Development of high performance sealable films based on biodegradable/compostable blends

• Development of laminar morphology provides significantly toughened compostable blend films based on poly(lactic acid).
• The seal strength of blend samples has increase by addition of seal modifier to be comparable to commercial seal grade polyethylene based resins.
• The Seal and Hot-tack initiation temperatures can be improved in order to have wider operation window.

In this study, the seal behavior of toughened blends of poly(lactic acid) (PLA) and polycaprolactone (PCL) was investigated in details. The blended samples were prepared using melt blending in a twin-screw extruder and were processed in the form of cast films of about 30 μm in thickness. Scanning electron microscopy (SEM) study of the morphology of the blends shows that laminar morphology develops in blends of 20% and 40% dispersed phase. Analysis of the thermal behavior of the blends using DSC thermograms reveals significant effect of blending on hindering the crystallization of PCL, resulting in lower crystallinity for samples with high PLA content. Latter provide blends with more amorphous phase and chain mobility, which help lowering the Seal and Hot-tack initiation temperatures. Blending is shown to decrease Seal and Hot-tack initiation temperatures up to 30 °C compared to neat PLA. In addition, this technique is proven to be successful to increase the Hot-tack strength of the blends to a comparative level to commercially available seal grade resins at about 1100 g/25.4 mm for PCL content of 40%. The results indicate that elongation at break increases from about 4% for pure PLA to almost 150% for the blend of 40% PCL and over 400% when PCL content reaches 60%. Higher toughness is an important property for a flexible package and prevents defects caused by its handling and storage conditions.