Synthesis of aluminum ethylphenylphosphinate flame retardant and its application in epoxy resin

A novel flame retardant additive, aluminum ethylphenylphosphinate (AEPP), was synthesized from diethyl phenylphosphonite and aluminum chloride hexahydrate, and characterized by FTIR, ¹H NMR, and ³¹P NMR. AEPP was added into diglycidyl ether of bisphenol A epoxy resin (EP) cured by bisphenol A‐formaldehyde novolac resin. The flame retardancy of the cured EP was investigated by limited oxygen index, UL 94 test, and cone calorimeter test. The results revealed that the EP composite containing 15% AEPP had a limited oxygen index value of 28.2% with a UL 94 V‐0 rating. The incorporation of AEPP effectively decreased the peak heat release rate and the total heat release in cone calorimeter test analysis. Scanning electron microscopy results showed that the introduction of AEPP benefited to the formation of a smooth and continuous char layer during combustion of the flame retarded EP. The thermogravimetric analysis results indicated that the incorporation of AEPP promoted the initial decomposition of EP matrix, but AEPP/EP composites had a higher char yield at high temperatures. Moreover, the flexural properties of the flame retarded EP composites were studied.     

Flame retardancy and pyrolysis behavior of an epoxy resin composite flame-retarded by diphenylphosphinyl-POSS

To reduce the flammability of epoxy resin (EP), a flame retardant (designated as D-POSS) containing diphenylphosphinyl and polyhedral oligomeric silsesquioxane (POSS) was constructed by aminopropyl-isobutyl POSS and diphenylphosphinyl chloride. The chemical structure of D-POSS was fully characterized, then it was used to enhance the flame retardancy of EP. When the flame-retardant EP composite contained 4 wt% D-POSS, its limiting oxygen index value was 29.0% and it achieved UL 94 V-1 rating. Also, its peak of heat release rate (pk-HRR), total heat release (THR) and total smoke production were decreased by 35.3%, 30.3%, and 38.3%, respectively. Moreover, the results from cone calorimeter disclosed that diphenylphosphinyl group and POSS group in D-POSS showed a strong synergistic effect in inhibiting pk-HRR, THR, and smoke production, promoting the charring formation of EP material, and forming an intumescent char layer. Additionally, the theoretical THR reduction of flame-retardant EP composite was calculated by the equation deduced from the standard, and it was almost same with the practical THR reduction. Notably, some silicon oxide enriched on the residue's surface. The phenomenon led to form a double-layer residue that consisted of white yarn-like outer char and normal intumescent inner char. This double-layer residue was contributed to enhance EP composite's flame retardancy.     

The effect of traditional flame retardants,nanoclays and carbon nanotubes in the fire performance of epoxy resin composites

The effectiveness of distinct fillers, from micro to nano‐size scaled, on the fire behaviour of an epoxy resin and its carbon fibre reinforced composites was assessed by cone calorimetry. The performance was compared not only regarding the reaction to fire performance, but also in terms of thermal stability, glass transition temperature and microstructure. Regarding the fire reaction behaviour of nanofilled epoxy resin, anionic nanoclays and thermally oxidized carbon nanotubes showed the best results, in agreement with more compact chars formed on the surface of the burning polymer. For carbon fibre reinforced composite plates, the cone calorimeter results of modified resin samples did not show significant improvements on the heat release rate curves. Poorly dispersed fillers in the resin additionally caused reductions on the glass transition temperature of the composite materials. Copyright © 2016 John Wiley & Sons, Ltd.     

Comparative study on thermal decomposition and combustion behavior of glass‐fiber reinforced poly(1,4‐butylene terephthalate) composites containing trivalent metal (Al,La, Ce) hypophosphite

High fire hazards of glass‐fiber reinforced polymer composites have greatly limited their development and application. To reduce their flammability, the composites have to be treated with flame retardants. This work examines the use of three trivalent metal (Al, La, Ce) hypophosphites as halogen‐free flame retardants for glass‐fiber reinforced poly(1,4‐butylene terephthalate) (GRPBT) composites. The aim of this study is to quantitatively investigate the effect of metal hypophosphites on the thermal decomposition and combustion behavior of GRPBT composites by means of cone calorimeter and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG‐FTIR) techniques. The peak heat release rate and total smoke production of GRPBT/cerium hypophosphite (CHP) composite evaluated by cone calorimeter are reduced, respectively, by around 76 and 44% compared to the results of GRPBT. The volatilized esters measured by TG‐FTIR in the decomposition of GRPBT/CHP are decreased by about 69%. The results showed that rare earth hypophosphites can effectively inhibit the thermal decomposition and combustion behaviors of GRPBT in comparison with aluminum hypophosphite. POLYM. COMPOS., 34:1832–1839, 2013. © 2013 Society of Plastics Engineers     

Joint flame‐retardant effect of triazine‐rich and triazine/phosphaphenanthrene compounds on epoxy resin thermoset

To obtain a more efficient flame‐retardant system, the extra‐triazine‐rich compound melamine cyanurate (MCA) was coworked with tri(3‐9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide‐2‐hydroxypropan‐1‐yl)?1,3,5‐triazine‐2,4,6‐trione (TGIC–DOPO) in epoxy thermosets; these were composed of diglycidyl ether of bisphenol A (DGEBA) epoxy resin and 4,4′‐diaminodiphenyl methane (DDM). The flame‐retardant properties were investigated by limited oxygen index measurement, vertical burning testing, and cone calorimeter testing. In contrast to the DGEBA/DDM (EP for short) thermoset with a single TGIC–DOPO, a better flame retardancy was obtained with TGIC–DOPO/MCA/EP. The 3% TGIC–DOPO/2% MCA/EP thermoset showed a lower peak heat‐release rate value, a lower effective heat of combustion value, fewer total smoke products, and lower total yields of carbon monoxide and carbon dioxide in comparison with 3% TGIC–DOPO/EP. The results reveal that MCA and TGIC–DOPO worked jointly in flame‐retardant thermosets. The dilution effect of MCA, the quenching effect of TGIC–DOPO, and their joint action inhibited the combustion intensity and imposed a better flame‐retardant effect in the gas phase. The 3% TGIC–DOPO/2% MCA/EP thermoset also exhibited an increased residue yield, and more compositions with triazine rings were locked in the residues; this implied that MCA/TGIC–DOPO worked jointly in the condensed phase and promoted thermoset charring. The results reveal the better flame‐retardant effect of the MCA/TGIC–DOPO system in the condensed phase. Therefore, the joint incorporation of MCA and TGIC–DOPO into the EP thermosets increased the flame‐retardant effects in both the condensed and gas phases during combustion. This implied that the adjustment to the group ratio in the flame‐retardant group system endowed the EP thermoset with better flame retardancy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43241.     

Experimental and numerical investigations on the thermal response of multilayer glass fibre/unsaturated polyester/organoclay composite

Organoclay glass fibre reinforced polymer (GFRP) nanocomposites are fabricated using the vacuum assisted resin transfer moulding. The unsaturated polyester resin is prepared with and without organoclay involving mechanical mixing, sonication, dilution solvent and heat treatment. Three levels of organophilic clay content are added, and its influences on the fire performance of composite samples are investigated. A novel numerical procedure combining pyrolysis analysis of the organoclay‐composites and the fire dynamic simulation of the combustion process are developed to validate the thermal responses obtained from the cone calorimetry experiments. Kinetic parameters obtained from the TGA tests and pyrolysis analyses are used as inputs for the models measuring the fire growth index and total heat release. To account for multilayer composite structure and organoclay distribution, three numerical models are proposed including composite (CPS), component (CPN) and CPN‐layer models. While CPS model assumes the homogeneity of the composite, later models consider multilayer effects with uniform (CPN model) or concentrated (CPN‐layer model) distribution of organoclay. Numerical results are compared with experimental ones in terms of total heat release, fire growth index. Finally, the fire resistance and total smoke release of the polyester/glass composites with the addition of organoclay will be evaluated taking into account influences of the fabrication processes.     

Fire performance and post‐fire mechanical properties of polymer composites coated with hybrid carbon nanofiber paper

In this study, glass fiber reinforced polyester composites were coated with carbon nanofiber/clay/ammonium polyphosphate (CCA) paper and carbon nanofiber/exfoliated graphite nanoplatelets/ammonium polyphosphate (CXA) paper. The composites were exposed to a heat flux of 35 kW/m² during the cone calorimeter testing. The testing results showed a significant reduction in both heat release rates and mass loss rates. The peak heat release rate (PHRR) of CCA and CXA composite samples in the major decomposition period are 23 and 34% lower than the control sample, respectively. The time to reach the PHRR for the CCA and CXA composite samples are ～ 125% longer than the control sample. After the composite samples were exposed to heat for different time periods, their post‐fire mechanical properties were determined by three‐point bending testing. The three‐point bending testing results show that the composite samples coated with such hybrid papers exhibit more than 20% improvement in mechanical resistance at early stages of combustion. The mechanism of hybrid carbon nanofiber paper protecting the underlying laminated composites is discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of fire‐retardant additives and a surface insulative fabric on fire performance and mechanical property retention of polyester composites

This study investigates the simultaneous use of conventional fire‐retardant additives and an insulative intumescent thermal barrier/mat to improve the fire performance and mechanical property retention of glass‐fibre‐reinforced polyester (GRP) composites. Significant reductions in the peak heat release rate (PHRR) and total heat release (THR) were observed from measured cone calorimetric data following the addition of nitrogen, phosphorous, halogen containing and hydroxylated fire‐retardant additives. Some fire‐retarded glass‐fibre‐reinforced composites further protected by an intumescent mat containing silicate fibres, expandable graphite and borosilicate glass bound together by an organic matrix show further reductions in PHRR. Despite improving the fire retardancy of the composites, the presence of fire‐retardant additives alone does not improve flexural modulus retention following exposure to a heat source. However, the introduction of a ‘passive’ fire proofing insulative fabric enhances fire performance while preserving the mechanical properties of composites exposed to high heat fluxes or fires. Copyright © 2010 John Wiley & Sons, Ltd.     

Influence of the oxidation state of phosphorus on the decomposition and fire behaviour of flame-retarded epoxy resin composites

A systematic and comparative evaluation of the pyrolysis of halogen-free flame-retarded epoxy resins containing phosphine oxide, phosphinate, phosphonate, and phosphate (phosphorus contents around 2.6 wt.%) and the fire behaviour of their carbon fibre composites is presented. Decomposition pathways are proposed based on the thermal analysis (TG), TG coupled with evolved gas analysis (TG-FTIR), kinetics and analysis of the residue with FTIR and XPS. All organophosphorus-modified hardeners containing phenoxy groups lead to a reduced decomposition temperature and mass loss step for the main decomposition of the cured epoxy resin. With increasing oxidation state of the phosphorus the thermally stable residue increases, whereas the release of phosphorus-containing volatiles decreases. The flammability of the composites was investigated with LOI and UL 94 and the fire behaviour for forced-flaming conditions with cone calorimeter tests performed using different irradiations. The flame retardancy mechanisms are discussed. With increasing oxidation state of the phosphorus additional charring is observed, whereas the flame inhibition, which plays the more important role for the performance of the composites, decreases. The processing and the mechanical performance (delamination resistance, flexural properties and interlaminar bonding strength) of the fibre-reinforced composites containing phosphorus were maintained at a high level and, in some cases, even improved. The potential for optimising flame retardancy while maintaining mechanical properties is highlighted in this study.     

Synthesis and characterization of a functional polyhedral oligomeric silsesquioxane and its flame retardancy in epoxy resin

A functional polyhedral oligomeric silsesquioxane (NPOSS) with two epoxy ring groups was synthesized via the reaction between trisilanolisobutyl-POSS and triglycidyl isocyanurate, and then a halogen-free epoxy composite containing silicon/nitrogen was prepared. The results of microscale combustion calorimeter indicate that the presence of NPOSS (10% weight ratio) in epoxy resin (EP) can decrease its peak heat release rate by about 30%. The thermal oxidation and degradation behaviors of EP and EP/NPOSS composites were characterized by DSC, TG, FTIR-TG and dynamic FTIR. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to explore the char residues of composites. The thermal degradation and flame retardant mechanism has been evaluated. NPOSS can retard the movement and scission of polymeric chains of EP and form a stable charred layer in the condensed phase to prevent the underlying materials from further combustion.     

Effect of processing conditions on physical properties of 3‐aminophenoxyphthalonitrile/epoxy laminates

To develop high performances of polymer composite laminates, differential scanning calorimetry and dynamic rheological analysis studies were conducted to show curing behaviors of 3‐aminophenoxyphthalonitrile/epoxy resin (3‐APN/EP) matrix and define cure parameters of manufacturing processes. Glass fiber reinforced 3‐APN/EP (GF/3‐APN/EP) composite laminates were successfully prepared through different processing conditions with three parameters such as pressures, temperatures, and time. Based on flexure tests, dynamic mechanical analysis, thermal gravimetric analysis, and scanning electron microscope, the complementary catalytic effect of the three processing parameters is investigated by studying mechanical behavior, thermomechanical behavior, thermal behavior, and fracture morphology of GF/3‐APN/EP laminates. The 50/50 GF/3‐APN/EP laminates showed a significant improvement in flexural strength, glass transition temperature (T_g), and thermal stability with favorable processing parameters. It was also found that the T_g and thermal stability were significantly improved by the postheated treatment method. The effect of manufacturing process provides a new and simple route for the polymer–matrix composites application, which indicates that the composites can be manufactured at low temperatures. But, they can be used in a high temperature environment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39746.     

Investigation of ammonium polyphosphate dilution with ground eggshells and lignin through the study of natural fibre composite flammability

The interactions of Calcium carbonate (e.g., eggshell powder) and Lignin with ammonium polyphosphate (APP) when used as fire retardants were investigated. Three mixing ratios - 1:3, 1:1, and 3:1, were used with natural fibre reinforced composites containing a hemp mat and an epoxy matrix manufactured using a light resin transfer moulding (L-RTM) process. The thermal decomposition of the retardant mixtures and composites was investigated using thermogravimetric analysis (TGA). The findings showed that even though the decomposition reactions of APP with eggshell powder and lignin mixtures interacted and overlapped, the same interactions could not be seen in the composites. In the composite form while the residue was affected by the retardant, the decomposition reactions were driven primarily by the hemp and epoxy. Flammability of the composites was studied by testing to 20, 35, 50, and 75 kW/m² with a cone calorimeter, and determining the critical heat flux. While the samples with eggshell powder had higher ignition times, the critical heat flux for ignition was 13 kW/m² for all sample groups except for a ratio of 1:3 APP to eggshell powder, which was 14 kW/m². The lowest burning rates (mass loss and heat release) occurred in composites containing only APP, however, the addition of eggshell powder or lignin at even a ratio of 3:1 APP to either provided a notable reduction.     

Physical gelation in ethylene-propylene copolymer melts induced by polyhedral oligomeric silsesquioxane (POSS) molecules

The rheological behavior of ethylene-propylene (EP) copolymers containing polyhedral oligomeric silsesquioxane (POSS) molecules was investigated by means of wide-angle X-ray diffraction (WAXD), oscillatory shear, stress and strain controlled rheology in the molten state and dynamic mechanical analysis (DMA) in the solid state. WAXD results showed that the majority of POSS molecules in the EP melt were present in the crystal form. Oscillatory shear results showed that the EP/POSS nanocomposites exhibited a solid-like rheological behavior compared with the liquid-like rheological behavior in the neat resin, i.e. POSS caused physical gelation in EP. While POSS exhibited only a minimum effect on the flow activation energy of EP, the high POSS concentration samples were found to induce higher yield stress than the neat resin. This behavior was similar to the Bingham rheology, indicative of a structured fluid. DMA results indicated that the presence of POSS increased the Young's modulus as well as the T_g of the EP copolymer. These results suggested that two types of interactions contributed to the physical gelation in EP/POSS melts were present: the strong particle-to-particle interactions between the POSS crystals and the weak particle-to-matrix interactions between the POSS crystals and the EP matrix.     

Synthesis of EP‐POSS mixture and the properties of EP‐POSS/epoxy,SiO2/epoxy,and SiO2/EP‐POSS/epoxy nanocomposite

The hybrid material of EP‐POSS mixture was synthesized by the hydrolysis and condensation of (γ‐glycidoxypropyl) trimethoxysilane. A series of binary systems of EP‐POSS/epoxy blends, epoxy resin modified by silica nanoparticles (SiO₂/epoxy), and ternary system of SiO₂/EP‐POSS/epoxy nanocomposite were prepared. The dispersion of SiO₂ in the matrices was evidenced by transmission electron micrograph, and the mechanical properties, that is, flexural strength, flexural modulus, and impact strength were examined for EP‐POSS/epoxy blends, SiO₂/epoxy, and SiO₂/EP‐POSS/epoxy, respectively. The fractured surface of the impact samples was observed by scanning electron micrograph. Thermogravimetry analysis were applied to investigate the different thermal stabilities of the binary system and ternary system by introducing EP‐POSS and SiO₂ to epoxy resin. The results showed that the impact strength, flexural strength, and modulus of the SiO₂/EP‐POSS/epoxy system increased around by 57.9, 14.1, and 44.0% compared with the pure epoxy resin, T_i, T_max and the residues of the ternary system were 387°C, 426°C, and 25.2%, increased remarkably by 20°C, 11°C and 101.6% in contrast to the pure epoxy resin, which was also higher than the binary systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 810‐819, 2013     

Mechanical and thermal enhancements of benzoxazine‐based GF composite laminated by in situ reaction with carboxyl functionalized CNTs

An easy and efficient approach by using carboxyl functionalized CNTs (CNT‐COOH) as nano reinforcement was reported to develop advanced thermosetting composite laminates. Benzoxazine containing cyano groups (BA‐ph) grafted with CNTs (CNT‐g‐BA‐ph), obtained from the in situ reaction of BA‐ph and CNT‐COOH, was used as polymer matrix and processed into glass fiber (GF)‐reinforced laminates through hot‐pressed technology. FTIR study confirmed that CNT‐COOH was bonded to BA‐ph matrices. The flexural strength and modulus increased from 450 MPa and 26.4 GPa in BA‐ph laminate to 650 MPa and 28.4 GPa in CNT‐g‐BA‐ph/GF composite, leading to 44 and 7.5% increase, respectively. The SEM image observation indicated that the CNT‐COOH was distributed homogeneously in the matrix, and thus significantly eliminated the resin‐rich regions and free volumes. Besides, the obtained composite laminates showed excellent thermal and thermal‐oxidative stabilities with the onset degradation temperature up to 624°C in N₂ and 522°C in air. This study demonstrated that CNT‐COOH grafted on thermosetting matrices through in situ reaction can lead to obvious mechanical and thermal increments, which provided a new and effective way to design and improve the properties of composite laminates. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

An Excellent Intrinsic Transparent Epoxy Resin with High Flame Retardancy: Synthesis,Characterization, and Properties

In this paper, a novel multifunctional, liquid, and colorless curing agent, namely DPTA, is prepared through diphenylphosphinic chloride (DPPC) and tetraethylenepentamine (TEPA). Different measurements confirm that the DPTA is prepared successfully and the cured DPTA‐EPs simultaneously display excellent flame retardancy and transparency. The resulting DPTA‐EP system reaches high optical transmittance up to 90% within the visible region. Meanwhile, the introduction of the flame‐retardant groups in DPTA‐EP does not deteriorate the mechanical behaviors compared with that of reference sample TEPA‐EP. More importantly, with only 15 wt% DPTA addition, the resulting DPTA‐EP with 1.6 mm passes UL‐94 V‐0 rating, and limiting oxygen index reaches 29.0%. Moreover, the peaks of heat release rate and total smoke production of DPTA‐EP are largely reduced by 43.1% and 58.8%, respectively, further verifying the excellent smoke‐suppression efficiency and flame retardancy. The analyses from both cone calorimeter (CC) and thermogravimetric (TG) results suggest that the satisfactory flame retardancy of cured DPTA‐EP dominates in the gaseous phase. The earlier release of large amount of non‐combustion gas and phosphorus containing groups improve the flame‐retardant efficiency.     

Red phosphorus–controlled decomposition for fire retardant PA 66

The thermal degradation and the combustion behavior of glass fiber–reinforced PA 66 materials containing red phosphorus were investigated. Thermogravimetry (TG), TG coupled with FTIR, and TG coupled with mass spectroscopy were used to investigate the thermal decomposition. The flame retardant red phosphorus was investigated with respect to the decomposition kinetics and the release of volatile products. The combustion behavior was characterized using a cone calorimeter. Fire risks and fire hazards were monitored versus external heat fluxes between 30 and 75 kW/m². Red phosphorus acts in the solid phase and its efficiency depends on the external heat flux. The use of red phosphorus results in an increased amount of residue and in a corresponding decrease in total heat release. The decrease of the mass loss rate peak results in a corresponding decrease of the peak heat release. With increasing external heat flux applied the first effect on the total heat release decreases linearly, whereas the second effect on the peak heat release expands linearly. The investigation provides insight into the mechanisms of how the fire retardant PA 66 is achieved by red phosphorus controlling the degradation kinetics. Taking into account that a decrease of the volatile products also leads to a decrease of heat production in the flame zone and that the char acts as heat transfer barrier, a reduced pyrolysis temperature is suggested as a further feedback effect. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2060–2071, 2002     

ZnS as fire retardant in plasticised PVC

The flame retardant effect of zinc sulphide (ZnS) in plasticised poly(vinyl chloride) (PVC‐P) materials was investigated. PVC‐P containing different combinations of additives such as 5% ZnS, 5% of antimony oxide (Sb₂O₃) and 5% of mixtures based on Sb₂O₃ and ZnS were compared. The thermal degradation and the combustion behaviour were studied using thermogravimetry (TG), coupled with FTIR (TG–FTIR) or with mass spectroscopy (TG–MS), and a cone calorimeter, respectively. A detailed and unambiguous understanding of the decomposition and release of the pyrolysis products was obtained using both TG–MS and TG–FTIR. The influence of ZnS, Sb₂O₃ and the corresponding mixtures on the thermal decomposition of PVC‐P was demonstrated. Synergism was observed for the combination of the two additives. The combustion behaviour (time to ignition, heat release, smoke production, mass loss, CO production) was monitored versus external heat fluxes between 30 and 75 kW m^?2 with the cone calorimeter. Adding 5% of ZnS has no significant influence on the fire behaviour of PVC‐P materials beyond a dilution effect, whereas Sb₂O₃ works as an effective fire retardant. Synergism of ZnS and Sb₂O₃ allows the possibility of replacing half of Sb₂O₃ by ZnS to reach equivalent fire retardancy. © 2002 Society of Chemical Industry     

Flame retardancy and thermal degradation behaviors of epoxy resins containing bisphenol a bis (diphenyl phosphate) oligomer

Bisphenol A bis(diphenyl phosphate) oligomer (BBO) as flame retardant was synthesized, whose structure was characterized by IR and NMR. In all, 20% weight mixture polyphosphoric acid (APP) and BBO was doped into epoxy resins (EPs) to get 26.0% of limiting oxygen index and UL 94 V‐0. The degradation behavior of EP‐containing BBO/APP was studied by thermogravimetry, differential thermogravimetry, scanning electron microscopy, and cone calorimeter. The activation energies for the decomposition of EP samples are obtained using the method of Kissinger. The experimental results exhibited that for EP‐containing BBO/APP, compared with EP, initial decomposition temperature, maximum temperature at the peak position (T_m), and the activation energy for the decomposition are decreased, whereas the maximum weight loss rate (R_max), char yields, and the inherent thermal stability are increased. Meanwhile, heat release, smoke production, and CO yield and CO₂ yield of EP‐containing BBO/APP are much decreased compared with those of EP. The thermal degradation mechanism of EP‐containing BBO/APP has been proposed. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

The study of char forming on OPS/PC and DOPO‐POSS/PC composites

Polyhedral oligomeric octaphenyl silsesquioxane (OPS) and polyhedral oligomeric silsesquioxane containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO‐POSS) with polycarbonate (PC) were each prepared by twin screw extrusion. Their flammability was studied by cone calorimetry under different heat fluxes (35 and 50 kW/m²). In the cone calorimeter testing, thermocouples were used to measure the temperature at the top and bottom of the composites. Compared to the DOPO‐POSS/PC composite, the char layer of the OPS/PC composite is better for preventing heat transfer, the temperature change indicates that OPS/PC composite has a longer period of char formation, and the organization of their char materials are different. The DOPO‐POSS/PC composite has a harder char layer than the OPS/PC composite, but the OPS/PC composite char layer is more compact. The char layer macrostructure was studied with scanning electron microscopy (SEM) and EDS, which indicated that there are many bubbles and pores in the DOPO‐POSS/PC composite. EDS showed that there was some Si content in the exterior and interior char for the DOPO‐POSS/PC composite; there is a greater Si content in the exterior OPS/PC char residue than in the interior. The storage modulus of OPS/PC composite was higher than the PC control and DOPO‐POSS/PC composite at low frequencies. The values of η* of the OPS/PC composite were higher than the PC control and DOPO‐POSS/PC composite at low frequencies; also, the PC control exhibits a quasi‐Newtonian regime, but the OPS/PC and DOPO‐POSS/PC composites exhibit typical shear‐thinning behavior. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39892.