Analysis of the Suitability of Poly(lactic acid) in Rotational Molding Process

Fabrication of electrospun nanofibers with moisture-triggered carvacrol release in fresh produce packaging

In this study, by incorporating polyethylene glycol (PEG) into the polylactic acid (PLA) nanofibers, a moisture-controlled system was developed in the release of carvacrol to the food package headspaces. With the use of electrospinning technology, an optimized solution (80:20 [PLA:PEG] polymer mixture incorporated with a carvacrol content of 20% [w/w polymer]) generated nanofibers with excellent encapsulation efficiency, loading capacity, and controlled release of carvacrol at different humidity levels. Carvacrol was prevented from release when the fibers were kept in dry states. When placed in food packaging with high humidity levels, the nanofibers manifested high and continuous release of carvacrol into the headspace. The shelf life of strawberries determined by visual inspection was extended for 2 extra days when packaged with the optimized nanofibers and had a significantly lower yeasts and mold counts (4.28 ± 0.34 log CFU/g) compared to strawberries packaged without nanofibers (5.22 ± 0.47 log CFU/g) 3 days after applying the nanofibers (p < 0.05). PRACTICAL APPLICATION: The nanofibers with PEG content as developed in this study represent a step forward in practical application of the electrospinning technology to enhance food quality in food preservation.

Rotational Molding of Poly(Lactic Acid)/Polyethylene Blends: Effects of the Mixing Strategy on the Physical and Mechanical Properties

In this study, blends of poly(lactic acid) (PLA)/linear medium density polyethylene (LMDPE) at different weight ratios were prepared by rotational molding. Two mixing strategies were used to evaluate the effect of phase dispersion on the physical and mechanical properties: (i) Dry-blending (DB) using a high shear mixer, and (ii) melt-blending (MB) using a twin-screw extruder. Thermal, morphological, and mechanical analyses were performed on the neat polymers and their blends. The thermal analysis was completed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and the blends prepared by MB had lower thermal stability than the ones prepared via DB due to some thermo-oxidative degradation through the double thermal process (extrusion and rotomolding). The morphology of the rotomolded parts showed that DB generated larger particle sizes (around 500 µm) compared to MB (around 5 µm) due to the shear and elongational stresses applied during extrusion. The tensile and flexural properties of the rotomolded parts combined the PLA stiffness with the LMDPE toughness independent of the blending technique. Neat PLA presented increments in tensile strength (54%) and flexural strength (111%) for DB compared with MB. A synergistic effect in impact strength was observed in blends with 12 and 25 wt. % of PLA prepared by DB.