Effect of time and of precursor molecule on the deposition of hydrophobic nanolayers on ethyelene tetrafluoroethylene–silicon oxide substrates

A method was developed for generating transparent and hydrophobic nanolayers chemisorbed onto flexible substrates of ethylene tetrafluoroethylene–silicon oxide (ETFE–SiOx). In particular, the effect of the deposition time and of the precursor molecule on the nanocoating process was analyzed with the aim of pursuing an optimization of the above method in an industrial application perspective. It was found that precursor molecule of triethoxysilane allowed to obtain better hydrophobic properties on the SiOx surface in shorter times compared to trichlorosilane, reaching the 92 % of final contact angle (CA) value of 106° after only 1 h of deposition. The optical properties and surface morphology were also assessed in function of time, revealing that an initial transparency reduction is followed by a subsequent transmittance increase during the self assembly of fluoroalkylsilanes on the SiOx surface, coherently with the surface roughness analysis data. Encouraging results were also obtained in terms of oleophobic properties improvement of the nanocoated surfaces

Effect of short-chain branching on melt fracture behavior of metallocene and conventional poly(ethylene/α-olefin) copolymers

A phenomenon that can represent a great problem in melt processing is extrudate distortion. This effect can range in intensity from a loss of gloss to gross distortion and is the factor that limits the production rate in certain processes such as the blown film extrusion of linear low-density polyethylene (LLDPE). The aim of this work was to investigate the effects that molecular weight distribution and short-chain branch length have on the observed melt fracture phenomena for poly(ethylene/-olefin) resins with similar weight comonomer content and molecular weight. The flow stability analysis conducted in this study has shown that, even increasing of few carbon atoms the short-chain branch length of the resins, the surface melt fracture phenomena are reduced and/or eliminated. Moreover, the comparison between the metallocene (mLLDPE) and conventional LLDPE samples, with the same comonomer (hexene), showed that the metallocene-catalyzed resin exhibits early onset and more severe melt fracture, due to its narrower molecular weight distribution

Stiffness constants prediction of nanocomposites using a periodic 3D-FEM model

Predictive models, which enable the prediction of nanocomposite properties from their morphologies and account for polymer orientation, could greatly assist the exploitation of this new class of materials in more diversified and demanding market fields. This article focuses on the prediction of effective elastic properties (Young's moduli) of polymer nanocomposite films (copolyamide-6/nanoclay) using 3D analytical (based on the Mori-Tanaka theory) and 3D finite element (FE) models. The analytical model accounts for the orientation of polymer chains induced by drawing. 3D FE model exploits the representative volume element concept and accounts for the nanocomposite morphology as determined from transmission electron microscopy experiments. Model predictions were compared with experimental results obtained for nanocomposite films produced by means a pilot-scale film blowing equipment and collected at different draw ratios

DURABILITY AND MECHANICAL PROPERTIES OF NANOCOPOSITE FIBER REINFORCED CONCRETE

In this study we investigated the influence of polypropylene/organoclay fibers on durability and mechanical behaviour of concrete. Pure polypropylene fibers and polypropylene nanocomposite fibers of two different lengths (20 and 60 mm) have been mixed in concrete at two volume fractions (0.1% and 0.3%). Nanoclay addition increases fibers elastic modulus (about 27%) reducing ductility. Workability of concrete is greatly influenced by fibers length and volume fraction: increasing these two values workability decreases. Fibers are not influent on compressive and flexural strength while post-cracking toughness is increased. Nanocomposite fibers have a better pull-out strength due to a better friction during slipping, but this doesn’t ensure a better adhesion. Water absorption, freeze/thaw cycles and sulfate attack test demonstrate that increasing fibers volume fraction, durability of concrete increases

Effect of polymer/organoclay composition on morphology and rheological properties of polylactide nanocomposites

In this work the relationships between system composition, polymer–organoclay interaction, morphology and rheological response, under shear, and elongational flow, of different melt compounded polylactic acid (PLA)/organoclay nanocomposites are investigated, with the aim to properly select the better organoclay for a well-specified PLA grade and processing technology. Polylactide nanocomposites are prepared using two commercial polylactide grades (PLA 4032D and PLA 2003D) and two different organomodified montmorillonites (Cloisite 30B and Nanofil SE3010). FTIR analysis evidences the occurrence of stronger polymer/organoclay interactions for the system PLA4032D+C30B, resulting in a higher clay dispersion and exfoliation levels. Moreover, rheological tests at low shear rates show that, if PLA 2003D is used as polymer matrix (differing from PLA4032D by the presence of a high molecular weight tail), a better dispersed nanomorphology can be obtained with Nanofil SE3010, characterized by a double d-spacing compared to Cloisite 30B, despite the higher polar character of this latter nanofiller. On the other hand, elongational rheological measurements evidence for NSE3010-based hybrids a marked extensional thickening, whilst the stronger polar interactions between the phases in both the polylactide grades filled with C30B, determine increments in elongational viscosity, but inhibit the strain hardening behavior

Effect of biaxial drawing on morphology and properties of copolyamide nanocomposites produced by film blowing

In this work, extensional behavior in non-isothermal and isothermal conditions of copolyamide-based nanocomposites was analyzed and correlated to bubble stability in the film blowing processing of these materials. The higher values of transient extensional viscosity and melt strength of the nanocomposites, compared to the neat matrix, imply that they are able to better resist the extensional external force during bubble formation. Oxygen barrier and mechanical properties of the films were investigated and correlated to the resulting polymer crystal structure and filler morphology. At the higher draw ratios and blow up ratios the nanocomposite specimens were present essentially in the mesomorphic b-form, nevertheless, significant improvements in barrier and mechanical properties of the hybrid films were observed, likely due to a good dispersion and orientation of the silicate platelets in the polymer matrix

Use of polypropylene fibers coated with nano-silica particles into a cementitious mortar

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

Preparation and performance analysis of active packaging PET films combining oxygen scavenging with barrier properties for shelf life extension of sensitive foods

The aim of this work was to prepare and evaluate the scavenging performance and the oxygen absorption kinetics of active food packaging PET films, containing a novel auto-activated, copolyester-based oxygen scavenger, which includes in its formulation also a copolyamide phase for enhanced passive gas barrier. Films at three different scavenger content (5%, 10% and 20% by weght) were produced by cast film technology, analyzed in terms of morphology and scavenging activity and tested to verify their effectiveness in preserving the quality of oxygen sensitive foods, performing preliminary shelf life tests on slices of cooked ham. The results highlighted that the films at 10% scavenger loading showed the most homogeneous dispersion and distribution of the reactive domains inside the PET matrix, the best scavenging performances and high potential in prolonging the shelf life of sensitive food matrices

Development of Biodegradable PBS/PVOH-based Films and Evaluation of Performance for Food Packaging Applications

The objective of this work deals with the realization of high O2-barrier blown films based on novel biodegradable blends of Polybutylene succinate (PBS) and Poly-vinyl alcohol (PVOH) for food packaging applications. Blends at different PBS/PVOH weight ratios (100/0, 80/20, 60/40, 0/100 wt%) were produced and their processability and miscibility was preliminary assessed by means of dynamic shear rheological tests. Afterwards, blown films were realized and then characterized in terms of chemical properties and oxygen barrier performance. The results revealed that, although immiscible, polymers in the blend show some degree of interaction. Moreover, as the concentration of PVOH in the films increased, a significant decrease in oxygen permeability was obtained with respect to the neat PBS film, up to 42% for the PBS/PVOH 60/40 sample. The findings of this study highlighted the promising perspectives of these films as sustainable packaging for sensitive foods with high O2-barrier requirements

Sustainable Active PET Films by Functionalization With Antimicrobial Bio-Coatings

The realization of antimicrobial films through the incorporation of active agents into a polymer matrix is a promising alternative to the direct addition of antimicrobials into the food matrix. To this aim, the goal of this work was to develop a sustainable, food packaging solution with antimicrobial effectiveness and high functional performance, based on Ethyl-Nα-dodecanoyl-L-arginate (LAE). Active biodegradable coatings, easy soluble to be removed, were realized by spreading a Polylactic acid/LAE coating solution, at different antimicrobial concentration (from 0 to 20%), on a recyclable Polyethylene-terephthalate substrate. The antimicrobial activity of the multilayer films was tested in vitro against E.Coli CECT 434 strain as pathogenic agent in liquid culture media. Moreover, the LAE chemical interaction with the PLA matrix was investigated, as well as its effect on the adhesion, wetting, optical and barrier properties of the films. The results pointed out that that the minimum LAE concentration incorporated already guarantees an antimicrobial activity comparable to commercial antimicrobial packaging solutions, and that, among the systems investigated, 10% LAE is the minimum concentration guaranteeing total inhibition without significantly altering the functionalities of the developed systems