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The more efficient and hydrophobic modificated ammonium polyphosphate (M-APP) and charring agent (M-CA) were prepared based on sol–gel method, and they were used in the preparation of water-resistant and flame-retardant polypropylene (PP) composites. The results showed that the contact angles of M-APP and M-CA were 135.11° and 137.89°, respectively. The flame-retardant and thermal properties of the PP composites were also studied. The results showed that the flame retardancy of PP loaded with 30 mass% intumescent flame retardant (M-APP/M-CA = 3:1) was significantly increased. The limiting oxygen index (LOI) reached 36.8% and passed UL-94 V-0. The peak heat release rate and total heat release of the PP composite decreased from 1011.77 to 134.43 kW·m−2 and 100.58 to 6.86 MJ·m−2, respectively. The peak smoke production rate and total smoke release decreased from 0.13 to 0.0056 m2·s−1 and 1453.09 to 74.82 m2·m−2. The PP composite with M-APP/M-CA = 3:1 also exhibited excellent water resistance, and it could still reach UL-94 V-0 after soaking in 70 ℃ water for 168 h. [ABSTRACT FROM AUTHOR]

Melamine–formaldehyde resin-coated bamboo fiber (MFBF) and ammonium polyphosphate (MFAPP) were prepared, and then flame-retardant polypropylene (PP)/bamboo fiber composites based on MFBF/MFAPP were obtained by melt blending. The water resistance, flame retardant, and thermal properties of the composites were studied. The results show that MFBF and MFAPP have excellent water resistance with the water contact angles 130.85° and 119.78°, respectively. Compared with pure PP, the limit oxygen index (LOI) of the prepared composite increased from 18.5 to 25.5% with the UL-94V-0 rating. The peak heat release rate of the composite decreased from 1011.8 to 344.3 kW·m−2 and the total heat release decreased from 100.6 to 58.8 MJ·m−2. Meanwhile, the total smoke release decreased from 1453.3 to 922.0 m2·m−2. After soaking in 70 °C water for 36 h, the composite still reached the V-0 rating in UL-94 test, demonstrating a good water resistance. This work provides an effective method to improve the water resistance and flame retardancy of PP/bamboo fiber composites. Melamine–formaldehyde resin-coated bamboo fibers (MFBF) and ammonium polyphosphate (MFAPP) were prepared, then flame-retardant PP/BF composites were obtained based on MFBF/MFAPP. The results show that prepared composite exhibited excellent water resistance and flame-retardant properties. [ABSTRACT FROM AUTHOR]

Polymethylsilsesquioxane (PMSQ) aerogels have been developed for diverse applications owing to their excellent flexibility and hydrophobicity. PMSQ aerogels, however, are limited by their flammability and low thermal stability. In this study, transparent and robust PMSQ aerogels were synthesized using an environmentally friendly flame retardant, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-vinyltrimethoxysilane (DOPO) in a facile one-pot manner and successfully dried under ambient pressure without cracks. Briefly, methyltrimethoxysilane (MTMS) and another synthesized precursor, DOPO-vinyltrimethoxysilane (DOPO-VTMS), where DOPO and VTMS were covalently bonded, were used to prepare a DOPO-VTMS MTMS aerogel via co-hydrolytic condensation. The DOPO-VTMS MTMS aerogel showed excellent flame retardancy with a peak heat release rate of 23.48 W g−1, which is 60% lower than that of the MTMS aerogel. It also exhibited enhanced thermal stability, as confirmed by thermogravimetric analysis, originating from the synergistic effect of P and Si. Furthermore, the compressive strength of the DOPO-VTMS MTMS aerogel was 26 times higher than that of the MTMS aerogel. With superior thermal properties and mechanical robustness, the preparation strategy employed in this study can contribute to the development of PMSQ aerogels for various applications such as thermal insulation for buildings, flame-retardant airspace dust collectors, or fire preventive coatings for fabrics. [ABSTRACT FROM AUTHOR]

A phosphazene-based flame retardant (PBFA) was synthesized by hexachlorocyclotriphosphazene and N-aminoethylpiperazine. To improve the flame retardancy of polypropylene (PP), PBFA and pentaerythritol derivatives (PEPA) were mechanically mixed to form a water resistance intumescent flame retardant (IFR). The flammability and thermal properties of the PP composites were analyzed by vertical burning test (UL-94), limit oxygen index, thermogravimetric analysis (TGA) and cone calorimeter test (CCT). The results indicate that there was a synergistic effect between PBFA and PEPA at a suitable mass ratio. When the mass ratio of PBFA/PEPA was 2:1, the PP composites can successfully achieve UL-94 V 0 rating. Compared with pure PP, the peak heat release rate and the total heat release were decreased by 75.40 and 15.38%, respectively; moreover, the total smoke production decreased by 22.11% during 0–465 s. The residual char after CCT was characterized by Fourier transform infrared spectrometer (FTIR). A strong pyrophosphate absorption peak was found in FTIR, indicating that the IFR mainly played a flame-retardant mechanism in the condensed phase. [ABSTRACT FROM AUTHOR]

Leakage, low thermal conductivity and flammability are the crucial factors that severely restrain the applications of the organic phase change material (PCM). A series of nanocomposite phase change material (HNTs-PCM) was prepared by dispersing halloysite nanotubes (HNTs) in capric acid (CA) with various mass fraction loadings (0.5%, 0.75%, 1% and 2%) through a blending method. The FTIR indicated that HNTs-PCM are only physically combined by HNTs and capric acid. The leakproof test showed that HNTs can inhibit the leakage of PCM. And the diameters of PCM with 0.75% HNTs are 4.3 cm and 3.2 cm at 35 °C and 45 °C. Among all samples, PCM with 0.75% HNTs possessed the best dispersivity. Hot-wire technique and infrared thermal imager proved that the addition of HNTs improves the thermal energy storage efficiency of PCM. The melting time and setting time were decreased by 46.67% and 43.65%. The DSC suggested that the melting peak temperatures and latent heat of HNTs-PCM reduced from 32.85 to 32.40 °C and 147.65 J g−1 to 137.65 J g−1 when the mass fraction of HNTs increased from 0 to 2%. The cone calorimeter test indicated that the HNTs restrain the heat and smoke release of rigid polyurethane foam composite containing HNTs-PCM during the combustion process. The peak of heat release rate and total heat release were decreased to 295.82 kW m−2 and 157.50 MJ m−2 after adding HNTs. Besides, the total smoke production decreased to 23.49 m2. These tests revealed that the HNTs have the potential to enhance the thermal storage capacity, leakage resistance and flame-retardant properties of PCM. [ABSTRACT FROM AUTHOR]

Aluminum trihydrate (ATH) of different sizes is added to polypropylene (PP) to prepare a composite which will have both good fire-retardant and mechanical properties. PP/ATH (nano or micro) composites are more fire-resistant and having appreciable mechanical properties as compared to virgin PP. Addition of maleic anhydride-functionalized polypropylene (MAPP) to the composite to increase the compatibility between PP and ATH (nano or micro). The need for developing the mechanical properties of flame-retardant composites is discussed in this paper. The influence of concentration of ATH (nano or micro) in PP/ATH (nano or micro)/MAPP composites is presented. The mechanical, thermal, morphological and flame-retardant properties were studied and discussed. The tensile modulus, hardness and flame-retardant properties increase, while elongation at break and tensile strength decreases with the increase in ATH (nano or micro) content. [ABSTRACT FROM AUTHOR]

The microencapsulation of flame retardants can avoid the problems of water absorption and loss. In this paper, hydrophobic microcapsule-encapsulated ammonium polyphosphate (HMAPP) was prepared by ion exchange and Stöber method and applied to the preparation of hydrophobic flame-retardant kraft paper by impregnation. The microscopic morphology and element analysis of the hydrophobic microcapsules tested by TEM and SEM showed that nano-scale particles with a size of about 100 nm have been successfully prepared, and the core–shell structure has been formed. HMAPP constructed a rough structure with low surface energy on the surface of kraft paper and provided the kraft paper with hydrophobic property. The water contact angle of kraft paper reached 122.7 ° after treated by HMAPP, while it also enhanced the physical strength of the paper. Kraft had the self-extinguishing phenomenon after treated by HMAPP, which attached to the surface of kraft paper were heated and melted to release ammonia to dilute combustible gas and oxygen, and formed a flame-retardant layer containing SiO2 particles, phosphoric acid, metaphosphoric acid, pyrophosphoric acid, and carbon flakes on the fiber surface. There were C–C, C–O–C bonds in the carbon layer after flame-retardant treatment, indicating that the pentose contained in fiber has not been completely destroyed. In addition, the presence of Si and P elements in the residual carbon indicates that the decomposed flame retardant adheres to the surface of the fiber to block the heat transfer and flame spread. [ABSTRACT FROM AUTHOR]

The cone calorimeter is an efficient instrument used to evaluate the reaction-to-fire properties of measured materials via simulating a forced combustion bench-scale fire scenario. With the increasing use of polymers and plastics in society, it is particularly significant to investigate their combustion behaviors using the cone calorimeter due to their inherent flammability. Therefore, with the aim to provide guidance for developing novel fire-safe polymer composites, this review discusses polymer combustion behaviors under different key operating parameters and setup geometries in a cone calorimeter, including external heat flux, ventilation conditions, ignition source, and sample geometry (thickness and size). Measured reaction-to-fire properties during combustion within the cone calorimeter, such as heat release, smoke production, and gas analysis, are also fully discussed. Lastly, nanofillers in polymer composites and their fire behaviors in cone calorimetry are explored through example polymer systems, including polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(methyl methacrylate) (PMMA), polyamide (PA), and acrylonitrile–butadiene–styrene (ABS). [ABSTRACT FROM AUTHOR]

Water retention and thermostability of powders and films of whey protein isolate (WPIp, dWPIf), sodium alginate (NaALGp, NaALGf), and their dry hydrospheres were evaluated by thermogravimetric analysis to demonstrate the importance of the gelling cation, for the first time in the case of the protein, and some potential applications. WPIp retained less water (7.1%) than ALGp (20.4%) due to the greater hydrophilicity of the polysaccharide. The difference was smaller for the films (12.3% and 18.8%, respectively) due to the incorporation of water during protein denaturation. Dried ALG beads retained less water than the film and the water content was dependent on the crosslinking cation (CaALGs > ZnALGs > CdALG). Protein films and spheres exhibited water retention very similar to CaALGs. The degradation of ZnALGs (smallest radius cation used and monodentate coordination) began at the lowest temperature (168 °C) and exhibited the highest mass loss as compared to CaALGs (171 °C) or CdALGs (176 °C, both with bidentate coordination). For the protein, Zn2+ also exhibited the lowest degradation peak temperature. Pyrolisis of powders, films and spheres demonstrate that the protein is more stable than the polyssacharide. Therefore, it can act as a better flame retardant agent than alginate. On the other hand, only alginate spheres were suitable for the production of activated carbon (190.0 m2 g−1) and the recovery of metal oxides. [ABSTRACT FROM AUTHOR]

An ionic liquid (IL) functionalized graphene oxide (ILGO) containing phosphorus was prepared by GO and ionic liquid ([BMIM]PF6), whose structure was characterized via XRD, FTIR, TG and EDS. Then combined with flame retardants (ammonium polyphosphate-APP and expandable graphite-EG), ILGO acting as synergistic agent was introduced into flexible polyurethane foam (FPUF) to modify its flame retardancy, which was assessed by UL-94, TG, limiting oxygen index (LOI) test and cone calorimeter test (CCT). The results show that the FPUF composites with 0.05 phr ILGO, 7.5phr EG and 7.5phr APP got a LOI of 29.0% and passed the V-0 rating for UL-94, while that for FPUF/EG/APP composites is only 26.7 and not classified at the same loading. The results of CCT showed that ILGO could reduce heat release, smoke suppression and toxic gas production of the FPUF composites. For the FPUF/EG/APP/ILGO composites, the PHRR, THR and TSP were decreased by 24.6%, 32.6% and 18.5%, respectively, compared with the FPUF/EG/APP/GO composites. TG and morphology of char residue reveals that the IL expedite the formation of dense and continuous charring layer and physical isolating effect of GO, which is the inherent reason for the good flame retardancy. [ABSTRACT FROM AUTHOR]

Expandable graphite (EG) is a kind of halogen-free flame retardant with high efficiency, but EG produces a lot of smoke when used. In order to reduce the smoke produced by EG flame retardant, layered double hydroxide (LDH)-coated EG was designed and prepared by the hydrothermal method to form composite EG@LDH with core–shell structure and used as flame retardant for polyvinyl alcohol (PVA). When EG@LDH particle content reaches 25%, UL-94 test reaches V-0 rating, limiting oxygen index reaches 33.8%, and the density of smoke is reduced by 75.4% compared with ordinary EG. These results are due to LDH's ability to produce stable oxides during combustion, as well as water vapor that absorbs heat and smoke, protecting the expanded graphite carbon layer from destruction. EG@LDH could suppress the "popcorn effect" of EG, improve the flame-retardant performance, expand the application scope of EG and have a broad application prospect in PVA and resin flame retardant with the characteristics of low cost and environmental protection. [ABSTRACT FROM AUTHOR]

Lignin-based epoxy resins containing phosphorus (P) and nitrogen (N) elements were prepared by blending the epoxy resin (EP) with different amounts of lignin-based flame retardant additive (Lig-F). The thermal performance of EP thermosets was performed via thermogravimetric analysis coupled with Fourier transformation infrared spectroscopy (TG-FTIR). The results showed that the presence of Lig-F had significant influence on thermal stability (tested by TG) and flame retardancy (determined by limited oxygen index, vertical burning and cone calorimeter) of EP thermosets. 1H NMR and FTIR analyses confirmed the successful synthesis of flame retardant (DOPO-PA) and modification of lignin, and the evolution of gas produced by thermal decomposition was different with different quantities of Lig-F added. Finally, the activation energy (E) of cured 10% Lig-F/EP was measured by two different methods, namely Flynn–Wall–Ozawa and Kissinger-Akahira-Sunoe, which was obviously higher than that of neat EP. [ABSTRACT FROM AUTHOR]

A UV-curing flame-retardant coating with varying mass content of bisphenol A epoxy acrylate (BAEA), 2-hydroxyethyl methacrylic acid phosphate (PM-2) and polyurethane acrylate (PUA) were prepared, improving the flame-retardant and mechanical properties of jute/polypropylene (PP) composites. BAEA is the main film-forming prepolymer. Phosphate ester groups in PM-2 can promote the formation of carbon layer during combustion, and PM-2 can also be used as a good adhesion binder to improve the coating adhesion levels. The flexible long chain in PUA could reduce the shrinkage of the coating and provide further adhesion. To avoid the oxygen inhibition of the radical polymerization, isopropylthioxanthone and triethanolamine were used to reduce the reaction between photoinitiator phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide and oxygen. Compared to the uncoated composites (J–P), the peaks of heat release rate and total smoke production of coated composites decreased and limiting oxygen index values increased significantly, which revealed that the coatings showed effective fire protection effect. The bending strength of the coated composites can increase by 90% over uncoated sample J–P. This simple, low-cost and environmentally friendly UV-curing coating has good adhesion and can effectively improve the flame-retardant and mechanical properties of composites, which expand application of the flame-retardant fiber composites. [ABSTRACT FROM AUTHOR]

A novel compound (bis(3-hydroxyaminophenyl) phenyl phosphine oxide) (BHAPPO) was synthesized as a flame retardant based on bisphosphoramide structure. Rigid polyurethane foam (RPUF) formulations were prepared with different BHAPPO and ammonium polyphosphate (APP) content to investigate both flame retardant property of BHAPPO and the possible synergistic effect of BHAPPO and APP against RPUFs. FT-IR, 1H-NMR and 31P-NMR spectroscopy analysis confirmed the expected structure of BHAPPO. Flame retardancy and thermal degradation behavior of RPUFs were determined by limiting oxygen index (LOI) test and thermogravimetric analysis (TGA). The flame retardant property of novel BHAPPO against the prepared RPUF samples was confirmed. The synergetic effect of BHAPPO and APP combination both on reducing the flammability and enhancing the char formation of RPUFs was also confirmed with a dependence on their ratio. The compatibility effect of BHAPPO on mechanical and morphological properties of RPUFs was also investigated by compression test and SEM analysis. Fire behaviors and the effect of using flame retardant additives in polyurethane foam were investigated using a cone calorimeter. Carbon dioxide amount was found lower for flame retardant PU foam. [ABSTRACT FROM AUTHOR]

Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and N atoms. Nuclear magnetic resonance spectroscopy confirmed the structure for the prepared triethanolaminodiethyl phosphate (P-OH). Effective construction of polyurethane foam was achieved between P-OH and toluene-2,4-diisocyanate with inclusion of polyethylene glycol (PEG) and polydimethylsiloxane (PDMS). It was then characterized by TGA, DSC, AFM, and XRD. The analyses indicated that the foams were amorphous, but reduced PEG/P-OH (w/w) content changes slightly the microphase separation. An increase in PDMS/PEG ratio in the polyurethane has increased glass transition temperature from 168.3 °C to 177.3 °C. The polyurethane systems were considered as being "slow-burning" with a level of UL-94 V-0, and their ignition delay time was estimated to have eight seconds. This polyurethane system can be used successfully in specific applications for energy-saving measures in buildings. [ABSTRACT FROM AUTHOR]

Wood is favored by furniture and decorative materials due to its beautiful color and texture, lightweight and high strength, but the thermal stability and flame retardants of wood have not been well solved. In this paper, metal salt-doped ammonium polyphosphate silicon gel (Cu, Mn/APP/Gel) was trapped in the wood cell wall and cell cavity by vacuum-pressure infusion method and vacuum drying method. Compared with unmodified wood, Cu, Mn/APP/Gel impregnated wood can rapidly enhance the flame retardant and smoke suppression capability of wood due to the catalysis of Cu2+ and Mn2+, and the total heat release rate, heat release rate peak value, mean heat release rate, smoke produce rate, total smoke release, CO and CO2 yield (YCO, YCO2) are obviously reduced. The electronic microscope picture of the burned carbon layer shows that the Cu, Mn/APP/Gel doped wood no longer has a clear and beautiful carbon layer formed by cell structure, but completely forms a whole. It is this dense and firm carbon layer structure that effectively inhibits the thermal decomposition of wood and has a role in flame retardant and smoke suppression. This study proposed an environment-friendly and green scheme for flame retardant modification of wood. [ABSTRACT FROM AUTHOR]

A series of chitosan-modified inorganic oxyacid salt flame retardants (IOS-CS) were synthesized and used as flame retardants to improve the fire resistance of poly(vinyl chloride) (PVC) composites while improving the mechanical properties of the materials. The thermal stability of the material was analyzed by TG test; the flame-retardant and smoke suppression properties were evaluated by limiting oxygen index (LOI) and cone calorimeter test, and the mechanical properties were analyzed by tensile test and impact test. The TG results showed that the addition of flame retardant can promote the early cross-linking decomposition of PVC composites, not only advance the decomposition temperature of the material but also promote the formation of char layer and increase the char residual content. LOI and cone calorimeter test results showed that stannate chitosan (Sn-CS) can improve flame retardant and smoke suppression more effectively than other samples. Compared with pure PVC, the addition of Sn-CS increased its LOI from 26.6 to 30.5% and reduced the total heat release value and total smoke release by 18.23% and 52.55%, respectively. At the same time, the addition of the flame retardants had no large deterioration effect on the mechanical properties of the material. The tensile properties of flame-retardant PVC were slightly reduced compared with pure PVC, and the impact resistance was even improved to some extent. [ABSTRACT FROM AUTHOR]