Effect of the Processing-Induced Morphology on the Mechanical Properties of Biodegradable Extruded Films Based on Poly(lactic acid) (PLA) Blends

Abstract

Biodegradable films based on poly(lactic acid) blends were obtained by cast extrusion. Their tensile and fracture behavior was investigated and the effect of the processing conditions through the extrusion rolling speed on this behavior was analyzed. In uniaxial tensile tests, all films presented completely ductile behavior exhibiting a defined yield point, strain softening after this point and a plateau before fracture. Fracture behavior was determined through quasi-static fracture tests on deeply double edge notched tensile specimens. The film obtained at the lowest rolling speed exhibited completely ductile behavior hence, the Essential Work of Fracture methodology was applied to characterize its fracture. The film processed at intermediate rolling speed, on the other hand, presented ductile fracture or ductile instability depending on the ligament length and the film obtained with the highest rolling speed exhibited a transition regime fracture. In order to compare the fracture behavior of the different films, the J-integral at maximum load J max was adopted. Differences in the films fracture behavior were correlated to the processing-induced morphology.

Modern Biodegradable Plastics—Processing and Properties: Part I

“…Addition of PBS to a polymer (like PLA) increases the degree of crystallinity and flexibility without reducing biodegradability [20,21]. The presence of pure PLA component in the bioplastic was supported by its determined T g (at around 61-65 • C in amorphous D-lactide isomer) and T m at approximately 147 • C (for partially crystalline L-lactide isomer) [19,21,48,[63][64][65]. For the first heating cycle of PLA, the DSC curve revealed glass transition of LDPE, PBS and PLA (in this order), followed by melting of LDPE and PBS (T m at about 121 • C), and finally, melting of PLA.…”

“…However, plastic film made form unmodified PLA sees limited packaging applications; it is very brittle and relatively poor in resistance to permeation by gases, especially oxygen [18]. It is why plastic film is often made from blends with a PLA matrix [19][20][21]. References state that a small addition of exfoliated mineral fillers can improve flexibility in PLA [22,23], whereas PLA mixed with polyhydroxybutyrate (PHB) effectively reduces permeability to gases, while improving resistance to moisture, making the PLA film, produced with this formulation, an attractive packaging material [24,25].…”

A novel PLA high oxygen barrier multilayer film/foam

“…[ 3,4 ] Despite these attractive properties, this environmentally‐friendly biopolymer has some drawbacks that need to be addressed, as low impact resistance, poor heat stability, and barrier properties. [ 8,9 ] These factors may have limited its applicability in some areas, especially in applications where high oxygen and water barrier is important. [ 10 ] For instance, in food packaging where high barrier protection is important, replacement of PET by PLA may not be feasible, since the barrier properties of PLA are not in par with PET.…”

“…[ 1,5,10 ] Efforts are continuously made to produce new materials to overcome these issues, including new polymerization routes to produce high molecular weight PLA, blending, addition of fillers, foaming, annealing, and orientation. [ 7,8,11–17 ]…”

“…[1,5,10] Efforts are continuously made to produce new materials to overcome these issues, including new polymerization routes to produce high molecular weight PLA, blending, addition of fillers, foaming, annealing, and orientation. [7,8,[11][12][13][14][15][16][17] Foaming technology is a well know process to enhance impact resistance and ductility of polymer matrix and widely used in industry to produce polymeric products with outstanding properties and low production cost. [18] There are several processing technologies that enable the production of PLA foams.…”