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Summary: Layered double hydroxides (LDH) are chemical compounds that can be added to polymeric resins to confer fire retardant characteristics. The focus of this work is to study the incorporation of LDH intercalated with dodecylsulfate anions into epoxy resins. The mechanical properties were investigated using tensile, flexural and impact mechanical tests. The flame-retardant properties were assessed using horizontal (UL 94 HB) and vertical burning (UL 94 V) tests. The highest tensile strength was obtained for the composite with 3 wt% of LDH, whereas the highest flexural strength was found by incorporating 1 wt% of LDH. All samples containing LDH showed self-extinguishing behavior in the vertical test and lower burning rate than pristine epoxy.

A novel cheap macromolecular intumescent flame retardants (Si-MIFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus-silicon characterized by IR. Epoxy resins (EP) were modified with Si-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Si contents of 3.0 % get a LOI of 27.5% and char yield of 23.8%. Dilatation, SDR and MSD of EP/Si-MIFR decreased. The degradation behavior of the EP/Si-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Si and P at the residue were increased.

Bisphenol A bis( diphenyl phosphate) oligomer (BDP) as flame retardants (FR) was synthesized, whose structure was characterized by IR. 30% weight BDP was doped into epoxy resins (EP) to get 26.2 % of LOI and UL 94 V-0. The degradation behavior of EP containing BDP was studied by TG, SEM and cone calorimeter. In the thermal degradation of EP containing BDP, the initial decomposition temperature, Tm and heat release and smoke production are decreased while Rmax, char yields, and inherent thermal stability are increased. Surface of the char is dense and compact, which can isolate the transfer of mass and heat between the materials and the flame to protect the unburned materials.

Mg–Al–Fe ternary layered double hydroxides (LDHs) were synthesized based on Bayer red mud by a calcination–rehydration method, and characterized using powder X-ray diffraction and thermogravimetric analysis techniques. The synergistic flame-retardant effects of red phosphorus (RP) in ethylene vinyl acetate (EVA)/LDHs composites were studied with the limiting oxygen index (LOI), the UL 94 test, the cone calorimeter test (CCT), and the smoke density test (SDT). And, the thermal degradation behavior of the composites was examined by thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR) analysis. Results showed that the LOI values of the composites with RP were basically higher than those of the pure EVA sample and composites containing LDHs only. And the addition of a suitable amount of RP in EVA/LDHs/RP composites can apparently favor UL 94 test. In the UL 94 test there was a V-1 rating and dripping phenomena for the composites containing 50 % LDHs. However, the composites containing 47.5 % LDHs and 2.5 % red phosphorus did not drip. The CCT results indicated that the heat release rate (HRR) of the EVA/LDHs/RP composites with a suitable amount of RP decreased in comparison with that of the EVA/LDHs composites. The SDT showed that RP was helpful to smoke suppression. TG-FTIR data showed that the EVA/LDHs/RP composites show a higher thermal stability than the EVA/LDHs composites. A suitable amount of RP in EVA/LDHs/RP composites resulted in an increase in LOI values, a decrease in the HRR, the achievement of the UL 94 V-1 rating with no dripping phenomenon, a good smoke suppression character, and a high thermal stability.

Microencapsulated ammonium polyphosphate (MEAPP) with a shell of epoxy resin (EP) is prepared by in situ polymerization, and characterized by FTIR and SEM. The results of FTIR and SEM show that APP is microencapsulated by a layer of EP. After microencapsulation, a great improvement in water resistance is observed from the experiment of water resistance. And then, MEAPP is incorporated into EP to obtain flame retarded EP (FREP). The flammability of FREP is studied by UL 94 and Limiting Oxygen Index (LOI) Tests, and their thermal stability is evaluated by thermogravimetric analysis (TGA). At the loading of 6 wt.%, EP/MEAPP and EP/APP composites both meet the request of UL 94 V-0 rating, though the LOI value of EP/MEAPP is a little lower than that of EP/APP. However, after water treatment (75°C, 6 days), EP/MEAPP (6 wt.%) maintains the V-0 level in UL 94 test, while EP/APP does not pass any rating at the same loading. The thermal degradation behaviors of MEAPP in EP composite are also investigated by thermog...

Sol–gel technology was applied in tailoring novel wood-made-inorganic composites with improved thermal and fire properties. In practice, composites materials were prepared by impregnating pine sapwood wood with nano-scaled precursor solutions derived from titanium(IV) isopropoxide followed by a thermal curing process. Thermal and fire properties were evaluated by thermal analysis and cone calorimetry, whereas flammability was specified by oxygen index (LOI) and UL 94 test. Peak heat release rates were moderately reduced indicating fire retardance potential in terms of flame spread attributed to the appropriate protection layer action of the titania-based depositions. LOI (oxygen index) values of these composites were increased up to 38 vol.% in comparison to 23 vol.% for untreated wood. The flame retardancy performance depends on the fire scenario and is strongly influenced by wood loading and crack-free deposition of the titania layers inside the composite.

This work aims to develop glass-fiber reinforced poly(1,4-butylene terephthalate) (GRPBT) composites with enhanced mechanical, thermal stability, and flame retardancy properties using a novel compound, cerium hypophosphite (CHP). Mechanical performance studies showed that both the storage modulus and the tensile strength increased first and then decreased with increasing CHP content. For the GRPBT composite with 15 wt % of CHP, the storage modulus value at 30 °C was 3 times that of GRPBT. Thermogravimetric analysis (TGA) illustrated that low loading of CHP could improve the thermal stability of GRPBT composites. The volatilized esters measured by TGA coupled with FTIR (TGA-FTIR) in the decomposition of GRPBT with 20 wt % of CHP are decreased by about 69%. The combustion properties were evaluated by limiting oxygen index (LOI), Underwriters Laboratories 94 (UL 94), and cone calorimeter testing. For GRPBT containing 20 wt % of CHP, it achieved a V-0 classification with a high LOI (28.5%). Additionally, the peak heat release rate (PHRR) and total smoke production (TSP) were respectively reduced by around 76% and 45% as compared to the results obtained from GRPBT.

Poly(vinyl alcohol) (PVA) is a polymer of great value due to its wide spread applications. The present article describes the effect of sodium hydroxide on the flammability, thermal degradation, and tensile strength properties of PVA. The PVA/sodium hydroxide composite films at different loading levels of sodium hydroxide, i.e., 0.5, 1, 2, 3, and 4.5 wt % were prepared by solution casting technique. Dynamic thermogravimetry was used to study the thermal degradation behavior of samples at four different linear heating rates, i.e., 2.5, 5, 10, and 20 °C min−1 under nitrogen atmosphere. The degradation activation energy values were calculated using reliable and preferred multiple-heating rate methods. Limiting oxygen index (LOI) and UL 94 tests were carried out to check the flammability behavior of the samples. The presence of sodium hydroxide in PVA brought significant changes in the thermal and flammability performance. PVA/sodium hydroxide samples though showed lower initial decomposition temperature, but overall more thermal stability results as evidenced from the higher activation energy and char residue values. LOI and UL 94 tests indicate that sodium hydroxide greatly enhanced the flame retardancy of PVA/sodium hydroxide films. Based on the thermal and flammability level, the optimum concentration of sodium hydroxide is worked out. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

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

Epoxy resin (EP) is one of the main polymers in electrical and electronic applications. In this work, flame-retardant epoxy resin composites based on aluminum diethylphosphinate (Al(DEP)) and aluminum methylethylphosphinate (Al(MEP) were prepared using aromatic amine 4, 4-diaminodiphenylmethane as curing agent. The flammability, thermal degradation, flexural properties, and morphologies of composites were investigated with respect to the filler loading and filler type. Results showed that both Al(MEP) and Al(DEP) were efficient flame retardants for EP and a low dosage (15 wt%) is enough to achieve the important criterion UL 94 V-0. Limiting oxygen index (LOI) of composites is increased with filler loading (phosphorus content) and reached of 32.2% for 15 wt% of Al(MEP) and 29.8 for 15 wt% of Al(DEP). The char formation and flexural modulus of composites are also improved by adding the two fillers. However, the flexural strength of all the composites decreased with increasing filler loading. In comparison with Al(DEP)/EP, Al(MEP)/EP provides a higher flammability, better thermal stability and char formation but inferior flexural properties. Scanning electron microscopy revealed that the dispersion of Al(DEP) filler in the EP matrix is more uniform and exhibits better compatibility with EP matrix, which in turn generates better flexural strength and higher modulus when compared with Al(MEP)-filled EP composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Summary — In this work the possibility to apply graphite oxide (GO) as an intumescent flame retardant added in situ during suspension polymerization of styrene was studied. Synthesis of GO was carried out starting from natural flake graphites with different carbon content and particle size (between 45 and 500 µm). The obtained products were examined using elemental and scanning electron microscopy (SEM) analysis, Fourier transform infrared spectroscopy (FT-IR) as well as X-ray powder diffractometry (XRD). Thermal stability and expansion properties of GO were also investigated. It was stated that with an increase in particle size GO exhibited a lower degree of oxidation while the temperature of maximum decomposition rate increased. The highest expansion volume at 600 °C was observed for GO prepared from graphite with large-sized plates (300 and 500 µm). In order to prevent the dispersion of hydrophilic GO in an aqueous phase during the polymerization of styrene, GO was modified with organofunctional silane. Polystyrene with added GO (15 wt. %) reached HF-1 rating in the UL 94 horizontal burning test, however it failed to pass the required vertical flame test. The modification with melamine-formaldehyde resin (MF) resulted in an increase of GO thermal stability. Polystyrene with 15 wt. % of GO-MF additive obtained maximum ratings HF-1 and V-O in the UL 94 flame test. An attention should be paid to safe handling of GO which, although stable at ambient conditions, may undergo highly exothermic decomposition, e.g. when subjected to mechanical impact at moderately elevated temperature.

An inorganic azo diphosphonate (INAZO), (KO)2(O)P-N N-P(O)(OK)2·4H2O, was synthesized and tested as a novel type of flame retardant additive for castor oil and oligomeric methylene diphenyl diisocyanate (PMDI) based two component polyurethane adhesive with or without using dolomite ((CaMg(CO3)2) as filler. Flammability according to UL 94 test and performance under forced-flaming conditions (cone calorimeter) were investigated at the additive loadings of 5, 10 and 20 wt %. It was shown that INAZO improves flame retardancy by significantly reducing heat release rate (HRR), maximum average rate of heat emission (MARHE) and total smoke release (TSR) values in comparison to CaMg(CO3)2 filled polyurethane adhesives. The macroscopic structure of the sample residues after cone calorimeter measurement was also analysed. The action mechanism of the developed INAZO flame retardant is suggested to be mainly in the condensed phase. UL 94 V-0 rating was achieved in the vertical burning test when 10 wt % loading of INAZO was used, whereas the reference flame retardant ammonium polyphosphate (APP) required a loading of 20 wt % to reach the V-0 classification.

The flame-retardant of Lanthanum phenylphosphinate(LaPi) was prepared and its combination with intumescent flame retardant (IFR) in polypropylene (PP) was analysed using thermogravimetric analysis (TGA), limiting oxygen index (LOI) and the UL-94 test. Compared with using IFR alone, using the combination of LaPi and IFR gained the better classification in the UL 94 test thanks to the combination of the different mechanisms. When 20 wt% loading of flame retardant of LaPi and IFR, a halogen-free V-0 PP material was achieved with a LOI of 31%.

Two steps were used in the synthesis of a microencapsulated intumescent flame retardant (MIFR). First bis (1-oxo-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane-4-methylol) phosphate melaminium salt (Melabis) was synthesized. Then the Melabis was encapsulated with melamine resin to obtain the MIFR. Its structure was characterized by XPS, SEM, and elemental analysis, and the factors affecting microencapsulation were identified and discussed. Epoxy resins (EP) were modified with the MIFR to prepare flame-retardant EP, whose flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI) tests. The microcapsules (20% by weight) were added to EP in order to achieve an LOI of 29.5% and a UL 94 rating of V-0. The thermal properties of epoxy resins containing the MIFR were investigated by thermogravimetry (TG) and differential thermogravimetry (DTG). The FR decreased by weight loss, Rmax (the maximum weight loss rate), and the thermal stability of EP while promoting the formation of an effective charring layer. The char structures were studied by SEM. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers

A novel flame retardant poly(vinyl alcohol) (PVA)/melamine polyphosphate (MPP)–graphene nanocomposite has been prepared by solvent blending. Results from X-ray diffraction (XRD) and transmission electron microscopy (TEM) suggest that an excellent dispersion of exfoliated graphene and MPP in the PVA matrix was achieved. The thermal and flammability properties of the nanocomposite were investigated using thermogravimetry, cone calorimetry, and flammability tests (UL 94 and LOI). The presence of both MPP and graphene in the polymer matrix led to an enhanced thermal stability and significantly reduced flammability for the nanocomposite. PVA composites filled with 10 wt% MPP and 1 wt% graphene (PVA/G1/MPP10) achieved the LOI value of 29.6 and UL-94 V0 grade. Compared to pure PVA, the peak heat release rate (PHRR) of PVA/G1/MPP10 is reduced by about 60%. Meanwhile, the mechanical properties of PVA/G1/MPP10 composites exhibit almost no deterioration compared with pure PVA. The morphology and composition of residues generated after cone calorimeter tests were investigated by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The SEM images showed the compact and dense intumescent char jammed with graphene sheets was formed for PVA/G1/MPP10 during combustion. The results of XPS confirmed that carbon content of the char for PVA/G1/MPP10 is increased obviously by the combination effect of the flame retardant MPP and graphene.

A novel cheap macromolecular intumescent flame retardants (Zn-MIFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus-silicon characterized by IR. Epoxy resins (EP) were modified with Zn-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Zn contents of 3.0 % get a LOI of 27.5% and char yield of 20.5%. Dilatation, SDR and MSD of EP/Zn-MIFR decreased. The degradation behavior of the EP/Zn-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Zn and P at the residue were increased.

The pyrolysis and flame retardancy of a bisphenol A polycarbonate/silicon rubber/bisphenol A bis(diphenyl phosphate) (PC/SiR/BDP) blend were investigated and compared to those of PC/BDP and PC/SiR. The impact modifier SiR consists mainly of poly(dimethylsiloxane) (PDMS > 80 wt %). The pyrolysis of PC/SiR/BDP was studied by thermogravimetry (TG), TG–FTIR to analyze the evolved gases, and a Linkam hot stage cell within FTIR as well as 29Si NMR and 31P NMR to analyze the solid residue. The fire performance was determined by PCFC, LOI, UL 94, and a cone calorimeter under different external irradiations. The fire residues were studied by using ATR-FTIR as well as the additional binary systems PC + PDMS, PC + BDP, and BDP + PDMS, focusing on the specific chemical interactions. The decomposition pathways are revealed, focusing on the competing interaction between the components. Fire retardancy in PC/SiR/BDP is caused by both flame inhibition in the gas phase and inorganic-carbonaceous residue formation in the c...

Halogen free fire-retardant silicon rubber compounds for cable covering materials were prepared, using Magnesium hydroxide (MH), microencapsulated red phosphorous (MRP) as a synergist agent. Tensile Test was used to testify the mechanical properties. Limiting oxygen index (LOI) and UL 94 test were used to characterize the flammability of the developed formulations. Thermal analysis (TA) was used to characterize their thermal properties.

Halogen free fire-retardant silicon rubber compounds were prepared, using red phosphorus combined with magnesium hydroxide as flame retardants. The flame retardant mechanisms of red phosphorus, magnesium hydroxide were studied by means of comprehensive decomposition studies and combustion tests. The study is intended to illuminate prerequisites and the potential of red phosphorus as a fire retardant for silicone rubber in the condensed phase. The flammability was determined by limited oxygen indices （LOI） and UL 94 test. Thermo-oxidative decomposition kinetics were characterized by thermo-gravimetric analysis (TG). The activation energies were determined using the Friedman method, which do not require knowledge of the reaction mechanism (RM). The results show that the MVMQ/MH/RP composite has a higher thermal stability and lower flammability.

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based compounds containing resorcinol bis(diphenyl phosphate) (RDP) and poly(dimethyl-diphenyl siloxane) (PDMDPS) were prepared through melt extrusion, and their flammability characteristics and mechanical properties were evaluated. The incorporation of RDP enhanced the flame retardancy of PPO compounds, but hardly made them obtain the UL 94 V-0 rating unless RDP and PDMDPS were combined. Studies on the residual chars after vertical burning test suggested that the excellent flame retardancy be correlated with the retention from the combination effects of silica and phosphate in the char, whose cross-linked silica enhanced the formation of a compact char to retard combustion. Thermogravimetric analysis indicated that the presence of PDMDPS and RDP improved the char yielding as well as the decomposition temperature of PPO compounds. Moreover, the Izod impact strength was improved significantly in the presence of RDP and PDMDPS, and this toughening effect was attributed to the deformation and multiple cracks induced by PDMDPS, which enhances the impact energy absorption of the matrix. This work provides a very effective flame retarding formulation for PPO compounds with improved impact toughness. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Flame retardancy for thermoplastics is a challenging task where chemists and engineers work together to find solutions to improve the burning behavior without strongly influencing other key properties of the material. In this work, the halogen-free additives aluminum diethylphosphinate (AlPi-Et) and a mixture of aluminum phosphinate (AlPi) and resorcinol-bis(di-2,6-xylyl phosphate) (AlPi-H + RXP) are employed in neat and reinforced poly(butylene terephthalate) (PBT), and the morphology, mechanical performance, rheological behavior, and flammability of these materials are compared. Both additives show submicron dimensions but differ in terms of particle and agglomerate sizes und shapes. The overall mechanical performance of the PBT flame-retarded with AlPi-Et is lower than that with AlPi-H-RXP, due to the presence of larger agglomerates. Moreover, the flow behavior of the AlPi-Et/PBT materials is dramatically changed as the larger rod-like primary particles build a percolation threshold. In terms of flammability, both additives perform similar in the UL 94 test and under forced-flaming combustion. Nevertheless, AlPi-Et performs better than AlPi-H + RXP in the LOI test. The concentration required to achieve acceptable flame retardancy ranges above 15 wt %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

This article studies the relationship between the distribution of organically modified montmorillonite (OMMT) and the flammability of flame retardant polypropylene which consists of polypropylene (PP), brominated epoxy resin-antimony oxide (BER-AO) and OMMT. Polypropylene-graft-maleic anhydride (PP-g-MAH) was used to increase the polarity of PP and aid the dispersion of OMMT. Two model systems, PP/BER-AO/OMMT and PP/PP-g-MAH/BER-AO/OMMT composites, have been prepared by melt blending. TEM studies reveal a significant change in the distribution of OMMT for these two systems. For the first composites, OMMT platelets are aggregated in the BER-AO domains, whereas for the second composites, OMMT platelets are dispersed in the PP matrix. The flame retardant properties of the second composite reflected by UL 94 vertical burning test and cone calorimetry are better than that of the first one. When OMMT platelets aggregate in BER-AO domains as in the first composite, the BER-AO associated with OMMT may agglomerate into long ribbon-like structures during burning, inducing uneven distribution of BER-AO. As a result, loose and uneven residues are formed at the end of combustion. In comparison, OMMT platelets dispersed in polymer matrix are more efficient at stabilizing the polymer and preventing aggregation of BER-AO during burning, which induce thick and uniform char layers at the end of combustion. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Endothermically decomposing mineral fillers, such as aluminium or magnesium hydroxide, magnesium carbonate, or mixed magnesium/calcium carbonates and hydroxides, such as\ud naturally occurring mixtures of huntite and hydromagnesite are in heavy demand as sustainable, environmentally benign fire retardants. They are more difficult to deploy than the\ud halogenated flame retardants they are replacing, as their modes of action are more complex, and are not equally effective in different polymers. In addition to their presence (at levels up to 70%), reducing the flammable content of the material, they have three quantifiable fire\ud retardant effects: heat absorption through endothermic decomposition; increased heat capacity of the polymer residue; increased heat capacity of the gas phase through the presence of water or carbon dioxide. These three contributions have been quantified for eight of the most common fire retardant mineral fillers, and the effects on standard fire tests such as the LOI, UL 94 and cone calorimeter discussed. By quantifying these estimable\ud contributions, more subtle effects, which they might otherwise mask, may be identified.

Wood, one of the flammable material, was treated with aqueous solution of guanidine nitrate (GUN) and also with small amount of bases like N,N-dimethylformamide, 4-dimethylaminopyridine, pyridine, and triethylamine in the treating solution. These bases catalyze the impregnation of GUN as indicated by increase in mass gain percentage, elemental analysis, and scanning electron microscopy. To study their thermal behavior, dynamic thermogravimetry (TG) and derivative thermogravimetry (DTG) analysis under nitrogen atmosphere have been applied from ambient temperature to 973 K on all samples, at multiple linear heating rates 2.5, 5, 10, and 20 K min−1. Non-isothermal, “model free” iso-conversional multiple heating rate methods, Ozawa–Flynn–Wall (O–F–W) and modified Coats–Redfern are used to calculate activation energy of samples. The activation energy of samples is found in the range 109–208 kJ mol−1. Thermal parameters like overall pyrolysis duration, maximum mass loss rate, corresponding to DTG peak maximum and percentage char yield calculated at 873 K from TG curves are used to appraise the flammability of samples. Also, flammability of samples is determined by reliable methods namely limiting oxygen index and underwriters laboratories 94 (UL 94) test. The aforesaid study indicates that base catalyzed impregnated samples are less flammable than those impregnated with only GUN and untreated ones.

Flame retarded ethylene-vinyl acetate copolymer (EVA) was prepared in a melt process containing melamine phosphate (MP), or MP in combination with dipentaerythritol (DPER) as flame retardants. The influence of MP and MP/DPER on flame retardant properties of EVA was investigated by limiting oxygen index (LOI) and UL 94 test. Thermal decomposition of the flame retardants and flame retarded EVA composites was studied by the thermogravimetric analysis. The results show that MP used alone in EVA does not exerts good flame retardancy, even at a loading of 50wt%. It is found that the flame retardant properties of the EVA/MP/DPER composites is greatly improved when a suitable amount of MP substituted by DPER. Moreover, mechanical properties of the EVA composites were studied.

The known flame-retardant synergism between phosphorus-based additives and metal oxides, already used for petroleum-based plastics, has been extended to bio-based materials. The pyrolysis and the flame-retardancy properties of aluminium phosphinate (AlPi) in combination with nanometric iron oxide and antimony oxide on a poly(3-hydroxy-butyrate-co-3-hydroxyvalerate)/poly(butylene adipate-co-terephthalate) (PHBV/PBAT) blend were investigated. Better fire retardancy, ascribed to increases in intermediate char, favoured improvements in the UL 94 classification. Both the phosphorus and the nanofiller components participate simultaneously in the flame-retardancy mechanism: the first acting as flame inhibition in the gas phase, and the second promoting cross-linking in the solid phase. Redox reactions between iron oxide and the phosphinate additive were confirmed by XRD analysis and provided further evidence of the activity of metal compounds.

SUMMARY Fire safety is dependent on reliable information on material properties, particularly relating to burning behaviour. The Underwriters Laboratory UL-94 test is a widely used simple Bunsen burner test for vertically upward flame spread. Aryl polyetheretherketones (PEEK) are polymers of exceptional thermal stability, typically decomposing at around 600°C and forming 50% carbonaceous char residue. Tests on seven PEEK polymers, and two related materials, in independent laboratories have revealed large inconsistencies in both the final broad classification and the scatter within each set of test results. In many cases, this variance is so large that if samples from the same batch of many of the materials were repeatedly submitted to test laboratories, this would ultimately result in one set remaining below the maximum burn time criteria, and so meeting the least flammable V-0 rating. Initial data are presented indicating that a larger ignition source actually results in shorter burning times and more consistent burning behaviour. The reported behaviour of PEEK indicates that the inconsistencies reported here are not a function of inconsistencies in the material itself but rather a consequence of the low applied heat flux of the test method being very close to the critical heat flux for ignition of the PEEK polymer, which is rather high. With higher applied heat fluxes, this generates sufficient heat for a protective char to form, creating an effective barrier to further flame spread. Copyright © 2011 John Wiley & Sons, Ltd.

Polyamide (nylon) 11 (PA11) were melt-blended by dispersing low concentrations of nanoparticles (NPs), namely nanoclays (NCs) and carbon nanofibers (CNFs) via twin-screw extrusion. To enhance their thermal and flame retardant (FR) properties, an intumescent FR additive was added to the mechanically superior NC and CNF PA11 formulations. For neat and NP-reinforced PA11 as well as for PA11 reinforced by both intumescent FR and select NPs (NC or CNF), decomposition temperatures by TGA, flammability properties by UL 94, and cone calorimetry values were measured. All PA11 polymer systems infused with both NPs and FR additive had higher decomposition temperatures than those infused with solely FR additive. For the PA11/FR/NC polymer blends, Exolit® OP 1312 (FR2) is the preferred FR additive to pass the UL 94 V-0 requirement with 20 wt%. For the PA11/FR/CNF formulations, all Exolit® OP 1311 (FR1), OP 1312 (FR2), and OP 1230 (FR3) FR additives passed the UL 94 V-0 requirement with 20 wt%.

This work aims to develop halogen-free poly(1,4-butylene terephthalate) (PBT) composites with enhanced flame retardancy using ecofriendly flame retardants, aluminum hypophosphite (AHP) and melamine derivatives (melamine polyphosphate and melamine cyanurate). Microscale combustion calorimetry and thermal gravimetric analysis/infrared spectrometry (TG-IR) technique were used to investigate the potential fire hazards of these PBT composites. For the PBT composites with the incorporation of AHP and melamine derivatives, the heat release capacity (HRC) which is an indicator of a material fire hazard was significantly reduced, and the intensities of a variety of combustible or toxic gases detected by TG-IR technique were remarkably decreased. Moreover, a loading of 20 wt % flame retardant mixture fulfilled the PBT composites high limited oxygen index (LOI) and V-0 classification in UL 94 testing. An intumescent flame retarded mechanism was speculated in this work, because numerous bubble-like char residues were found on the surface of the samples containing flame retardant mixture after LOI testing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The hexaphenylamine cyclotriphosphazene (HPACTPZ) was synthesized using titrating technology of hexachlorocyclotriphosphazene solution and the synthesis parameters were investigated, and the structure of HPACTPZ was analyzed by FTIR and NMR in this paper. Using HPACTPZ synthesized in the work as flame retardant, the epoxy molding compound(EMC) for packaging of large-scale integrated circuits with halogen-free flame retardance was prepared. The results have shown that the flame retardance of EMC flame-retardanced by HPACTPZ was up to UL 94 V0 rating(3.2mm) and the oxygen index of the EMC was up to 35.8%, which indicates that HPACTPZ has much better flame retardance for EMC than traditional halogen flame-retardants. Meanwhile, HPACTPZ accelerated the curing reaction rate of EMC, which can be used for manufacturing the quick-curing EMCs or afterward-curing-free EMCs.

Pyrolysis and fire behaviour of a phosphorus polyester (PET-P-DOPO) have been investigated. The glycol ether of the hydroquinone derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was used as a reactive halogen-free flame retardant in PET-P-DOPO. PET-P-DOPO is proposed as an alternative to poly(butylene terephthalate) (PBT) with established halogen-free additives. It exhibits a high LOI (39.3%) and achieves V-0 classification in the UL 94 test. Three different mechanisms (flame inhibition, charring and a protection effect by the intumescent char) contribute to the flame retardancy in PET-P-DOPO and were quantified with respect to different fire risks. The fire load was reduced by 66% of the PBT characteristic. The reduction is the superposition of the relative reduction due to flame inhibition (factor 0.625) and charring (factor 0.545). The peak of heat release rate (pHRR) was reduced by 83% due to flame inhibition, charring and the protection properties of the char (factor 0.486). The strength of all three mechanisms is in the same order of magnitude. The intumescent multicellular structure enables the char to act as an efficient protection layer. PBT flame-retarded with aluminium diethylphosphinate was used as a benchmark to assess the performance of PET-P-DOPO absolutely, as well as versus the phosphorus content. PET-P-DOPO exhibits superior fire retardancy, in particular due to the additional prolongation of the time to ignition and increase in char yield. PET-P-DOPO is a promising alternative material for creating halogen-free flame-retarded polyesters.

Two novel, halogen-free, phosphorus-based oligomeric flame retardants are investigated in the commercial epoxy resin RTM6 and ∼70 wt.% carbon fibre RTM6 composites (RTM6-CF) with respect to pyrolysis and fire behaviour. The flame retardants are based on 9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide (DOPO) units linked to the star-shaped aliphatic ground body tetra-[(acryloyloxy)ethyl] pentarythrit (DOPP), or heterocyclic tris-[(acryloyloxy)ethyl] isocyanurate (DOPI), respectively. The glass transition temperature is reduced by adding DOPP and DOPI, but the mechanical properties of the composites (e.g. interlaminar shear strength (ILSS) and Gc in mode I and II) remain unchanged. Decomposition models are proposed based on mass loss, evolved gas analysis (TG–FTIR) and condensed product analysis (hot stage cell within FTIR). The fire behaviour is investigated comprehensively (UL 94, limiting oxygen index (LOI) and cone calorimeter). Both flame retardants act in the gas phase through flame inhibition and in the condensed phase through charring. The UL 94 of RTM6 is improved from HB to V-1 and V-0; the LOI from 25% to 34–38%. Peak heat release rate (PHRR) and total heat evolved (THE) are lowered by 31-49% and 40–44%, respectively. Adding CF increases the residue, reduces the THE, but suppresses the charring due to RTM6 and flame retardants. Thus the THE of RTM6-CF is reduced by about 25% when DOPI and DOPP are added. However, UL 94: V-0 and LOI of 45% and 48% are achieved with ∼0.6 wt.% phosphorus.

In this paper, β-cyclodextrin (CD) was used as effective “green” carbon source to replace pentaerythritol (PER) in an intumescent flame retardant (IFR). The combination of CD with traditional acid resource ammonium polyphosphate (APP) and/or blowing agent melamine (MA) at different weight ratios exhibited outstanding char-forming ability. It was demonstrated that strong interactions occurred in APP-CD and MA-CD systems through thermogravimetric analysis (TGA). Mechanisms of esterification between APP and CD or dehydration between MA and CD were discussed. The APP/MA/CD complexes showed doubled char residue of those calculated based on three single components in nitrogen atmosphere. For instance, the char residue of CD-APP (at the weight ratio of 1:1) complex was 38 wt% at 700°C, while the calculated char formation was only 19 wt% in N2. After addition of these complexes into polylactic acid (PLA), the flammability of these PLA resins was evaluated by limited oxygen index (LOI) and vertical combustion (UL-94). The TGA results indicated that the cyclodextrin mixed with APP and MA as a “green” char agent demonstrated outstanding char formation ability for PLA. When the complex contained CD/APP/MA at weight ratio of 1/2/1 and the addition amount of complex in PLA was 20 wt%, the PLA composites showed LOI values of 34.2 and passed UL 94 V0 rating, and the char residue of the PLA composite was 17.4 wt% at 700°C while only 7.4 wt% was achieved for the calculated composition. Copyright © 2011 John Wiley & Sons, Ltd.

The tri(o-phenylenediamine) cyclotriphosphazene (TPCTP) was synthesized using titrating technology of hexachlorocyclotriphosphazene solution and the synthesis parameters were investigated, and the structure of TPCTP was analyzed by FTIR in this paper. Using TPCTP synthesized in the work as flame retardant, the epoxy molding compound(EMC) for packaging of large-scale integrated circuits with halogen-free flame retardance was prepared. The results have shown that the flame retardance of EMC flame-retardanced by TPCTP was up to UL 94 V0 rating(1.6mm) and the oxygen index of the EMC was up to 34.5%, which indicates that TPCTP has much better flame retardance for EMC than traditional halogen flame-retardants. Meanwhile, TPCTP accelerated the curing reaction rate of EMC, which can be used for manufacturing the quick-curing EMCs or afterward-curing-free EMCs.

The effect of a hybrid system of nanoclay and triphenyl phosphate (TPP) on the fire retardancy of a polycarbonate (PC)/acrylonitrile–butadiene–styrene (ABS) blend was examined in this study. The nanoclay in the polymers decreased the peak heat release rates (PHRRs) with no significant effect on the ease of ignition and times to extinguishment. Improvements in the flame retardancy were observed only when nanoparticles were used with conventional flame-retardant (FR) additives. Thermogravimetric analysis (TGA), cone calorimetry, and limited oxygen index (LOI)/UL 94 (Underwriters Laboratory) testing were used to investigate the thermal degradation, fire behavior, and flammability of the materials. The results show that when we used a combination of TPP and nanoclay as an FR system, degradation of the polymer blends was reduced as the TGA curves shifted to higher temperatures. PHRR in cone calorimetry testing decreased from 1032 kW/m2 for the PC/ABS blend to 300 kW/m2 for the PC/ABS/(12% TPP–2% nanoclay) sample, and the LOI increased from 23 to 35%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Microencapsulated ammonium polyphosphate (MAPP) is prepared using hydroxyl silicone oil by in situ polymerization and characterized by XPS. Microencapsulation gives MAPP better water resistance and flame retardance compared with APP in thermoplastic polyurethane (TPU). Thermal stability and fire resistance behavior have been analyzed and compared. The LOI value of the TPU/MAPP composite is higher than that of the TPU/APP composite. The UL 94 rating of the TPU/MAPP composite is V-0 at the 20 wt% additive level, whereas TPU/APP gives V-2 rating at the same loading level. The water resistant properties of the TPU composites are studied. Results of the cone calorimeter and microscale combustion calorimeter experiment show that MAPP is an effective flame retardant in TPU compared with APP.

Bis(2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane-4-methanol) melaminium salt (Melabis) and microcapsules of Melabis with melamine resin shell as flame retardants (FR), respectively, were synthesized. Their structures were characterized by NMR, IR, SEM, TG and element analysis. 20% weight of microcapsules was doped into epoxy resins (EP) to get 28.5 % of LOI and UL 94 V-0. The heat and smoke release of EP containing microcapsules was valued by cone calorimeter.

Conventional thermally durable materials such as metals are being replaced with heat resistant engineering polymers and their composites in applications where burn-through resistance and structural integrity after exposure to fire are required. Poly aryl ether ether ketone (PEEK) is one such engineering polymer. Little work has been published with regards to the flammability of PEEK and its filled composites. The current study aims to assess the flammability and fire behaviour of PEEK and its composites using thermogravimetric analysis, pyrolysis combustion flow calorimetry, limiting oxygen index, a vertical flame resistance test, and fire (cone) calorimetry.

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.

The flammability and synergistic flame-retardant effects of fumed silica (SiO2) in ethylene vinyl acetate (EVA)/aluminum hydroxide (ATH) blends were studied with limiting oxygen index measurements, UL 94 testing, cone calorimeter testing (CONE), and thermogravimetric analysis (TGA). The results show that the addition of a given amount of fumed SiO2 can apparently improve UL 94 rating. The CONE data indicated that the addition of fumed SiO2 greatly reduced the heat release rate. The TGA data showed that this synergistic flame-retardant mechanism of fumed SiO2 in the EVA/ATH materials was mainly due to the physical process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A novel charring agent, poly(p-propane terephthalamide) (PPTA), was synthesized with terephthaloyl chloride and 1,2-propanediamine through solution polycondensation at a low temperature. PPTA was used together with ammonium polyphosphate (APP) to prepare a novel intumescent flame retardant (IFR) for an acrylonitrile butadiene styrene (ABS) resin. The flammability and thermal stability of the IFR–ABS composites were investigated with limiting oxygen index, UL 94 vertical burning, and thermogravimetric analysis tests. The results showed that the IFR system had excellent flame retardancy and antidripping properties for ABS. The thermogravimetric curves suggested that there was a distinct synergistic effect of PPTA and APP, and this effect greatly promoted the char formation of the IFR–ABS composites and hence improved the flame retardancy. Additionally, the structure and morphology of char residues were studied with Fourier transform infrared and scanning electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The pyrolysis and fire behavior of halogen-free flame-retarded DGEBA/DMC, RTM6 and their corresponding 60 vol.-% carbon fibers (CF) composites were investigated. A novel phosphorous compound (DOPI) was used. Its action is dependent on the epoxy matrix. DGEBA/DMC and DOPI decompose independently of each other. Only flame inhibition occurs in the gas phase. RTM6 shows flame inhibition and a condensed phase interaction increasing charring. Both mechanisms decrease with increasing irradiance, whereas in RTM6-CF charring is suppressed at low ones. RTM6 + DOPI shows a higher LOI (34.2%) than DGEBA/ DMC + DOPI and a V-0 classification in UL 94. Adding CF only enhances the LOI, DOPI + CF leads to a superposition in LOI for DGEBA/DMC-CF + DOPI (31.8%, V-0) and a synergism for RTM6-CF + DOPI (47.7%, V-0).

The pyrolysis and the flame retardancy of poly(butylene terephthalate) (PBT) containing aluminum diethylphosphinate (AlPi) and nanometric Fe2O3 were investigated using thermal analysis, evolved gas analysis (Thermogravimetry-FTIR), flammability tests (LOI, UL 94), cone calorimeter measurements and chemical analysis of residue (FTIR). AlPi mainly acts as a flame inhibitor in the gas phase, through the release of diethylphosphinic acid. A small amount of Fe2O3 in PBT promotes the formation of a carbonaceous char in the condensed phase. The combination of 5 and 8 wt% AlPi, respectively, with 2 wt% metal oxides achieves V-0 classification in the UL 94 test thanks to complementary action mechanisms. Using PBT/metal oxide nanocomposites shows a significant increase in the flame retardancy efficiency of AlPi in PBT and thus opens the route to surprisingly sufficient additive contents as low as 7 wt%. Copyright © 2010 John Wiley & Sons, Ltd.

We have developed novel multifunctional flame retardant polymer composites that exhibit better fire performance. Flame retardant polymer composites are prepared by infusing woven carbon fibers with phosphoric-acid-modified crosslinked diglycidylether of bisphenol-A epoxy matrix through the resin infusion under flexible tooling (RIFT) process. In this paper, we have explored various design factors of the fire retarding epoxy resin by modifying the resin physically as well as chemically. Different flame retardant epoxy samples are evaluated by compression test, UL 94, thermogravimetric analysis and dynamic mechanical thermal analysis. The fabricated flame retardant polymer composites have been characterized using in-plane shear test, to estimate the structural properties, and UL-94 test, to estimate the fire performance. In this study, a flame retardant composite, simultaneously exhibiting a UL-94 rating of V-0 and a shear modulus of 9.5 GPa, has been reported.

Exhaustion of fossil fuels, tremendous increase of materials demand, and unpredictable prices of petroleum based products urge upon the sustainable development. Three different epoxy resins have been synthesized from monoglyceride of Mesua ferrea L. seed oil and epichlorohydrin with and without other dihydroxy compound like tetrabromobisphenol-A (TBPA) and bisphenol-A (BPA). The synthesized epoxy resin were characterized by measurement of physical properties like epoxy equivalent, viscosity, hydroxyl value, saponification value, acid value, etc., and spectroscopic techniques like FTIR and 1H NMR. High thermostability with initial decompositions temperature of 225–265°C was observed for the cured resins and 75 mol % BPA based resin exhibits the highest thermostability. Newtonian flow behavior was observed for all resins as indicated by the rheometric study (CVO 100). The flame retardency rating of TBPA based epoxy was found to be V1 as tested by UL 94. The performance characteristics as coating materials were studied by the measurement of gloss, impact resistance, scratch hardness, tensile strength, elongation at break, adhesive strength, and chemical resistance. The results indicate the suitability of the synthesized resins as coating materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

To improve the fire retardancy performance of polyamide 6 (PA 6), layered silicates are used in combination with multi-walled carbon nanotubes (CNTs) to address the issue of packing density and uniformity of the protective inorganic barrier formed at the burning surface of the nanocomposites during combustion. Benzimidazolium is used to modify the silicate layers instead of conventional alkyl ammonium surfactants to tackle the issue of thermal stability. However, the poor dispersion of the modified layered silicates in PA 6 has a significant negative effect on the fire performance of the materials and offsets the positive effect of CNTs. Also, the results point to the apparent contradictions with different fire exposure tests; that is, significant reductions in heat release and mass loss rates in the cone calorimetry test do not imply a higher rating in the UL 94 vertical burning test.

Cyclotriphosphazene derivatives were synthesized for use as a non-halogen flame retardant for ABS. Hexachlorocyclotriphosphazene was reacted with phenol, catechol, or 2,3-dihydroxynaphthalene, respectively, and the fire retardant ability of each product in ABS resin was characterized by UL 94 and LOI tests. The mechanical properties of ABS compounds containing one of these flame retardants were also examined. The derivative (HNCP) synthesized from 2,3-dihydroxynaphthalene showed the best flame retardance among these derivatives studied. Synergistic effects with novolac were observed in the cases using the derivative (PNCP) obtained from phenol, but little synergistic effects were observed in cases using HNCP.

A series of UV-curable flame-retardant resins was obtained by blending phosphate acrylate (BTP) in different ratios with epoxy acrylate resin (EA). The flammability was characterized by limiting oxygen index (LOI), UL 94 flammability rating and cone calorimeter, and the thermal degradation of the flame-retardant resins was studied using thermo gravimetric analysis (TGA), and real-time Fourier transform infrared (RTFTIR). The results indicated that the flame-retardant efficiency increases with the addition of BTP. The heat release rate with the addition of BTP decreases greatly. The TGA data showed that EA/BTP blends have lower initial decomposition temperatures and higher char residues than pure EA, whereas BTP has the lowest initial decomposition temperature and the highest char residue. The RTFTIR study indicates that the EA/BTP blends have lower thermal oxidative stability than the pure EA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Co-microencapsulated ammonium polyphosphate and pentaerythritol [M(A&P)] was prepared using a hydroxyl silicone oil by in situ polymerization method, and characterized by X-ray photoelectron spectroscopy. The flame-retardant effect of M(A&P) in polypropylene (PP) is evaluated using limiting oxygen index, UL 94 test, cone calorimeter test, and thermogravimetric analysis. The flame-retardant properties of the PP/M(A&P) composites are much better than those of the PP/ammonium polyphosphate/ pentaerythritol composites. Moreover, the thermal stability and the water resistance properties of the PP/M(A&P) composites are improved compared with the PP/APP/PER composites.

This study evaluates the thermal stability of pine needle fiber reinforced polypropylene composites up to 30 wt% fiber loading, which is one of the important parameters for the processing, and also to investigate the effect of compatiblizer on thermal properties of treated pine needle fiber polypropylene (TPNF/PP) composites. The thermal stability of the composites were determined with TGA, DTG and DSC under identical conditions. The thermal stability of TPNF/PP composites decreased with the increase of TPNF. No significant changes occurred in the melting temperature of PP with the increase in TPNF loading. The chemical composition of treated pine needle fiber was also determined. The effect of 2% and 6% MA-g-PP content in the composites shows the char yield reduction at 525°C compared with composites without MA-g-PP content. DSC analysis shows that as the TPNF loading increases crystallinity reduces. TPNF/PP composite behaves like V-2 category of the UL-94 test. Functional groups present in the TPNF/PP composites were detected by FTIR spectroscopy.