Flexible and Tough Poly(lactic acid) Films for Packaging Applications: Property and Processability Improvement by Effective Reactive Blending

Abstract

This study demonstrates a practical means to overcome inherent brittleness problem of poly(lactic acid) (PLA) and make PLA feasible as packaging material. PLA with suitable processability is utterly required for package manufacturers, where flexible, tough PLA film is essential for packers and end users. Highly flexible PLA films with 60-fold increase in elongation at break (Eb) over that of the neat PLA were successfully produced by integrating effective reactive blending and economical film blowing process. The 'two-step' blending was used to prepare PLA compound; poly(butylene adipate-co-terephthalate) (PBAT -another biodegradable polymer) was first blended with 0.5-1% chain extender (epoxy-functionalized styrene acrylic copolymer) (ESA), followed by subsequent blending with PLA in twin-screw extruder. Blown films of reactive blend of PLA/PBAT/ESA (80/20/1) showed impressively high Eb of 250% versus a very low Eb of 4% for the neat PLA. Resulting blown films still possessed high modulus of 2 GPa, yield stress of 50-60 MPa and good toughness of~100 MPa. Significant enhancement in the film's ductility was attributed to homogeneous blend with developed fine strand-like structure as a result of effective in situ compatibilization and good interfacial adhesion between the PLA and PBAT. PLA/PBAT/ESA blend also offered improved processability. Resulting films had acceptable haze of~10% for common packaging, and clearer film close to PLA (≤2%) could be obtained by designing PLA skin layers in multilayer structure. Films of PLA/PBAT/1%ESA exhibit potential as packaging material; their mechanical and optical properties are comparable with or even exceed some existing films used in the market.

The morphological, mechanical, rheological, and thermal properties of PLA/PBAT blown films with chain extender

“…The cold crystallization temperature of the PLA in the films was decreased by 6°C, indicated that the PBAT enabled improvement of the crystallization ability of PLA in the films, as previously reported . From Figure , the peak of cold crystallization became wider with increasing PBAT content.…”

Micromorphology, mechanical, crystallization and permeability properties analysis of HA/PBAT/PLA (HA, hydroxyapatite; PBAT, poly(butylene adipate‐co‐butylene terephthalate); PLA, polylactide) degradability packaging films

“…Poly(butylene adipate‐ co ‐butylene terephthalate (PBAT) is a copolymer of polybutylene adipate glycol (PBA) and polybutylene terephthalate (PBT). So, it not only has good impact resistance and heat resistance but also has good ductility and elongation at break . Hydroxyapatite (HA) is the main component of the bones and teeth of invertebrates and vertebrates.…”

“…So, it not only has good impact resistance and heat resistance but also has good ductility and elongation at break. 9,10 Hydroxyapatite (HA) is the main component of the bones and teeth of invertebrates and vertebrates. It has broad application prospects in many fields due to its good biocompatibility, adsorption, ion exchange, low crystallization temperature and good thermal stability.…”

Improved heat shrinkage and mechanical performances of polyethylene trilayer blown film prepared via novel multilayer coextrusion method

“…The latter which can take full advantages of desirable component properties, such as high strength, thermoformability, and barrier properties, gradually becomes one of the most widely applied methods for heat‐shrink film fabrication. However, the improvement of TD performance of blown film depends on high blow‐up ratio (BUR) defined as the ratio of final film‐tube diameter to die diameter, apart from changing the die geometry . The draw‐down ratio (DDR) is defined as the ratio of film velocity at the nip roll to average velocity in the die.…”

“…However, the improvement of TD performance of blown film depends on high blow-up ratio (BUR) defined as the ratio of final film-tube diameter to die diameter, apart from changing the die geometry. 13,14 The draw-down ratio (DDR) is defined as the ratio of film velocity at the nip roll to average velocity in the die. Generally, DDR is larger than BUR in film blowing, making the performance of blown film along TD less than that along machine direction (MD).…”