1,721,643 research outputs found
Layer-by-layer assemblies on plastic films or fabrics: can surface engineering processes mimic additive manufacturing techniques at a nano-to-micro scale?
No full textSo far, the additive manufacturing (AM) techniques developed for plastic materials allowed fulfilling such important goals as no shape limits in manufacturing process, full customisation on the single plastic artefact, localised production and limited waste material. Hence, nowadays it is possible to design the envisaged products not following the constricting conventional manufacturing processes but just focusing on their specific function. However, the AM approach seems to be essentially focused on a macro scale level, because of the thickness of the deposited layers. On the other hand, it could be useful to build up assemblies, the thickness of which could be within the nano-to-micro scale: in this context, the Layer-by-Layer (LbL) approach could be very useful. The very first work, which described the principles of this technique, was published in 1966 by Iler. Surprisingly, the potential of the LbL remained hidden till the early 1990s, when Decher and coworkers developed a practical method for the deposition based polyanions and polycations; nowadays, this technique can be tailored to produce nanostructured films, the complex functionality of which can be related to the two following categories: i) Tailoring of surface interactions for improving physical and chemical properties: as every object interacts with the environment via its surface, all the properties that depend on this interaction are dictated by the surface functionality; ii) Fabrication of surface-based functional devices: the sequence used during the deposition defines the final multilayer architecture and thus the device properties. In its simplest description, the LbL consists in an alternate adsorption of chemical species on a chosen substrate exploiting one interaction, which takes place between the selected species, as the driving force for the multilayer build-up; up to now, most of the multilayer films have been fabricated using mainly the electrostatic attraction, although this is not a prerequisite. In fact, there are many others interactions such as donor/acceptor, hydrogen bonding, covalent bonds, stereocomplex formation or specific recognition that have been utilized for the multilayer deposition. This work is aimed at demonstrating that the LbL approach may represent a possible AM strategy for obtaining functional architectures at a nano-to-micro-scale. Furthermore, some examples of the assemblies specifically devoted to enhance the barrier properties or the fire retardancy of the LbL-treated substrates (plastics films or fabrics) will be presented
FIRE RETARDANCY OF TEXTILES THROUGH SURFACE ENGINEERING METHODS: RECENT ADVANCES
No full textFlame retardants (FRs) for textiles have undergone and still undergo a significant evolution toward the fulfillment of the recent EU and USA directives that are imposing the use of low impact, high sustainable products, as well as the seeking for very efficient, low cost systems that could replace halogenated chemicals at an industrial scale. In this context, new phosphorus and nitrogen flame retardants have been synthesized, demonstrating their availability as suitable FR products for both natural and synthetic fibers/fabrics. In parallel, the strong development of nanomaterials and nanotechnology has opened new pathways for successfully exploiting their nano-size in order to achieve outstanding thermal, mechanical, electrical, barrier, …, features in the designed nanocomposite structures, which the nanomaterials have been embedded in. Among the different potential combinations of nanostructures with flame retardants products possessing environmentally-friendly features, some surface engineering methods have been designed at a lab scale, showing a good potential and in some cases the possibility of up-scaling at least at pre-industrial level. In particular, the use of Layer by Layer nanoarchitectures and of sol-gel derived nanoparticles and nanocoatings for conferring flame retardant features to different types of fabrics has been thoroughly investigated. Although the setup of these two surface engineering methods is quite different, their common peculiarity refers to the possibility of locating the flame retardant "product" specifically on the textile surface, where it is primarily needed: indeed, the surface is the place where the degradation of the polymer starts to occur, as a consequence of the exposure to a heat flux or of a flame application. Therefore, the proposed surface engineering approaches can effectively limit or stop the fire propagation, avoiding, at the same time, an overcharge of the FR additive within the polymer substrate and without changing the bulk properties of this latter. The present work is aimed at summarizing the recent attempts for conferring fire retardant features to both natural and synthetic fabrics (namely, cotton, polyester and their blends), trying to exploit the aforementioned surface engineering approaches at a lab scale. More specifically, an overall view of the Layer by Layer and of sol-gel methods will be given; then, some examples of flame retarded textiles will be described. In addition, some of the potentialities associated with the use of suitable biomacromolecules (namely proteins and nucleic acids) as novel low-environmental impact flame retardant additives in surface engineering methods will be presented. Finally, the current limitations of the proposed surface engineering technologies will be briefly summarize
Nanocomposite thermomechanical and barrier-property enhancements
No full textSociety of Plastics Engineer
Biomacromolecules-based fire retardants for textiles
No full textNowadays, the real need for new flame retardants for textile substrates, which could be able to combine high efficiency together with low environmental impact, is pushing both the academic and industrial efforts toward the seeking for and the design of new possible solutions: among the different possibilities that deserve investigation, biomacromolecules seem to show some peculiarities that make them suitable candidates for replacing the halogenated or phosphorous-based flame retarded chemicals currently employed for conferring flame retardant features to cellulosic and polyester fabrics. In this context, the present work will discuss the specific flame retardant properties that such biomacromolecules as ribonucleic acids and proteins can provide to textiles, highlighting the current drawbacks and limit
Recent advances on fire retardant coatings on textiles: an overview
No full textThis presentation is aimed at describing the recent surface engineering approaches that can be exploited for conferring fire retardant features to both natural and synthetic fabrics, particularly referring to cotton, polyester and their blends. More specifically, the potentialities offered by the sol-gel and the Layer by Layer techniques are thoroughly discussed: indeed, these methods can be used for the building up of fully inorganic and/or hybrid organic/inorganic coatings that can effectively protect the underlying fabric substrate from the exposure to a flame or a heat flu
Fire retardant coatings based on biomacromolecules: towards a sustainable approach
No full textThis work is aimed at describing the feasibility of the use of biomacromolecules (such as proteins and nucleic acids) as sustainable flame retardant coatings for textiles and also plastic materials. In fact, such compounds as caseins, hydrophobins, whey proteins and nucleic acids could represent a valuable potential alternative to the flame retardants (based on phosphorus or phosphorus/nitrogen compounds) currently available for textiles and plastic substrates. It is worthy to mention that some of the selected biomacromolecules are by-products deriving from the agro-food industry: in this context, their utilization as effective flame retardants could contribute to their further valorization. In addition, it is possible to overcome the problems related to the high cost of some of the selected biomacromolecules (such as nucleic acids) by recovering them from exhausted biomasses or vegetable scraps, using low environmental impact methods. Finally, the fireproof features provided by coatings based on these biomacromolecules are discussed, also taking into account the possible strategies for overcoming some of their current limitations
Recent surface engineering methods for improving the flame retardant features of textiles
No full textFabrics flammability represents a major limitation to their use and hence to the development of most textile-based advanced technologies. Recent environmental and safety concerns are leading to progressive phasing out of versatile and effective halogen-based fire retardants, which, so far, ensured an effective textile fire hazard control. Furthermore, their replacement with phosphorous or phosphorous-nitrogen systems has allowed achieving acceptable performances, regardless of the "strong" chemistry usually behind their synthesis and application. Among the intensive efforts that are being made to develop new, environmentally safe, textile fire protection approaches, the recognition of the paramount role played by the textile surface during combustion and the exploitation of the new nanotechnologies developed for surface engineering seem to offer a promising perspective for textile fire retardancy. This work is aimed at discussing the recent surface engineering methods, namely sol-gel technique and layer by layer assemblies (exploiting fully inorganic, hybrid and organic architectures), which are able to slow down the polymer combustion even to extinguishment, complying fire safety rules of specific applications, through the creation of a surface barrier to heat and mass transfer across the textile surfac
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