Synthesis of a bio-based triazine derivative and its effects on flame retardancy of polypropylene composites

A triazine derivative CC–Cy was synthesized using cytosine (Cy) and cyanuric chloride (CC). The CC–Cy was used as a charring agent and combined with ammonium polyphosphate (APP) to form an intumescent flame-retardant (IFR) system. The IFR system was applied to improve the flame retardancy of polypropylene (PP). Moreover, bisphenol-A bis(diphenyl phosphate) (BDP) was introduced in the IFR system to regulate the suitability between the IFR and PP. The results showed the PP containing 20 wt % APP and 5 wt % CC–Cy achieves the UL-94 V-2 rating. While the PP with 18 wt % APP/CC-Cy (4:1) and 3 wt % BDP obtains the UL-94 V-0 rating indicating the improved flame-retardant efficiency. Thermal degradation behaviors and char morphology both showed that the reactions between APP and CC–Cy promote the formation of char residues, and BDP works in gas phase to enhance the flame retardancy of PP composites. Thus, a synergistic IFR system based on APP, CC–Cy, and BDP is formed, which can protect PP from fire effectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47367.     

Microencapsulation of ammonium polyphosphate: Preparation,characterization, and its flame retardance in polypropylene

Microencapsulated ammonium polyphosphate (MCAPP) with a melamine–formaldehyde (MF) resin coating layer was prepared by in situ polymerization. MCAPP was characterized by Fourier transform infrared, X‐ray photoelectron spectroscopy, and so on. The results show that the microencapsulation with MF resin leads to a decrease in the particles' size and water absorption. The flame retardant action and mechanism of MCAPP and ammonium polyphosphate (APP) in polypropylene are studied using limiting oxygen index (LOI) and UL 94 test, and their thermal stability is evaluated by thermogravimetric analysis. The LOI value of the PP/MCAPP composite at 30 wt% loading is 30.5%, whereas the corresponding value of the PP/APP composite is only 20%. Moreover, the LOI values of the PP/MCAPP/PER composites are higher than the ones of the PP/APP/PER composites. In the UL 94 test, the PP/MCAPP/PER composites with suitable ratios of MCAPP to PER can reach the V‐0 rating, and the best rating of the PP/APP/PER composites is V‐1. V‐1. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Synergistic effect between silicone‐containing macromolecular charring agent and ammonium polyphosphate in flame retardant polypropylene

A novel silicone‐containing macromolecular charring agent (Si‐MCA) was synthesized via polycondensation, and it was combined with ammonium polyphosphate (APP) to flame retard polypropylene (PP). The results showed that Si‐MCA exhibited a good synergistic effect with APP in flame retardant PP. When the content of APP was 18.7 wt % and Si‐MCA was 6.3 wt %, the limiting oxygen index value of the PP/APP/Si‐MCA composite was 33.5%, and the vertical burning (UL 94) test classed a V‐0 rating. The peak heat release rate, total heat release, average mass loss rate, and total smoke production of the composite were also decreased significantly. Moreover, the PP/APP/Si‐MCA composite showed an outstanding water resistance. After soaking in 70°C water for 168 h, the PP/APP/Si‐MCA composite could still reach a UL 94 V‐0 rating at 20.0 wt % IFR loading, whereas the PP/APP/PER composite failed to pass the UL 94 test even at 25.0 wt % IFR loading. Thermogravimetric analysis, thermogravimetry‐Fourier transform infrared spectrometry, and scanning electron microscopy‐energy dispersive X‐ray spectrometry results revealed that a compact and thermostable intumescent char was formed by APP/Si‐MCA during burning, thus effectively improved the flame retardancy of PP. The possible synergistic mechanism between APP and Si‐MCA was also discussed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41580.     

Crosslinking of β-cyclodextrin and combining with ammonium polyphosphate for flame-retardant polypropylene

This work presents the synthesis of crosslinked hexamethylene diisocyanate β-cyclodextrins (HDI-CDs) by reacting β-cyclodextrin (β-CD) with HDI as a crosslinking agent at different feed ratios. As a novel char-forming agent, the HDI-CDs are combined with ammonium polyphosphate (APP) and applied in polypropylene (PP) to form intumescent flame-retardant composites. The structure of HDI-CDs is characterized by Fourier transform infrared spectra (FTIR), ¹³C nuclear magnetic resonance spectroscopy, and nitrogen adsorption–desorption test. The thermogravimetric analysis (TGA) results indicate that HDI-CDs have better char-forming performance than β-CD. FTIR spectra, X-ray diffraction, and Raman spectra characterization demonstrate that the reaction between HDI-CDs and APP contributes to the formation of a more stable char layer than β-CD and APP. According to the results of TGA, scanning electron microscopy, limiting oxygen index (LOI), UL-94, and X-ray photoelectron spectroscopy test, when the crosslinking degree of HDI-CDs is high enough (not less than β-CD:HDI = 1:3.6), the PP/APP/HDI-CDs composites can form a compact and dense char layer during combustion. Among all composites, PP/APP/HDI-CD(4) shows the best flame-retardant performance, which can pass the UL 94 V-0 rating with an LOI value of 32.8% when the loading of flame retardants is 28 wt %. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48320.     

Application of waste silicon rubber composite treated by N2 plasma in the flame-retardant polypropylene

The waste silicon rubber composite insulator (WSiRC) was applied along with ammonium polyphosphate (APP) and pentaerythritol (PER) to improve the flame retardancy of polypropylene (PP) in this study. Considering the compatibility among PP, WSiRC, and flame-retardant additives, WSiRC was treated by acid and N₂ plasma to obtain the plasma-treated WSiRC (PLSiR), which decreases the amount of the inorganic additive and grafts amino groups onto the surface of the silicon rubber. The infrared spectrocopy (IR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) confirm that NH₂ groups have been grafted onto the surface of PLSiR. The TGA data also show that PLSiR had the char improving ability and promote the crosslink of APP, which results in its promotion for the flame retartancy of PP proved by the data of limiting oxygen index (LOI), UL94 rating and cone tests. It is also showed that PLSiR is superior than the WSiRC treated only by acid (ASiR) due to the differences in the structure and polarity. Moreover, the improvement of PLSiR on the flame retardancy of PP is dependent on its amounts. It is indicated that the 1 wt % loading of PLSiR in PP with APP and PER has the highest LOI value of 30.9 and reached UL94 rating V-0. The peak heat release rate (pHRR) and total heat release (THR) values are also decreased by 68.7 and 15%, respectively. SEM and Raman results show the condensed mechanism is ascribed to the PP/APP-PER/PLSiR system because the quality of char affect the flame retardancy of PP. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48187.     

Synthesis of a novel char-forming agent (PEIC): Improvement in flame retardancy,thermal stability,and smoke suppression for intumescent flame-retardant polypropylene composites

A novel char-forming agent named PEIC was designed and synthesized combining pentaerythritol octahydrogen tetraphosphate (PEPA) and tris(2-hydroxyethyl) isocyanurate. PEIC was combined with the silica-gel-microencapsulated ammonium polyphosphate (OS-MCAPP), preparing intumescent flame-retardant polypropylene (PP) composites. The results of the limiting oxygen index (LOI) show that the composite containing 30 wt % IFR with OS-MCAPP:PEIC = 2:1 presents the optimal LOI of 32.7%. Meanwhile, the cone calorimeter tests show that its peak heat release rate is 432 kW m⁻², which decreases by 62.1% compared with that of pure PP, showing a high-efficient flame retardancy. The exhibited UL-94 V-0 rating for all the composites indicates that the IFR composed of PEIC and OS-MCAPP has high-efficient flame retardancy in PP. The analysis of residue char reveals that PEIC could improve the quality of char in compactness, intumescentia, and the degree of graphitization. Further, the effect of IFR on the mechanical properties of PP composites was also evaluated and discussed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48296.     

Synergistic effects of hydroxy silicone oil on intumescent flame retardant polypropylene system

The effects of hydroxy silicone oil as a synergistic agent on the flame retardancy of intumescent flame retardant polypropylene composites (IFR-PP) were studied, and the IFR system mainly consisted of the ammonium polyphosphate (APP), melamine (MEL) and pentaerythritol (PER). The UL 94 rating, thermogravimetric analysis (TGA), cone calorimeter (CONE) and digital photograph were used to evaluate the synergistic effects of hydroxy silicone oil (HSO). It has been found that the PP composite containing only APP, MEL and PER does not show good flame retardancy at 30% additive level. The cone calorimeter results show that the heat release rate, mass loss rate, mass, total heat release, carbon monoxide and carbon dioxide of PP/APP/MEL/PER/HSO composites decrease in comparison with the PP/APP/MEL/PER composite. The digital photographs demonstrated that HSO could promote to form the homogenous and compact intumescent char layer. Thus, a suitable amount of HSO plays a synergistic effect in the flame retardancy.     

Preparation and characterization of double shell microencapsulated ammonium polyphosphate and its flame retardance in polypropylene

Microencapsulated ammonium polyphosphate (MUFAPP) with a double shell is prepared by in situ polymerization, and is characterized by FTIR, XPS and SEM, etc. The microencapsulation of APP can increase its flame retardance and water resistance in PP. The flame retardant action of MUFAPP and APP in PP are studied using LOI and UL 94 test, and their thermal stability is evaluated by TG. The LOI value of the PP/MUFAPP composite at the same loading is higher than that of PP/APP composite. The LOI values of the PP/MUFAPP/ dipentaerythritol are higher than that of the PP/MUFAPP, and UL 94 ratings of most ternary composites are raised to V-0 at 30 wt.% loading. The results of the cone calorimeter also indicate that MUFAPP is an effective flame retardant in PP. The thermal degradation behaviors of APP and MUFAPP are studied using TG and dynamic FTIR.     

Flame retardant and mechanical properties of epoxy composites with ammonium polyphosphate and hyperbranched silicon-containing polymers

The epoxy resin was mixed with ammonium polyphosphate (APP) and hyperbranched silicon-containing polymers (HBP-B2). The cured composites were investigated by thermogravimetric analysis, Underwriters Laboratory standard for the flammability properties under vertical burning (UL-94V), and limited oxygen index (LOI) test methods. The LOI of 43.5 and could be obtained at the weight ratio of 70:25:5 for the epoxy resin:APP:HBP-B2, Sample A25B5, and the LOI was higher than that of the composite with 30 wt % APP only, Sample A30B0, of which the LOI was 34.5. It suggested that the HBP-B2 could cooperate with the epoxy/APP composite to form a more effective protection layer during combustion, which resulted in a higher second-stage thermal degradation temperature. During the UL-94V test, the flame was extinguished immediately once the burner was removed. Furthermore, the tensile and impact strength of the epoxy/APP composite could also be improved by using HBP-B2 compound as the toughening agent. The composite containing 20% of APP and 10% of HBP-B2, Sample A20B10, still had excellent flame retardant properties with a V-0 rating. Moreover, the tensile strength and impact strength of that composite got 19 and 25% increases compared with the Sample A30B0, which contained 30% of APP only. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48857.     

Vinyl polysiloxane microencapsulated ammonium polyphosphate and its application in flame retardant polypropylene

Vinyl polysiloxane microencapsulated ammonium polyphosphate (MAPP) was prepared by a sol-gel method using vinyltrimethoxysilane as a precursor to improve its thermal stability and hydrophobicity. The MAPP was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and thermogravimetric analyzer (TGA). The results showed that ammonium polyphosphate (APP) was successfully coated with vinyl polysiloxane. MAPP and pentaerythritol (PER) were used together to improve the flame retardancy of polypropylene (PP). The flame retardant properties of PP composites were investigated by limiting oxygen index (LOI), UL-94 test, TGA and SEM. When the MAPP was added as a flame retardant, with PER as a char forming agent, the LOI of PP/MAPP/PER composites was 33.1%, and it reached the UL-94 V-0 level. The results also demonstrated that the flame retardant properties of PP/MAPP/PER composites were better than those of PP/APP/PER composites at the same loading. Moreover, the addition of flame retardant and carbon forming agent could promote the crystallization behavior of PP.     

Synthesis of amino trimethylene phosphonic acid melamine salt and its application in flame‐retarded polypropylene

Amino trimethylene phosphonic acid melamine salt (MATMP) was synthesized and used as acid source and blowing agent in intumescent flame‐retarded polypropylene (PP); its compositions were characterized by Fourier transform infrared spectroscopy and X‐ray powder diffraction. An intumescent flame retardant (IFR) system composed of MATMP, pentaerythritol (PER), and PP was tested by limiting oxygen index (LOI), UL‐94, cone calorimeter tests, and thermogravimetric analysis and compared with an ammonium polyphosphate (APP)/PER system. The results showed that MATMP had better water resistance than APP, the LOI value of PP/MATMP/PER composite can reach 30.3%, and a UL‐94 V‐0 rating can be reached at 25 wt % IFR loading. The amount of residual char of IFR MATMP/PER was 20.3 and 9.5 wt % at 400 and 600 °C, respectively. A thermooxidative degradation route and a possible flame‐retardant mechanism of IFR were proposed according to the analysis of evolved gases and residual chars. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46274.     

苯基聚硅氧烷微胶囊化聚磷酸铵的制备及其在PP中阻燃性能研究

采用苯基三甲氧基硅烷为前驱体,通过溶胶凝胶法制备出苯基聚硅氧烷微胶囊化聚磷酸铵（MAPP）。将MAPP作为阻燃剂,季戊四醇（PER）作为成炭剂,制备阻燃聚丙烯（PP）。用傅里叶红外光谱、扫描电子显微镜、能谱仪及热重分析仪对MAPP进行表征。结果表明,聚磷酸铵（APP）被苯基聚硅氧烷成功包覆;较之APP,MAPP的热稳定性和疏水性显著提高;MAPP的阻燃性能优于APP,PP/MAPP/PER复合材料达到V-0级别;阻燃剂及成炭剂的加入对PP的结晶行为有促进作用。     

凹凸棒对聚丙烯/聚磷酸铵/季戊四醇复合材料阻燃性能及力学性能的影响

以聚丙烯为基体,多聚磷酸铵(APP)/季戊四醇(PER)/凹凸棒(ATP)为复配阻燃剂(其中APP/PER质量比为3:1),通过熔融共混的方法制备聚丙烯复合材料.采用透射电子显微镜(TEM)考察原土ATP的微观形貌和PP/APP/PER/ATP复合材料的阻燃性能及力学性能.实验结果表明:ATP与APP/PER对PP有协同阻燃作用.当ATP质量含量为2%,复配阻燃剂APP/PER/ATP总量为26%时,PP/APP/PER/ATP复合材料的氧指数为32%,拉伸强度比纯PP提高4.3%,冲击强度比纯PP也提高15.2%.     

Study of Fire Retardancy and Thermal and Mechanical Properties of HDPE-Wood Composites

This article reports a study of flame retardancy and thermal and mechanical properties of wood-plastic composites (WPCs) based on high-density polyethylene and pine flour. The study shows that sample composition plays an important role in WPCs' properties. The influence of additives like fillers (SiO₂ or CaCO₃) and flame retardants ammonium polyphosphate (APP) and pentaerythritol (PER) on WPCs' properties has been considered. The best properties are shown in samples using SiO₂ as filler and treated with the intumescent fire retardant APP/PER. Such samples have excellent fire retardancy with V-0 rating (UL-94 test) and imply that APP/PER fire retardant ensures effective fire retardancy for WPCs.     

Flame retardancy of unsaturated polyester composites with modified ammonium polyphosphate,montmorillonite, and zinc borate

Ammonium polyphosphate (APP) was modified using a new method, where the resulting modified APP (MAPP) was obtained by mixing APP with unsaturated polyester resin (UPR). MAPP was more effective in improving the flame retardancy of UPR than APP which was due to the improved dispersion of MAPP in UPR composite. Then, the UPR composites were prepared based on dimethyl methylphosphonate, MAPP, montmorillonite, and zinc borate. Finally, the flame-retardant and mechanical properties of the UPR composites were analyzed using the limited oxygen index (LOI), thermogravimetric analysis, UL-94 vertical burning test, scanning electron microscopy, cone calorimetry, mechanical tests, and viscosity measurements. The LOI and UL-94 tests showed that the flame-retardant properties clearly improved with the addition of fillers in the UPR composites compared to pristine UPR. The synergistic effect of Si- and P-containing flame retardants in this composite resulted in the LOI value increasing from 18.9 to 31.3% and achieved the UL-94 V-0 rating. Moreover, the heat release rate was lower than the pristine UPR. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47180.     

Surface modification of magnesium hydroxide and its application in flame-retardant oil-extended styrene–ethylene–butadiene–styrene/polypropylene composites

Magnesium hydroxide (MH) was modified with triethoxysilane and polymethyl–vinyl silicone rubber and used to prepare flame-retardant oil-extended styrene–ethylene–butadiene–styrene (O-SEBS)–polypropylene (PP) composites. The water contact angle of modified magnesium hydroxide (MMH) reached 141°; this indicated that MMH possessed excellent hydrophobic properties. The samples (1.6 mm) passed the UL-94 V-0 rating during vertical burning tests when the loading amount of MH or MMH was 70 wt %. This indicated the modification did not decrease the flame-retardant properties of MH. The tensile strength and elongation at break values of the MMH–O-SEBS–PP composites increased by 20.4 and 88.9%, respectively, compared with those of the MH–O-SEBS–PP composites. The modification of MH enhanced the interfacial compatibility between the flame retardant and the matrix; thus, the mechanical performance was enhanced. Moreover, MMH was scarcely extracted after water treatment for 168 h at 70 °C. As a result, the mechanical properties and flame retardancy of the MMH–O-SEBS–PP composites were well maintained after the water treatment. The modification of the MH endowed the O-SEBS–PP composites with an excellent compatibility and water-resistant performance. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47129.     

Microencapsulation of APP‐I and influence of microencapsulated APP‐I on microstructure and flame retardancy of PP/APP‐I/PER composites

In this article, the microencapsulated ammonium polyphosphate crystalline with form I (APP‐I) coated with melamine‐formaldehyde (MF) was prepared by in situ polymerization. Results of Fourier transform infrared spectra (FTIR), thermogravimetry (TG) energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) demonstrate that APP‐I is successfully microencapsulated with MF. Compared with APP‐I, the microencapsulated APP‐I with MF (MFAPP‐I) is of much smaller spheroidal particle size and lower solubility in water. In this study, the polypropylene (PP)/APP‐I/penpaerythritol (PER) and PP/MFAPP‐I/PER composites are prepared, and flame retardancy, thermal stability, and microstructure of corresponding composites are carefully investigated by limiting oxygen index (LOI), UL‐94 testing, TG, EDS, and SEM. Experimental results show that PP/MFAPP‐I/PER composites have advantages over PP/APP‐I/PER composites in terms of flame retardant properties and water resistance. Results of TG, SEM, and EDS show that the microencapsulated APP‐I with MF resin is conducive to increase the amount of residual yield and improve thermal stability of PP/MFAPP‐I/PER composites and the compatibility and dispersion of MFAPP‐I. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of charring agent THEIC on flame retardant properties of polypropylene

Tris(2‐hydroxyethyl) isocyanurate (THEIC) was used as charring agent and combined with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) for polypropylene (PP). The flame retardancy and combustion performance of PP/IFR composite was tested by limiting oxygen index (LOI), UL‐94 vertical burning test and cone calorimeter. The results showed that PP/IFR composite had highest LOI of 34.8 and obtained V‐0 rating when 30 wt % IFR was loaded and mass ratio APP/THEIC was 2 : 1. The peak heat release (PHRR) and total heat release (THR) values of PP composite containing FRs were remarkably reduced compared with that of pure PP. However, water resistant test demonstrated the PP/IFR composite had poor flame retardant durability, both the LOI value and UL‐94 V‐rating decreased when PP/IFR composite was soaked in water at 70°C after 36 h. The degradation process and the char morphology of IFR and PP/IFR composite were investigated by TGA and SEM images. The possible reaction path between APP and THEIC in the swollen process was proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41214.     

Modified polyaniline and its effects on the microstructure and antistatic properties of PP/PANI‐APP/CPP composites

Polypropylene (PP) composites that contain poly(aniline) (PANI) and ammonium polyphosphate crystalline form II (APP‐II) have both antistatic and flame‐retardant properties. In the present study, double anti‐functional PANI was prepared via in situ polymerization in the presence of APP‐II. Analysis of the Fourier transform infrared spectra demonstrated that PANI was synthesized successfully with APP‐II and that modified PANI (PANI‐APP) was obtained. Next, PP/PANI‐APP/chlorinated poly(propylene) (CPP) and PP/PANI/CPP composites were prepared. The results showed that the volume resistivity of the PP/PANI‐APP/CPP composite was at least 100 times less than that of the PP/PANI/CPP composite. The microstructures of the corresponding composites were investigated carefully by scanning electron microscopy and wide angle X‐ray diffraction. The areas of the conductive regions and the percentage crystallinity of PP in the PP/PANI‐APP/CPP composite were distinctly higher than those in the PP/PANI/CPP composite, i.e., by about 10% and 7%, respectively. In addition, experimental analyses of the limiting oxygen index and thermogravimetry showed that the PP/PANI‐APP/CPP composite had advantages compared with PP in terms of its flame‐retardant properties thermal stability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40732.     

Intumescent Flame Retardation of EVA Using Microencapsulated Ammonium Polyphosphate and Pentaerythritols

With a melamine-formaldehyde (MF) resin coating layer, microencapsulated ammonium polyphosphate (MCAPP) is prepared by in situ polymerization and is characterized by XPS and water leaching test. The microencapsulation of APP with the MF resin leads to a decrease in the particle's water leaching rate. The flame-retardant action of MCAPP and APP in EVA are studied using LOI and UL 94 test, and their thermal stability is evaluated by thermogravimetric analysis (TGA). The LOI value of the EVA/MCAPP composite at the same loading is higher than the value of the EVA/APP composite. In comparison with the EVA/MCAPP composites, it is found that the LOI values of the EVA/MCAPP/PER and EVA/MCAPP/DPER ternary composites at the same additive loading increase, and UL 94 ratings of most ternary composites are raised to V-0. The water-resistant properties of the EVA composites are studied, and the results of the composites containing with APP and MCAPP are compared. Moreover, the peroxide cross-linking of the EVA composites is investigated, and the mechanical properties and thermal stability of the composites increase after the cross-linking.