Abstract
Polylactide (PLA) is the most widely used biopolymer, but its poor ductility and scarce gas barrier properties limit its applications in the packaging field. In this work, for the first time, the properties of PLA solvent-cast films are improved by the addition of a second biopolymer, i.e., poly(decamethylene 2,5-furandicarboxylate) (PDeF), added in a weight fraction of 10 wt%, and a carbon-based nanofiller, i.e., reduced graphene oxide (rGO), added in concentrations of 0.25–2 phr. PLA and PDeF are immiscible, as evidenced by scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy, with PDeF spheroidal domains showing poor adhesion to PLA. The addition of 0.25 phr of rGO, which preferentially segregates in the PDeF domains, makes them smaller and considerably rougher and improves the interfacial interaction. Differential scanning calorimetry (DSC) confirms the immiscibility of the two polymer phases and highlights that rGO enhances the crystallinity of both polymer phases (especially of PDeF). Thermogravimetric analysis (TGA) highlights the positive impact of rGO and PDeF on the thermal degradation resistance of PLA. Quasi-static tensile tests evidence that adding 10 wt% of PDeF and a small fraction of rGO (0.25 phr) to PLA considerably enhances the strain at break, which raises from 5.3% of neat PLA to 10.0% by adding 10 wt% of PDeF, up to 75.8% by adding also 0.25 phr of rGO, thereby highlighting the compatibilizing role of rGO on this blend. On the other hand, a further increase in rGO concentration decreases the strain at break due to agglomeration but enhances the mechanical stiffness and strength up to an rGO concentration of 1 phr. Overall, these results highlight the positive and synergistic contribution of PDeF and rGO in enhancing the thermomechanical properties of PLA, and the resulting nanocomposites are promising for packaging applications.
Highlights
Poly(lactic acid) (PLA) is one of the most interesting and widely used biopolymers.PLA is a biodegradable and bioderived thermoplastic linear aliphatic polyester [1,2] widely applied in the packaging and textile fields due to its high elastic modulus (2–3 GPa), good mechanical strength (40–60 MPa), good processability, and high optical transparency [3,4,5].the application of PLA for packaging items is generally circumscribed to rigid thermoformed products, because its scarce strain at break, toughness, and gas permeation properties and its high moisture sensitivity limit its use as a flexible packaging film [2]
Nanocomposites, the reduced graphene oxide (rGO) is preferentially distributed in the PDeF domains, which can accommodate most of the rGO until a certain nanofiller content (0.5 phr)
This work explored the role of PDeF (10 wt%) and rGO (0.25–2 phr), alone and combined, on improving the thermomechanical properties of PLA films prepared by solvent casting
Summary
Poly(lactic acid) (PLA) is one of the most interesting and widely used biopolymers.PLA is a biodegradable and bioderived thermoplastic linear aliphatic polyester [1,2] widely applied in the packaging and textile fields due to its high elastic modulus (2–3 GPa), good mechanical strength (40–60 MPa), good processability, and high optical transparency [3,4,5].the application of PLA for packaging items is generally circumscribed to rigid thermoformed products, because its scarce strain at break, toughness, and gas permeation properties and its high moisture sensitivity limit its use as a flexible packaging film [2]. Poly(lactic acid) (PLA) is one of the most interesting and widely used biopolymers. PLA is a biodegradable and bioderived thermoplastic linear aliphatic polyester [1,2] widely applied in the packaging and textile fields due to its high elastic modulus (2–3 GPa), good mechanical strength (40–60 MPa), good processability, and high optical transparency [3,4,5]. Among the techniques to address these drawbacks, one of the most efficient and low-cost methods is to blend PLA with other polymers [6,7]. As the scientific literature demonstrates, PLA-based blends have been prepared with several traditional polymers and biopolymers [8,9,10,11]. Our group has recently blended PLA with several members of an interesting and novel family of biopolymers, i.e., the poly(alkylene 2,5-furandicarboxylate)s (PAFs)
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