. In addition, thermal stability, crystallization behavior, mechanical as well as nanomechanical properties were investigated. FTIR spectra showed the characteristic bands corresponding to PLA and PHB and their rather molecular interaction. Py-GC/MS showed the characteristics peak of d-limonene as well as the thermal degradation products of PLA and PHB. d-limonene amount after processing was higher in PHB incorporated samples. PHB produced a reinforcing effect in PLA matrix and therefore an improvement in the oxygen barrier properties and the surface water resistance. Moreover, Scanning Confocal Microscopy surface images showed the dispersion of PHB crystal in PLA matrix. The influences of plasticization process on the mechanical properties showed that d-limonene provoked an increase in elongation at break. Disintegrability under composting conditions was also investigated and it was observed that PHB delays the PLA disintegrability under composting while d-limonene speed it up. In brief, the best results regarding structural, thermal, barrier and mechanical properties were found for the ternary PLA–PHB–LIM film.

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