Smoke suppressant in flame retarded thermoplastic polyurethane composites: Synergistic effect and mechanism study

Considerable smoke and toxic volatiles generation has compromised the application of thermoplastic polyurethane (TPU) and caused a great threat to human life. Here, nano-MgFe layered double hydroxide (MgFe-LDH) with uniform particle size was synthesized to reduce smoke density and toxic gases of TPU composites using ammonium polyphosphate (APP) as a flame retardant agent. The results show that the combination of 16 wt.% APP and 4 wt.% MgFe-LDH greatly decreased the smoke density (D20min and Ds, max), smoke production rate (SPR) and heat release rate (HRR) of TPU composites. Furthermore, the MgFe-LDH synergist demonstrated high efficiency in decreasing total volatiled products and toxic volatiles evolved, such as the CO, HCN and isocyanates. The reason was mainly attributed to the chemical reaction between MgFe-LDH and APP, which can promote the compactness of char layers with fine microstructure formed in the decomposition process of MgFe-LDH/APP/TPU composites. The protective char layers could act as barriers between combustion zone and matrix to protect the unburned substrate and promote smoke suppression effect.

An Effective Green Porous Structural Adhesive for Thermal Insulating,Flame-Retardant,and Smoke-Suppressant Expandable Polystyrene Foam

To develop an efficient way to overcome the contradiction among flame retardancy,smoke suppression,and thermal insulation in expanded polystyrene(EPS)foams,which are widely used insulation materials in buildings,a novel"green"porous bio-based flame-retard ant starch(FRS)coating was designed from starch modified with phytic acid(PA)that simultaneously acts as both a flame retardant and an adhesive.This porous FRS coating has open pores,which,in combination with the closed cells formed by EPS beads,create a hierarchically porous structure in FRS-EPS that results in superior thermal insulation with a lower thermal conductivity of 27.0 mW·(m·K)^(-1).The resultant FRS-EPS foam showed extremely low heat-release rates and smoke-production release,indicating excellent fire retardancy and smoke suppression.The specific optical density was as low as 121,which was 80.6%lower than that of neat EPS,at 624.The FRS-EPS also exhibited self-extinguishing behavior in vertical burning tests and had a high limiting oxygen index(LOI)value of 35.5%.More interestingly,after being burnt with an alcohol lamp for 30 min,the top side temperature of the FRS-EPS remained at only 140℃with ignition,thereby exhibiting excellent fire resistance.Mechanism analysis confirmed the intumescent action of FRS,which forms a compact phosphorus-rich hybrid barrier,and the phosphorus-containing compounds that formed in the gas phase contributed to the excellent flame retardancy and smoke suppression of FRS-EPS.This novel porous biomass-based FRS system provides a promising strategy for fabricating polymer foams with excellent flame retardancy,smoke suppression,and thermal insulation.

Preparation and Characterization of Tung Oil Toughened Modified Phenolic Foams with Enhanced Mechanical Properties and Smoke Suppression

In this study,we prepared a series of tung oil phenolic foams(TPF)by a one-pot method.The FT-IR and 1H NMR spectra confirm the successful Friedel-Crafts grafting of phenol to the long-chain alkyl group in tung oil.Modified TPFs exhibit enhanced mechanical properties,including compressive and flexural strengths of up to 0.278±0.036 MPa and 0.450±0.017 MPa,respectively,which represent increases of 68.75%and 86.72%over those of pure phenolic foam(PF).SEM spectra reveal the TPF microstructure to have uniform hexagonal cell morphology,narrower cell size distribution,and smaller mean cell size,suggesting enhanced mechanical properties.The TPF total smoke release decreased by 74.23%,indicating that the long alkyl chain significantly improves smoke suppression of the combusting foam.However,due to the flammability of the alkyl chains,the TPF limiting oxygen index decreases with increasing tung oil content.Moreover,TPF exhibits reduced thermal stability and high-temperature charring rate,elevated peak and mean heat release rates,and higher total heat release compared with pure PF.Therefore,future research will focus on the use of tung oil modified flame retardant to provide more robust phenolic foams.

Flame Retardancy, Smoke Suppression Effect and Mechanism of Aryl Phosphates in Combination with Magnesium Hydroxide in Polyamide 6

The flammability, smoke emission behavior and mechanical properties of two oligomeric aryl phosphates [bisphenol A bis（diphenyl phosphate） （BDP） and resorcinol bis（diphenyl phosphate） （RDP）] combined with magnesium hydroxide （MH） in polyamide 6 （PA6） have been investigated. Combining 5 wt% BDP, 50 wt% MH imparts a limiting oxygen index （LOI） of 40.9% and UL94 V-0 rating to PA6, meanwhile the peak rate of smoke release （pRSR）, total release of smoke （TSR） and Izod notched impact strength are 41%, 33% and 233% relative to the corresponding value of 55 wt% MH without BDP, respectively. Dynamic mechanical analysis （DMA） indicates that the improvement of toughness attributes to the enhanced compatibility between MH and PA6 by adding BDP. Furthermore, based on the comprehensive analysis of thermogravimetry （TG）, cone calorimeter and SEM-EDX investigations, possible flame retardancy and smoke suppression mechanisms were revealed. Besides the fuel dilution and barrier effect of MH, the combination of MH and RDP shows an additional flame inhibition effect. The combination of MH and BDP results in a dominant condensed phase barrier effect which leads to obvious reduction on smoke emission and flammability.

Durable flame-retardant,smoke-suppressant,and thermal-insulating biomass polyurethane foam enabled by a green bio-based system

Bio-based polyurethane foam has attracted increasing attentions due to eco-friendliness and fossil feedstock issues.However,the inherent flammability limits its application in different fields.Herein,we demonstrate a green bio-based flame-retardant system to fabricate polyurethane foam composite with durable flame retardancy,smoke suppression,and thermal insulation property.In this system,the green bio-based polyol(VED)with good reactivity and compatibility plays a role of flame retardant and EG acts as a synergistic filler.As a result,the LOI value of foam composite increased to 30.5 vol.%and it achieved a V-0 rating in the UL-94 vertical burning test.Additionally,the peak heat release rate(pHRR)and the total smoke production(TSP)decreased by 66.1%and 63.4%,respectively.Furthermore,the foam composite maintained durable flame retardancy after accelerated thermal aging test,whose thermal-insulating property was maintained even after being treated in high-humidity environment with 85%R.H.for a week.This work provides a facile strategy for durable flame retardancy and long-term thermal insulation performance,and creates opportunities for the practical applications of bio-based foam composites.

Comparative Study on the Properties of Inorganic Silicate and Organic Phenolic Prepolymer Modified Poplar Wood by Vacuum Cycle Pressurization

To enhance mechanical properties and improve flame retardancy and smoke suppression of fast-growing poplar wood in wood applications,the wood was impregnated and modified.An organic phenolic prepolymer and inorganic sodium silicate was used as contrasting impregnation modifiers and wood samples were impregnated by a bionic“respiration”method with alternating positive and negative pressure.The weight percentage gain,density increase ratio,mechanical properties(bending and compressive strength and hardness),and water absorption rate of inorganic and organic-impregnated modified poplar wood(IIMPW and OIMPW,respectively)were compared and these properties in IIMPW were found to be higher than those of OIMPW with the exception of the water absorption rate which was lower than the OIMPW.This was attributed to the superior absorption of sodium silicate that also improved the impregnation,reinforcement,and dimensional stability in the IIMPW.The chemical structure,crystalline structure,internal morphology,flame retardancy,smoke suppression,and thermal stability of IIMPW and OIMPW were characterized by FT-IR,XRD,SEM,CONE,and TGA.FT-IR and XRD results showed that,although IIMPW cellulose crystallinity reduced the most,more chemical bonds were come into being in IIMPW,which explained the better physical and mechanical properties of IIMPW.Compared with OIMPW,IIMPW had better flame retardant and smoke suppression performance.

Pavement structure and materials design for sea-crossing bridges and tunnel:Case study of the Hong Kong-Zhuhai-Macao Bridge

With the continuous development of bridge and tunnel construction technologies,large-scale sea-crossing bridges and tunnels have gradually become the preferred choice for regional traffic.The construction technology of Hong Kong-Zhuhai-Macao Bridge(HZMB),one of the most representative sea-crossing passageways,is instructive for the construction of other large sea-crossing infrastructures.At present,the pavement design method of sea-crossing passageways lacks pertinence as it still refers to specifications for design of common pavement.Therefore,it is necessary to consider the bridge and tunnel pavement of HZMB as a typical example to analyze key technical problems encountered in its design,construction and operation.Novel solutions for material selection and structural design built upon the analysis of such critical problems should thus follow up.Based on comprehensive literature research,it can be found that environmental variability,tunnel closure,structural differential settlement and expansion deformation are the key technical problems faced by pavement of sea-crossing passageways.In view of the environmental variability,the steel deck-paving material and structure design of GMA-10 t SMA-13 is innovatively proposed.As for the closure of immersed tube tunnel,warm-mix flame retardant asphalt mixture is used to control pavement design through key indexes such as temperature and limit oxygen index.Regarding the deformation of immersed pipe joints,BJ200 asphalt seamless expansion joint material is introduced,which effectively satisfies the multi-directional deformation between pipe joints and ensures the smoothness of the road surface and driving comfort.For segmental joints,double-layer waterproof-coiled material is used to effectively prevent reflective cracks while ensuring the continuity of asphalt concrete pavement.Therefore,this paper provides a panel of ideas and methods for the pavement design of the same type of sea-crossing passageways.

Facile Synthesis of a Novel Bio-Based P-N Containing Flame Retardant for Effectively Reducing the Fire Hazards of Epoxy Resin

In this work,a bio-based flame retardant(Cy-HEDP)was synthesized from cytosine and HEDP through a facile salt-forming reaction and embedded into epoxy matrix to improve the flame retardancy and smoke suppression performance.The product Cy-HEDP was well characterized by FTIR,^(1)H and^(31)P NMR and SEM tests.On the basis of the results,by adding 15 wt%Cy-HEDP,the EP15 can pass UL-94 V-0 rating,and the total smoke production(TSP)as well as total heat release(THR)can be decreased by 61.05%(from 22.61 to 8.7 m^(2)/m^(2))and 39.44%(from 103.19 to 62.50 MJ/m^(2))in comparison to the unfilled EP,reflecting the attenuated smoke toxicity and impeded heat generation.According to the analysis results of residual char,it can be concluded that Cy-HEDP possessed the ability to promote the formation of continuous and dense char layers,which would be a physical barrier to insulate oxygen and prevent heat feedback during the combustion of EP.This work provide inspiration towards developing bio-based flame retardant,probably extending the prospects to other polymeric material system.

Influence of Beta-Cyclodextrin Functionalized Tin Phenylphosphonate on the Thermal Stability and Flame Retardancy of Epoxy Composites

To enhance the thermal stability and flame retardancy of epoxy resin(EP),beta-cyclodextrin(β-CD)is successfully introduced into the layered tin phenylphosphonate(SnPP),which is incorporated into EP matrix for preparing EP/β-CD@SnPP composites.The results indicate that the addition ofβ-CD@SnPP obviously improve the thermal stability and residual yield of EP composites at higher temperature.When the amount ofβ-CD@SnPP is only 4 wt%,EP/4β-CD@SnPP composites pass V-1 rating,and LOI value is up to 30.8%.Meanwhile,β-CD@SnPP effectively suppress the heat release and reduce the smoke production of EP/β-CD@SnPP composites in combustion,and the peak heat release rate(PHRR),total heat release(THR),smoke production rate(SPR)of EP/6β-CD@SnPP composites reduce by 28.4%,33.0%and 44.8%by comparison with those of pure EP.The good flame retardancy and smoke suppression are ascribed to the synergistic effect of excellent carbon-forming capability and fire retardancy ofβ-CD@SnPP.

Preparation and Characterization of Flame Retardant and Low Smoke Releasing Oil-resistant EVA/NBR Blends

Nano-SiO2 and/or MoO3 were introduced to ethylene-vinyl acetate/nitrile butadiene rubber （EVA/NBR） blends containing magnesium hydroxide （MH） and red phosphorus （RP） to further improve the mechanical properties, oil resistance, smoke suppression and flame retardancy. The results indicated that the tensile strength and oil resistance were significantly improved by incorporating nano-SiO2. Smoke suppression tests for EVA/NBR blend samples showed that both nano-SiO2 and MoO3 can significantly reduce smoke release amount. The flammability characterization indicated that the blended sample with an LOI value of 33.0 could achieve V-0 level in the UL-94 test. Cone calorimetry test data showed the peak heat release rate was 67% lower than that for pure EVA/NBR. Thermal analysis showed that the presence of both nano-SiO2 and MoO3 was beneficial to promoting char formation of the EVA/NBR blends. Char residual analysis suggested that MoO3 aggregated in solid phase during combustion.

Effect of surface modification of ammonium polyphosphate-diatomite composite filler on the flame retardancy and smoke suppression of cellulose paper

Ammonium polyphosphate-diatomite composite filler(APP-diatomite composite filler)was modified with silane coupling agent KH550 to improve the flame retardancy of filled paper.Cone calorimeter was used to analyze the heat and smoke releasing rates,as well as smoke toxicity of the filled paper.The distribution of the composite filler particles in paper and the morphology of the charred residues after combustion were investigated by scanning electron microscope(SEM),and the chemical structure of the charred residues was studied with fourier transform infrared spectroscopy(FTIR).Results show that the peak heat releasing rate(PHRR),total heat release(THR)and peak mass loss rate(PMLR)of the filled paper with the modified APP-diatomite decreased markedly,compared with those for the control paper,while the charred residue after combustion increased.In addition,the filled paper had an increased peak rate of smoke release(RSR)and increased total smoke release(TSR)and peak CO production rates,but a decreased peak CO_(2) production rate.It was also found that part of the carbon element in the charred residue of the paper loaded with the modified APP-diatomite was in the forms of C=C=C,C≡C and C≡N,and the charred residue had a relatively more intact structure without apparent fiber breakage and longitudinal cracks.

A biobased flame retardant towards improvement of flame retardancy and mechanical property of ethylene vinyl acetate

A new biobased flame retardant(MHPA)with remarkable compatibility was synthesized via a facile and low-cost neutralization reaction of magnesium hydroxide(MH)and phytic acid(PA).By blending the prepared MHPA into ethylene vinyl acetate(EVA),the fire retardancy,smoke suppression and mechanical properties of the composites were significantly improved.When 50 wt%of MH was added into EVA matrix,the value of limiting oxygen index(LOI)reached 26.1%.Whereas,when 10 wt%MH in the EVA composites(with initial 50 wt%MH)was replaced by MHPA,the resulted EVA composites had a LOI value of 30.8%,indicating high efficiency of addition of MHPA to improve flame retardancy.Moreover,the heat release rate(HRR)and total smoke production(TSP)of the EVA composites reduced by 54.4%and 27.6%,respectively,suggesting that incorporation of MHPA could effectively hinder rapid degradation of EVA composites during burning process.The fire-retardant mechanism may reside in that the MHPA combined with MH can present the excellent carbonization and expansion effects.This study illustrates that the biobased MHPA has a broad application prospect to develop flame-retardant EVA composites.