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The aim of this work was to study the influence of drawing process on the mechanical properties of polyethylene/clay fibers. To this extent, three different PE/clay blends (3, 5 and 10 wt.%) were prepared by melt compounding in a twin-screw extruder. The investigated clay was a commercial organically modified montmorillonite (Dellite 67G). After compounding fibers were produced by a single-screw extruder and drawn at different draw ratios. At increasing draw ratio an increase of elastic modulus and tensile strength was attained. The presence of clay layers increases fibers ductility hindering fibrils formation during the drawing process. Moreover, at increasing clay contents a decrease of tensile strength for high draw ratios was observed. These results demonstrated that the dispersed clay layers can be re-aggregated by the uniaxial flow induced by the drawing process resulting in a decay of mechanical properties at high draw ratios. [ABSTRACT FROM AUTHOR]

In this work a new organosilylated clay was successfully synthesized by functionalization of a natural sodium montmorillonite (MMT) by (3-glycidyloxypropyl)trimethoxysilane (GOPTMS). This organosilylated clay was used as nanofiller for preparation, by solvent casting, of poly(lactic acid) nanocomposite systems. Similar systems, containing as nanofiller the commercial Cloisite 30B (i.e. a natural sodium montmorillonite organically modified with alkylammonium salt), were also prepared for comparison. All the obtained nanocomposite films were characterized using several techniques (XRD, permeability and mechanical tensile tests). Obtained results pointed out that nanocomposite system containing the organosilylated clay showed a better intercalation of the polymer chains into the clay layers and a higher improvement of the oxygen barrier properties, when compared to both the neat PLA film and the PLA film loaded with Cloisite 30B. [ABSTRACT FROM AUTHOR]

The barrier performance of multilayer polymeric films for food applications has been significantly improved by incorporating oxygen scavenging materials. The scavenging activity depends on parameters such as diffusion coefficient, solubility, concentration of scavenger loaded and the number of available reactive sites. These parameters influence the barrier performance of the film in different ways. Virtualization of the process is useful to characterize, design and optimize the barrier performance based on physical configuration of the films. Also, the knowledge of values of parameters is important to predict the performances. Inverse modeling and sensitivity analysis are sole way to find reasonable values of poorly defined, unmeasured parameters and to analyze the most influencing parameters. Thus, the objective of this work was to develop a model to predict barrier properties of multilayer film incorporated with reactive layers and to analyze and characterize their performances. Polymeric film based on three layers of Polyethylene terephthalate (PET), with a core reactive layer, at different thickness configurations was considered in the model. A one dimensional diffusion equation with reaction was solved numerically to predict the concentration of oxygen diffused into the polymer taking into account the reactive ability of the core layer. The model was solved using commercial software for different film layer configurations and sensitivity analysis based on inverse modeling was carried out to understand the effect of physical parameters. The results have shown that the use of sensitivity analysis can provide physical understanding of the parameters which highly affect the gas permeation into the film. Solubility and the number of available reactive sites were the factors mainly influencing the barrier performance of three layered polymeric film. Multilayer films slightly modified the steady transport properties in comparison to net PET, giving a small reduction in the permeability and oxygen transfer rate values. Scavenging capacity of the multilayer film increased linearly with the increase of the reactive layer thickness and the oxygen absorption reaction at short times decreased proportionally with the thickness of the external PET layer. [ABSTRACT FROM AUTHOR]

Fiber reinforced cementitious composite (FRCC) materials have been widely used during last decades in order to overcome some of traditional cementitious materials issues: brittle behaviour, fire resistance, cover spalling, impact strength. For composite materials, fiber/matrix bond plays an important role because by increasing fiber/matrix interactions is possible to increase the behaviour of the entire material. In this study, in order to improve fiber to matrix adhesion, two chemical treatments of polypropylene fibers were investigated: alkaline hydrolysis and nano-silica sol-gel particles deposition. Treatmtents effect on fibers morphology and mechanical properties was investigated by scanning electron microscopy (SEM) and tensile tests. SEM investigations report the presence of spherical nano-silica particles on fiber surface, in the case of sol-gel process, while alkaline hydrolysis leads to an increase of fibers roughness. Both treatments have negligible influence on fibers mechanical properties confirming the possibility of their use in a cementitious mortar. Pullout tests were carried out considering three embedded length of fibers in mortar samples (10, 20 and 30 mm, respectively) showing an increase of pullout energy for treated fibers. The influence on fiber reinforced mortar mechanical properties was investigated by three-point flexural tests on prismatic specimens considering two fibers length (15 and 30 mm) and two fibers volume fractions (0.50 and 1.00%). A general increase of flexural strength over the reference mix was achieved and an overall better behaviour is recognizable for mortars containing treated fibers. [ABSTRACT FROM AUTHOR]

Three commercial flexible polyurethane foams used for mattress have been submitted to chemical-physical analyses, water vapor permeability and compression mechanical tests, in order to understand the relationships among their composition, structure, and some functional properties of interest for bedding applications. The results demonstrated that all the three foams have open cell morphology and similar cell structure, with average cell diameters ranging from 430 to 510 micron and wide cell size distribution. As a consequence, they also show comparable water vapor transport behavior. On the contrary, their mechanical response, in terms of hysteresis loss, surface firmness and resistance to bottoming out, was found strongly dependent on their chemical structure and molecular mobility, as inferred from infrared spectroscopy analysis. [ABSTRACT FROM AUTHOR]

A preliminary study on bi-layer virgin/contaminated polypropylene co-extruded films was performed in order to evaluate the possibility to realize an effective functional barrier in PP-based multi-layer systems. In particular, the specific migration in 10% v/v aqueous ethanol of two surrogate contaminants (phenyl-cyclohexane and benzophenone) contained in the contaminated layer across the PP functional barrier was measured at different times and the results were compared with those obtained from a contaminated mono-layer polypropylene film. Moreover, the thermal and mechanical performances of the produced films were investigated. [ABSTRACT FROM AUTHOR]

A preliminary study on bi-layer virgin/contaminated polypropylene co-extruded films was performed in order to evaluate the possibility to realize an effective functional barrier in PP-based multi-layer systems. In particular, the specific migration in 10% v/v aqueous ethanol of two surrogate contaminants (phenyl-cyclohexane and benzophenone) contained in the contaminated layer across the PP functional barrier was measured at different times and the results were compared with those obtained from a contaminated mono-layer polypropylene film. Moreover, the thermal and mechanical performances of the produced films were investigated. [ABSTRACT FROM AUTHOR]

This work deals on the possibility to improve performances of PLA-based nanocomposite films, for packaging applications, through conveniently tuning materials and processing conditions in melt compounding technology. In particular, two types of polylactic acid and different types of filler selected from montmorillonites and bentonites families were used to prepare the hybrid systems by using a twin-screw extruder. The effect of biaxial drawing on morphology and properties of the nanocomposites, produced by film blowing, was investigated. [ABSTRACT FROM AUTHOR]

In this work we report on the preparation and characterization of a biodegradable active PLA film (aPLA), intended for food packaging applications. The film was obtained by cast extrusion blending a commercial PLA matrix with an active system, developed in our laboratory and based on PLA microparticles containing a-tocopherol (aTCP) as natural antioxidant agent. In order to optimize the film composition and processing, the active microparticles were preliminarily characterized with the aim to evaluate their morphology (size and shape), thermal resistance and a-tocopherol content. The aPLA film, produced with a 5wt% of aTCP, was characterized in terms of performance and activity. The experimental results demonstrated that the aPLA film has mechanical, thermal, barrier and optical properties adequate for packaging applications and shows oxygen scavenging activity and prolonged exhaustion lag time, compared to pure PLA films. [ABSTRACT FROM AUTHOR]

This work is a preliminary study about the use of hemp powder as filler in a biopolymer, i.e. polylactic acid (PLA), and the following use of such composites in the 3D printing via FDM technique. In particular, hemp powder (diameter between 75 and 180 µm) was added via melt-compounding into PLA 4043D at three different volume percentages (1, 3 and 5%). Rheological properties of the blends were determined using a rotational rheometer resulting in a decrease of complex viscosity at increasing hemp loading. PLA/hemp filaments (diameter of 2.85 mm) were produced using a single screw extruder. Dynamic mechanical analysis (DMA) on PLA/hemp filaments reported an increase of storage modulus at increasing hemp volume fraction, but compared to the neat PLA filament only the PLA+5%H blend has a higher storage modulus. Finally, filaments were used to print, using a commercial printer (Ultimaker 3, Netherlands), dog-bone specimens for tensile tests. PLA/hemp printed samples exhibited always higher elastic modulus than PLA specimens and it increases at increasing hemp content. [ABSTRACT FROM AUTHOR]

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, PLA 4032D was melt compounded in a twin screw extruder with a layered silicate (Cloisite 30B) at 4 wt%. Then, using a single screw extruder, PLA and PLA/clay filaments were produced so as to obtain the required diameter (1.75 mm). Finally, dog-bone specimens were 3D printed via FDM technique using three different temperatures (185, 200 and 215°C) and such specimens were mechanically tested in tensile mode. Dynamic mechanical analysis (DMA) on PLA/clay filaments reported an increase of storage modulus both at 35°C and 70 °C (8 and 40 %, respectively) in comparison to the PLA filament. Differential scanning calorimetry (DSC) demonstrated the ability of nanoclay to act as nucleating agent because cold crystallization temperature decreased of about 10°C. Finally, nanocomposite 3D printed samples exhibited always higher elastic modulus than PLA specimens and it increases at increasing printing temperature. [ABSTRACT FROM AUTHOR]

The coating technology is a strategic solution to improve the properties of flexible packaging films. Indeed, additional functional layers are often designed and added as coating on the substrate, in order to improve the characteristic of the flexible packaging and to meet the requirements for the desired gas or vapour barrier, for adhesion and sealing, or for improving the film printability, its aesthetics and durability. Moreover, this technology allows to functionalize a polymeric substrate applying materials with different chemistry, rheology, thermal and structural characteristics. BOPET films are widely used for food packaging applications thanks to their good gas barrier and mechanical properties, high transparency and for the excellent printability. In regard to sealing performance, BOPET films show poor sealing properties so they are mostly submitted to lamination processes with polyethylene. Nevertheless, this solution compromises the PET recyclability and influences the gas permeability of the multilayer PET based structures. The aim of this work is to investigate on the effect of nanocomposite biodegradable coatings for BOPET substrates in enhancing the heat sealing strength of eco-compatible PET/PLA films. At this regards, different percentages of Cloisite C30B (0%, 2% and 4%wt/wt) have been added to PLA by solution intercalation technique and the nanocomposite biodegradable materials produced have been applied on BOPET commercial films by casting. The BOPET coated films have been characterized in order to evaluate the heat sealing strength and the mechanical, gas permeability and surface properties. The results have shown that the addition of nanoclay in PLA coating significantly enhance the hot tack properties of the PET/PLA system produced, while the oxygen and water vapour permeability are slightly increased if compared to pure BOPET films. [ABSTRACT FROM AUTHOR]

Currently, the growing consumption of polymer products creates large quantities of waste materials resulting in public concern in the environment and people life. The efficient treatment of polymer wastes is still a difficult challenge and the recycling process represents the best way to manage them. Recently, many researchers have tried to develop nanotechnology for polymer recycling. The products prepared through the addition of nanoparticles to post-used plastics could offer the combination of improved properties, low weight, easy of processing and low cost which is not easily and concurrently found by other methods of plastic recycling. In this study materials, obtained by the separation and mechanical recycling of post-consumer packaging films of small size (

In recent years, changes in life standards have promoted the diffusion of Ready to Cook (RTC) and Ready to Eat (RTE) products for microwave ovens. However, the main limits in microwave (MW) ovens usage are often related to the proper choice of packaging materials suitable for such technology. In fact, packages for microwaveable RTC and RTE foods should ensure adequate preservation of the product before cooking/heating such as high barriers to gases and aromas and adequate control of water vapor transmission. In addition, microwaveable packaging material must be transparent to MW, thermally stable and resistant to the mechanical stress induced by the accumulation in the head space of volatile substances produced during the cooking. Polymeric materials are good candidates for microwaveable packaging thanks to their transparency to MW. In the last years a great interest is devoted to developing innovative solution based on the use of additives or systems that act as susceptors or heating enhancers for improving the characteristics of polymers in cooking/heating in MW ovens. The present work was focused on the production and characterization of nanocomposite copolyester based films suitable for microwaveable food packaging applications. The matrices selected consist in two PET copolymers modified with carbon black (ULTRA STD) and with titanium oxide (ULTRA NA). Nanocomposite co-extruded multilayer films were produced using different percentages (0%, 2% and 4%wt/wt) of Cloisite 20A (C20A). Films were analyzed for evaluating the effect of nanofiller on the morphology and barrier properties. Moreover, to verify the effectiveness of the designed systems in reducing the cooking times of meat products, MW heating tests were carried out on pork meat hamburgers in MW oven at varying supplied powers. The cooking tests have pointed out that the selected matrices are efficient in reducing cooking times and that even low concentration of C20A acts as heating enhancers of PET. [ABSTRACT FROM AUTHOR]

The blown extrusion of poly(lactic acid) presents several challenges mainly due to its poor elongation properties. This work deals on the possibility to enhance the processabiliy of PLA by film blowing by functionalizing the polymer with nanosilicates. In particular, two types of polylactic acid (PLA 4032D and PLA 4042D) and different types of filler, selected from montmorillonites (Cloisite 30B) and bentonites (Nanofil SE3010) families, were used to prepare the hybrid systems by using a twin-screw extruder. The interaction between the polymer and the clay was evaluated by FTIR analysis and correlated to the structure of the obtained nanocomposites in terms of clay dispersion. All the samples were then submitted to rheological measurements both in shear and elongational mode. [ABSTRACT FROM AUTHOR]

Thermoplastic polyurethanes (TPUs) have been widely used for a variety of applications such as fibers, coating, adhesives, and biomedical items because of their melt processability and versatile properties essentially related to their intrinsic two-phase segmented structure. However, their low stiffness and tensile strength as well as their weak barrier properties still limit their use. Currently, improvements of functional properties of plastics are usually obtained by the inclusion of nanofillers which, in this case, should be able to modify the segregated hard/soft domains of TPU matrix. In this frame, noteworthy results have been already achieved by using carbon based fillers as carbon nanotubes, graphene, graphene oxide, carbon nanofibers and so on. In this frame, this research was focused on blown films based on TPU composites including 0.2%, 0.5% and 1% of a commercial graphene oxide (GO). These latter were obtained according to a two-step procedure: a co-solvent methodology to obtain a concentrated TPU/graphene master followed by a dilution with the neat TPU matrix by extrusion melt compounding. Film samples were analyzed in terms of thermal, structural and barrier properties. Preliminary results indicated structural modifications of the TPU matrix as a result of the GO included with consequent influences on the water vapor barrier properties. [ABSTRACT FROM AUTHOR]