1,721,041 research outputs found
Self-cleaning and self-sanitizing coatings on plastic fabrics: Design, manufacture and performance
No full textSelf-cleaning and self-sanitizing coatings are of utmost interest in several manufacturing domains. In particular, fabrics and textile materials are often pre-treated by impregnation or incorporation with antimicrobial pesticides for protection purposes against bacteria and fungi that are pathogenic for man or other animals. In this respect, the present investigation deals with the design and manufacture of self-cleaning and self-sanitizing coatings on plastic fabrics. The functionalization of the coatings was yield by incorporating active inorganic matter alone (i.e., photo-catalytic TiO2 anatase and Ag(+) ions) inside an organic inorganic hybrid binder. The achieved formulations were deposited on coextruded polyvinylchloride-polyester fabrics by air-mix spraying and left to dry at ambient temperature. The performance of the resulting coatings were characterized for their self-cleaning and self-sanitizing ability according to standardized testing procedure and/or applicable international regulations
Effect of the substrate and interface on micro-scratch deformation of epoxy-polyester powder coatings
No full textThe role of the interface on the deformation response in scratch tests of epoxy-polyester films deposited by electrostatic spraying is investigated. A comparative study of the scratch deformation behaviour of films deposited on micro- and macro-corrugated rigid substrates and on ‘soft’ silicon sub-layers is made. Scratch deformation parameters were evaluated by contact gauge inductive profilometry, whilst morphological examinations of the residual scratch patterns were performed by electron microscopy.
3-Response models based on a 2-D and 3-D reconstruction of the scratch pattern during the application and after the release of the load were used to perform the deformation response analysis and calculate the key geometrical features of the residual scratch patterns. In particular, the influence on the residual scratch patterns of the applied loads, sliding speeds, contact geometries, and the test modes were looked into
Manufacturing of steel foams by Slip Reaction Foam Sintering (SRFS)
No full textThis manuscript deals with the manufacture of steel foams by Slip Reaction Foam Sintering (SRFS). Closed cell steel foams were synthesized by steel powders, H3PO4, silica and water. Experimental tests were performed to study the influence of steel powders, H3PO4, silica and water weight% on the overall mechanical performance of the steel foams. The analysis of each operational parameter was performed by ANalysis Of VAriance (ANOVA). The experimental findings revealed the manufactured metal foams were characterized by mechanical energy absorption as high as 10mJ, making these materials very promising in several technological fields. Further, the use of a statistical approach allowed to identify the best settings of the process parameters, with reduced silica and H3PO4 content and increased water concentration found to increase the energy absorption capability and the overall product quality
Hard polyurethane coatings on compliant polycarbonate: An application of the 3D deformation response model to scratch visibility
No full textThe present investigation deals with the design of a transparent protective coating and its application on flat substrates in polycarbonate. The experimental analyses looked into the formulation of the coating material, the best strategy to deposit it as well as the characterization of the coated substrates. Visual appearance and morphological features of the coatings were studied by combined scanning electron microscope and contact gauge surface profiler. Their scratch and wear endurance were assessed by progressive and constant load scratching procedure and dry sliding linear reciprocating tribological tests. Imaging analyses were also used to evaluate the deformation response of the coating material to scratch and wear. Analytical modeling was developed accordingly, thus allowing to establish a strict relation between the design criteria of the coatings, the overall (coating + substrate) material performance and the loading conditions. The experimental findings showed the organic coatings were able to significantly improve the micro-mechanical and tribological response of the bare polycarbonate, thus making it available for a large share of applications where high performant, scratch and wear resistant materials are an ineluctable pre-requisite. © © 2013 Elsevier B.V. All rights reserved
Advances in design and manufacturing of environmentally friendly and biocide-free antifouling/foul-release coatings: replacement of fluorinate species
No full textAmphiphilic coatings are nowadays described as the most promising strategy for the achievement of an effective and eco-friendly antifouling marine paint, based on a physical principle. Nevertheless, most of the preparations imply the introduction of fluorinate chemicals for the formation of the hydrophobic moieties, which are potentially toxic for the marine environment in the case of an accidental release. The present work evaluates the possibility of removing fluorinate species for the implementation of such coatings and their replacement with analogous long-alkyls. In particular, this work presents an easily implementable procedure for the manufacturing of an amphiphilic system that exploits the reactivity of a commercially available –OH-rich hybrid polysiloxane resin. The resin was first modified through sol–gel chemistry that was used in the grafting of a silane-bearing hydrophobic long-alkyl chain, while the introduction of the hydrophilic moieties was conducted contextually to the curing process, through the reaction with a commercially available PEG-ilate isocyanate hardener. The effective persistence of the amphiphilic character with respect to the replacement of the fluorinate silane by the alkylsilane was ensured by the measurement of the hysteresis contact angle. The effectiveness of the persistence of the antifouling/foul-release properties was assessed through testing against the adhesion and deposition of egg white, as a proteinaceous probe, Mytilus edulis (mussel) and Ulva intestinalis (algae). All the tests indicated that the amphiphilic coating prepared from long-alkyl silane performed even better than fluorinate silane-containing samples in this hybrid coating system resulting from the fusion of a xerogel and a resin. The results suggested that the use of a long alkyl silane was an effective alternative to the use of potentially noxious fluorinate silanes, with advantages that boost the ecological benefits and also include the performance of the coating
High performance composite coatings on plastics: UV-curable cycloaliphatic epoxy resins reinforced by graphene or graphene derivatives
No full textIn this work, the design and manufacture of functional composite coatings on plastic substrates were investigated. In particular, graphene nano-platelets and graphene derivatives, that is, graphene reduced oxide modified by amino organo-silane compounds, were used to reinforce a radiation curable cycloaliphatic epoxy resin. The resulting composite materials were deposited on polycarbonate. The chemical structure of the coatings was characterized by FT-IR. Physical properties of the coatings, especially thermal stability, were evaluated by differential scanning calorimetry. Chemical endurance of the coatings was tested by dipping in acidic, saline and basic environments. Special protocols were, then, developed to evaluate the friction of the coatings as well as their potential to prevent the adhesion of contaminants on their surface (i.e., anti-soiling properties). Mechanical performance of the coatings was evaluated by pencil test (pencil hardness) and progressive load scratch test (scratch hardness). Graphene-reinforced cycloaliphatic epoxy resins were found to ensure good combination of physical, chemical and mechanical properties. Therefore, they can be considered attractive functional materials to deposit on advanced plastic substrates
Design and manufacture of photoluminescent coatings on stainless steel substrates
No full textPhotoluminescent coatings were designed by dispersing SrAl2O4:Eu2+, Dy3+ photoluminescent pigments in a silicone epoxy hybrid binder hardened with a bifunctional silane which possesses a reactive primary amino and hydrolysable ethoxysilyl groups. The resulting emulsions were deposited by an automatic drawdown applicator on AISI 304 stainless steel flat substrates and allowed to dry at ambient conditions. The visual appearance of the coatings was analyzed by combined contact gauge profilometry and field emission gun scanning electron microscopy. Mechanical and tribological properties of the coatings were analyzed by scratch and linear reciprocating ball-on-flat sliding wear tests. Photoluminescence was characterized by capturing high resolution images of the surface with a digital camera and monitoring the decay of the intensity of the emitted photoluminescent radiations. High adherent, durable and partially transparent photoluminescent coatings were achieved with a very simple, reproducible and eco-sustainable process, suitable for a wide range of substrates and large scale applications
High-Density Polyethylene/SrAl2O4:Eu2+, Dy3+ Photoluminescent Pigments: Material Design, Melt Processing, and Characterization
No full textHigh-density polyethylene is a thermoplastic polymer which is extensively involved in the manufacturing of plastic components by injection or blow molding in several industrial domains. Among others, high-density polyethylene is the ideal candidate for the fabrication of indoor and outdoor furniture and general plastic items. In this respect, photoluminescence might be of great relevance as it can replace or support conventional lighting systems in pathway markers and safety signs. In this framework, photoluminescent high-density polyethylene was achieved by the dispersion of SrAl2O4:Eu2+, Dy3+ functional pigments by twin-screw extrusion. The resulting compound was, subsequently, injection molded to form flat substrates. Characterization of the mechanical properties of the photoluminescent plastic substrates was performed by instrumented flat and scratch indentation as well as by dry sliding linear reciprocating tribological tests. Photoluminescence of the substrates was evaluated by digital imaging technique and quantitative measurements of the emission spectra. Experimental findings state that highly performant and enduring photoluminescent plastics can be achieved by compounding high-density polyethylene with SrAl2O4:Eu2+, Dy3+ photoluminescent pigments. Injection molding of the engineered material can lead to plastic items characterized by good mechanical performance and reliable photoluminescent emission over a reasonable time range
Graphene-modified poly(lactic acid) for packaging: Material formulation, processing and performance
No full textManufacturing of plastics by compostable polymers is of crucial relevance to limit the environmental impact and reduce oil consumption. Performance of compostable polymers is often mediocre, although they could be improved by physical and chemical routes. In this work, Poly(Lactic Acid) (PLA) is modified for improved performance by two different routes: (1) by physically dispersing Graphene Nano-Platelets (GNP) in the organic matrix; (2) by the physical dispersion and covalent bonding of PLA and Amino-Functionalized Nano-Silica (A-fSiO2). Functionalization of the PLAs after compounding and pelletizing was assessed by combined Fourier Transform Infrared (FT-IR). In addition, thermal analysis was performed by Differential Scanning Calorimetry (DSC). Mechanical response was evaluated on compression molded flat slabs of the modified PLAs by Pencil and progressive and constant load scratch tests. Chemical endurance was evaluated on compression molded flat slabs of the modified PLAs by dipping in aggressive acidic, basic, and saline environments. Finally, the modified PLAs were successfully injection molded to manufacture high performance coffee capsules, whose thermal stability and suitability to coffee brewing were demonstrated. © 2015 Wiley Periodicals, Inc
Cast extrusion of low gas permeability bioplastic sheets in PLA/PBS and PLA/PHB binary blends
No full textBinary blends based on polylactic acid (PLA) and other biodegradable polyesters from renewable sources (namely, polybutylene succinate (PBS) and poly-3-hydroxybutyrate (PHB)) were prepared by reactive compounding extrusion. The achieved polymeric compounds were reprocessed by cast extrusion to manufacture the corresponding bioplastic sheets. Three different binary blends, one of which also including tocopherol, an oxygen scavenger, were investigated to ensure high-barrier of the bioplastic sheets to oxygen permeation. Physical, mechanical and chemical properties of the bioplastic sheets were, therefore, comparatively evaluated by differential scanning calorimetry, infrared spectroscopy, tensile tests and gas permeability. The experimental results showed a remarkable improvement in the oxygen barrier properties, especially on sheets manufactured in the PLA/PHB binary blend, without negatively affecting their thermo-mechanical response. Based on experimental evidences, the PLA/PHB binary blend is found to be extremely promising for the development of bio-based and biodegradable polymeric materials with low oxygen permeation, that is, for the development of suitable alternatives to conventional and highly pollutant oil-based plastics
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