Development of PBS/Nano Composite PHB-Based Multilayer Blown Films with Enhanced Properties for Food Packaging Applications.

Biobased and biodegradable plastics have emerged as promising alternatives to conventional plastics offering the potential to reduce environmental impacts while promoting sustainability. This study focuses on the production of multilayer blown films with enhanced functional properties suitable for food packaging applications. Films were developed through co-extrusion in a three-layer film configuration, with Polybutylene Succinate (PBS) and Polybutylene Succinate Adipate (PBSA) as the external and internal layers, respectively. The functional layer consisted of Polyhydroxybutyrate (PHB) enhanced with nanoclays Cloisite® 30B at varying weight ratios. Films were also processed by manipulating the extruder screw speed of the functional layer to investigate its impact on the functional properties. Rheology, mechanical strength, and barrier performance were characterised to establish correlations between processing conditions and functional layer blends (Cloisite® 30B/PHB) on the properties of the resultant films. Rheological test results indicated that the system with 5% Cloisite® had the best polymer/nanofiller matrix dispersion. Mechanical and permeability tests showed that by varying the process conditions (the alteration of the thickness of the functionalized layer) resulted in an improvement in mechanical and barrier properties. Furthermore, the addition of the nanofiller resulted in a stiffening of the film with a subsequent decrease in permeability to oxygen and water vapour.

Cellulose/Polyhydroxybutyrate (PHB) Composites as a Sustainable Bio-Based Feedstock to 3D-Printing Applications.

In this work, we have studied the potential application for 3D-printing of a polymer made from combining a biodegradable and biocompatible polymer (i.e., polyhydroxybutyrate, PHB) with natural bio-based fiber (i.e., cellulose). To this end, a masterbatch at 15 wt.% in filler content was prepared by melt-blending, and then this system was "diluted" with pure PHB in a second extrusion phase in order to produce filaments at 1.5 and 3 wt.% of cellulose. For comparison, a filament made of 100% virgin PHB pellets was prepared under the same conditions. All the systems were then processed in the 3D-printer apparatus, and specimens were mainly characterized by static (tensile and flexural testing) and dynamic mechanical analysis. Thermogravimetric analysis, differential scanning calorimetry, spectroscopic measurements, and morphological aspects of PHB polymer and composites were also discussed. The results showed a significant negative impact of the process on the mechanical properties of the basic PHB with a reduction in both tensile and flexural mechanical properties. The PHB-cellulose composites showed a good dispersion filler in the matrix but a poor interfacial adhesion between the two phases. Furthermore, the cellulose had no effect on the melting behavior and the crystallinity of the polymer. The addition of cellulose improved the thermal stability of the polymer and minimized the negative impact of extrusion. The mechanical performance of the composites was found to be higher compared to the corresponding (processed) polymer.

Assessment of Melt Compounding with Zeolites as an Effective Deodorization Strategy for Mixed Plastic Wastes and Comparison with Degassing.

The emission of off-odors from mechanically recycled plastics severely limits their re-introduction into the market for the production of new objects, for the same use or even for less demanding applications, thus hindering the implementation of an effective circular economy for plastics. The addition of adsorbing agents during the extrusion of polymers represents one of the most promising strategy to reduce the odorous emissions of plastics, due to its characteristics of cost-effectiveness, flexibility and low energy consumption. The novelty of this work lies in the assessment of zeolites as VOC adsorbents during the extrusion of recycled plastics. They appear more suitable than other types of adsorbents, due to their ability to capture and "hold" the adsorbed substances at the high temperatures of the extrusion process. Moreover, the effectiveness of this deodorization strategy was compared with the traditional degassing technique. Two types of mixed polyolefin wastes, coming from completely different collection and recycling processes, were tested: Fil-S (Film-Small), deriving from post-consumer flexible films of small size, and PW (pulper waste), which is the residual plastic waste obtained from the paper recycling process. The melt compounding of the recycled materials with two micrometric zeolites (zeolite 13X and Z310) resulted as more effective in the off-odors removal with respect to degassing. In particular, the highest reduction (-45%) of the Average Odor Intensity (AOI) was measured for both PW/Z310 and Fil-S/13X systems at 4 wt% of the zeolites' amount, compared with the corresponding untreated recyclates. Finally, by combining degassing and melt compounding with zeolites, the best result was obtained for the composite Fil-S/13X, whose Average Odor Intensity resulted as quite close (+22%) to the one of the virgin LDPE.

New Materials and Technologies for Durability and Conservation of Building Heritage.

The increase in concrete structures' durability is a milestone to improve the sustainability of buildings and infrastructures. In order to ensure a prolonged service life, it is necessary to detect the deterioration of materials by means of monitoring systems aimed at evaluating not only the penetration of aggressive substances into concrete but also the corrosion of carbon-steel reinforcement. Therefore, proper data collection makes it possible to plan suitable restoration works which can be carried out with traditional or innovative techniques and materials. This work focuses on building heritage and it highlights the most recent findings for the conservation and restoration of reinforced concrete structures and masonry buildings.

Development of Novel Blown Shrink Films from Poly(Lactide)/Poly(Butylene-Adipate-co-Terephthalate) Blends for Sustainable Food Packaging Applications.

Heat-shrinkable films, largely made of polyolefins and widely employed in the packaging sector as collation or barrier films, due to their short service life, are held responsible for high environmental impact. One possible strategy for reduction in their carbon footprint can be the use of biodegradable polymers. Thus, this work aimed to develop novel, heat-shrinkable, fully biodegradable films for green packaging applications and to analyze their functional performance. Films were obtained from blends of amorphous polylactic acid (PLA) and poly(butylene-adipate-co-terephthalate) (PBAT) at different mass ratios and compatibilized with a chain extender. They were produced by means of a lab-scale film blowing extrusion apparatus and characterized in terms of physical-mechanical properties and shrinkability. The influence of the processing parameters during the extrusion blowing process on the films' behavior was investigated, highlighting the effects of blend composition and stretching drawing conditions. Shrinkage tests demonstrated that the produced films have shrinkability values in the typical range of mono-oriented films (ca. 60-80% in machine direction and ca. 10-20% in transverse direction). Moreover, the shrinkage in machine direction increases both with the mass flow rate, the take-up ratio to blow-up ratio and the bubble cooling of the film blowing process, and with the PLA content into the blend. In particular, films at higher PLA content also exhibit higher transparency and stiffness.

Use of Hazelnut Perisperm as an Antioxidant for Production of Sustainable Biodegradable Active Films.

Utilization of food-waste-derived bioactive compounds with biodegradable polymers is an attractive strategy leading innovation in the food packaging sector and contributing to reduce the environmental concerns of plastic packaging disposal. In this field, this work is aimed to use hazelnut perisperm as an antioxidant agent in the production of biodegradable polymeric films for active packaging applications. For this purpose, hazelnut perisperm of a selected particle size (<250 µm) at different percentages (0%, 5% and 10% by weight) was added to a bioderived and compostable polymer suitable for food contact, known as Ecovio®. The blends were produced by a twin-screw extrusion process, while active films were prepared with a pilot lab-scale film blowing plant. The films were characterized in terms of physical−mechanical properties (thermal, tensile, oxygen barrier, optical, sealing ability) and antioxidant activity (DPPH), to investigate their potential use as active packaging. The results showed that the presence of the hazelnut perisperm confers significant antioxidant activity to the films, which is useful in counteracting lipid oxidation and preserve the quality of lipophilic foods, e.g., nut-dried fruits. An extension of the sealability temperature range of the films without compromising their strength was also highlighted. Moreover, the hazelnut perisperm causes a gradual decrease in the stiffness and mechanical strength of the films and an increase in the ductility of the system.

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.

Development of Eco-Sustainable PBAT-Based Blown Films and Performance Analysis for Food Packaging Applications.

In this work, eco-sustainable blown films with improved performance, suitable for flexible packaging applications requiring high ductility, were developed and characterized. Films were made by blending two bioplastics with complementary properties-the ductile and flexible poly(butylene-adipate-co-terephthalate) (PBAT) and the rigid and brittle poly(lactic acid) (PLA)-at a 60/40 mass ratio. With the aim of improving the blends' performance, the effects of two types of PLA, differing for viscosity and stereoregularity, and the addition of a commercial polymer chain extender (Joncryl®), were analyzed. The use of the PLA with a viscosity ratio closer to PBAT and lower stereoregularity led to a finer morphology and better interfacial adhesion between the phases, and the addition of the chain extender further reduced the size of the dispersed phase domains, with beneficial effects on the mechanical response of the produced films. The best system composition, made by the blend of PBAT, amorphous PLA, and the compatibilizer, proved to have improved mechanical properties, with a good balance between stiffness and ductility and also good transparency and sealability, which are desirable features for flexible packaging applications.

Preparation and Characterization of Polypropylene/Carbon Nanotubes (PP/CNTs) Nanocomposites as Potential Strain Gauges for Structural Health Monitoring.

Polypropylene/carbon nanotubes (PP/CNTs) nanocomposites with different CNTs concentrations (i.e., 1, 2, 3, 5 and 7 wt%) were prepared and tested as strain gauges for structures monitoring. Such sensors were embedded in cementitious mortar prisms and tested in 3-point bending mode recording impedance variation at increasing load. First, thermal (differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA)), mechanical (tensile tests) and morphological (FE-SEM) properties of nanocomposites blends were assessed. Then, strain-sensing tests were carried out on PP/CNTs strips embedded in cementitious mortars. PP/CNTs nanocomposites blends with CNTs content of 1, 2 and 3 wt% did not show significant results because these concentrations are below the electrical percolation threshold (EPT). On the contrary, PP/CNTs nanocomposites with 5 and 7 wt% of CNTs showed interesting sensing properties. In particular, the best result was highlighted for the PP/CNT nanocomposite with 5 wt% CNTs for which an average gauge factor (GF) of approx. 1400 was measured. Moreover, load-unload cycles reported a good recovery of the initial impedance. Finally, a comparison with some literature results, in terms of GF, was done demonstrating the benefits deriving from the use of PP/CNTs strips as strain-gauges instead of using conductive fillers in the bulk matrix.

Study on Improving the Processability and Properties of Mixed Polyolefin Post-Consumer Plastics for Piping Applications.

This study focuses on the upgrading strategies to make Fil-s (acronym for film-small), a polyolefin-based material coming from the mechanical recycling of post-consumer flexible packaging, fit for re-use in the piping sector. The effects of washing treatments (at cold and hot conditions) and the addition of an experimental compatibilizer on the chemical-physical properties of Fil-s were first assessed. The measurements of some key properties (density, melt flow index, flexural modulus, yield strength), for both Fil-s as such and the different developed Fil-s based systems, was also conducted in order to evaluate the suitability of this complex and challenging waste stream to replace virgin PE-based pipe and fitting products, in compliance to ASTM D3350 standard. The outcomes of the present work contributed to define a code, for each Fil-s system investigated, useful for identifying the level of their performance in piping applications. All the recyclates were extruded as pipes by using a pilot scale plant, but the process resulted more stable and continuous with the compatibilized Fil-s, as it was deducible from its flow properties. Moreover, the best mechanical performances were exhibited by the hot-washed Fil-s pipes, with an increase in pipe stiffness equal to 65% respect to the unwashed sample.

Evaluation of the Suitability of Poly(Lactide)/Poly(Butylene-Adipate-co-Terephthalate) Blown Films for Chilled and Frozen Food Packaging Applications.

The use of biopolymers can reduce the environmental impact generated by plastic materials. Among biopolymers, blends made of poly(lactide) (PLA) and poly(butylene-adipate-co-terephthalate) (PBAT) prove to have adequate performances for food packaging applications. Therefore, the present work deals with the production and the characterization of blown films based on PLA and PBAT blends in a wide range of compositions, in order to evaluate their suitability as chilled and frozen food packaging materials, thus extending their range of applications. The blends were fully characterized: they showed the typical two-phase structure, with a morphology varying from fibrillar to globular in accordance with their viscosity ratio. The increase of PBAT content in the blends led to a decrease of the barrier properties to oxygen and water vapor, and to an increase of the toughness of the films. The mechanical properties of the most ductile blends were also evaluated at 4 °C and -25 °C. The decrease in temperature caused an increase of the stiffness and a decrease of the ductility of the films to a different extent, depending upon the blend composition. The blend with 40% of PLA revealed to be a good candidate for chilled food packaging applications, while the blend with a PLA content of 20% revealed to be the best composition as frozen food packaging material.

Erratum: Effect of Porosity and Crystallinity on 3D Printed PLA Properties. Polymers 2019, 11, 1487.

The authors wish to make a change to the published paper [...].

Nanotechnology-Based Strategy to Upgrade the Performances of Plastic Flexible Film Waste.

The aim of this work was to improve the performances of Fil-s (film-small), a recycled material obtained from plastic flexible film waste that is made of polyethylene and a minor amount of polypropylene, with traces of polar contaminants (polyamides, maleic anhydride, etc.). The idea was to upgrade the material's mechanical properties by applying a nanotechnology-based strategy that takes advantage of the composition of Fil-s. In particular, different amounts of copolyamide (CoPA) and its masterbatch with an organic-modified nanosilicate were melt compounded with Fil-s in a twin-screw extruder. The good affinity between Fil-s and CoPA, proved by means of spectroscopic and rheological analysis, allowed for the obtaining of a well-refined morphology for the neat and hybrid blends. This resulted in very interesting increments of the strain at break, which was particularly impressive (10 times higher) in the case of the blend with the lower amount of copolyamide masterbatch, but without sacrificing the stiffness and strength of Fil-s.

Effect of Porosity and Crystallinity on 3D Printed PLA Properties.

Additive manufacturing (AM) is a promising technology for the rapid tooling and fabrication of complex geometry components. Among all AM techniques, fused filament fabrication (FFF) is the most widely used technique for polymers. However, the consistency and properties control of the FFF product remains a challenging issue. This study aims to investigate physical changes during the 3D printing of polylactic acid (PLA). The correlations between the porosity, crystallinity and mechanical properties of the printed parts were studied. Moreover, the effects of the build-platform temperature were investigated. The experimental results confirmed the anisotropy of printed objects due to the occurrence of orientation phenomena during the filament deposition and the formation both of ordered and disordered crystalline forms (α and δ, respectively). A heat treatment post-3D printing was proposed as an effective method to improve mechanical properties by optimizing the crystallinity (transforming the δ form into the α one) and overcoming the anisotropy of the 3D printed object.

3D Printing of PLA/clay Nanocomposites: Influence of Printing Temperature on Printed Samples Properties.

In this study, the possibility of using a layered silicate-reinforced polylactic acid (PLA) in additive manufacturing applications was investigated. In particular, the aim of this work was to study the influence of printing temperature in the 3D printing process of PLA/clay nanocomposites. For this reason, two PLA grades (4032D and 2003D, D-isomer content 1.5 and 4, respectively) were melt-compounded by a twin screw extruder with a layered silicate (Cloisite 30B) at 4 wt %. Then, PLA and PLA/clay feedstock filaments (diameter 1.75 mm) were produced using a single screw extruder. Dog-bone and prismatic specimens were 3D printed using the FDM technique at three different temperatures, which were progressively increased from melting temperature (185⁻200⁻215 °C for PLA 4032D and 165⁻180⁻195 °C for PLA 2003D). PLA and PLA/clay specimens were characterized using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile tests. Moreover, the morphology of the 3D printed specimens was investigated using optical microscopy and contact angle measurements. The different polymer matrix and the resulting nanocomposite morphology strongly influenced 3D printed specimen properties. DMA on PLA/clay filaments reported an increase in storage modulus both at ambient temperature and above the glass transition temperature in comparison to neat PLA filaments. Furthermore, the presence of nanoclay increased thermal stability, as demonstrated by TGA, and acted as a nucleating agent, as observed from the DSC measurements. Finally, for 3D printed samples, when increasing printing temperature, a different behavior was observed for the two PLA grades and their nanocomposites. In particular, 3D printed nanocomposite samples exhibited higher elastic modulus than neat PLA specimens, but for PLA 4032D+C30B, elastic modulus increased at increasing printing temperature while for PLA 2003D+C30B slightly decreased. Such different behavior can be explained considering the different polymer macromolecular structure and the different nanocomposite morphology (exfoliated in PLA 4032D matrix and intercalated in PLA 2003D matrix).

Data on thermal conductivity, water vapour permeability and water absorption of a cementitious mortar containing end-of-waste plastic aggregates.

The data presented in this article are related to the research article entitled "Hygro-thermal and durability properties of a lightweight mortar made with foamed plastic waste aggregates" (Coppola et al., 2018) [1]. This article focuses the attention on thermal conductivity, water vapour permeability and water absorption of a lightweight cementitious mortar containing foamed end-of-waste plastic aggregates, produced via foam extrusion process [2]. Thermal conductivity, water vapour permeability and water absorption data are made available to allow comparison and/or extend the analysis. Experimental investigations showed that the presence of plastic aggregates decreased thermal conductivity, water vapour resistance and capillary water absorption.

Binders alternative to Portland cement and waste management for sustainable construction-part 1.

This review presents "a state of the art" report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1-the present paper-focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Binders alternative to Portland cement and waste management for sustainable construction - Part 2.

The paper represents the "state of the art" on sustainability in construction materials. In Part 1 of the paper, issues related to production, microstructures, chemical nature, engineering properties, and durability of mixtures based on binders alternative to Portland cement were presented. This second part of the paper concerns the use of traditional and innovative Portland-free lime-based mortars in the conservation of cultural heritage, and the recycling and management of wastes to reduce consumption of natural resources in the production of construction materials. The latter is one of the main concerns in terms of sustainability since nowadays more than 75% of wastes are disposed of in landfills.

Morphology Development and Mechanical Properties Variation during Cold-Drawing of Polyethylene-Clay Nanocomposite Fibers.

In this work, the influence of composition and cold-drawing on nano- and micro-scale morphology and tensile mechanical properties of PE/organoclay nanocomposite fibers was investigated. Nanocomposites were prepared by melt compounding in a twin-screw extruder, using a maleic anhydride grafted linear low density polyethylene (LLDPE⁻g⁻MA) and an organomodified montmorillonite (Dellite 67G) at three different loadings (3, 5 and 10 wt %). Fibers were produced by a single-screw extruder and drawn at five draw ratios (DRs): 7.25, 10, 13.5, 16 and 19. All nanocomposites, characterized by XRD, SEM, TEM, and FT-IR techniques, showed an intercalated/exfoliated morphology. The study evidenced that the nanoclay presence significantly increases both elastic modulus (up to +115% for fibers containing 10 wt % of D67G) and drawability of as-spun nanocomposite fibers. Moreover, at fixed nanocomposite composition, the cold-drawing process increases fibers elastic modulus and tensile strength at increasing DRs. However, at high DRs, "face-to-edge" rearrangement phenomena of clay layers (i.e., clay layers tend to rotate and touch each other) arise in fibers at high nanoclay loadings. Finally, nanocomposite fibers show a lower diameter reduction during drawing, with respect to the plain system, and surface feature of adjustable roughness by controlling the composition and the drawing conditions.

Performance properties, lactic acid specific migration and swelling by simulant of biodegradable poly(lactic acid)/nanoclay multilayer films for food packaging.

The aim of the study was the development of a multifunctional, high-performance, fully biodegradable multilayer polylactic acid (PLA) film for food packaging applications. In particular, sealable multilayer PLA-clay nanocomposite systems with different layouts in terms of composition and relative thickness of the layers, all consisting of a PLA-clay nanocomposite layer between two pure PLA layers for direct food contact, were designed and produced by blown film co-extrusion. The films obtained were analysed for their morphology, functional properties and lactic acid (LA)-specific migration in 50% ethanol. The results showed that, with respect to the unfilled multilayer system, taken as a reference, the nanocomposite films had significant improvements, up to about 40%, in their barriers to oxygen and tensile strengths, and resulted in being more easily sealable over a wide heat-sealing temperature range (80-100°C) with higher seal strength. Moreover, all films had LA migrations always well below the former generic overall migration limit of 60 mg kg-1 food (10 mg dm-2) of European Union Regulation No. 10/2011 (deleted by the amending Regulation No. 2016/1416), even if their morphology was strongly modified during the migration tests due to the strong swelling action of the used simulant (simulant D1 = 50% ethanol (aq.) (v/v)) towards PLA.