Polypropylene fibers containing dispersed clays having improved fire performance. I. Effect of nanoclays on processing parameters and fiber properties

Deflection Estimation Based on the Thermal Characteristics of Composite Deck Slabs Containing Macro-Synthetic Fibers

The purpose of this study was to evaluate the structural performance of composite deck slabs containing macro-synthetic fibers. after a fire by proposing a deflection estimation method for non-fireproof structural decks. Therefore, this study evaluated the fire resistance performance and deflection of deck slabs mixed with macro-synthetic fibers. Afterward, the deflection estimation method considering the thermal characteristics of concrete and deck plates was proposed. A material test was first conducted to evaluate the mechanical properties of concrete mixed with macro-synthetic fibers. This test found that the compressive strength and elasticity modulus of concrete mixed with macro-synthetic fibers was greater than that of general concrete. A flexural tensile test confirmed that residual strength was maintained after the maximum strength was achieved. The fire resistance of the deck slab was adequate even when a fire-resistant coating was not applied. The internal temperature was lowest for the specimen with macro-synthetic fibers. Deflection was evaluated using previously published equations and standards. The deflection evaluation confirmed that the temperature distribution should be applied differently in the estimation method that uses the thermal load of the deck slab.

Thermal characterization and flammability of polypropylene containing sepiolite-APP combinations

The effects of sepiolite on fire behavior of ammonium polyphosphate-based intumescent flame retardant (IFR)/polypropylene (PP) were investigated. The disaggregation of sepiolite bundles has been provided by wet-milling as the zeta potential value decreased from −9.6 to −31.3 mV. PP and additives were compounded by a twin-screw extruder and molded by injection. A total additive content of 20 wt% in PP and various proportions of sepiolite (1.0–10.0 wt%) in flame retardant (FR) formulation were studied. The flammability of the samples was measured by limit oxygen index (LOI) test and cone calorimetry. The LOI of neat PP (19%) was increased to 32.2% when sepiolite and IFR were used. The peak heat release rate of neat PP (1566.4 kW/m2) was also significantly reduced (94.7 kW/m2) when sepiolite was added with IFR. Thermal analyses results showed that, at higher temperature (700°C), IFR and sepiolite increased the char residue (9 wt%) compared to neat PP (0 wt%).

Facile synthesis of high strength hot-water wood extract films with oxygen-barrier performance

Biobased nanocomposite films for food packaging with high mechanical strength and good oxygen-barrier performance were developed using a hot-water wood extract (HWE). In this work, a facile approach to produce HWE/montmorillonite (MMT) based nanocomposite films with excellent physical properties is described. The focus of this study was to determine the effects of the MMT content on the structure and mechanical properties of nanocomposites and the effects of carboxymethyl cellulose (CMC) on the physical properties of the HWE-MMT films. The experimental results suggested that the intercalation of HWE and CMC in montmorillonite could produce compact, robust films with a nacre-like structure and multifunctional characteristics. This results of this study showed that the mechanical properties of the film designated F_CMC0.05 (91.5 MPa) were dramatically enhanced because the proportion of HWE, MMT and CMC was 1:1.5:0.05. In addition, the optimized films exhibited an oxygen permeability below 2.0 cm³μm/day·m²·kPa, as well as good thermal stability due to the small amount of CMC. These results provide a comprehensive understanding for further development of high-performance nanocomposites which are based on natural polymers (HWE) and assembled layered clays (MMT). These films offer great potential in the field of sustainable packaging.

New Flexible Flame Retardant Coatings Based on Siloxane Resin and Ethylene-Vinyl Chloride Copolymer

This work presents the effectiveness of a phosphorus-containing flame retardant based on siloxane resin and ethylene-vinyl chloride copolymer as a back-coating of fabrics. The possibility of improving flame retardant efficiency of this composition by introducing fumed silica, montmorillonite, carbon nanotubes, and graphite was evaluated. The effect of each additive on the efficiency of the composition was examined separately. Flammability tests of flame retardant-coated fabrics (natural and synthetic) were carried out using pyrolysis combustion flow calorimetry (PCFC), cone calorimetry, and limiting oxygen index determination. An assessment of the ignitability of upholstered furniture containing flame retardant fabric, resistance to washing, antifungal activity, and some of the utility properties of the final newly-developed flame-retardant coating was conducted.

Flame Retardant Polyamide Fibres: The Challenge of Minimising Flame Retardant Additive Contents with Added Nanoclays

This work shows that halogen-free, flame retarded polyamide 6 (PA6), fabrics may be produced in which component fibres still have acceptable tensile properties and low levels (preferably ≤10 wt %) of additives by incorporating a nanoclay along with two types of flame retardant formulations. The latter include (i) aluminium diethyl phosphinate (AlPi) at 10 wt %, known to work principally in the vapour phase and (ii) ammonium sulphamate (AS)/dipentaerythritol (DP) system present at 2.5 and 1 wt % respectively, believed to be condense phase active. The nanoclay chosen is an organically modified montmorillonite clay, Cloisite 25A. The effect of each additive system is analysed in terms of its ability to maximise both filament tensile properties relative to 100% PA6 and flame retardant behaviour of knitted fabrics in a vertical orientation. None of the AlPi-containing formulations achieved self-extinguishability, although the presence of nanoclay promoted lower burning and melt dripping rates. The AS/DP-containing formulations with total flame retardant levels of 5.5 wt % or less showed far superior properties and with nanoclay, showed fabric extinction times ≤ 39 s and reduced melt dripping. The tensile and flammability results, supported by thermogravimetric analysis, have been interpreted in terms of the mechanism of action of each flame retardant/nanoclay type.

Hemicelluloses/montmorillonite hybrid films with improved mechanical and barrier properties

A facile and environmentally friendly method was introduced to incorporate montmorillonite (MMT) as an inorganic phase into quaternized hemicelluloses (QH) for forming hemicellulose-based films. Two fillers, polyvinyl alcohol (PVA) and chitin nanowhiskers (NCH), were added into the hemicelluloses/MMT hybrid matrices to prepare hybrid films, respectively. The hybrid films were nanocomposites with nacre-like structure and multifunctional characteristics including higher strength and good oxygen barrier properties via the electrostatic and hydrogen bonding interactions. The addition of PVA and NCH could induce changes in surface topography, and effectively enhance mechanical strength, thermal stability, transparency, and oxygen barrier properties. The tensile strengths of the composite films F_PVA(0.3), F_PVA(0.5), and F_NCH(0.8) were 53.7, 46.3, and 50.1 MPa, respectively, which were 171%, 134%, and 153% larger than the F_QH-MMT film (19.8 MPa). The tensile strength, and oxygen transmission rate of QH-MMT-PVA film were better than those of quaternized hemicelluloses/MMT films. Thus, the proper filler is very important for the strength of the hybrid film. These results provide insights into the understanding of the structural relationships of hemicellulose-based composite films in coating and packaging application for the future.

Applications of nanotechnology in food packaging and food safety: barrier materials, antimicrobials and sensors

In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.

Flame retardant behavior of polyelectrolyte-clay thin film assemblies on cotton fabric

Cotton fabric was treated with flame-retardant coatings composed of branched polyethylenimine (BPEI) and sodium montmorillonite (MMT) clay, prepared via layer-by-layer (LbL) assembly. Four coating recipes were created by exposing fabric to aqueous solutions of BPEI (pH 7 or 10) and MMT (0.2 or 1 wt %). BPEI pH 10 produces the thickest films, while 1 wt % MMT gives the highest clay loading. Each coating recipe was evaluated at 5 and 20 bilayers. Thermogravimetric analysis showed that coated fabrics left as much as 13% char after heating to 500 degrees C, nearly 2 orders of magnitude more than uncoated fabric, with less than 4 wt % coming from the coating itself. These coatings also reduced afterglow time in vertical flame tests. Postburn residues of coated fabrics were examined with SEM and revealed that the weave structure and fiber shape in all coated fabrics were preserved. The BPEI pH 7/1 wt % MMT recipe was most effective. Microcombustion calorimeter testing showed that all coated fabrics reduced the total heat release and heat release capacity of the fabric. Fiber count and strength of uncoated and coated fabric are similar. These results demonstrate that LbL assembly is a relatively simple method for imparting flame-retardant behavior to cotton fabric. This work lays the foundation for using these types of thin film assemblies to make a variety of complex substrates (foam, fabrics, etc.) flame resistant.