Synthesis of bio‐based poly (cyclotriphosphazene‐resveratrol) microspheres acting as both flame retardant and reinforcing agent to epoxy resin

A highly cross‐linked poly (cyclotriphosphazene‐resveratrol) microsphere (PRV) was synthesized by using hexachlorocyclotriphosphazene (HCCP) and bio‐based resveratrol (REV) as raw materials, and the obtained PRV microspheres were applied to improve the flame retardancy and mechanical property of epoxy resin (EP). The TGA results showed that the PRV microsphere is an excellent charring agent and the char yield is as high as 62% at 800°C. The incorporation of PRV makes the initial degradation earlier yet significantly increases the char residue of EP composites. Moreover, the introduction of PRV microspheres into EP greatly promoted the flame retardancy performance. Under 3% of addition of PRV microspheres, the peak heat release rate (PHRR) and total heat release (THR) were decreased by 58.3% and 29.6%, respectively, the limited oxygen index (LOI) value was increased to 29.7% from 25.3% of pure EP. In addition, because of the uniform distribution in EP matrix and the enhancing effect of PRV microspheres, the mechanical properties including tensile modulus of EP composites were strengthened. PRV microspheres in this paper provide a possibility to synthesize a dual functional filler, which acts as both flame retardant and strengthening agent.     

Phosphorylated cellulose/Fe3+ complex: A novel flame retardant for epoxy resins

A novel flame retardant containing cellulose, phosphorus and ferrum complex (Cell‐P‐Fe) was successfully synthesized and then it was used as flame retardants in epoxy resins (EP). Due to the present of acid sources and carbon sources, the Cell‐P‐Fe exhibits improved thermal stability and flame retardant properties. The EP/Cell‐P‐Fe composites with 10 wt% of Cell‐P‐Fe show remarkably improved LOI and UL‐94 values compared with the flame retardants without ferrum. At the loading of 10.0 wt% flame retardants, the char yield for EP/Cell‐P‐Fe composites increased to 29.1 wt%, indicating the improved thermal stability at high temperature. Moreover, thermogravimetric analysis, morphology of char residues and FTIR results demonstrate that stable char layers are formed on the surface of the composites during the combustion, attributing to the catalytic carbonization effect of Fe and phosphorus and the present of cellulose as carbon source. The stable char layers, which can protect the underlying materials from heat and oxygen, play an important role in the flame retardancy enhancement.     

Preparation of Poly(phosphoric acid piperazine) and Its Application as an Effective Flame Retardant for Epoxy Resin

A phosphorus-nitrogen containing flame retardant additive of poly(phosphoric acid piperazine),defined as PPAP,was synthesized by the salt-forming reaction between anhydrous piperazine and phosphoric acid,and the dehydration polymerization under heating in nitrogen atmosphere.Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy,13C and 31p solid-state nuclear magnetic resonance measurements.The synthesized PPAP and curing agent m-phenylenediamine were blended into epoxy resin (EP) to prepare flame retardant EP thermosets.The effects of PPAP on the fire retardancy and thermal degradation behavior of cured EP/PPAP composites were investigated by limiting oxygen index (LOI),vertical burning (UL-94),thermogravimetric analysis/infrared spectrometry (TG-IR) and cone calorimeter tests.The morphologies and chemical compositions of char residues for cured epoxy resin were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS),respectively.The results demonstrated that the flame retardant EP thermosets successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 30.8％ when incorporating 5wt％ PPAP into the EP thermosets.The TGA results indicated that the synthesized PPAP flame retardant additive possessed high thermal stability and excellent charring capability.Meanwhile,the incorporation of PPAP stimulated the epoxy resin matrix to decompose and charring ahead of time due to its catalytic decomposition effect,which led to a higher char yield at high temperature.The morphological structures and the analysis results of XPS for char residues of EP thermosets revealed that the introduction of PPAP benefited the formation of a sufficient,more compact and homogeneous char layer containing phosphorus-nitrogen flame retardant elements on the material surface during combustion.The formed char layer with high quality effectively prevented the heat transmission and diffusion,limited the production of combustible gases,and inhibited the emission of smoke,leading to the reduction of heat and smoke release.     

Synthesis of a novel phosphorus‐containing curing agent and its effects on the flame retardancy,thermal degradation and moisture resistance of epoxy resins

A novel phosphorus‐containing compound diphenyl‐(1, 2‐dicarboxylethyl)‐phosphine oxide defined as DPDCEPO was synthesized and used as a flame retardant curing agent for epoxy resins (EP). The chemical structure of the prepared DPDCEPO was well characterized by Fourier transform infrared spectroscopy, and ¹H, ¹³C and ³¹P nuclear magnetic resonance. The DPDCEPO was mixed with curing agent of phthalic anhydride (PA) with various weight ratios into epoxy resins to prepare flame retardant EP thermosets. The flame retardant properties, combustion behavior and thermal analysis of the EP thermosets were respectively investigated by limiting oxygen index (LOI), vertical burning tests (UL‐94), cone calorimeter measurement, dynamic mechanical thermal analysis and thermogravimetric analysis (TGA) tests. The surface morphologies and chemical compositions of the char residues for EP thermosets were respectively investigated by scanning electron microscopy and X‐ray photoelectron spectroscopy (XPS). The water resistant properties of the cured EP were evaluated by putting the samples into distilled water at 70°C for 168 hr. The results revealed that the EP/20 wt% DPDCEPO/80 wt% PA thermosets successfully passed UL‐94 V‐0 flammability rating and the LOI value was as high as 33.2%. The cone test results revealed that the incorporation of DPDCEPO effectively reduced the combustion parameters of the epoxy resin thermosets, such as heat release rate and total heat release. The dynamic mechanical thermal analysis test demonstrated that the glass transition temperature (Tg) decreased with the increase of DPDCEPO content. The TGA results indicated that the incorporation of DPDCEPO promoted the decomposition of epoxy resin matrix ahead of time and led to a higher char yield and thermal stability at high temperatures. The surface morphological structures and analysis of the XPS of the char residues of EP thermosets revealed that the introduction of DPDCEPO benefited the formation of a sufficient, compact and homogeneous char layer with rich flame retardant elements on the epoxy resin material surface during combustion. The mechanical properties and water resistance of the cured epoxy resins were also measured. After water resistance tests, the EP/20 wt% DPDCEPO/80 wt% PA thermosets retained excellent flame retardancy, and the moisture adsorption of the EP thermosets decreased with the increase of DPDCEPO content in EP thermosets because of the existence of the P–C bonds and the rigid aromatic hydrophobic structure in DPDCEPO. Copyright © 2015 John Wiley & Sons, Ltd.     

Synergistic flame‐retardant effect of DOPO‐based derivative and organo‐montmorillonite on glass‐fiber‐reinforced polyamide 6 T

Herein, a bridged 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) derivative (PN‐DOPO) in combination with organ‐montmorillonite (OMMT) was used to improve the flame retardancy and mechanical properties of glass‐fiber‐reinforced polyamide 6 T (GFPA6T). The flame retardancy and thermal stabilities of the cured GFPA6T composites were investigated using limiting oxygen index, vertical burning (UL‐94) test, cone calorimeter test, and thermogravimetric analysis (TGA). The morphological analysis and chemical composition of the char residues after cone calorimeter tests were characterized via scanning electron microscopy and energy dispersive spectrometry. The results indicate that 2 wt% OMMT combined with 13 wt% PN‐DOPO in GFPA6T achieved a V‐0 rating in UL‐94 test. The peak heat release rate and total smoke release remarkably decreased with the incorporation of OMMT as compared to those of GFPA6T/15 wt% PN‐DOPO. The TGA results show that the thermal stability and residual mass of the samples effectively increased with the increase in OMMT content. The morphological analysis and composition structure of the residues demonstrate that a small amount of OMMT could help form a more thermally stable and compact char layer during combustion. Also, with the incorporation of OMMT, the layers consisted of more carbon‐silicon and aluminum phosphate char in the condensed phase. Furthermore, GFPA6T/PN‐DOPO/OMMT composites exhibited excellent mechanical properties in terms of flexural modulus, flexural strength, and impact strength than the GFPA6T/PN‐DOPO system. The combination of PN‐DOPO and OMMT has improved the flame retardancy and smoke suppression of GFPA6T without compromising the mechanical properties.     

A novel graphene hybrid for reducing fire hazard of epoxy resin

Epoxy resin (EP) is more and more important in many fields, but its application is limited due to the inflammability in air of EP. Therefore, reducing the fire hazard of EP is necessary. In this work, a kind of hybrid flame retardant (α‐ZrP‐RGO) consisting of a 2‐dimensional inorganic reduced graphene oxide (RGO) modified with a planar‐like α‐zirconium phosphate (α‐ZrP) particles was prepared successfully via 1‐step hydrothermal method. The effects of α‐ZrP‐RGO on the thermal performance, flame retardancy, and smoke suppression of EP were investigated by preparing EP composites containing both EP and α‐ZrP‐RGO. Thermogravimetric results revealed that α‐ZrP‐RGO could improve the char yield of EP at 700°C obviously. In addition, compared with pure EP, the peak heat release rate and the total heat release of EP composites were decreased significantly, while the limited oxygen index of EP composites was increased. Meanwhile, the smoke production rate of EP composites was reduced obviously with the addition of α‐ZrP‐RGO. The enhanced flame retardancy and smoke suppression of EP composites were mainly attributed to not only the physical barrier effect of both α‐ZrP and RGO but also the catalytic effect of α‐ZrP during the combustion process of EP composites.     

Simultaneously improving the flame retardancy and mechanical properties for polyamide 6/aluminum diethylphosphinate composites by incorporating of 1,3,5‐triglycidyl isocyanurate

The effect of 1,3,5‐triglycidyl isocyanurate (TGIC) as a synergistic agent on the fire retardancy, thermal, and mechanical properties for polyamide 6/aluminium diethylphosphinate (PA6/AlPi) composites were investigated in detail by limiting oxygen index; vertical burning (UL‐94); cone calorimeter; thermal gravimetric analysis; rheological measurements; and the tests of tensile, flexural, and Izod impact strength. The morphologies and chemical compositions of the char residue were investigated by scanning electron microscopy, X‐ray photoelectron spectroscopy, and Fourier transform infrared spectra. The results demonstrated that AlPi and TGIC exerted an evident synergistic effect for flame retardant PA6 matrix, and the PA6/AlPi/TGIC composites with the thickness of 1.6 mm successfully passed UL‐94 V‐0 rating with the limiting oxygen index value of 30.8% when the total loading amount of AlPi/TGIC with the mass fraction of 97:3 was 11 wt%. However, the samples failed to pass the UL‐94 vertical burning tests when AlPi alone is used to flame retardant PA6 matrix with the same loading amount. The thermal gravimetric analysis data revealed that the introduction of TGIC promoted the char residue formation at high temperature. The rheological measurement demonstrated that the incorporation of TGIC improved the storage modulus, loss modulus, and complex viscosity of PA6/AlPi/TGIC composites comparing with that of neat PA6 and PA6/AlPi composites due to the coupling reaction between TGIC and the terminal groups of PA6 matrix. The morphological structures of char residues demonstrated that TGIC benefited to the formation of more homogenous and integrated char layer with no defects and holes on the surface comparing with that of PA6/AlPi composites during combustion. The higher melt viscosity of composites and the integrated and sealed char layer effectively inhibited the volatilization of flammable gas into the combustion zone and then led to the reduction of the heat release. The results of mechanical properties revealed that the incorporation of TGIC enhanced the mechanical properties for PA6/AlPi/TGIC composites comparing with that of PA6/AlPi composites with the same loading amount of flame retardant caused by the chain extension effect of TGIC. As a result, the flame retardancy and mechanical properties of PA6/AlPi composites simultaneously enhanced due to the introduction of TGIC.     

微纳米钙钛矿型羟基锡酸钙的合成及对环氧树脂的阻燃性能

钙钛矿型羟基锡酸盐是近年来出现的新型高效阻燃消烟剂. 本文采用化学共沉淀法合成了微纳米钙钛矿型羟基锡酸钙[CaSn(OH)₆, CSH], 并利用扫描电子显微镜、 透射电子显微镜、 X射线衍射仪、 红外光谱仪和X射线光电子能谱仪等对其形貌和结构进行表征. 结果表明合成的CaSn(OH)₆为平均粒径500 nm的纯净正六面体, 粒径均一且分散性良好. 将CaSn(OH)₆应用于环氧树脂(EP)复合阻燃体系(CSH/EP), 并分别采用热重分析、 极限氧指数和锥形量热测试表征了其热降解行为和燃烧性能. 采用扫描电子显微镜、 红外光谱、 X射线衍射和拉曼光谱对EP复合材料的阻燃成炭机制进行探索. 结果表明, CaSn(OH)₆能显著提高EP复合材料的高温稳定性、 热释放速率、 热释放量、 烟释放量和极限氧指数数值. 特别是在很低添加量(0.5%, 质量分数)下, 阻燃消烟性能即得到极大提升, 热释放速率、 总放热量和一氧化碳释放量分别降低45.8%, 25.1%和31.3%. 此外, 由于CaSn(OH)₆在EP基体中的良好分散及较强的界面作用, CaSn(OH)₆在提升EP复合材料阻燃消烟性的同时还提升了EP复合材料的力学强度. 本文合成的CaSn(OH)₆可作为一种多功能的高效阻燃、 消烟和增强剂.     

磷杂菲类阻燃剂的合成及其与聚磷酸铵复合膨胀体系对环氧树脂的阻燃性能研究

以9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)、五硫化二磷(P2S5)为原料合成9,10-二氢-9-氧杂-10-磷杂菲-10-硫化物(DOPS),并将DOPS与聚磷酸铵(APP)组成复合阻燃剂,用于环氧树脂(EP)的阻燃改性.通过氧指数(LOI)、垂直燃烧(UL-94)、热失重(TGA)、锥形量热(CONE)和扫描电镜(SEM)等方法对改性后的环氧树脂的阻燃性能和阻燃机理进行了测试和分析.实验结果表明,DOPS/APP阻燃体系对EP具有很好的阻燃性能,且复配阻燃剂的阻燃效果比单一的阻燃剂阻燃效果好;其中,当阻燃剂的总添加量达到30%时即W_(DOPS)=10%、W_(APP)=20%时,阻燃EP复合材料的LOI值可达到29.2%,垂直燃烧等级达到UL-94 V-0级,残炭量可达49.3%.     

Flame retardant properties and mechanism of an efficient intumescent flame retardant PLA composites

The charring agent (CNCA‐DA) containing triazine and benzene rings was combined with ammonium polyphosphate (APP) to form intumescent flame retardant (IFR), and it was occupied to modify polylactide (PLA). The flame retardant properties and mechanism of flame retardant PLA composites were investigated by the limited oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis, microscale combustion calorimetry, scanning electron microscopy, laser Raman spectroscopy analysis and X‐ray photoelectron spectroscopy. The analysis from LOI and UL‐94 presented that the IFR was very effective in flame retardancy of PLA. When the weight ratio of APP to CNCA‐DA was 3:1, and the IFR loading was 30%, the IFR showed the best effect, and the LOI value reached 45.6%. It was found that when 20 wt% IFR was loaded, the flame retardancy of PLA/IFR still passed UL‐94 V‐0 rating, and its LOI value reached 32.8%. The microscale combustion calorimetry results showed that PLA/IFR had lower heat release rate, total heat release, and heat release capacity than other composites, and there was an obvious synergistic effect between APP and CNCA‐DA for PLA. IFR containing APP/CNCA‐DA had good thermal stability and char‐forming ability with the char residue 29.3% at 800°C under N₂ atmosphere. Scanning electron microscopy observation further indicated that IFR could promote forming continuous and compact intumescent char layer. The laser Raman spectroscopy analysis and X‐ray photoelectron spectroscopy analysis results indicated that an appropriate graphitization degree of the residue char was formed, and more O and N were remained to form more cross‐linking structure. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of surface chemical modification for aluminum hypophosphite with hexa‐(4‐aldehyde‐phenoxy)‐cyclotriphosphazene on the fire retardancy,water resistance,and thermal properties for polyamide 6

The surface chemical modified aluminum hypophosphite (AHP) defined as MAHP was successful prepared through P–H bonds on AHP surface reacted with the aldehyde groups in hexa‐(4‐aldehyde‐phenoxy)‐cyclotriphosphazene made in our lab. The wettability of the flame retardants was evaluated by water contact angle tests, and the water contact angle of the prepared MAHP dramatically increased from 0° for AHP to 145°, which indicated the surface modification made the superhydrophilic AHP into superior hydrophobic MAHP. The prepared MAHP and AHP, respectively, incorporated into polyamide 6 (PA6) matrix to prepare flame retardant PA6 composites and the fire retardancy and thermal degradation behavior of flame retardant PA6 composites were investigated by limiting oxygen index, vertical burning test (UL‐94), cone calorimeter, and thermogravimetric analysis tests. The morphologies and chemical compositions of the char residues for PA6 composites were investigated by scanning electron microscopy and X‐ray photoelectron spectroscopy, respectively. The water resistant properties of flame retardant PA6 composites were evaluated by putting the samples into distilled water at 70°C for 168 hr, and the mechanical properties for flame retardant PA6 composites were investigated by the tensile, flexural, and Izod impact strength tests. The results demonstrated that the PA6/MAHP composites successfully passed UL‐94 V‐0 flammability rating, and the limiting oxygen index value was 27.6% when the loading amount of MAHP was 21 wt%. However, there is no rating in vertical burning tests for PA6/AHP composite with the same amount of AHP, which indicated the surface modification of AHP enhanced the flame retardancy efficiency for PA6 composites. The morphological structures and analysis of X‐ray photoelectron spectroscopy of char residues revealed that the surface modification of AHP benefited to the formation of a sufficient, flame retardant elements rich, more compact and homogeneous char layer on the materials surface during combustion, which prevented the heat transmission and diffusion, limit the production of combustible gases, inhibit the emission of smoke and then led to the reduction of the heat release rate and smoke produce rate. The mechanical properties results revealed that the surface modification of AHP enhanced the mechanical properties, especially the Izod impact strength comparing with that of PA6/AHP composites with the same amount of flame retardant. After water resistance tests, the PA6/MAHP composites remained superior flame retardancy and presented continuous and compact char layer after cone calorimeter tests; however, the fire retardancy for PA6/AHP composite obviously decreased, and the char layer was discontinuous with big hole caused by the extraction of AHP by water during water resistance tests. Copyright © 2017 John Wiley & Sons, Ltd.     

Synthesis of a triazine-based macromolecular hybrid charring agent containing zinc borate and its flame retardancy and thermal properties in polypropylene

Abstract

A triazine-based macromolecular hybrid charring agent containing zinc borate (MCA-K-ZB) was synthesized and combined with ammonium polyphosphate (APP) to improve the flame retardancy of polypropylene (PP). The flame retardancy and thermal properties of PP composites were investigated using limited oxygen index, vertical burning test, and thermogravimetric analysis. The results showed APP/MCA-K-ZB can improve the flame retardancy of PP compared with APP/MCA-K/ZB. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The SEM result shows that MCA-K-ZB can improve the compactness and continuity of char residue compared with MCA-K/ZB, therefore improving the flame retardancy of PP composites.     

Synergistic effects of cerium phosphate and intumescent flame retardant on EPDM/PP composites

An intumescent flame retardant system composed of ammonium polyphosphate (APP) and pentaerythritol (PER) was used for flame retarding ethylene–propylene–diene‐modified elastomer (EPDM)/polypropylene (PP) blends. Cerium phosphate (CeP) was synthesized and the effect on flame retardancy and thermal stability of EPDM/PP composites based on intumescent flame retardant (IFR) were studied by limiting oxygen index (LOI), UL‐94, and thermogravimetic analysis (TGA), respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR) were used to analyze the morphological structure and the component of the residue chars formed from the EPDM/PP composites, and the mechanical properties of the materials were also studied. The addition of CeP to the EPDM/PP/APP/PER composites gives better flame retardancy than that of EPDM/PP/APP/PER composites. TGA and RT‐FTIR studies indicated that an interaction occurs among APP, PER, and EPDM/PP. The incorporation of CeP improved the mechanical properties of the materials. Copyright © 2010 John Wiley & Sons, Ltd.     

Low flammability and smoke epoxy resins with a novel DOPO‐based imidazolone derivative

In this work, a DOPO‐based imidazolone derivative named DHI was synthesized using DOPO, 5‐amino‐2‐benzimidazolinone and 4‐hydroxybenzaldehyde as raw materials. The chemical structure of DHI was characterized by ¹H‐NMR, ³¹P‐NMR and Fourier transform infrared spectra (FTIR). Then, a series of different flame‐retardant epoxy resin (EP) thermosets were prepared by mixing flame retardant DHI. The thermal properties of the cured EPs was investigated by thermogravimetry analysis (TGA) and differential scanning calorimeter (DSC), and the results showed the thermal stability and glass transition temperature (T_g) of the cured EP modified with DHI declined slightly compared with that of neat EP. The limited oxygen index (LOI) and UL94 test results exhibited DHI imparted good flame retardancy to EP. The EP‐4 (phosphorus content of 1.25%) possessed a LOI value of 36.5% and achieved a V‐0 rating. Furthermore, the peak of heat release rate (PHRR) and total heat release rate (THR) of EP‐4 decreased by 38.7% and 24.5%, respectively. Excitedly, the total smoke production (TSP) of EP‐4 sample declined by 62.5%, which meant DHI also made EP obtain excellent smoke suppression property. Moreover, the flame‐retardant mechanism was studied by scanning electron microscopy (SEM) and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS). It was reasonable inferred that DHI could not only promote EP to form dense char layer in condensed phase, but also restrain combustion in gaseous phase through catching the free radicals sourced from the degradation of EP.     

Co-flame retarding effect of ethanolamine modified titanium-containing polyhedral oligomeric silsesquioxanes in epoxy resin

A metal-doped organic and inorganic hybrid polyhedral oligomeric silsesquioxanes (POSS) with a titanium atom in the POSS cage and an ethanolamine substitute group in the corner, namely MEA-Ti-POSS, was synthesized through simple condensation reaction and substitute reaction. It was blended with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to form a kind of blending-type flame retardant system for the modification of epoxy resins. The thermal stability, flame retardancy and mechanical properties of cured epoxy resin composites were studied. Comparing with pure epoxy resin, the LOI value of EP/MEA-Ti-POSS/DOPO composites was raised from 25.2% to 32.7%, and the UL-94 grade reached V-0 level at a loading of the mixture of 5% MEA-Ti-POSS and 5% DOPO. In addition, the cone calorimetry results showed that the heat release rate, total heat release and total smoke production as well as smoke production rate were all reduced during the combustion of EP/MEA-Ti-POSS/DOPO composites. The residual char analysis revealed that carbon residues of EP/MEA-Ti-POSS/DOPO composite served as a physical protective layer to insulate the oxygen and combustible gases to reduce the ablation of the matrix. It was concluded that the mixture of MEA-Ti-POSS and DOPO not only effectively raised the thermal stability and flame retardancy of epoxy composited materials, but also improved their mechanical properties, which expanded a promising application of the metal-POSS derivatives as non-halogen additives in the flame retardant polymers.     

Fabrication of diatomite‐based microencapsulated flame retardant and its improved fire safety of unsaturated polyester resin

To achive excellent fire resistance, new microcapsule flame retardants (DMCAD and DMPPD) were prepared using 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide combined with melamine cyanurate or melamine polyphosphate as the shell material and diatomite as the core material. The successful assembly of DMCAD and DMPPD was detailed characterized by Fourier transform infrared (FT‐IR) spectra, X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Meanwhile, the flame retardancy and thermal stability of the unsaturated polyester resin (UPR)/DMCAD and UPR/DMPPD composites were also studied. The addition of DMCAD and DMPPD effectively improves the flame retardance properties of UPR, and the effect of DMPPD was better. The limiting oxygen index (LOI) of UPR/DMPPD‐3 increased by 11.6% when compared with that of UPR, and the sample achieved V‐0 rating. Moreover, the peak heat release rate (pHRR) and the total heat release (THR) rate of UPR/DMPPD‐3 were reduced by 67% and 26%, respectively. Under nitrogen condition and air condition, UPR/DMPPD showed better thermal stability and char‐forming ability from the thermogravimetric (TG) results. Residual char of the UPR composites was systematically analyzed with SEM and XPS. Finally, the flame retardant mechanism of DMPPD was proposed.     

双层包裹聚磷酸铵微胶囊合成及其在环氧树脂中阻燃研究

采用原位聚合法制备了蜜胺树脂(MF)和环氧树脂(EP)双层包裹聚磷酸铵(APP),得到一种新型核壳结构的微胶囊阻燃剂(EMFAPP).用傅里叶红外光谱(FTIR)和扫描电镜(SEM)对微胶囊的核壳结构进行了表征;用极限氧指数(LOI)、垂直燃烧等级测试(UL 94)对EMFAPP在EP中的阻燃性能进行了研究.EMFAPP在EP基体中阻燃性能优异,当其添加量大于7%时EP/EMFAPP均通过UL 94 V-0级,LOI值达27.0%以上.与未包裹APP相比,EMFAPP耐水性明显提高;经水处理(75℃,6天)后,EMFAPP/EP仍可保持良好的阻燃性能.采用热重分析对EMFAPP及其阻燃复合物的热降解行为进行了研究,EMFAPP能够促进成炭,EP/EMFAPP(8 wt%)在700℃残炭率达16.2%,但其低温稳定性有所下降.此外,利用热失重-红外联用对EMFAPP/EP的热降解行为进行了研究,探讨相关阻燃机理.     

Phenolic resin/polyhedral oligomeric silsesquioxane (POSS) composites: Mechanical,ablative, thermal,and flame retardant properties

Three different polyhedral oligomeric silsesquioxanes (POSS), trisilanolphenyl polyhedral oligomeric silsesquioxane (T‐POSS), octaaminophenyl polyhedral oligomeric silsesquioxanes (OAPS), and octaphenyl polyhedral oligomeric silsesquioxanes (OPS) were incorporated into phenolic resin (PR), respectively; PR/POSS composites were successfully prepared, and the properties of PR/POSS composites were studied. The limiting oxygen index (LOI), cone calorimeter, and thermal gravimetric analysis (TGA) were used for the estimation of flame retardancy and thermal stability. Oxyacetylene flame test and flexural strength test were used to study the ablative and mechanical properties of the PR/POSS composites. The results indicated that T‐POSS was more effective in improving the flame retardancy of PR than OAPS or OPS. Meanwhile, compared with pure PR, the second line ablation rates of PR/4% T‐POSS, PR/4% OAPS, and PR/4% OPS were significantly reduced by 53.3%, 61.9%, and 40.0%, respectively. In addition, the thermal stability and flexural strength of PR/4% T‐POSS were significantly higher than that of all other PR composites.     

A combination of POSS and polyphosphazene for reducing fire hazards of epoxy resin

Extensive application of epoxy resins (EPs) is highly limited by their intrinsic flammability. Combining EPs with nanoparticles and phosphorus‐nitrogen flame retardants is an effective approach to overcome the drawback. In this work, simultaneous incorporation of octa‐aminophenyl polyhedral oligomeric silsesquioxanes (OapPOSS) and polyphosphazene into EP was reported for the first time. Significantly, reduced peak of heat release rate and UL‐94 V‐0 rating were achieved by tuning suitable ratios of polyphosphazene and OapPOSS for EP composites. During combustion, polyphosphazene promoted char formation and released nonflammable gases such as CO₂, NH₃, and N₂ to dilute oxygen concentration and cool pyrolysis zone. Moreover, numerous phosphorus‐containing species acting as free radical scavengers were generated during degradation. Silicon dioxide evolving from OapPOSS protected char residues from thermal degradation. This study provides a novel method to fabricate high‐performance flame‐retardant EP composites, which have potential applications in the field of electrics and electronics.     

Synergistic effects of 4A zeolite on the flame retardant properties and thermal stability of a novel halogen‐free PP/IFR composite

The synergistic effects of 4A zeolite (4A) on the thermal degradation, flame retardancy and char formation of a novel halogen‐free intumescent flame retardant polypropylene composites (PP/IFR) were investigated by the means of limiting oxygen index (LOI), vertical burning test (UL‐94), digital photos, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), cone calorimeter test (CCT), laser Raman spectroscopy (LRS) and X‐ray photoelectron spectroscopy (XPS). It was found that a small amount of 4A could dramatically enhance the LOI value of the PP/IFR systems and the materials could pass the UL‐94 V‐0 rating test. Also, it could enhance the fire retardant performance with a great reduction in combustion parameters of PP/IFR system from CCT test. The morphological structures observed by digital and SEM photos revealed that 4A could promote PP/IFR to form more continuous and compact intumescent char layer. The LRS measurement, XPS and TGA analysis demonstrated that the compactness and strength of the outer char surface of the PP/IFR/4A system was enhanced, and more graphite structure was formed to remain more char residue and increase the crosslinking degree. Copyright © 2013 John Wiley & Sons, Ltd.