Use of Biochar as Filler for Biocomposite Blown Films: Structure-Processing-Properties Relationships

In this work, biocomposite blown films based on poly(butylene adipate-co-terephthalate) (PBAT) as biopolymeric matrix and biochar (BC) as filler were successfully fabricated. The materials were subjected to a film-blowing process after being compounded in a twin-screw extruder. The preliminary investigations conducted on melt-mixed PBAT/BC composites allowed PBAT/BC 5% and PBAT/BC 10% to be identified as the most appropriate formulations to be processed via film blowing. The blown films exhibited mechanical performances adequate for possible application as film for packaging, agricultural, and compost bags. The addition of BC led to an improvement of the elastic modulus, still maintaining high values of deformation. Water contact angle measurements revealed an increase in the hydrophobic behavior of the biocomposite films compared to PBAT. Additionally, accelerated degradative tests monitored by tensile tests and spectroscopic analysis revealed that the filler induced a photo-oxidative resistance on PBAT by delaying the degradation phenomena.

Nanosilicates in Compatibilized Mixed Recycled Polyolefins: Rheological Behavior and Film Production in a Circular Approach

Currently, plastic packaging represents a global challenge and has become a key point of attention for governments, media and consumers due to the visibility of the waste it generates. Despite their high resource efficiency, the perceived non-recyclability of polymeric films risks precluding them from being a relevant packaging solution in a circular economy approach. In this regard, the aim of this study was to implement a strategy to try closing the loop, via the mechanical recycling of post-consumer flexible packaging of small size (denoted as Fil-s) to obtain new films. In particular, two lots of Fil-s were used, which are PE/PP blends differing for the PP content and the presence of polar contaminants. The suitability for film blowing extrusion of these recycled materials, as such and after the addition of a compatibilizer and/or a lamellar nanosilicate, was evaluated. It was first evidenced that the difficulty of producing blown films with the pristine recycled materials, due to the frequent bubble breakages, occurring even at low draw ratios. Moreover, the shear and extensional rheological behavior of all Fil-s based systems was usefully correlated with their processability features, evidencing the key roles of the nanofiller to stabilize the bubble and of the compatibilizer to ensure a uniform film deformation, avoiding its premature breakage. Even if the adopted upgrading strategies allowed the production of blown films with both types of Fil-s, the different components of the recycled matrices were proven to significantly affect their processability and final film performances.

Interferometric Instrument for Thickness Measurement on Blown Films

Real-time measurement of plastic film thickness during production is extremely important to guarantee planarity of the final film. Standard techniques are based on capacitive measurements, in close contact with the film. These techniques require continuous calibration and temperature compensation, while their contact can damage the film. Different optical contactless techniques are described in literature, but none has found application to real production, due to the strong vibration of the films. We propose a new structure of low-coherence fiber interferometer able to measure blown film thickness during productions. The novel fiber-optic setup is a cross between an autocorrelator and a white light interferometer, taking the advantages of both approaches.

Investigation of the Recyclability and Compostability of Biopolymers Contaminated by Petroleum-Based Polymers

Nowadays, we can choose a carrier bag made of traditional LDPE or a biodegradable polymer to pack vegetables, bakery products, and other products in more and more shops. However, the customers and the selective waste collection system are not yet prepared for the separate collection of compostable biopolymers. Therefore, they are mixed in the plastic waste stream. Therefore, the aim of the study was to analyze the mechanical and optical properties, and the compostability of different low-density polyethylene (LDPE) and poly (butylene adipate-co-terephthalate) (PBAT) compounds. We made different compounds from LDPE and PBAT by twin-screw extrusion and blown films from the regranulates. We investigated the tensile and optical properties and the biodegradability of the blown films. The tensile test showed that the "contaminants" had a more significant effect on elongation at break than tensile strength. We observed that the haze of the LDPE-based blends increased with an increasing weight fraction of PBAT. We found that PBAT-based samples were completely disintegrated in 42 days, regardless of the weight fraction of LDPE.

Effect of Different Types of PLA on the Properties of PLA/PBAT Blown Films

In this work, blown films made by blends of poly (lactide) (PLA) and poly (butylene-adipate-co-terephthalate) (PBAT) in a 40/60 mass ratio were developed and characterized. Two types of PLA, differing for their viscosities, were employed, in order to evaluate their effect on the morphology and on the mechanical properties of the films. The blends exhibited a coarse morphology when the viscosity of the PLA employed was much higher than PBAT. Instead, the use of a PLA whose viscosity was closer to PBAT led to a decrease of the dimensions and to a better distribution and interfacial adhesion of the dispersed phase. Moreover, the finer and more homogenous morphology of the blend resulted in better mechanical performance of the system.

Effects of Nopal Mucilage (Opuntia ficus-indica) as Plasticizer in the Fabrication of Laminated and Tubular Films of Extruded Acetylated Starches

Normal and acetylated rice and waxy maize starches with a blend of nopal mucilage (Opuntia ficus-indica) and glycerol were used for the preparation of laminated and tubular films by extrusion and blown extrusion, respectively. The composition of the formulation was 70% starch (normal or acetylated), 20% glycerol, and 10% nopal mucilage ( w / w ). The degrees of substitution (DS) for acetylated rice starch (0.94) and waxy maize starch (0.76) present high potential for use as a polymeric matrix in packing materials. The use of nopal mucilage can improve the processability of extruded and tubular films by favoring the increase of some mechanical and functional properties. The films elaborated with nopal mucilage and glycerol present a homogeneous relief without breaking, adhesiveness, and contraction once formed. The elongation values of acetylated waxy maize starch films (33%) were higher than those of rice acetylated films (17%), while the blown films presented a 30% decrease in tensile strength, compared to the laminated films. Acetylation generated more hydrophobic material for the rice starch sample, which can be evidenced by a decreased solubility of the laminated films. Films of both sources of acetylated starch showed a significant decrease in water vapor permeability and showed a plasticized starch disposition-type layer without unmelted starch granules.

Bionanocomposite Blown Films: Insights on the Rheological and Mechanical Behavior

In this work, bionanocomposites based on two different types of biopolymers belonging to the MaterBi® family and containing two kinds of modified nanoclays were compounded in a twin-screw extruder and then subjected to a film blowing process, aiming at obtaining sustainable films potentially suitable for packaging applications. The preliminary characterization of the extruded bionanocomposites allowed establishing some correlations between the obtained morphology and the material rheological and mechanical behavior. More specifically, the morphological analysis showed that, regardless of the type of biopolymeric matrix, a homogeneous nanofiller dispersion was achieved; furthermore, the established biopolymer/nanofiller interactions caused a restrain of the dynamics of the biopolymer chains, thus inducing a significant modification of the material rheological response, which involves the appearance of an apparent yield stress and the amplification of the elastic feature of the viscoelastic behavior. Besides, the rheological characterization under non-isothermal elongational flow revealed a marginal effect of the embedded nanofillers on the biopolymers behavior, thus indicating their suitability for film blowing processing. Additionally, the processing behavior of the bionanocomposites was evaluated and compared to that of similar systems based on a low-density polyethylene matrix: this way, it was possible to identify the most suitable materials for film blowing operations. Finally, the assessment of the mechanical properties of the produced blown films documented the potential exploitation of the selected materials for packaging applications, also at an industrial level.