Emilia Garofalo

Effect of nanocomposite composition on shear and elongational rheological behavior of PLA/MMT hybrids

The present work focuses on the possibility of conveniently tuning materials in PLA based nanocomposites in order to improve their processability in manufacturing processes where extensional flow is mainly involved. Nanocomposites at a constant silicate loading were produced by melt compounding, using a commercial polylactide grade (PLA 4032D) and two different organo-silicates (Cloisite 30B and Nanofil SE3010). A morphological characterization in solid and molten state, realized by TEM investigations and shear rheological measurements, firstly pointed out the influence of composition on the nanostructure of the hybrid systems. All the samples were then submitted to uniaxial stretching and the rheological response of the different nanocomposites was correlated to the initial nanostructure and the different polymer-clay affinity.

Processing-structure-properties relationships in PLA nanocomposite films

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.

Three-layered coextruded cast films based on conventional and metallocene poly(ethylene/α-olefin) copolymers

Multilayer films of a conventional linear low-density poly(ethylene/α-octene) (LLDPE) and a metallocene linear low-density poly(ethylene/α-hexene) (mLLDPE) copolymers were produced by cast co-extrusion process. Coextruded films were obtained by varying the position and the relative thicknesses of the two polymers. Mechanical (tensile and impact) tests, permeability, haze and hot tack measurements were carried out on the produced films in order to verify the effect of layer composition and position on the performances of the coextruded samples. Thermal and atomic force microscopy characterizations of the three-layer structures were also performed to correlate the resulting morphology with the film properties. The experiments demonstrated that, at fixed composition, the structures having the mLLDPE copolymer as external layers exhibit generally better mechanical performances and a widening in the sealability temperature window due to a lowering of 5℃ in the seal-initiation temperature, with only a small increase (max 3.5%) in the film haze percentages. The oxygen permeability values do not seem to be significantly affected by the structure composition and layout.

Polylactide Nanocomposites As a New Solution for Eco‐compatible Packaging Materials

This work focuses on the possibility of improving performance properties of polylactide films for packaging applications by melt mixing silicate nanoparticles within PLA matrix. Nanocomposites at various silicate loadings were produced by cast‐film extrusion using two different temperature profiles. Oxygen barrier and mechanical properties of the produced films were investigated and correlated to their nanostructure through analytical techniques sensitive to different aspect of the same morphology, such as TEM, XRD and rheological analyses.

Upgrading of recycled plastics obtained from flexible packaging waste by adding nanosilicates

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 (<A3, that is <297×420 mm×mm) were provided by COREPLA. The physical, chemical and rheological characterization of these recycled plastics (denoted as Recyclate A and Recyclate B) evidenced that they are mainly constituted of polyethylene (PE) and of a small fraction of polypropylene (PP). PE/PP incompatibility has been proved and explained in many studies reported in the literature and it represents the main reason for the unsatisfactory mechanical properties of these recycled plastics. The aim of this work was to improve the mechanical properties of these recycled polymeric mixtures by the addition of two different types of organo-modified silicates, also taking advantage of the function of nanofillers as potential blend compatibilizers. In particular, three organoclays (Dellite 67G, sepiolite PM15 and sepiolite UNISA1), differing for the morphology (lamellar or acicular) and/or the type of organic modifier, were melt compounded with the recycled materials in a twin-screw extruder. The morphological, thermal, rheological and mechanical properties of the prepared nanocomposites were extensively discussed.

Modelling of mechanical behaviour of polyamide nanocomposite fibres using a three-phase Halpin-Tsai model

Abstract The aim of the present study is to correlate the features of the elongational flow-induced morphology to the mechanical properties of polyamide based nanocomposite fibres. Particular attention was paid to modelling the mechanical behaviour of the hybrids which were produced by fibre spinning technique and collected at different draw ratios. Tensile properties of as-spun and stretched fibres were investigated and correlated to their nanostructure through analytical techniques sensitive to different aspects of the hybrids morphology, such as X-Ray diffraction and TEM analysis. In particular, the TEM images of the nanocomposite systems showed intercalated/exfoliated morphology in all hybrids. For this reason, a three-phase Halpin-Tsai model, based on polyamide-6 matrix, exfoliated clay platelets and nanolayer intercalated clusters, was used to fit the experimental data. This method was applied to calculate the Young’s modulus of nanocomposite fibres both as-spun and stretched ones. Moreover, the model was used for predicting the effect of various morphological parameters including the exfoliation degree, clay layer and cluster aspect ratio.

Transport, mechanical and global migration data of multilayer copolyamide nanocomposite films with different layouts

Transport, mechanical and global migration data concern multilayer food packaging films with different layouts, all incorporating a layered silicate/polyamide nanocomposite as oxygen barrier layer, and a low-density polyethylene (LDPE) as moisture resistant layer in direct contact with food. The data are related to “Tuning of co-extrusion processing conditions and film layout to optimize the performances of PA/PE multilayer nanocomposite films for food packaging” by Garofalo et al. (2017) [1]. Nanocomposite multilayer films, with different relative layer thicknesses and clay types, were produced using a laboratory scale co-extrusion blown-film equipment and were analyzed in terms of transport to oxygen and water vapor, mechanical properties and overall migration. The results have shown that all the multilayer hybrid films, based on the copolyamide layer filled with Cloisite 30B, displayed the most significant oxygen barrier improvements and the best mechanical properties compared to the unfilled films. No significant alteration of the overall migration values was observed, as expectable [2], [3], [4]. The performance improvement was more relevant in the case of the film with the thinner nanocomposite layer.

Copolyamide/sepiolite nanocomposites with enhanced stiffness and toughness

Copolyamide nanocomposites, based on sepiolite needle-like clay, were prepared through melt extrusion at different silicate loadings. The hybrid materials were characterized in terms of both thermal and rheological properties. A fine dispersion of the nanoparticles was evidenced by the dynamic rheological behavior of the composites. Moreover, the presence of sepiolite does not cause changes in the overall crystallinity degree and crystal structure compared to the neat polymer. The effect of an increasing percentage of nanofiller on the mechanical performances of the nanocomposites was also evaluated. A remarkable combination of high stiffness and toughness, not already found in literature for this kind of nanocomposites, was achieved at the lower silicate amount.

Investigation on thermoformability of PLA by rheological and hot tensile tests

In this work the correlation between the thermoformability of different grades of polylactide acid (PLA 4032D, PLA 4042D and PLA 2003D) and their mechanical, thermal, and rheological properties was explored. In particular, hot tensile tests, at different stretching temperatures and crosshead speeds, were performed in order to identify an optimum windows of temperature and strain rate for improved thermoforming performance. The properties measured from the creep experiments were correlated with the propensity of PLA sheet to sag, while the unrecovered strains by the creep recovery tests were associated to mold replication attitude of the materials investigated.

Investigation on the use of PLA/hemp composites for the fused deposition modelling (FDM) 3D printing

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.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...