Simultaneous improvement in the flame retardancy and water resistance of PP/APP through coating UV-curable pentaerythritol triacrylate onto APP

To improve the flame-retardant efficiency and water resistance of ammonium polyphosphate(APP), the UV-curable pentaerythritol triacrylate(PETA) was used to microencapsulate APP via the UV curing polymerization method. The prepared PETA-microencapsulated APP(PETA-APP) was characterized by Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), and thermogravimetric(TG) analysis. PETA-APP was used as intumescent flame retardant(IFR) alone to flame retard polypropylene(PP). The water resistance of PP/PETA-APP composites was investigated, and the effect of PETA on the combustion behaviors of PP/APP composites was studied through limiting oxygen index(LOI), vertical burning test(UL-94) and cone calorimeter(CC) test, respectively. With 40 wt% of PETA-APP, the PP/PETA-APP system could achieve a LOI value of 30.0% and UL-94 V-0 rating after treatment in hot water for 168 h, while the LOI value of the system containing 40 wt% uncoated APP was only 19.2%, and it failed to pass the UL-94 rating. CC test results showed that the heat release rate(HRR), mass loss rate(MLR) and smoke production rate(SPR) of PP/PETAAPP system decreased significantly compared with PP/APP system, especially the peak of HRR was decreased by 51.4%. The mechanism for the improvement of flame reatardancy for PP/PETA-APP composites was discussed based on FTIR and X-ray photoelectron spectroscopy(XPS) tests. All these results illustrated that simultaneous improvement of flame retardancy and water resistance for PP/APP was achieved through coating UV-curable PETA onto APP.     

Synergistic effects of aluminum hypophosphite on intumescent flame retardant polypropylene system

The effects of aluminum hypophosphite(AHP) as a synergistic agent on the flame retardancy and thermal degradation behavior of intumescent flame retardant polypropylene composites(PP/IFR) containing ammonium polyphosphate(APP) and triazine charring-foaming agent(CFA) were investigated by limiting oxygen index(LOI), UL-94 measurement, thermogravimetric analysis(TGA), cone calorimeter test(CONE), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). It was found that the combination of IFR with AHP exhibited an evident synergistic effect and enhanced the flame retardant efficiency for PP matrix. The specimens with the thickness of 0.8 mm can pass UL-94 V-0 rating and the LOI value reaches 33.5% based on the total loading of flame retardant of 24 wt%, and the optimum mass fraction of AHP/IFR is 1:6. The TGA data revealed that AHP could change the degradation behavior of IFR and PP/IFR system, enhance the thermal stability of the IFR and PP/IFR systems at high temperatures and promote the char residue formation. The CONE results revealed that IFR/AHP blends can efficiently reduce the combustion parameters of PP, such as heat release rate(HRR), total heat release(THR), smoke production rate(SPR) and so on. The morphological structures of char residue demonstrated that AHP is of benefit to the formation of a more compact and homogeneous char layer on the materials surface during burning. The analysis of XPS indicates that AHP may promote the formation of sufficient char on the materials surface and improve the flame retardant properties.     

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.     

Flame-retardant Coating by Alternate Assembly of Poly（vinylphosphonic acid） and Polyethylenimine for Ramie Fabrics

A novel intumescent flame retardant coating,consisting of poly(vinylphosphonic acid)(PVPA) as the acid source and branched polyethylenimine(BPEI) as the blowing agent,was constructed on the surface of ramie fabrics by alternate assembly to remarkably improve the flame retardancy of ramie.The PVPA/BPEI coating on the surface of individual fibers of ramie fabric pyrolyzes to form protective char layer upon heating/burning and improves the flame retardancy of ramie.Thermogravimetric analysis reveals that the PVPA/BPEI-coated ramie fabrics left as much as 25.8 wt% residue at 600 °C,while the control(uncoated) fabric left less than 1.4 wt% residue.Vertical flame test shows that all PVPA/BPEI-coated fabrics have shorter after-flame time,and the residues well preserved the original weave structure and fiber morphology,whereas,the uncoated fabric left only ashes.Microscale combustion calorimetry shows that the PVPA/BPEI coatings greatly reduce the total heat release by as much as 66% and the heat release capacity by 76%,relative to those of the uncoated fabric.     

Dispersion of graphene oxide and its flame retardancy effect on epoxy nanocomposites

Graphene oxide was prepared by ultrasonication of completely oxidized graphite and used to improve the flame retardancy of epoxy.The epoxy/graphene oxide nanocomposite was studied in terms of exfoliation/dispersion,thermal stability and flame retardancy.X-ray diffraction and transmission electron microscopy confirmed the exfoliation of the graphene oxide nanosheets in epoxy matrix.Cone calorimeter measurements showed that the time to ignition of the epoxy/graphene oxide nanocomposite was longer than that of neat epoxy.The heat release rate curve of the nanocomposite was broadened compared to that of neat epoxy and the peak heat release rate decreased as well.     

AN EVA/UNMODIFIED NANO-MAGNESIUM HYDROXIDE/SILICONE RUBBER NANOCOMPOSITE WITH SYNERGISTIC FLAME RETARDANCY

A novel EVA/unmodified nano-magnesium hydroxide(NMH)/silicone rubber ternary nanocomposite was prepared by using a special compound flame retardant of NMH and silicone rubber(CFR).The flammability of the ternary composite was studied by cone calorimeter test(CCT).Synergistic effect on flame retardancy was found between silicone rubber and NMH.EVA/CFR ternary nanocomposite showed the lowest peak heat release rate(PHRR)and mass loss rate (MLR)among the samples of virgin EVA,EVA composites.The synergistic flame retardancy of silicone rubber and NMH in EVA system is attributed to the enhanced char layers in the condensed phase that prevents the heat and mass transfer in the fire.     

PROMOTION EFFECT OF MELAMINE ON FLAME RETARDANCY OF EPOXY RESINS CONTAINING CAGED BICYCLIC PHOSPHATE

Caged bicyclic phosphate (CBP) and its dimelamine salt (PDS) were synthesized and added to epoxy resins to obtain the flame retarded epoxy resin composites. The flammability of the composites was characterized by the limiting oxygen index (LOI) and cone calorimeter tests. The LOI values of flame retarded composites increase consistently with the increase of flame retardant amounts, and they are almost the same when the loading of CBP is the same as that of PDS,although the phosphorus content of PDS is much lower than that of CBP. The total heat release increases in the order of CBP30/ER ＜ PDS30/ER ＜ PDS15/ER ＜ CBP15/ER, whereas that of specific extinction area is CBP15/ER ＞ CBP30/ER ＞ PDS30/ER ≌ PDS15/ER. PDS exhibits more effective inhibition of oxidation of combustible gases. In the tests of thermogravimetric analyses (TG) and Fourier transform infrared spectroscopy (FT-IR), it is found that the degradation of the composites is influenced greatly by the addition of flame retardants. By scanning electron microscopy (SEM), a thick and tight char-layer is observed for PDS30/ER, resulting from the interaction of nitrogen species with phosphorus species.Therefore, the combination of CBP with melamine in the flame retarded system can improve the flame retardancy greatly.     

Flammability characterization and effects of magnesium oxide in halogen-free flame-retardant EVA blends

The effects of magnesium oxide(Mg O) on the flame retardant performance of intumescent systems based on ammonium polyphosphate(APP) and pentaerythritol(PER) in ethylene vinyl acetate copolymer(EVA) were studied. The results showed that Mg O affects both the quality and quantity of residual char. There is an optimal value for the loading amount of Mg O. More or less Mg O loading may cause the formation of defective char layers and worsen the flame retardancy of EVA. According to the results of limiting oxygen index(LOI), vertical flammability test(UL94 rating) and cone calorimetry(CONE), the best flame retardancy with a strong and well intumescent char is obtained from the sample with 1 wt% of Mg O, which has the highest LOI value of 27.9, UL94 rating of V-0 and the lowest peak heat release rate of 242 k W·m?2.     

Cyclotriphosphazene Fibre Reinforced Poly(benzoxazine-co-ε-caprolactam) Nanocomposites for Flame Retardant Applications

Cyclophosphazene nanotube(PZT) incorporated poly(benzoxazine-co-ε-caprolactam)(P(BZ-co-CPL)) nanocomposites were developed for improving flame retardant properties. The effects of PZT on the flammability properties of P(BZ-co-CPL) matrix were evaluated through UL-94 flammability test and limiting oxygen index(LOI). The UL-94 results of P(BZ-co-CPL)/PZT hybrid nanocomposites showed V-1 rating, whereas neat P(BZ-co-CPL) showed burning rating. The LOI values are increased from 25.4 to 31.4 for 1.5 wt% PZT incorporated P(BZ-co-CPL) nanocomposite systems. SEM was used to study the char morphology of P(BZ-co-CPL)/PZT after being exposed to UL-94 flammability test. Data from thermal studies indicate that the PZT incorporated P(BZ-co-CPL) systems possess better Tg and thermal degradation behavior when compared to the neat P(BZ-co-CPL). The values of dielectric constant are decreased with increasing temperature. From the values, it is ascertained that the P(BZ-co-CPL)/PZT systems exhibit stable dielectric behavior with regard to variation in temperature. The TEM images ascertain the uniform dispersion of PZT in the P(BZ-co-CPL) matrix.     

Synergistic effects of layered double hydroxide with phosphorus-nitrogen intumescent flame retardant in PP/EPDM/IFR/LDH nanocomposites

<正>Synergistic effects of layered double hydroxide(LDH) with intumescent flame retardanct(IFR) of phosphorus-nitrogen (NP) compound in the polypropylene/ethylene-propylene-diene/IFR/LDH(PP/EPDM/IFR/LDH) nanocomposites and related properties were studied by X-ray diffraction(XRD),transmission electron microscopy(TEM),scanning electron microscopy(SEM),limiting oxygen index(LOI),UL-94 test,cone calorimeter test(CCT) and thermo-gravimetric analysis (TGA).The XRD and TEM results show that the intercalated and/or exfoliated nanocomposites can be obtained by direct melt-intercalation of PP/EPDM into modified LDH and that LDH can promote the IFR additive NP to disperse more homogeneously in the polymer matrix.The SEM results provide positive evidence that more compact charred layers can be obtained from the PP/EPDM/NP/LDH sample than those from the PP/EPDM/LDH and PP/EPDM/NP samples during burning.The LOI and UL-94 rating tests show that the synergetic effects of LDH with NP can effectively increase the flame retardant properties of the PP/EPDM/NP/LDH samples.The data from the CCT and TGA tests indicate that the PP/EPDM/NP/LDH samples apparently decrease the HRR and MLR values and thus enhance the flame retardant properties and have better thermal stability than the PP/EPDM/LDH and PP/EPDM/NP samples.     

Thermal stability and flame retardancy of PET/magnesium salt composites

Nano-Mg(OH)₂ (nanometre magnesium hydroxide, nano-MH) was successfully introduced into the esterification and polycondensation system by in situ polymerization to obtain PET/magnesium salt composites (PETMS). The thermal properties and flame retardancy of PETMS were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), UL-94 vertical burning and limited oxygen index (LOI) test. The DSC and TGA results show that magnesium salts in the PET matrix have little effect on the thermal properties of PET, but a significant effect on the thermal stabilities of the composites. The results of LOI and UL-94 test show PETMS have higher LOI values (≥25%) and V-0 rating without melt dripping in the UL-94 test, indicating that PETMS have good flame retardancy and anti-dripping property. Moreover, the residues of magnesium salts and composites after TGA test were also studied by Fourier transform infrared spectroscopy (FTIR) to better understand the mechanism of flame retardancy, which reveals that magnesium salts accelerate the degradation of PET and catalyze the formation of char. The SEM results show the morphological structures of the char effectively protect the composites’ internal structures and inhibit the heat, smoke transmission and reduce the fuel gases when the fire contacts them.     

Synthesis of functionalized α-zirconium phosphate modified with intumescent flame retardant and its application in poly(lactic acid)

A novel functionalized α-zirconium phosphate (F-ZrP) modified with intumescent flame retardant was synthesized by co-precipitation method and characterized. Poly (lactic acid) (PLA)/F-ZrP nanocomposites were prepared by melt blending method. The thermal stability and combustion behavior of PLA/F-ZrP nanocomposites were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94), scanning electronic microscopy (SEM), and cone calorimeter test (CCT). The results showed that the addition of flame retardant F-ZrP slightly affect PLA's thermal stability, but significantly improve the flame retardancy of PLA composites. In comparison with neat PLA, the LOI value of PLA/F-ZrP was increased from 19.0 to 26.5, and the UL-94 rating was enhanced to V-0 as the loading of F-ZrP at 10%. SEM results suggested the introduction of F-ZrP in the PLA system can form compact intumescent char layer during burning. All these results showed that the F-ZrP performed good flame retardancy for PLA.     

Preparation and flammability of a novel intumescent flame-retardant poly(ethylene-co-vinyl acetate) system

A phosphorus-containing flame retardant, 4-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinan-2-yloxymethyl)-2,6,7-trioxa-1-phospha-bicyclo[2.2.2]octane-1-oxide (MOPO), was synthesized successfully and characterized. The flame retardancy and thermal behavior of a new intumescent flame-retardant (IFR) system for EVA, which was made of MOPO and ammonium polyphosphate (APP), were investigated by limiting oxygen index (LOI) test, vertical burning test (UL-94), cone calorimeter, and thermogravimetric analysis (TGA). An LOI value of 28.4 and UL-94 V-0 rating can be achieved when the total loading of MOPO and APP was 30 wt.%. The results from cone calorimeter indicate that both the heat release rate (HRR) and the total heat release (THR) of IFR-EVA decreased significantly compared with those of neat EVA. TG curves showed that the amount of residues increased significantly when intumescent additives were added; it also could be found that the LOI values increased with the increase in char residues. Meanwhile, morphology of the residues obtained from burning IFR-EVA in LOI test was studied through the SEM observations and rich compact char layers could explain the excellent flame retardance.     

磷化淀粉的合成及其与聚磷酸铵协效阻燃聚乳酸的性能研究

利用9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)和马来酸酐(MA)对淀粉进行改性得到磷化淀粉(DOPOMASt),通过红外光谱(FTIR)、核磁共振谱(1H-NMR)和X射线光电子能谱(XPS)确定其结构.利用DOPOMASt作为碳源,与聚磷酸铵(APP)复配后通过熔融共混制备了阻燃聚乳酸(PLA)...     

Synthesis of organo-modified α-zirconium phosphate and its effect on the flame retardancy of IFR poly(lactic acid) systems

Novel intumescent flame-retardant poly(lactic acid) (PLA/IFR)/organo-modified α-zirconium phosphate(OZrP) nanocomposites were prepared via incorporation of charring agent (CA), ammonium polyphosphate (APP) and OZrP into PLA. OZrP was synthesized directly by a solvent thermal method. The morphological characterization of PLA/IFR/OZrP nanocomposites was conducted by wide angle X-ray diffraction (WXRD) and transmission electron microscopy (TEM). The effect of the OZrP on flame retardancy and the thermal stability of PLA/IFR composites were studied by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test. The TGA data illustrated that the OZrP could increase the residue and significantly improve the flame retardancy of PLA/IFR/OZrP nanocomposites showing an excellent synergistic effect. The addition of OZrP to the flame-retardant PLA increases the LOI and enhances the UL-94 rating. Cone calorimeter tests gave clear evidence that the incorporation of OZrP into PLA/IFR composites resulted in the significant reduction of the heat release rate (HRR), low total heat release (THR) and high amount of char residues during combustion. The flame-retardant mechanism of PLA/IFR/OZrP nanocomposites may correspond to the intumescent flame-retardant mechanism and catalyzed carbonization mechanism caused by OZrP.     

Synergistic effects between a triazine-based charring agent and aluminum phosphinate on the intumescent flame retardance of thermoplastic polyether ester

The triazine-based charring agent (CFA) with perfect charring ability was synthesized and characterized. The synergistic effects between CFA and aluminum phosphinate (AlPi) on flame retardancy, thermal degradation, and flammability properties of thermoplastic polyester-ether elastomer (TPEE) were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test (CCT), thermogravimetric analysis (TGA), laser Raman spectroscopy (LSR) and scanning electron microscopy (SEM). The results from UL-94 test showed that, by compounding 14 wt% AlPi and 4 wt% CFA with TPEE, the LOI value reached 28.5% and the UL-94 rating reached V-0 (1.6 mm). TGA results indicated that there is good synergistic charring ability between CFA and AlPi, especially the increased residues at high temperature (T > 700 °C). The CCT test results showed that CFA could change the combustion behavior of TPEE and effectively accelerate the formation of expanded carbon layers. The residues after combustion were measured by LRS and SEM, demonstrating that CFA can promote the formation of dense and stable carbon layers during the combustion, which could inhibit the melt dropping and improve the fire retardancy of TPEE composites. Thus, CFA was a promising synergistic agent in halogen-free flame retardant TPEE.     

聚磷酸酯阻燃剂复配聚磷酸铵对环氧树脂阻燃性能的影响

合成了一种9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)的衍生物——聚苯氧基磷酸-2-10-氢-9-氧杂-磷杂菲基对苯二酚酯(POPP), 以间苯二胺(m-PDA)为固化剂, 环氧树脂(EP)为基料, POPP为阻燃剂, 复配聚磷酸铵(APP), 制备了不同磷含量的阻燃环氧树脂. 利用极限氧指数(LOI)和垂直燃烧(UL94)实验表征了环氧树脂的阻燃性能; 以热重分析、 锥型量热和扫描电镜分析了阻燃环氧树脂的热性能和表面形态. 研究结果表明, 阻燃剂总加入量(质量分数)为5%时即可达到UL94 V-0级, 同时LOI值为27.7%; 当总加入量为15%, 即w_POPP=5%, w_APP=10 %时, 其LOI值可达到33.8%. 随着磷含量的增加, 阻燃环氧树脂的初始降解温度略有降低, 但高温下的残炭率明显增加. POPP/APP的加入在很大程度上降低了环氧树脂的热释放速率、 有效燃烧热、 烟释放量和有毒气体释放量. 阻燃环氧树脂在高温下形成比较稳定的致密膨胀炭层, 为底层的环氧树脂主体隔绝了分解产物及热量和氧气交换, 增强了高温下的热稳定性.     

Effect of a phosphorus-containing flame retardant on the thermal properties and ease of ignition of poly(lactic acid)

An aryl polyphenylphosphonate, poly(9-oxa-10-(2,5-dihydro-xyphenyl) phospha-phenanthrene-10-oxide) phenylphosphonate (WLA-3), was used to prepare a flame-retardant poly(lactic acid) (PLA) by direct melt compounding. The thermal behaviour, burning behaviour and mechanical properties of the flame-retardant PLA systems have been investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), vertical burning test (UL-94), limiting oxygen index (LOI), cone calorimeter test (CCT) and tensile test. The flame retardance mechanism has been studied via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and P content analysis. The UL-94 ratings of PLA’s containing 7phr (W_7P) and 10phr (W_10P) of WLA-3 were enhanced to V-0 from no rating for neat PLA. However, the cone calorimetry of flame-retardant PLA (W_7P) only showed a little decrease in heat release rate (HRR), peak of heat release rate (PHRR) and total heat release (THR) compared to neat PLA. TGA results showed that the PLA containing different amounts of WLA-3 presented more complicated thermal decomposition behaviours than neat PLA. Additionally, the results from DSC and tensile tests showed that the addition of WLA-3 into PLA had a slight impact on the crystallization behaviours and tensile properties.     

磷腈类衍生物改性磷酸锆的合成及其复配聚磷酸铵对硅橡胶阻燃性能和力学性能的影响

利用原位插层反应制得磷腈类衍生物修饰的改性磷酸锆(F-ZrP),并用机械共混工艺制得阻燃硅橡胶复合材料(FRSR).采用X射线衍射(XRD)、透射电子显微镜(TEM)、傅立叶红外光谱(FTIR)、热重(TG)、扫描电子显微镜(SEM)分别对磷酸锆的结构及其在硅橡胶基体的分散进行表征,并结合FRSR的垂直燃烧(UL-94)、极限氧指数(LOI)、锥形量热测试及残渣表面形貌的观察,研究了不同份数的F-ZrP复配聚磷酸铵对FRSR阻燃性能的影响并和添加未改性磷酸锆的样品性能对比,并对阻燃机理进行初步探讨;最后分析FRSR的力学性能.结果表明:F-ZrP拥有更大的层间距,而且在FRSR中分散的更好;当1 phr F-ZrP和19 phr APP复配使用时,UL-94达V-0级且LOI值为31.4,热释放速率峰值为265.3 kW/m~2,拉伸强度达8.11 MPa,FRSR的阻燃性能和力学性能得到明显的改善.适量的F-ZrP和APP复配使用能在气相和固相发挥协效阻燃作用,F-ZrP与APP的并用能提高残渣质量并且使阻隔层更加紧实,致密.