Condensed Phase Flame Retardant Research Articles

Functionalized graphene oxide for fire safety applications of polymers: a combination of condensed phase flame retardant strategies

Graphene is promising for the fire safety applications of polymers, but the ease of burn out limits further developments. A novel strategy based on functionalized graphene oxide (FGO) is developed to overcome this challenge. Graphene oxide is functionalized with char-catalyzing agents and reactive compounds and incorporated into polystyrene. When FGO–polystyrene composites are degraded or burned, FGO catalyzes the char formation from polystyrene (Char A). Char A protects FGO from burning out and then FGO acts as a graphitic char (Char B). Because of the combination of Char A, Char B, the physical barrier effects of FGO, and the strong interfacial interactions of FGO and polymers, the fire safety properties of the FGO–polystyrene composites are improved, including decreased peak CO release rate (66% decrease), decreased peak CO2 release rate (54% decrease), decreased peak heat release rate (53% decrease), decreased thermal degradation rate (30% decrease), decreased total heat release (38% decrease), and increased char formation (7 times), etc. This strategy combines several condensed phase flame retardant strategies such as the nanocomposite technique, intumescent flame retardant systems and phosphorus–nitrogen synergism systems, and hence results in more significant improvements as compared with prior work.

Research on the Mechanism of a Novel Si/P Flame Retardant

A novel Si/P flame retardant was prepared using tetraethyl orthosilicate (TEOS) and phosphoric acid (H3PO4). Cotton fabric treated with the flame retardant was characterized by cone calorimetry, thermogravimetric analysis (TGA), X-ray fluorescence spectroscopy, and Fourier transform infrared spectroscopy. The peak heat release rate (pHRR) and total heat release (THR) of the fabric treated with TEOS/H3PO4 are lower than those of the fabric treated with TEOS or H3PO4 alone. The HRR and THR of the treated fabric decrease from 145.66 kW/m2 and 1.68 MJ/m2 to 70.76 kW/m2 and 0.67 MJ/m2, respectively. Total smoke production decreases from 0.080 to 0.014 m2/m2. TGA revealed that cellulose dehydration increases at low temperatures because of the addition of phosphoric acid and the production of charcoal. The generated charcoal is dense. The P and Si contents markedly increase, and exist in the charcoal in the form of P-O-C and Si-O bonds, respectively. On the basis of these results, we conclude that the main mechanism of TEOS/H3PO4 is that of a condensed-phase flame retardant. Good flame retardant synergism occurs between TEOS and H3PO4.

PP/LDH Nanocomposites via Melt-Intercalation: Synergistic Flame Retardant Effects, Properties and Applications in Automobile Industries

The structure, thermal behavior and flame retardant properties of polypropylene (PP) nanocomposites treated with complex flame retardants composed of layered double hydroxides (LDH) and ammonium polyphosphate (APP)/pentaerythritol (PER) intumescent flame retardant systems have been investigated by XRD, TEM, LOI, UL-94, and TGA analysis. The results showed that introduction of LDH nanofillers into the samples can obtain good flame retardant synergistic effects with APP/PER additives at appropriate LDH loadings. Such synergism between LDH and APP/PER in PP matrix can be explained by a proposed condensed phase flame retardant mechanism. And based on this study, different types of modified PP products were developed in a ten-thousand-ton scale to be used for the automobile industries, such as car bumpers and dashboards.

Preparation and film properties of tri(3,4-epoxycyclohexylmethyl) phosphate based cationically UV curing coatings

A facile synthesis of phosphorus-containing trifunctional cycloaliphatic epoxide resin, tri(3,4-epoxycyclohexylmethyl) phosphate (TECP), used for cationically UV curing coatings as a reactive-type flame retardant, was proposed. The molecular structure was confirmed by FTIR, 1H NMR and 31P NMR spectroscopic analysis. A series of flame retardant formulations by incorporating into a commercial difunctional cycloaliphatic epoxide resin, CYRACURE™ UVR-6110, were prepared, and exposed to a medium pressure lamp to form the cured films under the presence of diaryliodonium hexafluorophosphate salt as a cationic photoinitiator. Their flame retardancy examined by the limiting oxygen index showed the improvement up to 27 for 50 wt% TECP addition compared with 21 for pure UVR-6110. The Ts and Tg decreased from 86°C and 131°C to 55°C and 91°C, respectively, by using dynamic mechanical thermal analysis, whereas the tensile strength showed a slight increase (11%) with 50 wt% TECP addition. The thermogravimetric analysis (TGA) and real-time Fourier transform infrared spectroscopy (RT-FTIR) measurement demonstrated the condensed-phase flame retardant mechanism.

Thermal behavior of covalently bonded phosphonate flame‐retarded poly(methyl methacrylate) systems

AbstractPyrolysis studies of reactively flame‐retarded methyl methacrylate copolymers MMA/diethyl(acryloyloxymethyl)phosphonate (MMA/DEAMP) and MMA/diethyl(methacryloyloxymethyl)phosphonate (MMA/DEMMP) have been undertaken with a view to gaining information pertinent to the mechanisms of their flame‐retardant behavior. The homopolymer with and without the additive diethylethylphosphonate was also investigated for comparison purposes. Each system contained 3.5 wt% of phosphorus. A range of techniques, namely TG with EGA, DSC, SEM, laser and microfurnace pyrolysis mass spectrometry, and isothermal pyrolysis‐GC‐MS, enabled the study to be carried out under a range of conditions. In the case of the additive system, the additive was evolved prior to the polymer decomposition. Little or no char residue remained at the end of the decomposition. Thus, the additive acted almost completely in the vapor phase. In the case of the MMA/DEMMP and MMA/DEAMP copolymers, substantial char residues were formed with 1.0 and 2.5 wt% phosphorus contents, respectively. This is evidence that predominantly condensed phase flame retardation occurs in these systems. SEM studies showed the chars from both copolymers to have flaky and smooth surfaces. Both copolymer samples showed slower decomposition rates compared to PMMA, the MMA/DEAMP being the slowest. Decomposition of MMA/DEMMP occurred mainly via end‐chain scission with both MMA and DEMMP appearing concurrently, which would facilitate condensed‐phase flame‐retardant action. On the other hand, in the case of MMA/DEAMP, end‐chain scission is to some extent is inhibited so that both end and the slower random‐chain scission occur. As a result, the decomposition of the acrylate system was slower than that of the methacrylate copolymer. The former system yields more char which contains the higher percentage of phosphorus than does the methacrylate copolymer. Thus, MMA/DEAMP showed the greater condensed‐phase flame‐retardant action. This is consistent with the results of our previous flammability studies of these copolymers. The flame‐retardant abilities of these two phosphonate copolymers are assessed with reference to previous studies of their equivalent phosphate copolymers. Copyright © 2008 John Wiley & Sons, Ltd.

Synthesis and testing of nonhalogenated alkyne/phosphorus-containing polymer additives: Potent condensed-phase flame retardants

In this article, the syntheses and thermal properties of several alkyne- and phosphorus-containing materials are discussed. The materials were synthesized using substituted phenolic molecules which were added to phosphorus oxychloride. The materials synthesized include phosphine oxides, phosphates, diphosphates, and oligophosphates. The thermal properties of the synthesized materials were studied using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). In general, the DSC and TGA data showed that synthesized materials containing alkynes and phosphorus had good-to-excellent thermal stability with high-onset decomposition temperatures. Materials with a high alkyne-to-phosphorus ratio showed the highest char yields. DSC data showed crosslinking events for the alkynes and the phosphorus moieties. DSC also showed that the alkynes crosslinked at lower temperatures than the phosphates. Based on the TGA and DSC data of the alkyne-containing phosphorus materials, alkynes generally appeared to be better char-inducing groups than was phosphorus. The materials were blended into polycarbonate and tested for ignition resistance using the UL-94 flame test. In two cases, these halogen-free compounds, with their dual alkyne/phosphorous crosslinking mechanisms, are condensed-phase flame retardants that can be easily blended into polycarbonate at 10 wt % loadings to afford blends that give a UL-94 V-0 rating. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 707–718, 1999

The Effects of Flame Retardant Combinations in PVC-Epoxidised Natural Rubber Miscible Blends: Antimony Trioxide in Combination with Halogen and Non-Halogen Based Additives

Effects of antimony trioxide in combination with halogen and non-halogen based additives in a matrix of PVC/ENR miscible blends were studied for processibility, miscibility of blend components, strength properties, thermal stability, and flammability. Flammability measurements were carried out by limiting oxygen index measurement. The impairments in processibility and strength properties were within tolerable limits. Additive combinations did not alter the miscibility of blend components. Thermal stability was greatly influenced. Synergistic flame retardation of zinc borate with Sb2O3 with and without decabromodiphenyl ether was explained by a vapor phase- condensed phase flame retardation mechanism. The antagonistic effect of phosphorus/antimony was greatly deactivated by a halogen additive and/or zinc borate.

Char formation from polyolefins. Correlations with low-temperature oxygen uptake and with flammability in the presence of metal halogen systems

The oxidative degradation and combustion of polypropylene were investigated by simultaneous thermal analysis (STA) and by flammability measurements. STA shows that, while halogen compounds and metal oxides invariably increase char formation from the polymeric substrate, metal chelates can act both as inhibitors and as promoters of carbonisation. In general, however, there appears to be a direct correlation between the effect of an additive on oxygen uptake and that on char formation. Pro-oxidants which catalyse char formation are effective condensed-phase flame retardants, as a result of their producing fewer volatile species from the polymer.