Cyclotriphosphazene-Based Intumescent Flame Retardant against the

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Novel cyclotriphosphazene-based intumescent flame retardant (IFR) against the combustible polypropylene Panyue Wen, Qilong Tai, Yuan Hu, and Richard K.K. Yuen Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b01527 • Publication Date (Web): 06 Jul 2016 Downloaded from http://pubs.acs.org on July 9, 2016

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Industrial & Engineering Chemistry Research

Novel cyclotriphosphazene-based intumescent flame retardant (IFR) against the combustible polypropylene Panyue Wen,a,b Qilong Tai,a,b* Yuan Hu,a,b* Richard K. K. Yuenb,c a

State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai

Road, Hefei, 230026, PR China. b

Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute of University of Science and

Technology of China, 166 Ren’ai Road, Suzhou, 215123, PR China. c

Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee

Avenue, Kowloon, Hong Kong.

*Corresponding author. Fax/Tel: +86-551-63601664. E-mail address: [email protected] (Yuan Hu); [email protected] (Qilong Tai).

ACS Paragon Plus Environment


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Abstract Flame retardant polypropylene (PP) was obtained through appropriately blending with

microencapsulated

ammonium

cyclotriphosphazene-based

polyphosphate

char-forming

agent

(MAPP)

(CPCFA),

and

a

novel

synthesized

using

an one-pot method in high yield (86.5%). An increase in the limiting oxygen index (LOI) and the observation of a vertical burning (UL-94) V-0 rating as well as the reduction of the heat release rate (HRR) and residual mass of PP/MAPP/CPCFA blends compared to those for PP/MAPP demonstrated the effectives of a contribution of MAPP and CPCFA to PP in flame PP. Thermogravimetric analyses results demonstrated that the presence of CPCFA improved char formation for PP/MAPP/CPCFA blends in the either nitrogen or air atmosphere. Finally, an outstanding water resistance was also obtained for compositions in the weight ratio range of 3:1 to 2:1 (MAPP/CPCFA). After water soaking for 72 h, a UL-94 V-0 rating was still achievable. Introduction Phosphazene-containing polymeric materials had attracted considerable attention and been well-designed due to relatively benign combustion properties, such as less production of toxic gas, offering tremendous potential application as flame retardant.1 Specifically, polycyclotriphosphazene derivatives characterized with ring structure containing alternating phosphorus and nitrogen atom of two substituents was attached to the phosphorus atoms,2,3 which could happened a synergistic effect of phosphorus and nitrogen leading to an excellent flame retardancy and self-extinguish ability


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compared

to

similar compounds containing

phosphorus

alone.4-11 Various

polyphosphazenes had been developed in recent years.12-19 Their improved thermal stability and high char-yield were in common ascribed to the network-structure and high crosslink density. However, rare systems were utilized for flame retardancy of combustible thermoplastic, such as polypropylene. Polypropylene was a widely used thermoplastic because of its ease of processing, superior mechanical properties. While the LOI of 17% was a major disadvantage of PP, severely limited its application in some aspects required high flame retardancy.20 The incorporating IFR into PP was considered to be one of the most promising strategy, because of them being environmental-friendly, anti-dripping and low smoke compared to halogen-containing ones.21-26 Typically, a charring agent, an acid source, and a blowing agent were three indispensable ingredients of IFR. However, the traditional IFRs were mainly composed of small molecule compounds, such as ammonium polyphosphate/pentaerythritol/melamine (APP/PER/MEL). In addition, the larger dosage of IFR compound needed and the poor thermal stability with the polymer always impaired the flame retardancy of PP.26, 27 Therefore, more efficient and easily manipulated strategies for improving the flame retardancy of PP needed to be explored. Herein, we elaborately compiled cyclotriphosphazene-based char-forming agent (CPCFA) supplemented with microencapsulated ammonium polyphosphate (MAPP) into

polypropylene.

CPCFA

was

prefabricated

by

the

reaction

of

hexachlorocyclotriphosphazene and piperazine via one-pot method. With structural



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features similar to benzene ring, piperazine ring structure has good thermal stability compared to the straight-chain or branched alkyl diamine, while the reactive activity of amino groups containing piperazine ring was higher than that of phenyl. Besides, piperazine was cheap, easily available. The chlorine atoms with high reactivity from hexachlorocyclotriphosphazene could be utilized to covalently attach other flame retardant

components.

Therefore,

the

synthesis

of

designed

cyclotriphosphazene-based charring forming agent was anticipated to be simple and practical. The analysis of structure of CPCFA by fourier transform infrared spectroscopy (FTIR), elemental analysis, and solid-state 13C NMR spectra confirmed the successful preparation of CPCFA. The strategic incorporation of CPCFA with MAPP into PP was postulated to grant PP for better flame retardancy. The ratio of CPCFA to MAPP was carefully tuned to investigate the effect on thermal properties, combustion properties and water resistance properties of PP/MAPP/CPCFA composites. EXPERIMENTAL Materials PP resin (F401) was provided from Yangzi Petrochemical Co. (China) and used as received. Microencapsulated ammonium polyphosphate (MAPP) was obtained from Wuhu Keyan Chemical Material Technology Co., Ltd. (China), microencapsulated from melamine–formaldehyde resin (Figure S1). Hexachlorocyclotriphosphazene and piperazine were obtained from Aladdin. 1, 4-dioxane was dried by refluxing over sodium and distilled. All other commercially available chemicals were gained from


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Sinopharm Chemical Reagent Co. Ltd. and used as received. Synthesis of CPCFA The cyclotriphosphazene-based charring forming agent (CPCFA) was prepared via nucleophilic

substitution

reaction

between

piperazine

and

hexachlorocyclotriphosphazene (Scheme 1). Briefly, piperazine (0.8 mol) and anhydrous dioxane (500 mL) were charged into 1000 ml three-neck flask equipped with a reflux condenser. Thereafter, hexachlorocyclotriphosphazene (0.2 mol) dissolved in anhydrous dioxane (60 mL) was added dropwise into the reaction system, followed by stirring at 0°C. After 3 hr, alkali solution of sodium hydroxide (0.8mol) was gradually added for maintaining a pH of 8-9. The reaction system was stirred for 6 hr at 80 oC, followed by cooling to room temperature. The dispersion was filtered. The solid collected was washed with water and ethanol six times. The final product was dried at reduced pressure, yielding the char-forming agent (yield: 86.5%). Preparation of PP samples Vacuum drying at 80 oC for 24 hr was applied to PP, CPCFA and MAPP before banburying. The banburying at 180 oC with the roll speed of 100 rpm was conducted by a two-roll mixing mill (Rheomixer XSS-300, Shanghai Ke Chuang China). Briefly, PP resin (F401) was added into the mill for initiation of melting of the PP, followed by addition of CPCFA and MAPP with varying weight ratio. Another 15 min banburying was continued. The components of series of samples used for banburying were summarized in Table 1. Then, 3.2 mm thick specimens for the following tests were cut from 3.2 mm thick plaques which were pressed in a hot press at 180 °C.



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Characterizations FTIR spectra were measured using a Nicolet MAGNA-IR 750 spectrophotometer. Elemental analysis was recorded via the Vario EL III elemental analyzer. 13

C solid-state NMR spectra were recorded on a Bruker AVANCE III 400 WB.

Thermogravimetric analysis (TGA) was measured from a Q5000IRthermo-analyzer instrument (TA Co., USA) (3-10 mg sample, 20 oC /min heating rate). Limiting oxygen index (LOI) was evaluated by an HC-2 oxygen index meter (Jiangning Analysis Instrument Co., China) using the standard of ASTMD 2863. The vertical burning test was measured by CFZ-2 instrument named purchased from Jiangning Analysis Instrument. Samples of 100×6.5×3.2 mm3 dimensions for LOI test. 130.0 × 13.0 × 3.2 mm3 and 130.0 × 13.0 × 1.5 mm3 dimensions for the vertical test were used respectively. The combustion trials were carried out from the cone calorimeter (FTT, UK) with the procedure of ISO 5660 standard. For evaluation of the ability of water resistance, water soaking of the samples was conducted at 70 oC for varying time, followed by vacuum drying. LOI test and vertical test were applied to the dried samples. The microstructure of PP samples was studied from scanning electron microscopy (JSM6700F, 10.0 kV). RESULTS AND DISCUSSION Characterization of CPCFA The CPCFA synthesized by nucleophilic substitution reaction was initially


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well-characterized through FTIR and NMR spectrum. FTIR analysis determined the information of chemical bonds of CPCFA, as shown in Figure 1. The broad IR bands around 3260 cm-1 belonged to stretching vibration of N–H, while the characteristic absorption peaks of -CH2 was observed at about 2980 cm-1-2650 cm-1. The characteristic peaks at 850 cm-1 and at 1250-1305 cm-1 caused by stretching vibration of P-N and P=N confirmed the existence of phosphazene ring. More importantly, the band at 630 cm-1 characteristic of P-Cl absorbance peak of HCCP disappeared,5, 18 which indicated chlorine atoms have been consumed. To further clarify the structure of CPCFA, the elemental analysis was conducted and results were listed in Table S1. C, H and N obtained from theoretical calculation and measurements (calcd. for CPCFA: 27.59%, 4.60% and 32.18%; found: 26.24%, 5.37% and 31.85%). Furthermore, as shown in Figure 2, its

13

C solid-state NMR

spectrum characterized with two peaks at 43.81 ppm and 59.92 ppm indicated that the presence of two types of chemical environment of the carbon atoms, which might be resulted by the defective structures of cyclotriphosphazene-based char-forming agent (CPCFA) in consistent with the result of elemental analysis (Table S1). Therefore, it was exactly hard to characterize the structure of cyclotriphosphazene-based char-forming agent. Then, the thermal property of CPCFA was studied by thermogravimetric analysis. The thermal degradation of CPCFA under nitrogen displayed a two-step decomposition profile in the temperature ranges of 83-140 oC, 310-550 oC (Figure 3 and Table S2). The volatilization of trace water and some local defective areas in



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network-structural CPCFA resulted in the minor decomposition stage (83-140 oC). The major weight-loss stage appeared (310-550 oC) along with the elevation of temperature,

which

was

assigned

to

the

thermal

decomposition

of

the

phosphazene-bound piperazine. Particularly, the degradation rate culminated at approximately 422oC. This major decomposition had been reported to be beneficial for the formation of intumescent char.6, 8 Furthermore, the residue of CPCFA at 800 o

C in N2 atmosphere still maintained 52.5 wt%. It could be postulated that the high

char residue may arise from the occurrence of some crosslinking reactions during pyrolysis, such as the reported ring opening polymerization of the P=N structures.6, 30 The thermal degradation behavior of CPCFA under air atmosphere was also presented, which could be divided into three steps: the fist and second steps took place from 83-140 oC and 310-400 oC, which was similar to that under N2, the last one ranged from 400 oC to 800 oC, which indicated the degradation of final char.31 The investigations of thermal property verify the CPCFA was capable of inducing flame retardant effect as an efficient char forming agent. Thermal Degradation of PP Samples in Nitrogen and Air Atmosphere To demonstrate the flame retardation by CPCFA, we evaluated thermal stability of PP and PP/MAPP/CPCFA composites in either nitrogen or air atmosphere by TGA. The acquired results were given in Figure 4 and Figure 5 and the corresponding data were summarized in Table S3. According to general standard, it was defined as the onset decomposition temperature (Td) just higher than that of initiation of 5% weight loss.


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Temperature-dependent weight loss of pure PP under nitrogen captured an obvious one-step weight loss profile (350-480 oC) due to the random thermal scission in PP backbone. Pure PP with almost 2.2 % residue was cleaved to gaseous pyrolysis products above 500 oC (Table S3). The Td for the pure PP was approximately 385 oC. Although the Td of PP6 with addition of 30 wt% CPCFA (~315 oC) was lower than that of pure PP (~385 oC) resulting from the early degradation of CPCFA, the improved thermal stability was obtained above 409 oC. Especially, the char residue was raised to 16.9% at 800 oC compared with pure PP (2.2 %), mainly ascribed to the formation of CPCFA intumescent char as a physical barrier for reduction of further degradation in the inner matter. Meanwhile, the main decomposition of PP was delayed and 18.1 % char residue at 800 oC was obtained by the addition of 30 wt% MAPP (Table S3), attributed to the protective effect of the degraded products of MAPP like polyphosphoric acid and polymetaphosphate. Furthermore, the data in Table S3 and DTG curves in Figure 4b clearly indicated that the combination of MAPP and CPCFA descended the Tmax of flame retardant PP blends among all the samples (PP2 to PP5). The best thermal stability appeared for PP2 and PP4 and the most char residue (21.4 %) at 800 oC is obtained for PP2. These results validate the important role of relative ratio of acid source, carbonization agent and blowing agent in the formation of the most effective protective char layer. Thermal degradation of PP composites under air atmosphere was also conducted, which exhibited different degradation profile compared to that of in nitrogen atmosphere (Figure 5 and Table S3). Obviously, two-step weight loss profile was



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captured in air, characterized with retardation of the second step weight loss (433-800 o

C). The occurrence of second step weight loss was owing to the thermally unstable

char formed in the first step weight loss and re-oxidized. In particular, the best thermal stability for PP2 (highest char residue of 18.3% amongst all samples) was obtained, ascribed to a powerful physical barrier from the intumescent char layer formed in the first step weight loss for reduction of further degradation in the inner matter. The above TGA results proved the feasibility of CPCFA as an efficient char forming agent to retard PP. Additionally, To further investigate the positive effect between MAPP and CPCFA in PP matrix during thermal degradation, the experimental and calculated TG curves under nitrogen and air atmosphere of PP2 have been given in Figure 4 and Figure 5 , and the corresponding data were listed in Table S3. Comparing the theoretical and experimental degradation behavior of PP2, the char residues of experimental curves showed a clear increase compared to those of calculated under nitrogen and air atmosphere. Combustibility of flame retarded PP composites Similar to the improved thermal stability, the flammability of PP samples characterized by LOI value and UL-94 test was also anticipated to be increased. The LOI values and UL-94 results were summarized in Table 1. The PP1 with addition of 30 % MAPP achieved LOI value of 22% that was a little bit of superior to pure PP, while UL-94 V-0 rating (3.2mm and 1.5mm) was not obtained. The PP6 with addition of 30 % CPCFA exhibited striking potency to retard PP with LOI value of 29% and


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UL-94 V-0 rating (3.2mm) due to integrated action of CPCFA as typical IFR acid, char and gas sources. However, the UL-94 of PP7 with 25 % CPCFA failed to rearch V-0 rating (3.2mm and 1.5mm). Remarkable LOI values and UL-94 V-0 rating (3.2mm) were achieved with combined utilization of CPCFA and MAPP for all PP samples (PP2-PP5). Furthermore, only PP2 and PP3 could pass UL-94 V-0 rating (1.5 mm) while other samples (weight ratio of MAPP/CPCFA: 1/1 to 0/1) failed to maintain UL-94 V-0 rating(1.5 mm). In particular, a maximum LOI value of 37.5% was obtained for PP3 with weight ratio of MAPP to CPCFA being 2/1. According to the above results, it confirmed the important role of relative ratio of MAPP to CPCFA in inducing flame-retardant effect. Although high LOI values confirmed the flame-retardant effect of MAPP and CPCFA, it could not behave as robust indicators to exhibit retardant capacity in a real fire disaster due to small-scale sample used. In order to solve this problem, we conducted the other test, cone calorimeter analysis, a bench-scale fire test with presenting abundant information of combustion. Several evaluation indexes (Figure 6 , Figure 7 and Table S4), heat release rate (HRR), total heat release (THR), peak HRR (PHRR), and mass loss were obtained to reflect the combustion behavior.32 Conceivably, the combined utilization of CPCFA and MAPP strongly induced the flame-retardant effect, similar to the results from LOI value and UL-94 test. The PHRR values for all PP samples were decreased. As for PP2, PHRR of 113 kW/m2 was achieved, an 88.6 % reduction relatived to that of pure PP. In addition, the time achieving PHRR of PP2 increased to 427s and hysteresis phenomenon happened



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compared with that of pure PP (152s). In contrast to ignition of combustion for pure PP, all PP composites with combination of MAPP and CPCFA (PP2-PP5) displayed a reduced time to ignition (TTI), the reduction of TTI could be due to initial combustion of the flame retardants before these could play their role in the materials. The duration of burning for all samples was extended compared with those of pure PP and PP with 30% MAPP. Figure 7 shows the mass loss of PP samples, and the corresponding data were presented in Table 4. It was obvious that there are 5.8%, 26.8%, 26.4% and 24.4%, of residue chars left, respectively, for pure PP, PP2, PP3, and PP4 at the end of burning. The PP2 shows significantly higher residue chars, indicating that CPCFA and MAPP facilitated the carbonization of PP samples. More char residues meant less pyrolysis products and thus less combustion heat, which is in accordance with the PHRR behavior during cone calorimetry. For further judging fire risk of PP samples, two parameters, fire performance index (FPI) and fire growth index (FGI), were introduced.32 According to general standard, FPI and FGI were defined as the ratio of TTI and the PHRR and the ratio of PHRR and the TPHRR, respectively. A negative correlation existed between fire hazard and FPI, while a positive correlation between fire risk and FGI was widely accepted according to previous reports.32 The values of FPI and FGI of PP composites were summarized in Table S4. It was clearly seen that the fire risk factors for PP2 and PP4 were much lower than that of pure PP and other PP samples. Characterization of Char Residue of PP and Its Composites


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The intumescent char layer had been demonstrated to be as an excellent gas barrier during burning for regulation of combustion process and also as a physical barrier for reduction of further degradation in the inner matter. The content and morphology of char residues were two important aspects for flame retardancy. The camera pictures of the char residues for PP composites after cone calorimeter test were shown in Figure 8. Intuitively, nothing was left for pure PP. Sole addition of MAPP or CPCFA to PP could improve char residues. Moreover, the PP samples with combined utilization of MAPP and CPCFA, especially for PP2, PP3, and PP4, exhibited a high content and also a high expansion of char residues. The char layer of high expansion could reduce the transfer of gas and heat during combustion, ultimately inducing improved flame retardant effect to PP. To ascertain the morphology of char residues, they were subjected to SEM analysis (Figure 9). Obviously, PP1 with addition of MAPP has an insufficient char formation featured with macroporous appearance (Figure 9a). By contrast, the coverage and continuity of char layers were improved for all PP/MAPP/CPCFA systems. Only a few cavities were left for PP2, PP4, PP5 and PP6. The most eye-catching performance belonged to PP3, exhibiting a well-compact and continuous char layer beneficial to reducing the transfer of gas and heat during combustion. These results again confirmed the effectiveness of combined utilization of MAPP and CPCFA for the formation of charred layers, ultimately inducing improved flame retardant effect to PP. FTIR spectra of the inner and outer layer of char residues (PP3) (Figure S2) have



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been discussed for explaining the charring behavior. The typical bonds on the spectra were assigned to corresponding structure as shown in Figure S2. The existence of P–O–C chemical bonds in outer layer of char residues suggested that the cross-linking reaction occured between MAPP and CPCFA, which protected PP matrix during combustion. This point was testified by the FTIR spectra of inner layer of char residues (PP3), with the existence of C-H and C=O structure.33 Water Resistance of PP/IFR Composites LOI test and vertical test were applied to the dried samples. As for evaluation of the effect of water to PP composites, water soaking of the samples was conducted at 70 o

C for varying time and corresponding LOI values and UL-94 analysis were

re-assessed (Table 2 and Figure 10). In general, the LOI values decreased for all PP composites after water-soaking. However, the water soaking has less effect to PP2 and PP3, and UL-94 V-0 rating was still maintained. These results validated the important role of the ratio of MAPP and CPCFA in the keeping the ability of water resistance. The appropriate ratio of MAPP and CPCFA could endow PP composites with well-water-resistance.34 To further discuss the water resistance of the PP samples, the water solubility of MAPP and CPCFA were presented in Figure S3. The solubility values of MAPP were still higher than that of CPCFA at different times. After 10h later, CPCFA could still maintain a little change, which might be the reason for the outstanding water resistance of PP samples. CONCLUSION


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In this paper, we designed a novel cyclotriphosphazene-based charring forming agent (CPCFA) for flame retardancy of combustible polypropylene. A remarkable retardant effect to PP was induced with MAPP supplemention. The improved thermal degradation, thermal-oxidative stability and high char residues at the high temperature range were simultaneously achieved for PP/CPCFA/MAPP system. An appropriate ratio of MAPP and CPCFA (3/1 to 0/1) could result in the high amount of char residue, increased LOI values and a UL-94 V-0 rating. The cone calorimeter results showed the obviously decreased HRR and FGI of PP/MAPP/CPCFA composites relative to pure PP and PP with 30 wt% MAPP. SEM results indicated PP/MAPP/CPCFA systems formed the compact char residues during combustion, reducing the transfer of gas and heat, ultimately inducing improved flame retardant effect to PP. In addition, when the weight ratio of MAPP to CPCFA were 3/1 and 2/1, the PP composites achieved a V-0 rating after 72 hr soaking in water 70 oC.

Acknowledgements The work was ﬁnancially supported by the National Basic Research Program of China (973Program) (2012CB719701), Natural Science Foundation of Jiangsu Province. (BK20130369), Reseach Grants Council of the Hong Kong Special Administrative Region (CityU 11301015) and National Natural Science Foundation of China (51403196).

Associated Content Supporting Information The Supporting Information is available free of charge on the ACS Publications



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website at DOI. Elementary

analysis,

Structure

of

MAPP

microencapsulated

by

melamine–formaldehyde resin; The related TGA data and cone date of PP and its samples; FTIR spectra of char residues (PP3); Water solubility of APP and CPCFA (PDF)


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cyclotriphosphazene-containing polyurethanes. J. Appl. Polym. Sci. 2003, 90, 1357-64. (14) Diefenbach, D.; Allcock, H. R. Synthesis of cyclo- and polyphosphazenes with pyridine side groups. Inorg. Chem. 1994, 33, 4562-5. (15) Bose, S.; Mukherjee, M.; Das, C. K.; Saxena, A. K. Effect of polyphosphazene elastomer on the compatibility and properties of PES/TLCP composites. Polym. Composites. 2010, 31, 543-52.


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(16) Jimenez, J.; Laguna, A.; Molter, A. M.; Serrano, J. L.; Barbera, J.; Oriol, L. Supermolecular liquid crystals with a six-armed cyclotriphosphazene core: from columnar to cubic phases. Chem. Eur. J. 2011, 17, 1029-39. (17) Zhang, X.; Zhong, Y.; Mao, Z. P. The flame retardancy and thermal stability properties

of

poly

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terephthalate)/hexakis

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cyclotriphosphazene systems. Polym. Degrad. Stab. 2012, 97, 1501-1504. (18) Xu, M. J.; Xu, G. R.; Leng, Y.; Li, B. Synthesis of a novel flame retardant based on cyclotriphosphazene and DOPO groups and its application in epoxy resins. Polym. Degrad. Stab. 2016, 123, 105-114. (19) Green, J. Flame Retardant Polymeric Materials; Lewin, M.; Atlas, S. M.; Pearce, E. M., Eds.; Plenum Press: New York, 1982; Vol. 3. (20) Bourbigot, S.; Lebras, M.; Duquesne, S.; Rochery, M. Recent Advances for Intumescent Polymers. Macromol. Mater. Eng. 2004, 289, 499-511. (21) Camino, G.; Costa, L.; Trossarelli, L.; Costanzi, F.; Pagliari, A. Study of the Mechanism of Intumescence in Fire Retardant Polymers. 6. Mechanism of Ester Formation in Ammonium Polyphosphate Pentaerythritol Mixtures. Polym. Degrad. Stab. 1985, 12, 213-28. (22) Baljinder, K. K.; Horrocks, A. R. Complex char formation in flame-retarded fiber- intumescent combinations-II. Thermal analytical studies. Polym. Degrad. Stab. 1996, 54, 289-303. (23) Sabyasachi, G.; Gang, S.; Katherine, H.; Mark, H. E. Effect of nitrogen additives on flame retardant action of tributyl phosphate: Phosphorus-nitrogen synergism.



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Polym. Degrad. Stab. 2008, 93, 99-108. (24) Chiu, S. H.; Wang, W. K. Flame retardancy of polypropyle filled with ammonium polyphosphate, pentaerythritol and melamine additives. Polymer. 1998, 39, 1951- 55. (25) Wen, P. Y.; Wang, X. F.; Xing, W.Y.; Feng, X.M.; Yu, B.; Shi, Y.Q. Synthesis of a novel triazine-based hyperbranched char foaming agent and the study of its enhancement on flame retardancy and thermal stability of polypropylene. Ind Eng Chem Res. 2013, 52, 17015-22. (26) Chen, Y. H.; Liu, Y.; Wang, Q.; Yin, H.; Aelmans, N.; Kierkels, R. Performance of intumescent flame retardant master batch synthesized through twin-screw reactively extruding technology: effect of component ratio. Polym. Degrad. Stab. 2003, 81, 215-24. (27) Wang, Q.; Chen, Y. H.; Liu, Y.; Yin, H.; Aelmans, N.; Kierkeis, R. Performance of an intumescent-flame-retardant master batch synthesized by twin-screw reactive extrusion: effect of the polypropylene carrier resin. Polym. Int. 2004, 53, 439-48. (28) Mahapatra, S. S.; Karak, N. Hyperbranched polyamine: A promising curing agent for a vegetable oil-based poly(ester-amide) resin. Prog. Org. Coat. 2007, 60, 328−334. (29) Mahapatra, S. S.; Karak, N. s-Triazine containing flame retardant hyperbranched polyamines: Synthesis, characterization, and properties evaluation. Polym. Degrad. Stab. 2007, 92, 947−955. (30) Levchik, S.V.; Camino, G.; Luda, M. P.; Costa, L.; Lindsay, A.; Stevenson, D. Thermal decomposition of cyclotriphosphazenes. I. Alkyl-aminoaryl ethers. J. Appl.


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Table 1. LOI and UL-94 results of pure PP and PP/IFR systems. UL-94 rating

PP

MAPP

CPCFA

LOI (%)

(wt%)

(wt%)

(wt%)

±0.5

1.5 mm

3.2 mm

PP0

100

0

0

17

NR

NR*

PP1

70

30

0

22

NR

NR

PP2

70

22.5

7.5

33.5

V-0

V-0

PP3

70

20

10

37.5

V-0

V-0

PP4

70

15

15

37

V-1

V-0

PP5

70

10

20

35

NR

V-0

PP6

70

0

30

29

NR

V-0

PP7

75

0

25

27

NR

V-2

Sample

* NR, No rating.


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Table 2. The UL-94 testing results of PP samples after water treatment with different times. Sample

PP1

PP2

PP3

PP4

PP5

PP6

0hr

NR

V-0

V-0

V-0

V-0

V-0

24hr

NR

V-0

V-0

V-1

V-1

V-0

48hr

NR

V-0

V-0

V-1

V-1

V-2

72hr

NR

V-0

V-0

V-1

V-1

V-2



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table 1. LOI and UL-94 results of pure PP and PP/IFR systems. Table 2. The UL-94 testing results of PP samples after water treatment with different times. Scheme 1. The route for the synthesis of CPCFA. Figure 1. FTIR spectra of CPCFA(a) and HCCP(b). Figure 2. 13C solid-state NMR spectrum of CPCFA. Figure 3. TGA curves of CPCFA under nitrogen and air atmosphere. Figure 4. TG (a) and DTG (b) curves of various PP samples under N2 atmosphere. Figure 5. TG (a) and DTG (b) curves of various PP samples under air atmosphere. Figure 6. HRR (a) and THR (b) curves of various PP samples. Figure 7. Mass loss curves of various PP samples from cone calorimeter test. Figure 8. Front and side views of the residues of PP1, PP2, PP3, PP4, PP5, and PP6 after cone calorimeter test. Figure 9. SEM images of the char residues of PP1 (a), PP2 (b), PP3 (c), PP4 (d), PP5(e), and PP6 (f). Figure 10. The LOI values of PP/ CPCFA /MAPP systems after water treatment with different times.


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Scheme1



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Figure 1


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Figure 2



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Figure 3


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Figure 4



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Figure 5


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Figure 6



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Figure 7


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Figure 8



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Figure 9


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Figure 10



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For Table of Contents Only


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Cyclotriphosphazene-Based Intumescent Flame Retardant against the

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