Average Effective Heat Of Combustion Research Articles

Multifunctional and sustainable DOPO-derivative coating for flame-retardant, antibacterial and UV-protective of polyamide 56 protective biomaterials

Polyamide 56 (PA56) biomaterial with excellent flame retardancy, antibacterial and UV-protective properties is potentially applied in the field of security and protection. Here, a green and sustainable multifunctional coating (DOPO-ATU) was developed, and then it was applied to modify PA56 fabric. The DOPO-ATU showed excellent flame retardancy to PA56 fabric. With 7.8 % weight gain, the coated PA56 fabric possessed a high LOI value of 30.1 % and a low damaged length of 11.1 cm without dripping. In cone calorimeter test, the peak heat release rate and average effective heat of combustion decreased by 20.5 % and 46.4 % versus pristine one, showing excellent fire safety. Further analysis proved that DOPO-ATU mainly acted in the gas-phase through the action of diluting non-combustible gases and quenching free radicals. In addition, the coated PA56 fabrics also displayed excellent antibacterial property and UV-protective properties. This work provides a cleaner and sustainable approach for preparing multifunctional coating for PA56 protective biomaterials.

Aromatization of residue caused by group aggregation of hyperbranched ester macromolecule capped with benzene rings improved flame retardancy of epoxy resin

To investigate the effect of the distribution state of phosphophenanthrene groups within the branched structure on the flame retardant efficiency, the hyperbranched ester macromolecules Bz-DQMC-n (n = 1, 2, 3) capped with benzene rings were synthesized. The aggregation effect of phosphaphenanthrene groups in Bz-DQMC-n enhanced the flame retardancy of epoxy resins (EPs). At the same phosphorus contents of EPs, the Bz-DQMC-n/EP passed the V-0 rating, except for 2-(6-oxid-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)-1,4-benzenediol (DOPO-HQ)/EP without aggregated phosphaphenanthrene groups, which only reached the V-1 rating in UL 94 test. The Bz-DQMC-2 showed a better flame inhibition effect. The limiting oxygen index (LOI) value of the Bz-DQMC-2/EP reached to 39.3%, and the peak heat release rate (pk-HRR) value was 563 kW/m2, which decreased by 62.5% compared to neat EP. In addition, the total heat release (THR), and average effective heat of combustion (av-EHC) values of EP with Bz-DQMC-2 were also lower than that with Bz-DQMC-1 and Bz-DQMC-3 in the cone calorimetry test. The mechanism demonstrated that the aggregated phosphophenanthrene groups and benzene rings in Bz-DQMC-2 jointly promoted the formation of high-quality residue with more aromatic structures. Meanwhile, the concentrated release feature caused by group aggregation slightly enhanced the quenching effect in the gas phase. The aggregation effect of phosphophenanthrene groups in specific structures provides guidance for the development of high-efficiency DOPO-based flame retardants.

Silane coupling agent and carboxymethyl chitosan co‐modified boron nitride for preparing silicone acrylic emulsion‐based flame‐retarding coatings

AbstractHerein, the synergistic effect of the silane coupling agent (KH550) and carboxymethyl chitosan (CMCS) co‐modified boron nitride (BN) on the fireproof property of silicone acrylic emulsion‐based composite is investigated to explore halogen‐free coatings for flame‐retarding plywood. Firstly, KH550 and CMCS co‐modified BN improves its compatibility with the silicone acrylic emulsion. The results show that an appropriate loading of BN (2 wt%) enhances flame retardancy. The peak‐heat release rate decreases from 86.01 to 54.95 kW m−2, with the reduced fire growth index decreasing from 0.31 to 0.16 kW m−2 s−1, and the average effective heat of combustion drops from 0.99 to 0.85 kW g−1. Meanwhile, the x‐ray diffraction results demonstrate that the co‐modified BN reacts with the phosphoric acid generated by APP decomposition and transforms into BPO4, enhances the thermal insulation of the coating. The pyrolysis kinetics confirms that the co‐modified BN increases Eα at 300–380°C by 23.4% and Eα at 380–430°C by 21.5%. The water contact angle clarifies that the co‐modified BN significantly imparts higher water resistance to the coating. Generally, the high thermal conductivity of co‐modified BN effectively achieves heat dissipation and facilitates the uniform charring of the composite coating, leading to the as‐formed resilient residues for blocking flame development.

From physical mixtures to block copolymer: Impose outstandingly toughening and flame retardant effect to polypropylene

To explore new flame retardant molecules with higher flame retardancy and toughening effect, a series of non-halogen block copolymer flame retardants PAPO-MP were designed and synthesized. Importantly, compared with the control sample 24(7PAPP/3MPP)/76PP in which the intumescent flame retardant was physically blended, the mechanical properties of 24(7PAPO-3MP)/76PP with the block copolymer was greatly increased. Its impact strength and elongation at break of 24(7PAPO-3MP)/76PP were 55.1 kJ/m2 and 140.6%, increased by 166% and 965% in contrast to those of 24(7PAPP/3MPP)/76PP, respectively. Because the block copolymerized structure led to the low crystalline degree, 7PAPO-3MP can change its particle shape from lamellar to water droplet morphology during thermal processing, which contributed to better compatibility and stronger interaction with PP matrix under the action of maleic anhydride grafted polypropylene, thereby dramatically enhancing the mechanical properties of PP composites. When the addition amounts of 7PAPO-3MP were 20 wt% and 24 wt% in polypropylene (PP) composite, the two flame retardant PP composites all passed UL94 V-0 rating and had the LOI values of 28.1% and 30.2%, respectively. Their peak of heat release rate values was all decreased by over 81% compared with that of neat PP. Moreover, their total heat release and average effective heat of combustion were also decreased and brought higher residue yields. Moreover, the more release of P-containing components in block copolymer also imposed more effective gas-phase quenching effect and flame inhibition effect during combustion. The research on the block copolymer in PP composites revealed a superior way to construct high-performance non-halogen polyolefin materials.

Preparation and Mechanism of Toughened and Flame-Retardant Bio-Based Polylactic Acid Composites

As a biodegradable thermoplastic, polylactic acid (PLA) shows great potential to replace petroleum-based plastics. Nevertheless, the flammability and brittleness of PLA seriously limits its use in emerging applications. This work is focused on simultaneously improving the flame-retardancy and toughness of PLA at a low additive load via a simple strategy. The PLA/MKF/NTPA biocomposites were prepared by incorporating alkali-treated, lightweight, renewable kapok fiber (MKF) and high-efficiency, phosphorus-nitrogenous flame retardant (NTPA) into the PLA matrix based on the extrusion-injection molding method. When the additive loads of MKF and NTPA were 0.5 and 3.0 wt%, respectively, the PLA/MKF/NTPA biocomposites (PLA3.0) achieved a rating of UL-94 V-0 with an LOI value of 28.3%, and its impact strength (4.43 kJ·m-2) was improved by 18.8% compared to that of pure PLA. Moreover, the cone calorimetry results confirmed a 9.7% reduction in the average effective heat of combustion (av-EHC) and a 0.5-fold increase in the flame retardancy index (FRI) compared to the neat PLA. NTPA not only exerted a gas-phase flame-retardant role, but also a condensed-phase barrier effect during the combustion process of the PLA/MKF/NTPA biocomposites. Moreover, MKF acted as an energy absorber to enhance the toughness of the PLA/MKF/NTPA biocomposites. This work provides a simple way to prepare PLA biocomposites with excellent flame-retardancy and toughness at a low additive load, which is of great importance for expanding the application range of PLA biocomposites.

Full-scale fire testing of battery electric vehicles

The market share of electric vehicles, powered by lithium-ion batteries (LIB), has been expanding worldwide with the global momentum towards green technology and improving the driving range on one full-charge. Studies are, however, still required on the fire safety of the latest but unmatured technology due to a distinctive phenomenon called thermal runaway. In this study, a series of full-scale fire experiments were conducted, focusing on the understanding of thermal behaviours of battery electric vehicle (BEV) fires. To provide up-to-date information on BEV fires, the latest BEV model with a high electric-energy capacity (64 kWh) was selected. For comparative analysis purposes, a LIB pack and a BEV body were tested individually after being physically disassembled. An internal combustion engine vehicle and a hydrogen fuel cell electric vehicle were also tested. During testing, the combustion of the BEV fires continued for approximately 70 min, resulting in critical measures of burning being determined; peak heat release rate (pHRR), total heat released (THR), fire growth parameter, and the average effective heat of combustion were measured to be 6.51–7.25 MW, 8.45–9.03 GJ, 0.0085–0.020, and 29.8–30.5 MJ/kg, respectively. It was also observed that the pHRR and THR were governed by the combustion characteristics of typical combustible materials in the passenger cabin, rather than by that of particular contents in the LIB pack with thermal runaway. Instead, a jet fire intensively discharging from the LIB pack led to a rapid flame spreading to adjacent combustible components of the BEV, thereby accelerating the fire growth. The findings could contribute to the activities of the first responders to BEV fire accidents, fire safety engineers, and structural member designers. This study also makes public the measured thermal quantities for further studies on the fire safety of existing or designing car-parking related structures.

Fabrication of Highly Efficient Flame-Retardant and Fluorine-Free Superhydrophobic Cotton Fabric by Constructing Multielement-Containing POSS@ZIF-67@PDMS Micro-Nano Hierarchical Coatings.

The facile construction of a cotton fabric with excellent flame-retardant and water-proof abilities is of great interest for multitask requirements. Herein, a nonfluorine, highly efficient, and cost-effective multifunctional cotton fabric was fabricated via sequentially depositing a novel multielement-containing flame-retardant phosphorylated octa-aminopropyl POSS (PPA-POSS) and a fluorine-free superhydrophobic coating of zeolitic imidazolate framework-67@poly(dimethylsiloxane) (ZIF-67@PDMS). Influences of the PPA-POSS concentration and ZIF-67@PDMS formula on the fire retardancy and water repellency of treated cotton were systematically investigated. The optimized flame-retardant sample CTF3 with 6.2 wt % PPA-POSS exhibited a high limiting oxygen index (LOI) of 34% and self-extinguishing ability. CTF3 was further modified with a properly formulated superhydrophobic ZIF-67@PDMS coating. CTF3-PHB2 displayed enhanced thermal stability, flame retardancy, and outstanding superhydrophobicity. Thermogravimetric analysis (TGA) results demonstrated that CTF3-PHB2 presented a high char residue of 35.9%, which was 220.5% higher than that of the control cotton (11.2%). More importantly, the heat release rate (HRR), total heat release (THR), and average effective heat of combustion (av-EHC) values of CTF3-PHB2 were significantly reduced by 51.4, 56.2, and 68.4%, respectively, compared with those of a pure cotton fabric. Moreover, CTF3-PHB2 showed superhydrophobicity (WCA > 159.3°) and good mechanical abrasion resistance. In addition, CTF3-PHB2 also showed protective abilities such as antifouling, self-cleaning, and water/oil separation performances even for strong acid/alkali mixtures. Thereby, it is believed that the PPA-POSS@ZIF-67@PDMS coating is promising for application in multifunctional textile materials.

An eco-friendly and intumescent P/N/S-containing flame retardant coating for polyamide 6 fabric

This study focused on the construction of an eco-friendly and intumescent flame retardant (FR) coating for polyamide 6 (PA6) fabric. The intumescent FR coating, consisting of phytic acid, pentaerythritol and thiourea, was deposited onto PA6 fabric through dip-coating technique. The FR performance, anti-dripping ability, thermal stability, combustion behavior and mechanical property of the coated PA6 fabrics were explored. The severe dripping of coated PA6 fabric was totally eliminated, achieving an excellent FR performance at a low P (2.2%) and S (3.4%) content. Correspondingly, the LOI increased to 28.8% versus 23.2% of pristine one, displaying good flame retardancy. The char residue analyses confirmed the intumescent FR behavior of coated PA6 fabrics. The intumescent char layer played a major role in isolating the exchange of combustibles, oxygen and heat, leading to the significant reduction in heat release performance. The results of cone calorimetry test showed that the peak heat release rate and average effective heat of combustion of coated PA6 fabric decreased by about 36.5% and 34.4%, respectively versus pristine one. Meanwhile, the sulfur-based gases captured free radicals to interrupt the continuous combustion, leading to the significantly improved flame retardancy. Furthermore, the FR coating exerted little influence on the mechanical performance of PA6 fabric.

Hybrid composite board produced from wood and mineral stone wool fibers

Wood fiberboards are used extensively, mainly in the fields of furniture production, interior fittings, construction, etc. Mineral stone wool materials are used for heat and sound insulation in the construction industry. This study aimed to produce a new hybrid-based composite material by mixing fibers obtained from wood and mineral stone wool. For this purpose, hybrid fiberboards with 50, 40, 30, and 20% stone wool addition and a fiberboard group consisting of 100% pine and beech fibers (control sample) were produced in a hot press using thermoset-based urea formaldehyde and phenol formaldehyde resins. Statistical comparisons of the results were made for values of density, thickness swelling, and water absorption extents after 24 h immersion, bending strength and modulus of elasticity in bending, tensile strength perpendicular to the board surface (internal bond strength), and time to ignition (TTI) analysis. Additionally, percentage of mass loss (PML), average heat release rate (A-HRR), average effective heat of combustion (A-EHC), and mass loss rate (MLR) were studied. The results showed that as the stone wool content in the produced boards increased, the mechanical properties and thickness swelling decreased. The combustion results showed that the combustion resistance of the boards increased with increasing stone wool ratio.

A strategy to improve the compatibility of carboxyl methyl cellulose with silica fume‐based geopolymer inorganic siliceous coatings for flame‐retarding plywood

AbstractTo seek an effective strategy for improving the compatibility of carboxyl methyl cellulose (CMC) with silica fume‐based geopolymer composite flame‐retarding coatings, a novel silica aerogel (SA) doped inorganic siliceous hybrid coating is fabricated by sol–gel. Results show that an appropriate dosage (0.5 wt%) of SA ameliorates their compatibility thus imparting an enhanced flame resistance, evidenced by the lowest value of fire growth index (0.22 kW·m−2·s−1) decreased by 55% and the average effective heat of combustion (4.16 kW·kg−1) decreased by 31%, the raised flame retardancy index of 5.54 from 1 compared with the control. Because the SA improves the compatibility between the CMC and siliceous colloidal sol, due to its high reactivity, electrostatic repulsion involved in SiO(OH)3−, and high porosity, leading to an enhanced crosslinking during film‐forming of the hybrid coatings. Meanwhile, the reduction between CMC and silica occurs with a swelling fire shield, evidenced by the generated silicon involved in the as‐formed amorphous siliceous residues. Therefore, it proposed a new strategy for optimizing the compatibility of organic–inorganic hybrid fireproof coatings, revealing an efficient design of CMC/inorganic siliceous flame retardants, high‐value recycling technology of solid waste, low‐carbon, and sustainable materials.

A phosphaphenanthrene-benzimidazole derivative for enhancing fire safety of epoxy resins

In this work, a P/N-derived flame retardant (DOPO-BNM) was synthesized using 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 2-aminobenzimidazole, and 3-nitrobenzaldehyde as raw materials. The effects of DOPO-BNM on the flame retardancy, and thermal and mechanical performances of epoxy resin (EP) were comprehensively investigated. With the introduction of 8 wt% DOPO-BNM, the EP/8% DOPO-BNM sample passed a V-0 classification in vertical burning (UL-94) test, and its limiting oxygen index (LOI) increased to 32.5%. In comparison to the EP sample, the EP/8% DOPO-BNM sample exhibited 13.0%, 28.8%, 17.5%, 47.9% and 34.5% reductions in the peak heat release rate (PHRR), total heat release (THR), maximum average rate of heat emission (MARHE), total smoke production (TSP) and average effective heat of combustion (AEHC), demonstrating its enhanced fire safety. Furthermore, the char residue of EP/8% DOPO-BNM sample was increased by 41.2% relative to that of EP sample in the cone calorimetry test. During burning, DOPO-BNM mainly reduced the burning degree of volatiles, and also promoted the char formation. Additionally, DOPO-BNM slightly decreased the glass-transition temperature (Tg) of EP thermoset, while it remained the mechanical performances. In summary, the addition of DOPO-BNM not only effectively enhanced the fire safety of epoxy thermoset, but also maintained the thermal and mechanical properties.

A phosphorus/silicon/triazine‐containing flame retardant towards flame retardancy and mechanical properties of epoxy resin

AbstractA phosphorous/silicon/triazine‐containing flame retardant named DTD is synthesized and provides epoxy resin with enhanced flame retardancy and mechanical properties simultaneously. The modified epoxy with the DTD content of 18.1 wt% shows excellent flame retardancy, manifested in the limited oxygen index (LOI) value of 36.6% with UL‐94 V‐0 rating obtained. In the cone calorimeter test, its peak heat release rate (PHRR), total heat release (THR) and average effective heat of combustion (av‐EHC) are reduced by 43.7%, 45.0%, and 38.1% compared with neat epoxy resin, respectively. Besides, DTD exhibits a good charring capability, indicated by observation of an expanded char layer structure and the 160.3% increment in char residue after the cone calorimeter test. The mode of action of DTD is explained by the analysis of char residue and the pyrolysis behavior in the gas phase. In addition, DTD has good compatibility with epoxy resin, confirmed by single spike of tan delta and similar half‐peak width in dynamic mechanical analysis. While improving the flame retardancy, DTD also enhances the mechanical properties of epoxy resin. With 8.8 wt% of DTD content, the modified epoxy resin possesses desirable mechanical properties, with 36.0% and 18.9% increase in tensile strength and flexural strength, respectively.

Effect of phosphorus-containing modified UiO-66-NH2 on flame retardant and mechanical properties of unsaturated polyester

A novel phosphorus-containing flame retardant PZN@UiO-66-NH2 was synthesized by covalent bonding between HCCP and UiO-66-NH2, and applied in unsaturated polyester (UPR). The Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron energy spectra (XPS), scanning electron microscopy (SEM) was used to confirm the chemical structure of PZN@UiO-66-NH2. The appearance of new P-N-C bond indicated that HCCP was successfully reacted with UiO-66-NH2. The thermal stability and the flame-retardant properties of the UPR composites were characterized by thermogravimetric analysis (TGA), limiting oxygen index (LOI) and cone calorimeter test. The limiting oxygen index (LOI) of UPR composite with 4 wt% PZN@UiO-66-NH2 can reach 23.9%. Compared with pure UPR, the peak heat release rate (PHRR) value, total heat release (THR) value and average effective heat of combustion (av-EHC) value of UPR composite with 4 wt% PZN@UiO-66-NH2 dropped by 36.53%, 28.70%, 23.50%, respectively. The addition of PZN@UiO-66-NH2 slightly improved the impact performance of UPR composite. PZN@UiO-66-NH2 can solve UiO-66-NH2's agglomeration dilemma in UPR to some extent.

Preparation of melamine borate coated red phosphorus microcapsules and use of zinc borate as synergistic flame retardant in polyethylene

AbstractMicrocapsules (Mic‐MBP) based on the melamine borate coated red phosphorus (RP) were prepared, and its synergistic flame retardant with zinc borate (ZB) on polyethylene (PE) was investigated. The flame retardant properties of the PE/20% Mic‐MBP/10%ZB were superior to that of PE/20%RP/10%ZB. Furthermore, the limiting oxygen index of PE/20%Mic‐MBP/10%ZB was 25.2%, and PE/20%Mic‐MBP/10%ZB reached the UL‐94V‐0 rating. Compared with PE, the peak heat release rate (pk‐HRR), total heat release (THR) and average effective heat of combustion (av‐EHC) of PE/20%Mic‐MBP/10%ZB had decreased. In addition, the flame retardant mechanism was investigated by scanning electron microscopy (SEM), X‐ray diffraction (XRD), pyrolysis‐gas chromatography–mass spectrometry (PY‐GC–MS) and Fourier transform infrared spectroscopy (FT‐IR). The results showed that the residual char of PE/20%Mic‐MBP/10%ZB had thermal stability, and the formation of phosphorus free radicals and nonflammable gases effectively reduced the burning intensity of the gas phase. It indicated that Mic‐MBP/ZB showed a condensed and gas phase flame retardant effect.

The P/Si synergistic effect enduing epoxy resin with improved flame retardancy and outstanding mechanical properties

The bisphenol F epoxy resin (DGEBF) reacted with 10-(2,5-Dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (ODOPB) and phenyltrimethoxysilane (PTMS) to obtain a novel epoxy resin containing both phosphorus and silicon (EP-P/Si). EP-P/Si exhibited evidently improved flame retardancy, with a limited oxygen index value of 33.4% and UL-94 V-1 rating acquired. In cone calorimeter test, its peak heat release rate (PHRR), total heat release (THR), average effective heat of combustion (av-EHC), and total smoke production (TSP) were reduced by 36.0%, 19.5%,11.5%, and 7.2% compared with neat epoxy resin (EP), respectively, indicating that the P/Si synergistic effect not only improved the flame retardancy but also inhibited the smoke release. The flame retardancy mechanism was studied by analysis of char residue and pyrolysis behavior in gas phase. Scanning electron microscopy (SEM) results exhibited that EP-P/Si formed a dense and compact carbon layer acting as a barrier to inhibit further combustion. And the Fourier transform infrared (FTIR) spectra, laser Raman spectroscopy (LRS), and X-ray photoelectron spectroscopy (XPS) results indicated that it had good thermal stability. In addition, the pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) results suggested that the phosphorus-containing radicals (·PO2) that had quenching effect existed in the gas phase. While the flame retardancy got improved, EP-P/Si also exhibited excellent mechanical properties, with an improvement of 31.8%, 6.2%, and 369.7% in tensile strength, flexural strength, and impact strength compared with EP, respectively.

INVESTIGATION THE FIRE HAZARD OF PLYWOODS USING A CONE CALORIMETER

A high-efficiency fire retardant composition was prepared with dicyandiamide, phosphoric acid, boric acid, borax, urea and magnesium sulfate and it was used to process veneers which were then to prepare the plywood. Meanwhile, heat release and smoke release from combustion of plywood were tested by a cone calorimeter, including heat release rate, mass loss rate, CO yield, CO2 yield and oxygen consumption. Results showed that the plywood with this fire retardant treatment had the better flame-retardant performance and smoke suppression effect as well as the stronger char-forming capability compared to plywood without fire retardant treatment. The average heat release rate, total heat release, average effective heat of combustion, total smoke release, CO yield and oxygen consumption of the plywood with fire retardant treatment were decreased by 63.72%, 91.94%, 53.70%, 76.81%, 84.99% and 91.86%, respectively. Moreover, the fire growth index of plywood treated by fire retardant was relatively low (3.454 kW·m-2·s-1) and it took longer time to reach the peak heat release rate, accompanied with slow fire spreading. The fire performance index was relatively high (0.136 s·m2·kW-1) and it took longer time to be ignited, thus leaving a long time for escaping at fire accidents. The fire hazard of plywood with fire retardant treatment was low, and its safety level was high.

Deterioration mechanism on flame retardancy of aliphatic waterborne polyurethane-based hybrid coatings under ultraviolet radiation: Experiment and pyrolysis kinetics

Organic-inorganic hybrid intumescent flame retardant coating (IFRC) has been manifested as a promising solution to prevent fire spread of the plywood for indoor decoration. The aliphatic waterborne polyurethane (AWP)-based IFRC is prepared using the silicon-based aerogel, β-cyclodextrin, and nano-ZnO as the functional filler, and its ultraviolet-aging deterioration mechanism on flame retardancy is investigated through microstructure characterizations and pyrolysis kinetic calculation. The results show that the flame-retarding and smoke-suppressing properties of the IFRC gradually deteriorate with the prolonged ultraviolet exposure from 6 to 60 cycles, evidenced by the reduced flame retardancy index of 0.19 (drops from 1.00), the rising fire growth index from 0.87 to 1.45 kW m −2 s −1 , the increased average effective heat of combustion from 3.45 to 5.65 MJ·kg −1 , and the rising total smoke production from 91 to 153 m 2 . Because the ultraviolet radiation favors the chain scission of AWP and cleavage of –HN-CO-, crystallization of Zn 3 (PO 4 ) 2 , ZnP 4 O 11 , and SiP 2 O 7 for the IFRC during burning, leading to the reduced E α of 330–150 ℃ (decreases by 20%) approximately, presenting a reduced water contact angle and a fluffy char. It preliminary seeks the ultraviolet-aging flame-retarding mechanism with quantitative techniques and explores the condensed flame-retarding mechanism further. • Ultraviolet-aging deterioration mechanism of hybrid IFRCs is quantitatively investigated. • The ultraviolet radiation favors the crystallization of Zn 3 (PO 4 ) 2 , ZnP 4 O 11 , and SiP 2 O 7 . • The ultraviolet radiation contributes to the E α of 330–150 ℃ decreased by 20% approximately.

Surface Functionalization of Black Phosphorus via Amine Compounds and Its Impacts on the Flame Retardancy and Thermal Decomposition Behaviors of Epoxy Resin.

Recently, lots of effort has been placed into stabilizing black phosphorus (BP) in the air to improve its compatibility with polymers. Herein, BP was chemically functionalized by aliphatic amine (DETA), aromatic amine (PPDA) and cyclamine (Pid) via a nucleophilic substitution reaction, aiming to develop an intensively reactive BP flame retardant for epoxy resin (EP). The -NH2 group on BP-DETA, BP-PPDA and BP-Pid reacted with the epoxide group at different temperatures. The lowest temperature was about 150 °C for BP-DETA. The impacts of three BP-NH2 were compared on the flame retardancy and thermal decomposition of EP. At 5 wt% loading, EP/BP-NH2 all passed UL 94 V 0 rating. The limiting oxygen index (LOI) of EP/BP-PPDA was as high as 32.3%. The heat release rate (HRR) of EP/BP-DETA greatly decreased by 46% and char residue increased by 73.8%, whereas HRR of EP/BP-Pid decreased by 11.5% and char residue increased by 50.8%, compared with EP. Average effective heat of combustion (av-EHC) of EP/BP-Pid was lower than that of EP/BP-DETA and EP/BP-PPDA. In view of the flame-retardant mechanism, BP nanosheets functionalized with aliphatic amine and aromatic amine played a dominant role in the condensed phase, while BP functionalized with cyclamine was more effective in the gas phase.

Smoke suppression and thermal conductivity of epoxy resin modified byAl2O3and hyperbranched flame retardant

AbstractIn this work, aluminum oxide (Al2O3) was added to hyperbranched flame retardant (PTDOB) modified epoxy resin (EP) system to develop a novel EP thermoset (Al2O3‐PTDOB/EP) with superior comprehensive performance. Al2O3‐PTDOB/EP exhibited excellent flame retardancy, smoke‐suppressing effects, and enhanced mechanical properties due to the crack pinning effects caused by the introduction of Al2O3. In detail, the limiting oxygen index (LOI) and UL‐94 rating of Al2O3‐PTDOB/EP‐3 reached 34.6% and V‐0 rating, respectively. Cone calorimeter test showed that the total heat release, total smoke production (TSP) and average effective heat of combustion of Al2O3‐PTDOB/EP‐3 were reduced by 14.5, 27.3 and 19.2% in comparison to PTDOB/EP, respectively. Furthermore, the impact, tensile and flexural strengths of Al2O3‐PTDOB/EP‐3 were significantly improved by 16.7 28.4 and 10.7%, respectively, because the addition of Al2O3provided the carbon layer barrier and crack pinning effect for the EP matrix. Moreover, thermal conductivity of Al2O3‐PTDOB/EP was also improved due to the excellent thermal conductivity of Al2O3, which had broadened its application in the field of electronic packaging.

Fabrication of Anisotropic Polyphosphazene/Bio-based Poly(urethane-acrylate) composite foams with High Thermal Insulation and Flame Retardancy

Developing renewable porous materials with low thermal conductivity and high flame retardancy is of great significance in energy saving and fire safety. Herein, a series of bio-based anisotropic composite foams were fabricated from oil-in-water (o/w) high internal phase Pickering emulsions (Pickering HIPEs) stabilized by both bio-based poly (urethane-acrylate) (PUA) and poly (cyclotriphosphazene-co-4,4ʹ-sulfonyldiphenol) (PZS) particles. All Pickering HIPEs have good stability originated from the two kinds of particles irreversible adsorption at the oil-water interface and the formation of a “3D networks” of PUA particles aggregates in the aqueous phase. The microstructures and rheology of the double-particles stabilized HIPEs were adjusted by changing the contents of particles and the internal phase volume fractions. Then the anisotropic PZS/PUA composite foams with high porosity (up to 93.9%) and low thermal conductivity (down to 48.4 mW m−1∙K−1) were prepared by unidirectional freeze-drying these Pickering HIPEs. The anisotropic structure enhanced the mechanical strength in axial direction and thermal insulation property in radial direction. Compared with the PUA foam, loading only PZS of 10.7 wt%, the values of average heat release rate, total heat release and average effective heat of combustion of the composite foams were reduced by 19.3%, 12.8%, and 40.2%, respectively. Meanwhile, the value of limiting oxygen index was also increased from 16.3% to 18.2%, which was resulted from PZS functioned in the condensed phases during the combustion process. This work provides a strategy to prepare a kind of bio-based anisotropic foams which would find uses in the fields of fire safety and thermal insulation.