Effect of polysiloxane and silane‐modified SiO2 on a novel intumescent flame retardant polypropylene system

The effects of polysiloxane and silane‐modified SiO₂ (M‐SiO₂) on properties of intumescent flame retardant polypropylene (IFR‐PP) have been studied. The results demonstrate that both polysiloxane and M‐SiO₂ could effectively enhance the flame retardancy of the IFR‐PP, despite only 20 wt% loading of IFRs. Remarkably, the polysiloxane can clearly improve the water resistance of IFR‐PP. It can obtain UL‐94 V‐0 rating, and its LOI remains over 34% after the water treatment. The surface tension data, XPS data, and SEM sufficiently prove that the some of polysiloxane transfers to the IFR‐PP surface during processing. The TGA data show that the polysiloxane more effectively enhances the thermal stability of the IFR‐PP at high temperature and increases the char residue. The CONE results reveal that the polysiloxane can clearly change the decomposition behavior of PP and markedly reduce flammability parameters. The homogenous and compact intumescent char layers further confirm that polysiloxane is a very effective silicon‐containing additive for the flame retardancy and water resistance of the IFR‐PP. Copyright © 2010 John Wiley & Sons, Ltd.     

New pivot for investigating flame‐retarding mechanism: Quantitative analysis of zinc phosphate doped aliphatic waterborne polyurethane‐based intumescent coatings for flame‐retarding plywood

The quantitative analysis of zinc phosphate (ZnP) on the flame resistance of intumescent flame retardant coatings (IFRCs) is presented including cone calorimeter (CC) and pyrolysis kinetics, using aliphatic waterborne polyurethane (AWP) as the coating binder. The CC results show that an appropriate dosage (2 wt%) of ZnP in the AWP‐based coating constitutes an improved flame resistance, evidenced by the fire performance index increased from 0.41 to 0.71 seconds m² kW^?1, as well as the reduced fire growth index. The characterization analysis determines the dehydrated ZnP facilitates the formed amorphous char‐residue with a heat‐sink effect, leading to an increase in heat absorption, which climbs from the 253.00to 351.30 J·g^?1. Besides, the pyrolysis kinetics verifies that the 3D Jander model (n = 2) mainly governs the whole pyrolysis process of pure coatings by the modified Coats‐Redfern integral method. The ZnP‐containing coating exerts an improved E_α corresponding to 95–200°C, which climbs from 24.96 to 35.80 kJ mol^?1, leading to the formation of a continuous and compact char layer. It explores an effective quantitative analysis of the flame resistance of organic–inorganic hybrid IFRCs, deepening the flame‐retarding mechanism.     

Brazilian clays as synergistic agents in an ethylenic polymer matrix containing an intumescent formulation

The effect of two different Brazilian montmorillonitic clays in intumescent ammonium polyphosphate and pentaerythritol formulations was evaluated. Ethylene and butyl acrylate copolymer was used as polymeric matrix. The clays were added both to the pure polymer and to the polymer containing intumescent mixture. The influence of these mineral fillers on flame retardancy was investigated by thermogravimeric analysis (TG). The results show that these inorganic additives have a synergist effect in the polymeric composite containing the intumescent formulation.     

Study on combustion property and synergistic effect of intumescent flame retardant styrene butadiene rubber with metallic oxides

Effect of metallic oxides on flame retardancy and the thermal stability of styrene butadiene rubber (SBR) composites based on ammonium polyphosphate (APP) and pentaerythritol (PER) was studied by the limiting oxygen index (LOI), UL 94, the cone calorimeter tests, and thermogravimetry analysis (TGA), respectively. Scanning electron microscopy (SEM) and wide‐angle X‐ray diffraction (WAXD) were used to analyze the morphological structure and the component of the residue chars formed from the SBR composites accordingly. The addition of zirconium dioxide (ZrO₂) at a loading of 3.4 phr could improve the UL 94 test rating of the composite to V‐0. The TGA data illustrated that the metallic oxides could enhance the thermal stability of the SBR/Intumescent flame retardant additives (IFRs) composites at high temperature and increase the residue. Cone calorimeter test gave much clear evidence that the incorporation of ZrO₂ into SBR/IFRs composites resulted in the significant deduction of the heat release rate (HRR) values, and the SEM images showed that the char layers of the composites containing the metallic oxides became more compact. From the WAXD pattern, zirconium phosphate (ZrP₂O₇) may be formed by the reaction between ZrO₂ and APP. Due to the addition of ZrO₂ and the formation of ZrP₂O₇, the flame retardancy of the composite was improved. Copyright © 2009 John Wiley & Sons, Ltd.     

Synergistic effects of ferric pyrophosphate (FePP) in intumescent flame‐retardant polypropylene

Ferric pyrophosphate (FePP) was added to an ammonium polyphosphate (APP)—pentaerythritol (petol) intumescent flame retardant (IFR) system in polypropylene (PP) matrix, with subsequent investigation into the synergistic effect between FePP and the IFRs. Limited oxygen index (LOI), UL‐94 test and cone calorimeter test were employed to study the flame retardance of the synthesized flame retardant PP composites. Thermogravimetric analysis (TGA) and thermogravimetric analysis‐infrared spectrometry (TG‐IR) were used to study their thermal degradation characteristics and gas products. TG‐IR results demonstrate that there is no Fe (CO)₅ produced from PP/IFR/FePP system, which implies that the flame retardant mechanism of PP/IFR/FePP system is in the condensed phase rather than in the gas phase. Real time FTIR and X‐ray photoelectron spectroscopy (XPS) were used to monitor the thermal oxidative stability and the high temperature performance of the flame retardant PP composites. The real time FTIR spectra show that all peaks around 2900 cm^?1 almost disappear at 380°C for the PP/IFR system, meaning that PP decomposes completely at this temperature. But after the addition of 2 wt%wt% FePP, the peaks still exist till 400°C. XPS shows that the aliphatic carbon atom content in PP/23 wt%wt% IFR/2 wt%wt% FePP (63.8%) is much higher than the one without FePP, and the total oxygen atom content in PP/23 wt%wt% IFR/2 wt%wt% FePP is just 19.1%, while the one in PP/25 wt% IFR is as high as 35.7%. Copyright © 2009 John Wiley & Sons, Ltd.     

Enhancement of a hyperbranched charring and foaming agent on flame retardancy of polyamide 6

A hyperbranched polyamine was prepared using an A₂ + B₃ approach. It acted as a hyperbranched charring and foaming agent (HCFA) in combination with ammonium polyphosphate (APP) to form a new intumescent flame retardant (IFR) system for polyamide 6 (PA6). Effect of HCFA on flame retardant and thermal degradation properties of IFR‐PA6 was investigated by limiting oxygen index (LOI), UL‐94 vertical burning, cone calorimeter, and thermogravimetric analysis (TGA) tests. The IFR system presented the most effective flame retardancy in PA6 when the weight ratio of APP to HCFA was 2:1. The LOI value of IFR‐PA6 could reach 36.5 with V‐0 rating when the IFR loading was 30 wt%. Even if the loading decreased to 25 wt%, IFR‐PA6 could still maintain V‐0 rating with an LOI value of 31. TGA curves indicated that APP would interact with both PA6 and HCFA in PA6/APP/HCFA composite under heating. The interaction between APP and HCFA improved the char formation ability of IFR system and then much more char was formed for PA6/APP/HCFA composite than for PA6/APP. Therefore, better flame retardancy was achieved. Moreover, the structure and morphology of char residue were studied by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicated that compact and foaming char layer containing P‐O‐C structure was formed for PA6/APP/HCFA system during combustion. Copyright © 2010 John Wiley & Sons, Ltd.     

Fire hazard suppression of intumescent flame retardant polypropylene based on a novel Ni‐containing char‐forming agent

Reducing the fire hazard of polypropylene (PP) is an important research direction in the fields of fire safety materials. In this article, a novel Ni‐containing char‐forming agent (TTPN) was successfully synthesized, using tris(2‐hydroxyethyl) isocyanurate (THEIC), terephthalic acid, and nickel dihydrogen phosphate. Then, TTPN was combined with the silica‐gel microencapsulated ammonium polyphosphate (OS‐MCAPP) to prepare intumescent flame retardant PP composites. From the results of the limiting oxygen index (LOI) test and cone calorimeter, the composite containing 30% IFR (OS‐MCAPP: TTPN = 3:2) shows the highest LOI value of 33.5%, and its peak heat release rate is 275.5 kWm^?2, decreased by 79.0% and 37.4% than those of pure PP and the composite containing the char‐forming agent without Ni. Meanwhile, the composite containing TTPN present the best smoke and CO₂/CO suppression. The results indicate that TTPN has an excellent ability to dramatically reduce the fire hazard of PP.     

Synthesis of siloxane‐containing benzoxazine and its synergistic effect on flame retardancy of polyoxymethylene

A type of trialkoxysilane‐containing naphtholoxazine compound (Naph‐boz) was successfully synthesized and combined with ammonium polyphosphate/melamine (APP/ME) as an intumescent flame retardant (IFR) to improve the flame‐retardant efficiency of polyoxymethylene (POM). The Underwriters Laboratories 94 (UL94) vertical burning test, limiting oxygen index (LOI), cone calorimeter, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Raman spectral analysis were used to study the flame‐retardant properties and related mechanism. The results showed that the formulation with 20 wt.% of APP, 6 wt.% of ME, and 4 wt.% of Naph‐boz passed UL94 V‐1 rating, and the LOI value was improved to 40.3%. Compared with pure POM, the IFR with Naph‐boz had greater reduction in peak heat release rate (lower 74.9%) and total heat release (lower 40.2%). SEM images showed that compact and reinforcing charred layer was formed during the POM/IFR/4Naph‐boz samples combustion, which was beneficial at reducing and maintaining low combustion parameters throughout the cone calorimeter test. The synergistic flame‐retardant effect between Naph‐boz and APP/ME was considered as the reason for the improvement in flame retardancy POM. Furthermore, because of the Naph‐boz was conducive to the compatibility between the flame retardants and matrix, the notched Izod impact strength of POM/IFR/4Naph‐boz composite was higher than that of POM/IFR system.     

Synthesis of a novel hyperbranched and phosphorus‐containing charring‐foaming agent and its application in polypropylene

In this work, a novel hyperbranched and phosphorus‐containing triazine derivative (HPCFA) is synthesized. HPCFA is used as charring‐foaming agent and combined with ammonium polyphosphate (APP) as intumescent flame retardant to flame retard polypropylene (PP). PP/HPCFA/APP composite can achieve limited oxygen index value of 31% and pass UL 94V‐0 rating by addition of 20 wt% HPCFA/APP (1/2, w/w). Besides, HPCFA is compared with another hyperbranched charring‐foaming agent (HCFA). HPCFA and HCFA have similar chemical structure, and their only difference is that HPCFA has phosphorus‐containing unit in the main chain compared with HCFA. HPCFA/APP system exhibits superior flame retardancy compared with HCFA/APP system. Char residue analysis demonstrates that HPCFA/APP system can form denser and more compact char layer in comparison with that of HCFA/APP system.     

Preparation and Characterization of Core/Shell-like Intumescent Flame Retardant and its Application in Polypropylene

With a shell of starch-melamine-formaldehyde (SMF) resin, core/shell-like ammonium polyphosphate (SMFAPP) is prepared by in situ polymerization, and is characterized by SEM, FTIR and XPS. The shell leads SMFAPP a high water resistance and flame retardance compared with APP in polypropylene (PP). The flame retardant action of SMFAPP and APP in PP are studied using LOI, UL 94 test and cone calorimeter, and their thermal stability is evaluated by TG. The flame retardancy and water resistance of the PP/SMFAPP composite at the same loading is better than that of the PP/APP composite. UL 94 ratings of PP/SMFAPP can reach V-0 at 30 wt% loading. The flame retardant mechanism of SMFAPP was studied by dynamic FTIR, TG and cone calorimeter, etc.