Effects of two kinds of THEIC‐based charring agents on flame‐retardant properties of polylactide

Two charring agents tris (2‐hydrooxyethyl) isocyanurate terephthalic acid ester, (dimer/trimer mixture TT23, and tetramer TT4) were synthesized by using tris (2‐hydrooxyethyl) isocyanurate (THEIC) and terephthalic acid (TPA) as raw materials. These two charring agents were combined with ammonium polyphosphate (APP) to form intumescent flame retardants (IFR) for polylactide (PLA). The thermal stability of IFRs were tested by TGA, it is found that APP/TT4 mixture has a higher thermal stability and a better char forming ability than that of APP/TT23 mixture. The combustion properties and thermal stability of PLA/APP/TT23 and PLA/APP/TT4 composites were evaluated by UL‐94 burning tests, limiting oxygen index (LOI), cone calorimeter tests and TGA, the chemical structure of char residues were analyzed by FTIR and XPS. It can be concluded that PLA with 30 wt % of APP/TT4 (weight ratio 5 : 1) achieved the greatest flame retardancy. Moreover, the continuous and expansionary char layer observed from SEM images proved better char forming ability of TT4 than that of TT23. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42086.     

Synthesis of tris(2‐hydroxyethyl) isocyanurate homopolymer and its application in intumescent flame retarded polypropylene

A macromolecular homopolymer (named as Homo‐THEIC) was synthesized through self‐etherification of tris(2‐hydroxyethyl) isocyanurate (THEIC) molecules and used as charring agent. Its chemical structure was characterized by FTIR and ¹³C‐NMR. The charring agent was mixed with ammonium polyphosphate (APP) and applied in flame retarded polypropylene (PP). Results of UL‐94, LOI, and cone calorimeter test showed that the LOI of flame retarded PP can reach 32.8% and UL‐94 V‐0 rating can be achieved at 30 wt % loading. The heat release rate and smoke production rate during the combustion of PP were substantially reduced. TGA results indicated that the synergistic effect between APP and Homo‐THEIC existed and the addition of intumescent flame retardant (IFR) dramatically enhanced the thermal stability of PP. According to the results of TGA, SEM, TG‐FTIR, FTIR, and Raman, the char forming process of IFR can be separated into three stages: the formation of viscous phosphate ester (T _onset?330 °C), the expanding process along with the decomposition of phosphate ester and the release of a large amount of gases (330–480 °C), and the final formation of graphitic‐like char without any expanding feature (480–670 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44663.     

Synergistic effect between aluminum hypophosphite and a new intumescent flame retardant system in poly(lactic acid)

A hyperbranched charring agent (CT) was synthesized by triglycidyl isocyanurate and diethylenetriamine in water, and a new intumescent flame retardant (IFR) system was formed by ammonium polyphosphate (APP) and CT. The different formula and synergistic system between IFR and aluminum hypophosphite (AHP) have been studied through limit oxygen index (LOI), UL‐94, cone calorimetry test and TGA. It was found that the LOI for poly(lactic acid) (PLA) with 30 APP/CT (4:1) and 20 wt % IFR/AHP (3:1) were 41.2% and 43.5%, respectively, and the both could achieve UL‐94V‐0 rating with no melt dripping. The heat release rate (HRR), maximum HRR value and average mass loss rate of PLA could be dramatically decreased by combination of IFR and AHP while the thermal stability was greatly enhanced. The study of morphology and structure of char illustrated that more intumescent and compact char layer with good intensity was formed during the degradation of IFR/AHP, which resulting to better flame retardancy and anti‐dripping than IFR or AHP alone. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46359.     

Synthesis of novel triazine charring agent and its effect in intumescent flame‐retardant polypropylene

A novel charring agent (CNCA‐DA) containing triazine and benzene ring, using cyanuric chloride, aniline, and ethylenediamine as raw materials, was synthesized and characterized. The effects of CNCA‐DA on flame retardancy, thermal degradation, and flammability properties of polypropylene (PP) were investigated by limited oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), and cone calorimeter test (CCT). The TGA results showed that CNCA‐DA had a good char forming ability, and a high initial temperature of thermal degradation; the char residue of CNCA‐DA reached 18.5% at 800°C; Ammonium polyphosphate (APP) could improve the char residue of APP/CNCA‐DA system, the char residue reached 31.6% at 800°C. The results from LOI and UL‐94 showed that the intumescent flame retardant (IFR) containing CNCA‐DA and APP was very effective in flame retardancy of PP. When the mass ratio of APP and CNCA‐DA was 2 : 1, and the IFR loading was 30%, the IFR showed the best effect; the LOI value reached 35.6%. It was also found that when the IFR loading was only 20%, the flame retardancy of PP/IFR can still pass V‐0 rating in UL‐94 tests, and its LOI value reached 27.1%. The CCT results demonstrated that IFR could clearly change the decomposition behavior of PP and form a char layer on the surface of the composites, consequently resulting in efficient reduction of the flammability parameters, such as heat release rate (HRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP), and mass loss (ML). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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.     

Influence of polyamide 6 as a charring agent on the flame retardancy,thermal, and mechanical properties of polypropylene composites

In this work, polyamide 6 (PA6) as a charring agent has been used in combination with thermoplastic polyurethane (TPU)‐microencapsulated ammonium polyphosphate (MTAPP) forming intumescent flame retardants (IFRs) which applies in polypropylene (PP). The effects of the IFRs on the flame retardancy, morphology of char layers, water resistance, thermal properties and mechanical properties of flame‐retardant PP composites are investigated by limiting oxygen index (LOI), UL‐94 test, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and mechanical properties test. The results show that the PP/MTAPP/PA6 composites exhibit much better flame‐retardant performances than the PP/MTAPP composites. The higher LOI values and UL‐94 V‐2 of the PP/MTAPP composites with suitable amount of PA6 are obtained, which is attributed to the thick and compact char layer structure evidenced by SEM. The results from TGA and DSC demonstrate that the introduction of PA6 into PP/MTAPP composites has a great effect on the thermal stability and crystallization behaviors of the composites. Furthermore, the mechanical properties of PP/MTAPP/PA6 composites are also improved greatly due to the presence of PA6 as a charring agent. POLYM. ENG. SCI., 55:1355–1360, 2015. © 2015 Society of Plastics Engineers     

Synthesis of phospholipidated β‐cyclodextrin and its application for flame‐retardant poly(lactic acid) with ammonium polyphosphate

In this study, phospholipidated β‐cyclodextrin (PCD) was obtained by the condensation between β‐cyclodextrin and phenyl phosphonic acid dichloride, which was characterized by Fourier transform infrared (FTIR) spectra, ¹H‐NMR, and thermogravimetric analysis (TGA). The thermal stability and flame retardancy of the poly(lactic acid) (PLA) blends [PLA–ammonium polyphosphate (APP)–PCD] were measured by TGA coupled to FTIR spectroscopy, vertical burning test (UL‐94), limiting oxygen index (LOI), and cone calorimetry tests. The results show that the mass ratio and loading amount of APP and PCD affected the properties of PLA. When the loading of APP and PCD was 30 wt % and the mass ratio of APP to PCD was 5:1, the highest LOI value of 42.6% (that of neat PLA was 19.7%) and a UL‐94 V0 rating were achieved, and the reduction of the total heat release was greater than 80%. Even when the total amount of APP and PCD was decreased to 20 wt % with the same mass ratio, the flame‐retardant PLA still can achieved a UL‐94 V0 rating. The improved performance was explained by the formation of an intumescent, continuous, contact char layer. Moreover, the reaction between APP and PCD contributed to the improvement of the thermal stability of the char residue. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46054.     

Flame‐retardancy properties of tris(2‐hydroxyethyl) isocyanurate based charring agents on polypropylene

Tris(2‐hydroxyethyl) isocyanurate based charring agent (TBCA) was synthesized by melt polycondensation with tris(2‐hydroxyethyl) isocyanurate (THEIC) and terephthalic acid as raw materials. It was characterized by Fourier transform infrared spectroscopy, elemental analysis, ¹H‐NMR, and thermogravimetric analysis (TGA). TBCA was blended with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) for polypropylene (PP). The charring properties of TBCA was tested by flame retardancy in the PP/APP/TBCA (PP/IFR₂) composite and compared with that of the PP/APP/THEIC (PP/IFR₁) composite. The results show that PP/IFR₂ had lower flame‐retardant properties but better water resistance than that of the PP/IFR₁ composite because PP/IFR₂ could still obtain a V‐0 rating after it had been soaked in water at 70°C for 96 h, whereas PP/IFR₁ could not achieve any rating after 36 h. Their combustion performance was further evaluated by a cone calorimeter test, their thermal degradation processes were studied by TGA, and the morphology of the char residue was observed by scanning electron microscopy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41810.     

A novel bio-based charcoal-forming agent based on chitosan and phytate@Mg to improve the flame retardancy of poly(lactic acid)

A novel bio-based carbon forming agent (Mg@PA-CS) containing P and N elements was were synthesized using the complexation characteristics of chitosan (CS) and phytate (PA). The flame retardant behavior of poly(lactic acid) (PLA)/Mg@PA-CS/APP composites (addition of 20 wt% of different ratios of Mg@PA-CS and APP to polylactic acid composites) were investigated by the limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimetry test (CCT), and thermogravimetric analysis (TGA). Due to the biphasic flame retardant and synergistic effect, since the 20 wt% flame retardant system (Mg@PA-CS:APP = 1:2), PLA composites passed the UL-94 test V-0 rating, reached 34% LOI value. The peak heat release rate (PHRR) and total heat release rate (THR) were reduced to 1/2 of the pure PLA, char residue could be as high as 11.49% at 800°C. Moreover, the flame-retardant mechanism of PLA composites during thermal decomposition was analyzed using a scanning electron microscope (SEM) and the coupling techniques of TGA linked with FT-IR (TG-FTIR).     

Flame retardant and mechanical properties of epoxy composites containing APP−PSt core−shell microspheres

Ammonium polyphosphate (APP)–polystyrene (PSt) core–shell microspheres (CSPs) were synthesized via in situ radical polymerization. The core–shell structure was confirmed by transmission electron microscope (TEM). The results of optical contact angle measurements demonstrated a significant improvement in hydrophobicity of the modified APP. The obtained APP–PSt CSPs were added into epoxy (EP) system with various loadings. Effects of CSP on flame retardancy, thermal properties, heat release rate (HRR), smoke production, and mechanical properties of EP/CSP composites were investigated by limiting oxygen index (LOI), UL‐94 tests, thermogravimetric analysis (TGA), cone calorimeter, and tensile test. LOI and UL‐94 indicated that CSP remarkably improved the flame retardancy of EP composites. TGA showed that the initial decomposition temperature and the maximum‐rate decomposition temperature decreased, whereas residue yields at high temperature increased with the incorporation of microspheres. Cone calorimetry gave evidence that HRR, peak release rate, average HRR, and smoke production rate of EP/CSP composites decreased significantly. The morphology of char residues suggested that CSP could effectively promote EP to form high‐quality char layer with compact outer surface and swollen inner structure. Tensile strength of EP was enhanced with the addition of CSP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40218.     

Polyamide‐enhanced flame retardancy of ammonium polyphosphate on epoxy resin

An attractive intumescent flame retardant epoxy system was prepared from epoxy resin (diglycidyl ether of bisphenol A), low molecular weight polyamide (cure agent, LWPA), and ammonium polyphosphate (APP). The cured epoxy resin was served as carbonization agent as well as blowing agent itself in the intumescent flame retardant formulation. Flammability and thermal stability of the cured epoxy resins with different contents of APP and LWPA were investigated by limited oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results of LOI and UL‐94 indicate that APP can improve the flame retardancy of LWPA‐cured epoxy resins. Only 5 wt % of APP can increase the LOI value of epoxy resins from 19.6 to 27.1, and improve the UL‐94 ratings, reaching V‐0 rating from no rating when the mass ratio of epoxy resin to LWPA is 100/40. It is much interesting that LOI values of flame retardant cured epoxy resins (FR‐CEP) increase with decreasing LWPA. The results of TGA, FTIR, and X‐ray photoelectron spectroscopy (XPS) indicate that the process of thermal degradation of FR‐CEP consists of two main stages: the first stage is that a phosphorus rich char is formed on the surface of the material under 500°C, and then a compact char yields over 500°C; the second stage is that the char residue layer can give more effective protection for the materials than the char formed at the first stage do. The flame retardant mechanism also has been discussed according to the results of TGA, FTIR, and XPS for FR‐CEP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of a novel charring agent and its application in intumescent flame retardant polypropylene system

A novel halogen‐free charring agent bi(4‐methoxy‐1‐phospha‐2, 6, 7‐trioxabicyclo [2.2.2]‐octane‐1‐sulfide) phenylphosphate (BSPPO) was synthesized from phenylphosphonic dichloride (PPDC), and 4‐hydroxymethyl‐1‐phospha‐2, 6, 7‐trioxabicyclo[2.2.2]‐octane‐1‐sulfide (SPEPA) which was synthesized from pentaerythritol and thiophosphoryl chloride in this article. The structure of BSPPO and SPEPA was characterized by Fourier transform infrared (FTIR), ¹H‐NMR, ¹³C‐NMR, and ³¹P‐NMR. Combined with ammonium polyphosphate (APP) and melamine pyrophosphate (MPP), the flame retardance and dripping resistance of BSPPO added in polypropylene (PP) were investigated. The fire performance of the flame retardant PP system was investigated by limiting oxygen index (LOI), vertical burning test (UL‐94), and cone calorimeter. The thermal stabilities of the composites were studied by thermogravimetric analysis (TGA). The flame retardance mechanism was investigated by FTIR and scanning electronic micrograph (SEM). The mechanical properties and water solubility were also investigated. The residue of BSPPO is 40.6% at 600°C, which indicates BSPPO has excellent charring ability. The char residue of the polypropylene intumescent flame retardant (PP‐IFR) system is 22% at 600°C, which suggests that the flame retardation synergy of APP, BSPPO, and MPP is good. With the optimum formulation, the LOI of the IFR‐PP system is 32.0, and the UL‐94 is V‐0 rating. The heat release rate (HRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP), and mass loss rate (MLR) of IFR‐PP with the optimum formulation decrease significantly comparing to pure PP from cone calorimeter analysis. The FTIR and SEM results indicate that the char properties and the char yield have direct effect on the flame retardance and antidripping behaviors. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of a novel phosphorus‐containing compound on the flame retardancy and thermal degradation of intumescent flame retardant polypropylene

A novel flame retardant, tetra(5,5‐dimethyl‐1,3‐ dioxaphosphorinanyl‐2‐oxy) neopentane (DOPNP), was synthesized successfully, and its structure was characterized by FT‐IR, ¹H NMR, and ³¹P NMR. The thermogravimetric analysis (TGA) results demonstrate that DOPNP showed a good char‐forming ability. Its initial decomposition temperature was 236.4°C based on 1% mass loss, and its char residue was 41.2 wt % at 600°C, and 22.9 wt % at 800°C, respectively. The flame retardancy and thermal degradation behavior of novel intumescent flame‐retardant polypropylene (IFR‐PP) composites containing DOPNP were investigated using limiting oxygen index (LOI), UL‐94 test, TGA, cone calorimeter (CONE) test, and scanning electron microscopy (SEM). The results demonstrate that DOPNP effectively raised LOI value of IFR‐PP. When the loading of IFR was 30 wt %, LOI of IFR‐PP reached 31.3%, and it passed UL‐94 V‐0. TGA results show that DOPNP made the thermal decomposition of IFR‐PP take place in advance; reduced the thermal decomposition rate and raised the residual char amount. CONE results show that DOPNP could effectively decrease the heat release rate peak of IFR‐PP. A continuous and compact char layer observed from the SEM further proved the flame retardance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

多羟基结构三嗪成炭剂在膨胀阻燃PP中的应用

以二乙醇胺为侧链,三聚氯氰和哌嗪为主链,采用一锅法制备了一种多羟基三嗪成炭剂(CDP),将其与聚磷酸铵(APP)复配成膨胀阻燃剂(IFR)用于阻燃聚丙烯(PP)。采用垂直燃烧、极限氧指数、热失重分析等手段研究了阻燃PP的阻燃性能和热稳定性,并用扫描电子显微镜(SEM)对炭层形貌进行了研究。结果表明,APP和CDP具有良好的协同阻燃效果,当APP与CDP质量比为2∶1时,协同阻燃效果最优,仅添加20% IFR,即可使PP达到UL94 V–0级别,LOI为29.5%。热失重分析表明该复合材料在800℃具有最高的残炭量,SEM也显示形成了连续致密的炭层。     

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.     

Synergistic flame retardant effects of ammonium polyphosphate in ethylene‐vinyl acetate/layered double hydroxides composites

Mg–Al–Fe ternary layered double hydroxides (LDH) were synthesized based on bayer red mud by calcination‐rehydration method, and characterized using X‐ray diffraction and thermogravimetric analysis (TGA). The synergistic flame retardant effects of ammonium polyphosphate (APP) with LDH in ethylene‐vinyl acetate (EVA) composites were studied using limiting oxygen index (LOI), UL 94 test, cone calorimeter test (CCT), and smoke density test (SDT). The thermal degradation behavior of EVA/LDH/APP composites was examined by thermal gravimetric analysis‐fourier transform infrared spectrometry (TG‐FTIR). The results showed that LOI values decreased by incorporation of APP together with LDH; and, a suitable amount of APP in EVA/LDH composites can apparently improve UL 94 rating. The CCT results indicated that heat release rate (HRR) of the EVA/LDH/APP composites with APP decreased in comparison with that of the EVA/LDH composites. The SDT results showed that APP was helpful to suppress smoke. The TG‐FTIR data showed that the composites with APP had a higher thermal stability than the EVA/LDH composites at high temperature. POLYM. ENG. SCI., 54:766–776, 2014. © 2013 Society of Plastics Engineers     

Application of a novel halogen‐free intumescent flame retardant for acrylonitrile‐butadiene‐styrene

A novel intumescent flame retardant (IFR), containing ammonium polyphosphate (APP) and poly(tetramethylene terephthalamide) (PA4T), was prepared to flame‐retard acrylonitrile‐butadiene‐styrene (ABS). The flame retardation of the IFR/ABS composite was characterized by limiting oxygen index (LOI) and UL‐94 test. Thermogravimetric analysis (TGA) and TGA coupled with Fourier transform infrared spectroscopy (TG‐FTIR) were carried out to study the thermal degradation behavior of the composite and look for the mechanism of the flame‐retarded action. The morphology of the char obtained after combustion of the composite was studied by scanning electron microscopy (SEM). It has been found the intumescent flame retardant showed good flame retardancy, with the LOI value of the PA4T/APP/ABS (7.5/22.5/70) system increasing from 18.5 to 30% and passing UL‐94 V‐1 rating. Meanwhile, the TGA and TG‐FTIR work indicated that PA4T could be effective as a carbonization agent and there was some reaction between PA4T and APP, leading to some crosslinked and high temperature stable material formed, which probably effectively promoted the flame retardancy of ABS. Moreover, it was revealed that uniform and compact intumescent char layer was formed after combustion of the intumescent flame‐retarded ABS composite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synergistic effect of metal oxides on the flame retardancy and thermal degradation of novel intumescent flame‐retardant thermoplastic polyurethanes

The synergistic effects of some metal oxides on novel intumescent flame retardant (IFR)–thermoplastic polyurethane (TPU) composites were evaluated by limiting oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), cone calorimetry, and scanning electron microscopy. The experimental data indicated that the metal oxides enhanced the LOI value and restricted the dropping of the composites. The IFR–TPU composites passed the UL‐94 V‐0 rating test (1.6 mm) in the presence of magnesium oxide (MgO) and ferric oxide (Fe₂O₃) at 35 wt % IFR loading, whereas only the MgO‐containing IFR–TPU composite reached a UL‐94 V‐0 rating at 30 wt % IFR loading. The TGA results show that the metal oxides had different effects on the process of thermal degradation of the IFR–TPU compositions. MgO easily reacted with polyphosphoric acid generated by the decomposition of ammonium polyphosphate (APP) to produce magnesium phosphate. MgO and Fe₂O₃ showed low flammability and smoke emission due to peak heat release rate, peak smoke production rate, total heat release, and total smoke production (TSP). However, zinc oxide brought an increase in the smoke production rate and TSP values. Among the metal oxides, MgO provided an impressive promotion on the LOI value. The alkaline metal oxide MgO more easily reacted with APP in IFRs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Component ratio effects of hyperbranched triazine compound and ammonium polyphosphate in flame‐retardant polypropylene composites

A hyperbranched derivative of triazine group (EA) was synthesized by elimination reaction between ethylenediamine and cyanuric chloride. The different‐mass‐ratio EA and ammonium polyphosphate (APP) were mixed and blended with polypropylene (PP) in a constant amount (25%) to prepare a series of EA/APP/PP composites. The component ratio effect of EA/APP on the flame‐retardant property of the EA/APP/PP composites was investigated using the limiting oxygen index (LOI), vertical burning (UL‐94), and cone calorimetry tests. Results indicated that the EA/APP/PP (7.50/17.50/75.00) composite with the appropriate EA/APP mass ratio had the highest LOI, UL94 V‐0 rating, lowest heat release rate, and highest residue yield. These results implied that the appropriate EA/APP mass ratio formed a better intumescent flame‐retardant system and adequately exerted their synergistic effects. Furthermore, average effective combustion heat values revealed that EA/APP flame retardant possessed the gaseous‐phase flame‐retardant effect on PP. Residues of the EA/APP/PP composites were also investigated by scanning electron microscopy, Fourier‐transform infrared, and X‐ray photoelectron spectroscopy. Results demonstrated that the appropriate EA/APP mass ratio can fully interact and lock more chemical constituents containing carbon and nitrogen in the residue, thereby resulting in the formation of a dense, compact, and intumescent char layer. This char layer exerted a condensed‐phase flame‐retardant effect on EA/APP/PP composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41006.     

Effects of treated waste silicon rubber on properties of poly(lactic acid)/ammonium polyphosphate composites

Considering the massive waste silicone rubber composites (WSiRC) in electrical and electronic engineering industries every year, the utilization of WSiRC is a meaningful and urgent task. In this study, WSiRC was utilized after a simple treatment in the flame retardant polylactic acid (PLA). The TG data in N₂ indicated that the char residues at 700 °C of the PLA/ammonium polyphosphate(APP)/WSiRC samples are improved with the loading of WSiRC, which means that WSiRC could act as the carbonization promoter for the PLA blends. Moreover, it is found in LOI, UL94, and cone tests that WSiRC can only improve the flame retardancy of PLA in an appropriate loading range since the crosslink structure formed by WSiRC may interact with that formed by APP and jointly improve the char‐formation ability of PLA. However, too much WSiRC deteriorated the flame retardancy of PLA because of the effect of WSiRC cluster at its higher loading. The photographs of the char residue after the cone tests also manifested that. The cone data showed that WSiRC could suppress the production of smoke as well. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45231.