Synergistic Flame-retardant Mechanism Research Articles

Polycarbonate–acrylonitrile-butadiene-styrene blends with simultaneously improved compatibility and flame retardancy

Tri(2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-1-oxo-4-hydroxymethyl) phenylsilane (TPPSi) was employed as a flame retardant and polydimethylsiloxane-g-styrene-g-methyl methacrylate copolymer (PSM) as a compatibilizer in polycarbonate–acrylonitrile-butadiene-styrene (PC–ABS) blends. The effect of TPPSi and PSM on the flame retardancy and compatibilization of PC–ABS was investigated by UL-94 vertical burning tests, DMA and SEM. The results indicated that the PC–ABS blend with 8 wt% TPPSi and 5 wt% PSM possessed both high flame retardancy and impact strength. It was found that PSM played an effective compatibilization role in the PC–ABS–TPPSi blend and elevated the thermal stability of the blend. A synergistic flame-retardant mechanism between phosphorus and silicon was presented by TGA, SEM/EDX analysis, FT-IR and Raman spectra of the residue.

Nanoengineering core/shell structured brucite@polyphosphate@amine hybrid system for enhanced flame retardant properties

Abstract A novel organic-inorganic hybrid flame retardant consisting of a brucite core and a dodecylamine polyphosphate shell was synthesized by a facile nanoengineering route. The flammability characterization and synergistic flame retardant mechanism of the core/shell flame retardant (CFR) in ethylene-vinyl acetate (EVA) blends had been compared with EVA/physical mixture (PM, with the given proportion of brucite and dodecylamine polyphosphate as well as CFR) and EVA/brucite blends. With the same loading amount (40 wt%) of fillers in EVA, the peak heat release rate and smoke production rate of EVA/CFR blends were significantly reduced to 49% and 48% of that of EVA/PM blends, respectively. Meanwhile, the limiting oxygen index (LOI) was increased up to 32 (14.3% higher than that of EVA/PM blends) and the UL-94 test could achieve the V-0 rating. These remarkable properties were obtained just by nanoengineeing the core/shell structured brucite@polyphosphate@amine hybrid system, facilitating the formation of intact and compact residue with fence structure in process of polymer composite burning.

Preparation and properties of iron-based flame-retardant reinforcing agent

An iron-based flame-retardant reinforcing agent was prepared by hydrothermal method using ferric sulfate Fe2(SO4)3 and urea as starting materials. The product was characterized with respect to crystal structure and thermolysis behavior, respectively, by means of X-ray diffraction and thermogravimetric differential thermal analysis. Upon combining these with Fourier transform infrared spectroscopy, it was identified as ferric hydroxide oxide with a chemical composition of FeOOH·0.43H2O. The product was compounded with aluminum trihydroxide to flame-retard poly(ethylene- co-1-octene); the effect of FeOOH content on flame retardancy of the poly(ethylene- co-1-octene) was investigated, based on which the synergistic flame-retardant mechanism was discussed. The results show that addition of a small quantity of FeOOH can remarkably improve the flame retardance of poly(ethylene- co-1-octene)/aluminum trihydroxide compound. When the additive amount of FeOOH is 1.5 phr, the limiting oxygen index of the compound is 30.8%, and the vertical UL-94 flame test level reaches V-0.

A comprehensive study of the synergistic flame retardant mechanisms of halloysite in intumescent polypropylene

This work aims to evaluate the efficiency of halloysite as synergistic agent in an intumescent PP system based on a coated ammonium polyphosphate (IFR). The first part of the study analyses the thermal stability and fire performance of PP when using the intumescent formulation alone or in combination with the aluminosilicate nanotubes (HNTs). Cone calorimetry reveals that partial substitution of IFR by HNTs (3 wt.%) imparts substantial improvement in flame retardancy with reduced heat release rate and longer burning times. Additionally, a shift from V-1 to V-0 classification is achieved at the UL-94 test with only 1.5 wt.% HNTs. The second part provides a better understanding of the physical and chemical mechanisms of action of HNTs in the intumescent systems. The chemical evolution of the condensed phase during combustion is described by solid state NMR, and in particular using 2D NMR. Results indicate that halloysite speeds up the development of the intumescent shield, but also enhances its mechanical properties by physical reinforcement (i.e. aluminosilicate “skeleton-frame” for the phospho-carbonaceous structure) and/or by chemical interactions with IFR yielding to aluminophosphates. These new chemical species allow thermal stabilization of the char at high temperatures and provide good macro- and micro-structural properties. Both effects increase the mechanical strength of the protective layer during burning ensuring excellent heat and mass transfer limitations between gas and condensed phases.

Preparation and flame retardant properties of EVA/Mg(OH)2/La2O3 composites

The flammability characterisation and synergistic flame retardant mechanism of La2O3 in the ethylene vinyl acetate/Mg(OH)2 blends were studied by limiting oxygen index, UL 94 test and cone calorimeter test. The results showed that the addition of a given amount of La2O3 decreased the limiting oxygen index value somewhat but enhance the UL 94 test. The data obtained from the cone calorimeter test indicated that the addition of La2O3 greatly reduced the heat release rate and prolonged the ignition time.

Synergistic effects of ammonium polyphosphate/melamine intumescent system with macromolecular char former in flame-retarding polyoxymethylene

The improvement of the flame retardancy of polyoxymethylene (POM) is a world-wide difficult problem due to its zippered decomposition property. This paper reported the preparation of the flame-retarding (FR) POM with the synergistic combination of ammonium polyphosphate (APP)/melamine (ME) intumescent flame retardant system and macromolecular char former (MC). The UL94 testing, mechanical properties testing, thermogravimetric analysis (TGA), cone calorimetry and scanning electron microscopy (SEM) were used to investigate the corresponding structure, performance and synergistic flame retardant mechanism. The experimental results showed that, in the used macromolecular char formers (novolac, PA6 and TPU), the combination of novolac with APP/ME intumescent system has the best synergism in flame-retarding POM, greatly enhancing the quality of the formed condensed charred layer and hence the corresponding flame retardancy. The obtained FR POM composite could achieve flame retardancy of UL94 3.2 mm V-0 level and remarkably decreased heat release rate relative to pure POM. The synergistic effect of novolac was shown to be the char formed cross-linking reaction of it with APP. Due to the thermodynamic compatibility of novolac and POM, the prepared FR POM composite also has fairly good mechanical performance, having tensile strength of 49.1 MPa and Izod notched impact strength of 2.60 kJ/m2.

Synergistic flame retardant mechanism of fumed silica in ethylene-vinyl acetate/magnesium hydroxide blends

The flammability characterization and synergistic flame retardant mechanism of fumed silica in the ethylene-vinyl acetate/magnesium hydroxide (EVA/MH) blends were studied by cone calorimeter test (CCT), thermogravimetric analysis (TGA), limiting oxygen index (LOI), and UL-94 test. The results showed that the addition of a given amount of fumed silica apparently increased the LOI value and decreased the loading of MH in EVA blends while keeping the V-0 rating in the UL-94 test. The data obtained from the CCT indicated that the addition of fumed silica not only greatly reduced the heat release and mass loss rates, but also depressed the smoke release during the combustion of EVA/MH blends. The morphological and TGA data showed further evidence that this synergistic flame retardant mechanism of fumed silica in the EVA/MH materials is mainly due to the physical process of fumed silica acting as enhanced char/silica layers in the condensed phase which prevents the heat and mass transfer in the fire. By adding fumed silica into EVA/MH blends and reducing the total amount of fillers, the elongation at break of samples is doubled, while the fire resistance of the blends is maintained.