Preparation of a chitosan‐based flame‐retardant synergist and its application in flame‐retardant polypropylene

A novel flame‐retardant synergist, chitosan/urea compound based phosphonic acid melamine salt (HUMCS), was synthesized and characterized by Fourier transform infrared spectroscopy and ³¹P‐NMR. Subsequently, HUMCS was added to a fire‐retardant polypropylene (PP) compound containing an intumescent flame‐retardant (IFR) system to improve its flame‐retardant properties. The PP/IFR/HUMCS composites were characterized by limiting oxygen index (LOI) tests, vertical burning tests (UL‐94 tests), microscale combustion calorimetry tests, and thermogravimetric analysis to study the combustion behavior and thermal stability. The addition of 3 wt % HUMCS increased the LOI from 31.4 to 33.0. The addition of HUMCS at a low additive amount reduced the peak heat‐release rate, total heat release, and heat‐release capacity obviously. Furthermore, scanning electron micrographs of char residues revealed that HUMCS could prevent the IFR–PP composites from forming a dense and compact multicell char, which could effectively protect the substrate material from combusting. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40845.     

Polyamide‐enhanced flame retardancy of ammonium polyphosphate on epoxy resin

An attractive intumescent flame retardant epoxy system was prepared from epoxy resin (diglycidyl ether of bisphenol A), low molecular weight polyamide (cure agent, LWPA), and ammonium polyphosphate (APP). The cured epoxy resin was served as carbonization agent as well as blowing agent itself in the intumescent flame retardant formulation. Flammability and thermal stability of the cured epoxy resins with different contents of APP and LWPA were investigated by limited oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results of LOI and UL‐94 indicate that APP can improve the flame retardancy of LWPA‐cured epoxy resins. Only 5 wt % of APP can increase the LOI value of epoxy resins from 19.6 to 27.1, and improve the UL‐94 ratings, reaching V‐0 rating from no rating when the mass ratio of epoxy resin to LWPA is 100/40. It is much interesting that LOI values of flame retardant cured epoxy resins (FR‐CEP) increase with decreasing LWPA. The results of TGA, FTIR, and X‐ray photoelectron spectroscopy (XPS) indicate that the process of thermal degradation of FR‐CEP consists of two main stages: the first stage is that a phosphorus rich char is formed on the surface of the material under 500°C, and then a compact char yields over 500°C; the second stage is that the char residue layer can give more effective protection for the materials than the char formed at the first stage do. The flame retardant mechanism also has been discussed according to the results of TGA, FTIR, and XPS for FR‐CEP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The flame retardant group‐synergistic‐effect of a phosphaphenanthrene and triazine double‐group compound in epoxy resin

A flame retardant tri‐(phosphaphenanthrene‐(hydroxyl‐methylene)‐phenoxyl)‐1, 3, 5‐triazine (Trif‐DOPO) and its control samples are incorporated into diglycidyl ether of bisphenol‐A (DGEBA) and 4, 4′‐diamino‐diphenyl sulfone (DDS) to prepare flame retardant thermosets, respectively. According to the results of limited oxygen index (LOI), UL94 vertical burning test and cone calorimeter test, the Trif‐DOPO/DGEBA/DDS thermoset with 1.2 wt % phosphorus possesses the LOI value of 36% and UL94 V‐0 flammability rating, and Trif‐DOPO can decrease the peak of heat release rate (pk‐HRR) and reduce the total heat release (THR) of thermosets. All these prove better flame retardant performance of Trif‐DOPO than that of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide(DOPO). The residue photos of thermosets after cone calorimetry test disclose that Trif‐DOPO can promote the formation of thick and tough melting char layer for combined action of the flame retardant groups of Trif‐DOPO. The results from thermo gravimetric analysis (TGA) and pyrolysis‐gas chromatography‐mass spectrometry(Py‐GC/MS) show that the groups in Trif‐DOPO can be decomposed and produce PO₂ fragments, phosphaphenanthrene and phenoxy fragments, which can jointly quench the free radical chain reaction during combustion. Therefore, the excellent flame retardancy of Trif‐DOPO is attributed to its flame retardant group‐synergic‐effect. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39709.     

Effect of hydrated fillers and red phosphorus on the limiting oxygen index of poly(ethylene‐co‐vinyl actate)‐poly(vinyl butyral) and low density polyethylene‐poly(ethylene‐co‐vinyl alcohol) blends

The limiting oxygen index (LOI) values of EVA‐PVB and low density polyethylene (LDPE)‐poly(ethylene‐co‐vinyl alcohol) (EVOH) polymer blends containing hydrated filler‐type flame retardants and red phosphorus were measured. When used as the sole flame retardant, magnesium hydroxide [Mg(OH)₂] and alumina trihydrate (ATH) performed best in EVA and PVB, respectively. Magnesium hydroxide addition had a limited effect on the LOI of plasticized PVB, and addition of red phosphorus made little difference. This result is attributed to a mismatch between the decomposition temperature of Mg(OH)₂ and the temperature at which the PVB plasticizer vaporizes. Otherwise, low‐level addition of red phosphorus significantly improved LOI values. The presence of hydroxyl groups on the polymer backbone had a beneficial effect with respect to LOI values in ATH‐filled blends. An LOI value of 30 was achieved in EVOH with as little as 32% of ATH and 3% of red phosphorus. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Synergistic flame retardant effect of BiFeO3 in intumescent flame‐retardant polypropylene composites

The BiFeO₃ was used to intumescent flame retardant (IFR) polypropylene (PP) composites as a synergist. The limiting oxygen index (LOI) and UL‐94 tests indicated that there is an optimum synergistic concentration of BiFeO₃ in the PP/IFR composites. Thermogravimetric analysis (TG) results of flame retardant PP showed that the moderate of BiFeO₃ can reduce the decomposition rate of sample at high temperatures. TG of APP/PER/BiFeO₃ showed that BiFeO₃ main affects the third mass loss stage of APP/PER. So the morphology and composition of the char residue of APP/PER/BiFeO₃ composites were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and laser Raman spectroscopy (LRS). An appropriate amount of BiFeO₃ can react with APP/PER forming Bi O P and Fe O P bond, and so more P elements was involved in a crosslinking reaction to form more stable char residue, which can effectively increase the flame retardant properties of PP. POLYM. COMPOS., 38:2771–2778, 2017. © 2015 Society of Plastics Engineers     

Novel flame‐retardant epoxy composites containing aluminium β‐carboxylethylmethylphosphinate

A novel flame‐retardant aluminum β‐carboxylethylmethylphosphinate [Al(CEP)] was synthesizedby a simple process. The effect of Al(CEP) on the curing of epoxy resin (EP) was investigated with differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. The flame retardancy and thermal properties of Al(CEP)/EP were analyzed by a limiting oxygen index (LOI), vertical burning test (UL‐94), scanning electron microscopy (SEM) with energy‐dispersive X‐ray (EDX), gravimetric analyses, and DSC. Results disclosed that curing of EP is delayed by incorporating Al(CEP). The flexural strength of EP is reduced but the flexural modulus is increased by adding Al(CEP). Adding Al(CEP) depresses the decomposition of EP while leads to a increase in the glass transition temperature (T_g), in char formation and in flame retardancy of EP. EP containing 25 phr Al(CEP) provides LOI of 28.3% and passes UL‐94 V‐0 rating. SEM results show that the sample passing V‐0 rating can form the condensed char whereas porous char is observed from the sample failing in V‐0 rating after combustion. EDX analysis shows that the condensed char presents higher weight ratio of carbon to phosphorus than the porous char, indicating appropriate amount of Al(CEP) is necessary for formation of the stable char. POLYM. ENG. SCI., 55:657–663, 2015. © 2014 Society of Plastics Engineers     

Flame retarding mechanism of Polyamide 6 with phosphorus‐nitrogen flame retardant and DOPO derivatives

A novel flame‐retardant composite was prepared by introducing a phosphorus‐nitrogen flame retardant and DOPO‐SiO₂ into PA6. DOPO‐SiO₂ was synthesized successfully in a one‐step process. PA6/OP1314/DOPO‐SiO₂ achieved a UL 94 V‐0 rating with an LOI value of 31%. The maximum mass loss rate of decomposition decreased significantly and char residue increased to 11.6 wt % compared with that of pure PA6. The compacted and dense char was formed due to the combination of the P‐N flame retardant and DOPO‐SiO₂. The complex viscosity of PA6/OP1314/DOPO‐SiO₂ increased considerably which tend to prevent the dripping phenomenon. The flame‐retardant mechanism of PA6/OP1314/DOPO‐SiO₂ was also investigated by Fourier transform infrared spectroscopy FTIR at different temperatures and the pyrolysis products were investigated by pyrolysis gas chromatography/ mass spectrum (Py‐GC/MS). It was assumed that DOPO‐SiO₂ and the hypophosphite of OP1314 possess excellent flame retardancy during the gaseous phase. Meanwhile, melamine and phosphate reacted with the pyrolytic products of PA6 to protect the matrix during the condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42932.     

Preparation of borate–modified expandable graphite and its flame retardancy on acrylonitrile‐butadiene‐styrene resin

A borate‐modified expandable graphite (written as MEG) was prepared through one step intercalating reaction of natural graphite, using KMnO₄ as oxidant, H₂SO₄ and sodium tetraborate as intercalator and assistant intercalator, respectively. The dilatability, structure, element contents, thermal stability, and flame retardancy on acrylonitrile‐butadiene‐styrene (ABS) were investigated. Compared with the normal expandable graphite (written as EG, which was prepared with only H₂SO₄ as intercalator), the results show that MEG exhibits higher expandable property, thermal stability and flame retardancy on ABS. The EDS, FT‐IR, and XRD results reveal that borate has been inserted into graphite layers. With the addition of MEG or EG at a 30 wt%, LOI of 70ABS/30MEG composite improved to 27.9%, 2.2% higher than that of 70ABS/30EG. Moreover, the synergistic effect between MEG and traditional intumescent flame retardant (IFR, consists of ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MEL) with a mass ratio of 7.5:4.5:3.0) improves the LOI of 70ABS/15MEG/15IFR composite to 32.6%, and the UL‐94 level reaches V‐0. This synergistic efficiency is attributed to the formation of continuous and compact residual char. Addition of MEG together with IFR changes the ABS pyrolysis behavior, and there is not only physical synergy, but also chemical reaction. POLYM. COMPOS., 37:2673–2683, 2016. © 2015 Society of Plastics Engineers     

An effective intumescent flame retardancy of LDPE induced by the combination of APP and CNCO‐HA

A char‐forming agent poly(4,6‐dichloro‐N‐hydroxyethyl?1,3,5‐triazin‐2‐amine‐1,6‐diaminohexane) (CNCO‐HA) containing triazine rings was chosen for improving the flame retardant of low density polyethylene (LDPE). The synergistic effect of CNCO‐HA and Ammonium polyphosphate (APP) on the flame retardancy and char‐forming behavior of LDPE were investigated. The limited oxygen index (LOI) and vertical burning test (UL‐94) results indicated the optimal weight ratio of APP to CNCO‐HA was 3:1, and the LOI value of composite reached 31.0% with 30% intumescent flame retardant (IFR) loading. The cone calorimeter test analysis revealed that IFR presented excellent char forming and smoke suppression ability, and resulted in the efficient decrease of combustibility parameters. The thermogravimetric analysis results demonstrated that IFR reduced the thermal degradation rate at main stage of degradation. Scanning electron microscopy observed that IFR promoted to form a compact and continuous intumescent char layer. The Laser Raman spectroscopy spectra showed that larger graphitization degree was formed to enhance the strength of char, and Fourier transform infrared results presented that P‐O‐C and P‐O‐P structures in the residue char were formed to improve shield performance of the char layer to obtain better flame retardant properties of the composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43950.     

Flame retardation and thermal degradation of intumescent flame‐retarded polypropylene composites containing spirophosphoryldicyandiamide and ammonium polyphosphate

A novel halogen‐free intumescent flame retardant, spirophosphoryldicyandiamide (SPDC), was synthesized and combined with ammonium polyphosphate (APP) to produce a compound intumescent flame retardant (IFR). This material was used in polypropylene (PP) to obtain IFR‐PP systems whose flammability and thermal behavior were studied by the limiting oxygen index (LOI) test, UL‐94, thermogravimetric analysis, and cone calorimetry. In addition, the mechanical properties of the systems were investigated. The results indicated that the compound intumescent flame retardant showed both excellent flame retardancy and antidripping ability for PP when the two main components of the IFR coexisted in appropriate proportions. The optimum flame retardant formulation was SPDC:APP = 3:1, which gave an LOI value of 38.5 and a UL‐94 V‐0 rating. Moreover, the heat release rate, production of CO, smoke production rate, and mass loss rate of the IFR‐PP with the optimum formulation decreased significantly relative to those of pure PP, according to the cone calorimeter analysis. The char residues from the cone calorimetry experiments were observed by scanning electron microscopy, which showed that a homogeneous and compact intumescent char layer was formed. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Effect of a novel intumescent retardant for ABS with synergist Al(H<Subscript>2</Subscript>PO<Subscript>2</Subscript>)<Subscript>3</Subscript>

A novel intumescent flame retardant (IFR), containing ammonium polyphosphate (APP) and poly(hexamethylene terephthalamide) (PA6T), was prepared for acrylonitrile–butadiene–styrene (ABS). Limiting oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA) were used to investigate the flammability property and thermal stability of the IFR/ABS systems. It was found that the flame retardancy of the IFR/ABS systems was improved significantly. When the components of the IFR were 25% APP and 5% PA6T, the LOI value of IFR/ABS system reached to the maximum of 29, but only UL-94V-1 rating was passed. Thus, Al(H₂PO₂)₃ was incorporated into ABS/APP/PA6T system as a synergistic agent, it was found 2% addition of Al(H₂PO₂)₃ caused PA6T/APP/PA6T/Al(H₂PO₂)₃ (70/23.3/4.7/2) to pass V-0 rating of UL-94 test. Meanwhile, the TGA curves indicated that PA6T could be effective as a charring agent and there was a synergistic reaction between PA6T and APP, which effectively promoted the char formation of IFR/ABS composites. Moreover, the residual char obtained after the LOI test of the IFR/ABS was characterized by Fourier transform infrared spectra (FTIR). Results indicated that P–O–C chemical bond was formed in the residual char, which could indicate the cross-linking reaction between PA6T and APP could occur. Furthermore, scanning electron microscopy (SEM) was used to investigate the morphology of the residual char formed in the LOI tests. It was revealed that both ABS/APP/PA6T (70/25/5) and PA6T/APP/PA6T/Al(H₂PO₂)₃ (70/23.3/4.7/2) formed uniform and compact intumescent charred layers.     

Synthesis of a phosphorus‐ and nitrogen‐containing flame retardant and evaluation of its application in waterborne polyurethane

A phosphorus‐ and nitrogen‐containing intumescent flame retardant, pentaerythritol di‐N‐hydroxyethyl phosphamide (PDNP), was synthesized with phosphorus oxychloride, pentaerythritol, and ethanolamine as raw materials. Using the prepared PDNP as a chain extender, a series of flame‐retardant waterborne polyurethanes (WPU) were prepared, and their structures were characterized using NMR and Fourier transform infrared spectroscopy (FTIR). Additionally, the thermal properties and flame retardancy of WPU films were investigated by thermogravimetric analysis, limiting oxygen index (LOI) tests, cone calorimeter tests, and thermogravimetry‐FTIR. These results indicated that PDNP materials exhibit good char‐forming ability at high temperature and that PDNP‐modified waterborne polyurethane obtained an LOI value of 26.0% for a PDNP content of 9 wt %. Finally, the morphology and the element distributions of char residues of WPU were analyzed by scanning electron microscopy and energy dispersive spectrometry after combustion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46093.     

Influence of the pentaerythritol phosphate melamine salt content on the combustion and thermal decomposition process of intumescent flame‐retardant ethylene–vinyl acetate copolymer composites

Pentaerythritol phosphate melamine salt (PPMS) as a single‐molecule intumescent fire retardant was synthesized and characterized. The influence of the PPMS content on the combustion and thermal decomposition processes of intumescent‐flame‐retardant (IFR) ethylene–vinyl acetate copolymer (EVA) composites was studied by limiting oxygen index (LOI) measurement, UL 94 rating testing, cone calorimetry, thermogravimetric analysis, and scanning electron microscopy. The LOI and UL 94 rating results illustrate that PPMS used in EVA improved the flame retardancy of the EVA composites. The cone calorimetry test results show that the addition of PPMS significantly decreased the heat‐release rate, total heat release, and smoke‐production rate and enhanced the residual char fire performance of the EVA composites. The IFR–EVA3 composite showed the lowest heat‐release and smoke‐production rates and the highest char residue; this means that the IFR–EVA3 composite had the best flame retardancy. The thermogravimetry results show that the IFR–EVA composites had more residual char than pure EVA; the char residue yield increased with increasing PPMS content. The analysis results for the char residue structures also illustrated that the addition of PPMS into the EVA resin helped to enhance the fire properties of the char layer and improve the flame retardancy of the EVA composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42148.     

Flame retardancy in fabric consisting of cellulosic fiber and modacrylic fiber containing fine‐grained MoO3 particles

Flame retardancy of fabrics consisting of modacrylic fiber containing with various dispersed metal compounds and cellulosic fiber has been investigated by means of flame test (ISO15025 procedure A) and limiting oxygen index (LOI). It has been found that excellent flame retardancy is achieved by fine‐grained MoO₃ particles. The afterflame time in flame test and the LOI value are improved with decreasing particle size of MoO₃. The flame retardancy of MoO₃ (particle size; 0.1 µm) is comparable to that of Sb₂O₃. On the other hand, significant improvement in flame retardancy is not observed for other metal compounds although some metal oxides and a hydroxide in the present study are known as flame retardant or smoke suppressing agent in halogen containing polymer in previous studies. In order to clarify the mechanism of the observed flame retardancy by the addition of fine‐grained MoO₃, we have carried out X‐ray fluorescence spectrometry (XRF) measurement of the fabric specimen after the flame test and thermogravimetric analysis (TGA) of various types of samples. These analytical data indicated that MoO₃ works as halogen synergist in solid phase and the char of modacrylic fiber formed by addition of MoO₃ suppresses decomposition of the cotton blended in the fabric in the range of the ignition temperature. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel halogen‐free intumescent flame retardant containing phosphorus and nitrogen and its application in polypropylene systems

A novel halogen‐free intumescent flame retardant, pentaerythritol spirobisphosphoryl‐dicyandiamide (SPDC), was synthesized and characterized by FTIR, ¹H NMR, and ³¹P NMR spectra. The new flame retardant was used in polypropylene (PP) to prepare flame‐retardant materials whose flammability and thermal behavior were studied by the limiting oxygen index (LOI) method, thermogravimetric analysis (TGA), and cone calorimetry (CONE). The mechanical properties were also investigated. The results indicated that when the addition of SPDC reached 30 wt%, the material showed both excellent flame retardancy and anti‐dripping abilities for PP. Moreover, the LOI value of the PP‐IFR(30%) was 32.5, and it passed the UL‐94 V‐0 rating test. The CONE results revealed that in PP, SPDC(30%) significantly decreased the peak heat release, total heat release, and smoke relative to their values for pure PP. The morphological structures observed by SEM demonstrated that SPDC could promote the formation of a homogeneous and compact intumescent char layer. The TGA data showed that SPDC could enhance the thermal stability of PP and effectively increase the char residue formation. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Flame retardancy and water resistance of novel intumescent flame‐retardant oil‐filled styrene–ethylene–butadiene–styrene block copolymer/polypropylene composites

A novel halogen‐free flame‐retardant composite consisting of an intumescent flame retardant (IFR), oil‐filled styrene–ethylene–butadiene–styrene block copolymer (O‐SEBS), and polypropylene (PP) was studied. On the basis of UL‐94 ratings and limiting oxygen index (LOI) data, the IFRs consisted of a charring–foaming agent, ammonium polyphosphate, and SiO₂ showed very effective flame retardancy and good water resistance in the IFR O‐SEBS/PP composite. When the loading of IFR was only 28 wt %, the IFR–O‐SEBS/PP composite could still attain a UL‐94 V‐0 (1.6 mm) rating, and its LOI value remained at 29.8% after a water treatment at 70°C for 168 h. Thermogravimetric analysis data indicated that the IFR effectively enhanced the temperature of the main thermal degradation peak of the IFR–O‐SEBS/PP composites because of the formation of abundant char residue. The flammability parameters of the composites obtained from cone calorimetry testing demonstrated that water treatment almost did not affect the flammability behavior of the composite. The morphological structures of the char residue and fractured surfaces of the composites were not affected by the water treatment. This was attributed to a small quantity of IFR extracted from the composite. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39575.     

An easy‐to‐obtain silicone‐containing flame retardant and its effects on the combustion of polycarbonate

A novel silicone‐containing flame retardant (HSOBA) synthesized from hydrogen‐containing silicone oil and Bisphenol A via a simple approach has been incorporated into polycarbonate (PC) matrix to study its effects on the flame retardancy. The flame retardancy of PC/HSOBA composites is investigated by limiting oxygen index (LOI), vertical burning tests (UL‐94), and cone calorimeter measurement. The LOI value of the composites is 31.7 and the UL‐94 rating reaches V‐0, when the content of HSOBA is 3 wt %. Cone calorimeter data confirm that the HSOBA acts as an effective additive functioning both as flame retardants and as smoke suppressant. Evolution of the thermal behaviors of the composites tested by TGA, the morphological structures, and the constituent of char residue after LOI tests characterized by scanning electronic microscopy‐energy‐dispersive X‐ray analysis were used to explain the possible flame‐retardant mode. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Improving thermal and flame‐retardant properties of epoxy resins by a new imine linkage phosphorous‐containing curing agent

A new reactive phosphorus‐containing curing agent with imine linkage called 4, 4′‐[1, 3‐phenyl‐bis(9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl)dimethyneimino)]diphenol (2) was synthesized both via two‐pot and one‐pot procedure. The chemical structure of this curing agent was confirmed by FTIR, ¹H, ¹³C, and ³¹P NMR spectra. A series of thermosetting systems were prepared by using conventional epoxy resins (E51), 4, 4′‐diaminodiphenyl methane (DDM) and (2). Resins with different phosphorus contents were obtained by changing the DDM/(2) molar ratios. Their dynamic mechanical thermal, thermal and flame‐retardant properties were evaluated by dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and limiting oxygen index (LOI), respectively. All samples had a single T_g, which showed that these epoxy resins were homogeneous phase. Both the two char yields under nitrogen and air atmospheres increased with increasing content of (2) and the LOI values increased from 24.5 for standard resin to 37.5 for phosphorus‐containing resin, which indicated that incorporation of (2) could impart good thermal stability and excellent flame retardancy to the conventional epoxy thermosets. POLYM. ENG. SCI., 56:441–447, 2016. © 2016 Society of Plastics Engineers     

Effect of a novel phosphorus‐containing compound on the flame retardancy and thermal degradation of intumescent flame retardant polypropylene

A novel flame retardant, tetra(5,5‐dimethyl‐1,3‐ dioxaphosphorinanyl‐2‐oxy) neopentane (DOPNP), was synthesized successfully, and its structure was characterized by FT‐IR, ¹H NMR, and ³¹P NMR. The thermogravimetric analysis (TGA) results demonstrate that DOPNP showed a good char‐forming ability. Its initial decomposition temperature was 236.4°C based on 1% mass loss, and its char residue was 41.2 wt % at 600°C, and 22.9 wt % at 800°C, respectively. The flame retardancy and thermal degradation behavior of novel intumescent flame‐retardant polypropylene (IFR‐PP) composites containing DOPNP were investigated using limiting oxygen index (LOI), UL‐94 test, TGA, cone calorimeter (CONE) test, and scanning electron microscopy (SEM). The results demonstrate that DOPNP effectively raised LOI value of IFR‐PP. When the loading of IFR was 30 wt %, LOI of IFR‐PP reached 31.3%, and it passed UL‐94 V‐0. TGA results show that DOPNP made the thermal decomposition of IFR‐PP take place in advance; reduced the thermal decomposition rate and raised the residual char amount. CONE results show that DOPNP could effectively decrease the heat release rate peak of IFR‐PP. A continuous and compact char layer observed from the SEM further proved the flame retardance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Thermal degradation behaviors and flame retardancy of epoxy resins with novel silicon‐containing flame retardant

A novel macromolecular silicon‐containing intumescent flame retardants (Si‐IFR) was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus‐silicon characterized by IR. Epoxy resins (EP) were modified with Si‐IFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI). Twenty percentage of weight of Si‐IFR was doped into EP to get 27.5% of LOI and UL 94 V‐0. The degradation behavior of the flame retardant EP was studied by thermogravimetry, differential thermogravimetry, scanning electron microscopy, and X‐ray photoelectron spectroscopy analysis. The experimental results exhibited that when EP/Si‐IFR was heated, the phosphorus‐containing groups firstly decompose to hydrate the char source‐containing groups to form a continuous and protective carbonaceous char, which changed into heat‐resistant swollen char by gaseous products from the nitrogen‐containing groups. Meanwhile, SiO₂ reacts with phosphate to yield silicophosphate, which stabilizes the swollen char. The barrier properties and thermal stability of the swollen char are most effective in resisting the transport of heat and mass to improve the flame retardancy and thermal stability of EP. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013