1,721,012 research outputs found
Three organic/inorganic nanolayers on flexible foam allow retaining superior flame retardancy performance upon mechanical compression cycles
Full text linkRecyclable nanocomposite foams of Poly(vinyl alcohol), clay and cellulose nanofibrils – Mechanical properties and flame retardancy
No full textLayer-by-Layer nanostructured interphase produces mechanically strong and flame retardant bio-composites
No full textIn this manuscript, the Layer-by-Layer technique is used to modify the surface of flax fabrics using a quad-layer architecture (QL) prior to their assembly in polylactic acid biocomposites. The aim is to produce nanostructured interphases capable of conferring flame retardancy while maintaining mechanical properties. Only 2.5 QL significantly improve the flame retardancy and fire safety of the prepared composites as demonstrated by LOI values of 25.3%, considerably reduced flame spread rates and the substantial reduction in peak of heat release rate (−33%) and maximum average rate of heat emission (−30%) during cone calorimetry. Mechanical testing showed improved modulus and limited reductions in flexural strength. These results make the approach developed in this manuscript very attractive in the design of advanced biocomposites with optimized fire retardancy and mechanical properties
Green and Fire Resistant Nanocellulose/Hemicellulose/Clay Foams
Full text linkLightweight polymer foams from synthetic polymers are commonly used in a wide-spread spectrum of application fields. Their intrinsic flammability coupled with restrictions on flame retardant chemicals poses a severe threat to safety. Here, fire resistant foams comprising biobased components capable of replacing petroleum-based foams are investigated. Cellulose nanofibers are combined with 2D montmorillonite nanoplatelets and a native xyloglucan hemicellulose binder, using a water-based freeze casting approach. Due to the silicate nanoplatelets, these lightweight foams self-extinguish the flame during flammability tests. The limiting oxygen index is as high as 31.5% and in the same range as the best fire-retardant synthetic foams available. In cone calorimetry, the foams display extremely low combustion rates. Smoke release is near the detection limit of the instrument. In addition, the foams are withstanding the penetration of a flame torch focused on one side of the specimen (T on surface 800 °C) and structural integrity is maintained. At the same time, the unexposed side is insulated, as demonstrated by a through-thickness temperature drop of 680 °C cm−1. The results represent a tremendous opportunity for the development of fire-safe foams combining excellent sustainability with multifunctional performance
Graphite oxide nanocoatings as a sustaibale route to extend the applicability of biopolymer-based film
Full text linkIn this work, the Layer-by-Layer assembly of multilayered coatings comprising graphite oxide (GO) in combination with either chitosan or branched polyethylenimine was employed to modify the surface functional properties of polylactic acid (PLA) films. The aim is to extend the applicability of this biopolymer, which is of great industrial interest. Surface analyses by contact angle measurements and electron microscopy demonstrated the formation of a uniform GO layer, which enhanced the surface hydrophilicity. A 10 bi-layer coated film showed oxygen permeability reduced by 70% in both dry and humid conditions, compared to the neat PLA film. The use of a water soluble reducing agent allowed for the effective room temperature reduction of the GO deposited within the film, as evidenced by IR and contact angle measurements. GO reduction resulted in a significantly decreased surface resistivity and remarkable antistatic properties, suggesting possible applications in the field of antistatic packaging
Layer-by-layer modified low density cellulose fiber networks: A sustainable and fireproof alternative to petroleum based foams
No full textOverview on bonded magnets realization, characterization and adoption in prototypes
No full textIn the paper bonded magnets materials, their realization and adoption in electromechanical devices, are presented and evaluated. In particular the effects of different process parameters in their realization are deeply analyzed and described, supported by practical activities. Bonded magnets have been tested in various prototypes of rotating electrical machines and magnetic sensors; experimental results, comparing the performance of the devices equipped with these materials, with the original ones are presented. Furthermore a new magnetic material family is being explored, the Hybrid Magnetic Composites (HMC); they are prepared with both soft and hard magnetic powders, properly mixed with binders, and some examples of adoption in practical applications are proposed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Durable graphite oxide nanocoating for high performing flame retarded foams
Full text linkRecent developments in the design of water-based coatings encompassing platelet-like nanoparticles have clearly demonstrated the flame retardant potential of this approach for open cell flexible foams. However, the relatively high number of deposition steps required and the limited reports on the durability of the deposited coatings to multiple compression cycles currently represent the main constraints to this approach. This paper addresses these limitations by exploiting a few steps deposition procedure to produce coatings with durable flame retardant properties. Graphite oxide, sodium alginate and sodium hexametaphosphate were combined in a continuous protective coating that extends to the complex three-dimensional structure of the foam. The flame retardant properties of the coatings were evaluated before and after 1000 compression cycles. Even after such multiple deformations, the coated foams showed no melt dripping and self-extinguishment during flammability tests, as well as a highly reduced heat release rates (-70%) and total smoke release (-70%) during cone calorimetry tests. Furthermore, the ability to withstand the penetration of an impinging flame focused on one side of the coated foam for more than 5 min was also maintained. These results clearly demonstrate the durability of the coated foams, opening to real life application fields such as transports seats where high levels of flame retardancy must be maintained for long time under frequent mechanical stress
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