effectsofsizeofzincborateontheflameretardantpropertiesof ...ammonium polyphosphate (app) in tpu...

Research ArticleEffects of Size of Zinc Borate on the Flame Retardant Properties ofIntumescent Coatings

Ning Lu,1 Pengchao Zhang,1 Ya’nan Wu,1 Danqing Zhu,1 and Zhu Pan 2

1College of Safety Engineering, Chongqing University of Science and Technology, Chongqing, China2Centre for Infrastructure Engineering, Western Sydney University, Penrith, NSW 2747, Australia

Correspondence should be addressed to Zhu Pan; [email protected]

Received 25 March 2019; Revised 27 May 2019; Accepted 3 June 2019; Published 2 September 2019

Academic Editor: Qinglin Wu

Copyright © 2019 Ning Lu et al. This is an open access article distributed under the Creative Commons Attribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

This paper is aimed at assessing the fire retardancy and thermal stability of intumescent flame retardant (IFR) containingammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MEL). Zinc borate (ZB) was added at the loading of2%, 4%, 6%, 8%, 10%, and 12% by weight of IFR. The sizes of investigated ZB fall in 3 ranges: 1-2 μm, 2-5μm, and 5-10 μm.The performance of APP/PER/MEL was investigated by using thermogravimetry analysis (TGA), cone calorimeter test, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy, and energy-dispersive spectrometry. The resultsobtained from the above experiments show that the incorporation of ZB can improve the fire protection performance. A 77%decrease in total smoke production and 84.6% decrease in total heat release were achieved for the addition of 2wt% ZB(2-5 μm) in the IFR coating. TGA results indicate an increased amount of char residue. Compared to the control IFR coating,the char residue of IFR containing 2wt% ZB (2-5 μm) has increased approximately 1.5-fold, 10-fold, and 25-fold, at 600°C,700°C, and 800°C, respectively. The effective char formation results in excellent smoke suppression. Regarding smokesuppression performance, the order for smoke density is IFR/ZB (2-5 μm)< IFR/ZB (5-10μm)< IFR/ZB (1-2 μm), regardless ofinvestigated loading levels. The decline of smoke suppression performance for IFR/ZB (5-10 μm) and IFR/ZB (1-2 μm) isbelieved to be due to the poor char formation, as a result of a weak interaction of APP, PER, MEL, and ZB. This weakinteraction is caused by the decrease in the specific surface area and agglomeration of ZB particles for IFR/ZB (5-10 μm) andIFR/ZB (1-2μm), respectively.

1. Introduction

Flame retardant coatings are widely used to enhance theflame retardancy of various materials including flammablematerials (e.g., polymers and wood) and nonflammablematerials (e.g., steel) [1]. Flame retardant coatings may becategorised into two groups: intumescent fire retardantcoating and nonintumescent coating. Intumescent flameretardant (IFR) coatings swell in a fire to form a porouschar, leading to delay the decomposition and combustionof base materials under high temperature radiation. Theintumescent coatings are composed of char formation agents:ammonium polyphosphate-pentaerythritol-melamine (APP-PER-MEL). It is noted that these agents, together with resinsin IFR, produce dense smoke and toxic gas during the com-bustion. Analysis of the death in fire disasters shows that

around 85% of the casualty is a result of production of smokeand toxic gases [2]. Therefore, the research of smoke sup-pression of IFR systems has become a hot topic.

Jiao et al. [3] studied smoke suppression effects betweenferrous powder and ammonium polyphosphate (APP) inthe flame retardant thermoplastic polyurethane (TPU). Theresults showed that the addition of iron powder significantlyreduce the smoke generation rate and total smoke releaserate. Effects of iron powder on smoke suppression effectsdepend on the loading levels. The same authors [4] also triedto reduce smoke release of flame retardants by chemicallymodifying APP with ETA. When 12.5wt% of APP/ETAwas incorporated into TPU composites, the total smokerelease of the sample was reduced by 41.7%. Chen et al. [5]reported that ferrite yellow (FeOOH) can be used as an effec-tive smoke suppression agent and a good synergism with

HindawiInternational Journal of Polymer ScienceVolume 2019, Article ID 2424531, 15 pageshttps://doi.org/10.1155/2019/2424531

https://orcid.org/0000-0003-3389-4656https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/https://doi.org/10.1155/2019/2424531

ammonium polyphosphate (APP) in TPU composites. Yanet al. [6] investigated the effects of nanosilica on the flameretardancy and smoke suppression properties of IFR coat-ings. They found that the total smoke release is reduced by53.1% compared to the control coating, when 3wt% ofnanosilica was added into the IFR coatings. Xu et al. [7] pro-duced an IFR polypropylene (PP) composite by usingSCTCFA-ZnO combined with ammonium polyphosphate(APP). When the mass ratio of APP to SCTCFA-ZnO is2 : 1, the IFR system exhibits the best flame retardancy andsmoke suppression.

Besides the above smoke suppression agents, zinc borate(2ZnO·3B2O3·3.5H2O) has also been extensively used in aflame retardant as a smoke suppression agent. Fang et al.[8] developed flame retardant wood-polymer composites(WPCs) by utilizing zinc borate (ZB) as synergist with APP.During combustion, ZB and APP can produce carbonaceousfoam protecting the underlying material. He et al. [9] investi-gated the effects of APP and nano-ZB (nZB) on flame retar-dation and smoke suppression properties of wood. Theyfound that the total smoke production (TSP) of treated woodwith APP/nZB depends on the loading levels of nZB. Com-pared with wood treated with APP along, the TSP and meanyield of CO of wood treated with APP/nZB were reduced by78.43 and 71.43%, respectively, when the loading level of nZBwas 15wt%. Zhang et al. [10] investigated the smoke sup-pression of ZB and diantimony trioxide (Sb2O3) in epoxy-based IFR coatings. Results show that the values of heatrelease rate, smoke production rate, smoke factor, and firegrowth index all decreased significantly with the additionof ZB and Sb2O3. Tai et al. [11] investigated the effectsof organically modified iron-montmorillonite and ZB onthe thermal degradation behaviors and flame retardancyof melamine polyphosphate (MPP) flame-retarded glassfiber-reinforced polyamide 6 (GFPA6), and the results showthat replacing a certain proportion of MPP with ZnB orFe-OMT could improve the UL-94 rating of GFPA6/MPPcomposites to V0. Recently, Feng et al. [12] added ZB into anAPP/CNCA-DA polypropylene/IFR system. The flame retar-dancy and thermal stability of the PP/IFR system were inves-tigated. They suggested that the addition of ZB helps to forma compact and homogeneous char layer during combustion.As a result, the flame retardancy of PP/IFR is significantlyimproved. They also measured the TSP of PP/IFR andreported the minimum value at the loading level of 1wt%.However, the effects of ZB on the suppression of toxic gases(e.g., CO and CO2) have not been investigated in this study.Wu et al. [13] investigated the effects of ZB on both smokesuppression and toxicity reduction of an APP/PER polyethy-lene/IFR system. When ZB was introduced into the poly-ethylene/IFR system, the TSP value and carbon monoxideconcentration were reduced by 47% and 59%, respectively.However, the loading level (of ZB) has not been consideredin this study. A latest study [14] investigated the flame retar-dancy of APP/PER/MEL systems containing various loadinglevels of ZB. The loading level has been found to have a sig-nificant influence on the formation of the char layers. Doğanand Bayramlı [15] also identified the effect of a loading levelon the performance of IFR/ZB. In their study, ZB was used to

improve the flame retardancy of the PP/nanoclay/intumes-cent system composed of APP/PER. They reported that3wt% ZnB containing composite shows the highest rating(V0) according to the UL-94 test. It is noted that the ZBwith different particle size was used in the previous research[13–15]. The smaller ZB particles exhibit larger specific sur-face area which can absorb more smoke and dust duringcombustion, as compared to larger ZB particles. Therefore,the particle size has influence on the flame retardancy of acoating system containing ZB. However, effects of particlesize (of ZB) on the performance of an APP/PER coating havenot been reported in the literatures.

In this study, ZB with different particle size was thusadded into an APP/PER/MEL coating which was thenapplied to the surface of the wood. The IFR coatings with2wt%, 4wt%, 6wt%, 8wt%, and 10wt% of ZB were preparedby an orthogonal matrix design, which was similar to thestudy of Liu et al. [16]. Effects of ZB on the thermal degrada-tion, smoke suppression, and toxicity reduction of the IFRcoating have been investigated by thermogravimetry analysis(TGA), differential thermal analysis (DTA), scanning elec-tron microscopy (SEM), Fourier-transform infrared (FTIR)spectroscopy, cone calorimeter test (CCT), and infraredsmoke analysis.

2. Experimental Programs

2.1. Materials. To prepare the IFR systems, melamine (MEL),acrylic resin, and pentaerythritol (PER) were purchasedfrom Chengdu Kelong Chemical Reagent Factory. Ammo-nium polyphosphate (APP) was supplied by Shanghai Yua-nye Biotechnology Co. Ltd. Zinc borate, which was used asthe additive for smoke suppression, was supplied by Ji’nanShangshan Fine Chemical Co. Ltd.

Table 1: Interpretation of sample labels.

Sample label Addition amount Particle size

ZBS2% 2% 1-2 μm

ZBS4% 4% 1-2 μm

ZBS6% 6% 1-2 μm

ZBS8% 8% 1-2 μm

ZBS10% 10% 1-2 μm

ZBS12% 12% 1-2 μm

ZBM2% 2% 2-5 μm

ZBM4% 4% 2-5 μm

ZBM6% 6% 2-5 μm

ZBM8% 8% 2-5 μm

ZBM10% 10% 2-5 μm

ZBM12% 12% 2-5 μm

ZBL2% 2% 5-10 μm

ZBL4% 4% 5-10 μm

ZBL6% 6% 5-10 μm

ZBL8% 8% 5-10 μm

ZBL10% 10% 5-10 μm

ZBL12% 12% 5-10 μm

2 International Journal of Polymer Science

2.2. Sample Proportions. The IFR system mainly contains ofabout 30wt% of APP, 17wt% of MEL, 13wt% of PER, and14wt% of acrylic resin. The remaining ingredients are waterand additives. ZB was one of the additives used in this study.It was used in three size ranges: 1-2 μm, 2-5μm, and 5-10μm. Zinc borate was added into the IFR at six designedcontents of 2%, 4%, 6%, 8%, 10%, and 12% by weight. Theparticle size and loading level for each specimen are summa-rized in Table 1. The control coating contains no ZB.

2.3. IFR Preparation. The preparation of IFR systemsincludes the following procedures: grinding, sieving, mixing,and discharging. Firstly, fire retardant components, such asAPP, MEL, and PER, were ground to powder. Then, thepowders were sieved to allow them pass 200 mesh sieve.The sieved powders were mixed until the uniformity was

achieved. The acrylate resin, liquid assistant, and properamount of water were mixed at a speed of 1800 r/min. Thisslurry was mixed with the fire retardant components, togetherwith ZB in a mechanical mixer at a speed of 1500 r/min for30mins. Then, the mixing rate was adjusted to 750 r/minfor defoaming and discharging. The final IFR system wascollected and stored in a fridge at 25°C.

2.4. Preparation of Treated Wood. Five-layer plywood wasused for coating substrate. Before the coating procedures,plywood was cut in 100mm × 100mm × 4mm pieces. Thesmooth surface of the plywood plates showed no scars andobvious defects. The IFR coating used per square meter was500 ± 10 g. IFR slurry was coated on the surface of substraterepeatedly until the uniform coating was achieved. Two coat-ings were carried out at a 24-hour interval. During thisperiod, the coated substrates were dried at a constant temper-ature of 23 ± 2°C and relative humidity of 50 ± 5%. The masschanging due to drying action was not more than 0.5%.Three samples were prepared for each coating formulation.

2.5. Cone Calorimeter Test. The parameters such as time toignite (TTI), total heat release (THR), heat release rate(HRR), total smoke production (TSP), and smoke produc-tion rate (SPR) of samples were measured by the cone calo-rimeter (FTT 0007), following the procedures given by ISO5660-1 [17]. The sample was placed horizontally on thestainless steel sample shelf which was equipped with asbestosnet at the bottom. According to ISO 5660-1, the irradiancelevel (for cone calorimetry) can be adjusted in the range of10-100 kw·m-2. Carosio et al. [18] investigated the effects ofheat flux on the combustion properties of APP/acrylic sys-tems. They found the char-forming efficiency is higher at

Table 2: Results of a calorimeter test.

Sample TTI (s) pkHRR (KW·m-2) THR (MJ·m-2·k-1) pkSPR (m2·s-1) TSP (m2·m-2) CO concentration (%) Mass loss (%)Control IFR 657 47.60933 10.07 0.0212 2.8354 0.02053 32.3293

ZBS2% 1200 14.137189 5.1 0.02 2.1388 0.0067 26.4

ZBS4% 1200 12.043336 4.754 0.02116 4.87254 0.008 28.3

ZBS6% 720 87.21937 6.2775 0.02565 5.26761 0.02 33.9

ZBS8% 502 155.4174 29.7753 0.02583 5.92807 0.024 33.1

ZBS10% 658 157.0804 42.5755 0.03903 2.90155 0.0235 31.5

ZBS12% 525 87.85616 18.5764 0.02403 5.77973 0.0235 30.6

ZBM2% 1200 7.31162 3.4878 0.0057 0.65156 0.0055 27.2

ZBM4% 1200 7.60036 3.5078 0.00831 1.41365 0.0056 30.7

ZBM6% 1200 7.78613 2.8609 0.00873 1.58142 0.0058 37.8

ZBM8% 1200 9.23144 2.86398 0.00879 1.43465 0.006 33.3

ZBM10% 1200 8.44729 3.5163 0.00872 1.20418 0.0067 31.6

ZBM12% 1200 13.35113 8.4056 0.00843 1.31909 0.0073 32.6

ZBL2% 623 113.2588 29.3090 0.00696 1.77787 0.0214 35.8

ZBL4% 733 119.4576 23.5079 0.00904 1.96373 0.0206 37.9

ZBL6% 605 200.4741 23.5626 0.00865 1.45579 0.02397 26.4

ZBL8% 560 114.7912 27.0862 0.00772 1.83281 0.0283 28.4

ZBL10% 642 103.1524 27.8772 0.01159 0.93748 0.02438 29.4

ZBL12% 550 29.7767 19.5177 0.00848 0.855794 0.03 31.1

400

700

1000

1300

0 2 4 6 8 10 12

Igni

tion

time

(s)

Addition amount (%)

ZBSZBMZBL

Control IFR

Figure 1: Ignition time of wood treated with IFR/ZB coatings.

3International Journal of Polymer Science

25 kw·m-2 than that at 35 kw·m-2. 25 kw·m-2 was proposed toconduct cone calorimetry testing for acrylic fabrics [19]. It isnoted that this irradiance level is higher than the heat fluxlevel required for flashover which normally occurs at an inci-dent heat flux (at floor level) of 20 kw·m-2 [20]. Therefore, inthe current study, the samples were exposed to an incidentflux of radiant heat of 25 kw·m-2 in the first stage. Then, thecone calorimetry tests for samples Control IFR, ZBS2%,ZBM2%, and ZBL2% were also conducted at the heat fluxof 50 kw·m-2.

2.6. Infrared Smoke Analysis.MGA5 infrared smoke analyzerwas used to measure the concentration of CO in the smokewhich was produced by burning the specimens. The speci-men having a size of 25mm × 25mm × 6mm was placedon the metal net in the smoke box. The gas pressure of pro-pane was adjusted to 276 kPa. The sample was directlyignited with the propane burner, and the smoke producedwas completely collected in the test box.

2.7. Thermogravimetric-Differential Thermal Analysis. TGAand DTA were carried out on a TGA/DSC 3+ thermogravi-metric analyzer at a heating rate of 10°C/min. 2–4mg of the

sample was examined under both air atmosphere and nitro-gen atmosphere. The specimens were heated up to 900°C.

2.8. Fourier-Infrared Spectroscopy Experiments. The residualchar of IFR systems was collected after a cone calorimetertest. These char samples were examined by a Nicolet iS10FT-IR Spectrometer. To prepare pellets, the ratio of KBr toresidual char was 200 : 1, and the mixture was ground uni-formly in an agate mortar. The grounded powders were sub-jected to a compressive pressure of 20MPa for 1min to formKBr pellets.

2.9. Scanning Electron Microscopy and EDS Analysis. Themicrostructure of residual char was observed with a scanningelectron microscope (Hitachi S3700N). The residual charswere coated with gold palladium. The elemental compositionof samples was observed using EDAX (energy-dispersiveX-ray) spectrometry.

3. Results and Discussion

3.1. Combustion Performance. Cone calorimeter testing wascarried out to study the effects of ZB on the flammability ofIFR systems. The measured properties include TTI, THR,

0

10

20

30

40

0 300 600 900Time (s)

Control IFRZBS2% ZBS4%ZBS6%

ZBS8% ZBS10% ZBS12%

10.07

4.754

THR

(MJ·m

−2 ·k

g−1 )

(a) ZBS samples

0 300 600 900

Time (s)

Control IFRZBM2% ZBM4%ZBM6%

ZBM8% ZBM10% ZBM12%

10.07

2.3180

10

20

30

40

THR

(MJ·m

−2 ·k

g−1 )

(b) ZBM samples

0 300 600 900Time (s)

Control IFRZBL2% ZBL4%ZBL6%

ZBL8% ZBL10% ZBL12%

10.07

19.51

0

10

20

30

40

THR

(MJ·m

−2 ·k

g−1 )

(c) ZBL samples

Figure 2: Total heat release of wood treated with IFR/ZB coatings.


HRR, SPR, TSP, and mass loss. The values of these measuredproperties are summarized in Table 2.

The time to ignition was used as a measurement of ignit-ibility of materials. The ignition time of the samples is shownin Figure 1. Some samples were not ignited during the exper-iment; the exposure time of these samples was recorded asthe maximum TTI of 1200 s. The ignition time of substratescoated with the control coating (no ZB incorporated) is657 s. The incorporation of ZB with a large particle size (5-10 μm) has a little influence on TTI. On the other hand, theincorporation of ZB with a medium particle size (2-5 μm)increases TTI up to 1200 s. These trends are independenton the concentration of ZB in IFR coatings. The incorpora-tion of ZB with a small particle size (1-2 μm) increases TTIup to 1200 s at the loading levels of 2wt% and 4wt%. TTIdecreases as the ZBS concentration further increases.

THR results are presented in Figure 2. Figures 2(a),2(b), and 2(c) represent the total heat release curves of IFRcoatings incorporation of ZB with particle sizes of 1-2 μm,2-5μm, and 5-10μm, respectively. The THR value of thecontrol coating is 10.06MJ·m-2. When small ZB (1-2μm)was added into the IFR coating, the THR value decreases atthe loading levels of 2wt%, 4wt%, and 6wt%. The minimumvalue of 4.754MJ·m-2 was recorded when the loading level is4wt%. When medium ZB (2-5 μm) was added into the IFRcoating, the THR value decreases all investigated loadinglevels. The minimum value of 2.318MJ·m-2 was recorded at

a loading level of 2wt%. When large ZB (5-10 μm) wasadded, the THR value of modified IFR coating is higher thanthat of control IFR coating, regardless of the investigatedloading levels. When ZB with different particle size wasadded, the HRR curves of the IFR coating at an optimumloading level (corresponding to a minimum value of THR)are presented in Figure 3. The HRR curves of the controlIFR coating are also presented in Figure 3. The HRR valuesof all samples are presented in Table 2. The HRR value isinfluenced by the size of ZB and the loading level in a similarway as the THR value.

These results show that both the THR value and the HRRvalue are significantly reduced when medium ZB was addedinto the IFR coating. When the particle size is small, ZB tendsto agglomerate during mixing, leading to a poor dispersion.This may lead to the damage of formation of the char layerand thus increases the THR value and the HRR value, whenlarge amount of small ZB particles was added into the IFRcoating. When the particle size is large, ZB may have poorcompatibility with the fire retardant components due to thereduced surface area. This may be also unfavorable for theformation of the char layer, leading to the increase in theTHR value and the HRR value.

3.2. Smoke Suppression Performance. Smoke is the most com-mon cause of death in a fire disaster. Therefore, it is veryimportant to study the smoke suppression performance of

0

10

20

30

40

50

0 200 400 600 800 1000Time (s)

Control IFRZBS4%

12.043336

47.60933

HRR

(KW

·m−

2 )

(a) ZBS samples

0 200 400 600 800 1000Time (s)

Control IFRZBM2%

7.31162

47.60933

0

10

20

30

40

50

HRR

(KW

·m−

2 )

(b) ZBM samples

0 200 400 600 800 1000Time (s)

Control IFRZBL12%

47.60933

29.7767

0

10

20

30

40

50

HRR

(KW

·m−

2 )

(c) ZBL samples

Figure 3: Heat release rate of wood treated with IFR/ZB coatings.


IFR coatings with ZB [21]. The smoke produce rates mea-sured by a cone calorimeter for coated specimens are shownin Figure 4. The control coating has the largest SPR peak of0.0212m2/s at 140 s. When small ZB was added into theIFR coating at the loading level of 2wt%, the largest SPR peakat 115 seconds is 0.02m2/s. At the same loading level, whenmedium ZB was added into the IFR coating, the SPR peakat 120 seconds is 0.0057m2/s. This is the lowest SPR valuefor all specimens. Effects of ZB on SPR may be explainedby several reasons: (1) ZB can absorb dispersed solid (in asmoke) in the early stage of the combustion and (2) Zn gen-erated by the decomposition of ZB can promote formation ofchar and enhance the quality of char layer; the enhanced charlayer can hold back large amount of combustible gas and pre-vent oxidation reaction.

The total smoke production of wood treated with IFRsystems containing of ZB with a particle size range of 1-2 μm, 2-5μm, and 5-10μm is shown in Figures 5(a), 5(b),and 5(c), respectively. As it can be shown in Figure 5, the totalsmoke of the specimen with control coating is 2.8354m2/m2

and the TSP value of ZBS2% is less than that of the controlcoating. When a medium size was used, the addition of ZBdecreases TSP values. This is independent on the loadingof ZB. When a large size was used, the addition of ZBdecreases TSP values at the loading levels of 2wt%, 8wt%,

and 12wt%. The lowest TSP value was observed on ZBM2%,in which, the TSP value was reduced by 77.02%, as comparedto the control coating.

The smoke density (SD) is an important parameter toevaluate the performance of smoke suppression. The lowSD value is associated with high performance of smoke sup-pression. Figure 6 shows the SD results of wood treated withIFR/ZB coating. For ZBS, the SD value increases with theloading level. For ZBM, as loading level increases, the densityof smoke increases at a low ZB loading level and thendecreases at a high ZB loading level. For ZBL, the loadinglevel has a little influence on the DR value. ZBM2% showsthe lowest SDR value of 13.72%, which is significantly lowerthan that (25.32%) of the control coating. This result is con-sistent with TSR results obtained by using a cone calorimeter.

3.3. Effects of Particle Size on Combustion Performance andSmoke Suppression Performance at High Irradiance Level. Itcan be seen from the results presented in Section 3.1 and3.2 that the particle size has significant effects on the flameretardancy of IFR/ZB coatings. To further investigate sizeeffects, the loading level of 2wt% was selected for IFR/ZBcoatings with different particle size. It is noted that allIFR/ZBM coatings and some IFR/ZBS coating were notignited at fixed at an irradiance level of 25 kw·m-2. Therefore,

0

0.01

0.02

0.03

0.04

0 200 400 600 800Time (s)

Control IFRZBS2%ZBS4%ZBS6%

ZBS8%ZBS10%ZBS12%

0.02120.02SP

R (m

2 ·s−

1 )

(a) ZBS samples

0 200 400 600 800Time (s)

Control IFRZBM2%ZBM4%ZBM6%

ZBM8%ZBM10%ZBM12%

0.0212

0.0057

0

0.01

0.02

0.03

0.04

SPR

(m2 ·s

−1 )

(b) ZBM samples

0

0.01

0.02

0.03

0.04

SPR

(m2 ·s

−1 )

0 200 400 600 800Time (s)

Control IFRZBL2%ZBL4%ZBL6%

ZBL8%ZBL10%ZBL12%

0.02120.0069

(c) ZBL samples

Figure 4: Smoke production rate of wood treated with IFR/ZB coatings.


an irradiance level of 50 kw·m-2 was selected to carry out conecalorimetry tests. At a high irradiance level, woods coatedwith Control IFR, ZBS2%, ZBM2%, and ZBL2% were allignited, and the trend was similar with that at a low irradi-ance level. It can be seen from Figure 7 that the TTI of sub-strates coated with ZBM2% is the longest among all samples.

The THR and HRR curves of wood treated with ControlIFR, ZBS2%, ZBM2%, and ZBL2% at the irradiance level of50 kw·m-2 are presented in Figures (8) and (9), respectively.At Figure (8), Control IFR has the largest THR value of42.39 kw·m-2·kg-1. The addition of ZBS and ZBM reducesthe THR value to 17.98 kw·m-2·kg-1 and 11.81 kw·m-2·kg-1,respectively, while the addition of ZBM shows a little effectof the THR value. In Figure (9), the peak value of Control

0

2

4

6

0 200 400 600 800 1000Time (s)

Control IFRZBS2% ZBS4% ZBS6%

ZBS8% ZBS10% ZBS12%

2.8354

2.138TSP

(m2 ·m

−2 )

(a) ZBS samples

0.6516

2.8354

0

2

4

6

TSP

(m2 ·m

−2 )

0 200 400 600 800 1000Time (s)

Control IFRZBM2% ZBM4% ZBM6%

ZBM8% ZBM10% ZBM12%

(b) ZBM samples

2.8354

0.85560

2

4

6

TSP

(m2 ·m

−2 )

0 200 400 600 800 1000Time (s)

Control IFRZBL2% ZBL4% ZBL6%

ZBL8% ZBL10% ZBL12%

(c) ZBL samples

Figure 5: Total smoke production of wood treated with IFR/ZB coatings.

13

18

23

28

33

0 2 4 6 8 10 12 14

Max

imum

smok

e de

nsity

(%)

Addition amount (%)

ZBSZBMZBL

Control IFR

Figure 6: The maximum smoke density curve of wood treated withIFR/ZB coatings.

0

100

200

300

400

Control IFR ZBS2% ZBM2% ZBL2%

TTI (

s)

Samples

Figure 7: Ignition time of wood treated with IFR/ZB coatings(50 kw·m-2).


IFR is 284.2 kw·m-2. The addition of ZB can bring down thepeak HRR value. This is independent on a particle size.Among all samples, ZBM2% shows the lowest peak HRRvalue of 76.01 kw·m-2. According to the results of THR andHRR, the trend of samples Control IFR, ZBS2%, ZBM2%,and ZBL2% at a high irradiance level (50 kw·m-2) is consis-tent with the results at a low irradiance level (25 kw·m-2).

Figures 10 and 11 show the SPR curve and the TSP curveof IFR/ZB coatings, measured at an irradiance level of

50 kw·m-2. Again, results presented in these figures show asimilar trend to those obtained at an irradiance level of25 kw·m-2. The Control IFR has the largest peak SPR valueof 0.16m2·s-1, and the peak SPR value is reduced significantlyto 0.045m2·s-1 by the addition of ZBM2%. The TSP value ofControl IFR is 29.33m2·m-2, and the TSP value is reduced to6.12m2·m-2 after addition of ZBM2%.

0

20

40

60

80

0 200 400 600 800 1000 1200Time (s)

Control IFRZBS2%

ZBM2%ZBL2%

79.41

42.39

17.9811.81TH

R (M

J·m−

2 ·kg−

1 )

Figure 8: Total heat release of wood treated with IFR/ZB coatings(50 kw·m-2).

0

50

100

150

200

250

300

350

0 200 400 600 800 1000 1200Time (s)

Control IFRZBS2%

ZBM2%ZBL2%

284.2

192.38107.33 76.01H

RR (K

W·m

−2 )

Figure 9: Heat release rate of wood treated with IFR/ZB coatings(50 kw·m-2).

0

0.05

0.1

0.15

0.2

0 200 400 600 800 1000 1200Time (s)

Control IFRZBS2%

ZBM2%ZBL2%

0.16

0.13

0.081

0.045SPR

(m2 ·s

−1 )

Figure 10: Smoke production rate of wood treated with IFR/ZBcoatings (50 kw·m-2).

05

101520253035

0 200 400 600 800 1000 1200Time (s)

Control IFRZBS2%

ZBM2%ZBL2%

29.33

17.0314.65

6.12TSP

(m2 ·m

−2 )

Figure 11: Total smoke production of wood treated with IFR/ZBcoatings (50 kw·m-2).

0

0.01

0.02

0.03

0 2 4 6 8 10 12

Max

CO

con

cent

ratio

n (%

)

Loading amount (%)

ZBSZBMZBL

Control IFR

Figure 12: CO concentration wood treated with IFR/ZB coatings.

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16

Mas

s lo

ss (%

)

Addition amount (%)

ZBSZBMZBL

ZBS2%(50kw·m−2)ZBM2% (50kw·m−2)ZBL2% (50kw·m−2)

Control IFR

Control IFR (50kw·m−2)

Figure 13: Mass loss of wood treated with IFR/ZB coatings.


Based on the results presented in this section, the bestflame retardancy is achieved when medium ZB was intro-duced into the IFR coating.

3.4. Toxicity Reduction. In the process of the combustion ofpolymer, smoke released into the atmosphere may containmany toxic and noxious products such as CO, CO2, andnitrogen. It is believed that the death in a fire disaster ismainly due to the production of CO [22]. Therefore, the pro-duction of CO was selected as one of the parameters to eval-uate the effects of smoke suppression.

The variation in concentration of CO released fromeach sample is shown in Figure 12; the results showed thatspecimens (which were not ignited) have the lower CO con-centration in the experiments. The CO concentration ofZBM samples was lower than that of ZBS and ZBL, regardlessof loading levels. At all investigated loading levels, ZBL sam-ples exhibit higher values of CO concentration compared tothe control coating. As far as ZBS is considered, the CO con-centration of ZBS is lower than that of the control coating atloading levels of 2wt% and 4wt% but higher than that of thecontrol coating at 8% and 10%. Similar to the trend demon-strated by THR and TSP results, ZBM2% is an optimumcoating which could effectively reduce the produced COand favor the escape of people from a fire disaster.

3.5. Mass Loss. When exposed to a fire, the ratio of lossmass to initial mass of all coatings is shown in Figure 13.

The low mass loss suggests that large amount of solids(dispersed in a smoke) was captured by the residual char,indicating the good smoke suppression capacity. Theresults show that ZBL experienced higher mass loss com-pared to the control coating at ZB loading of 2wt% and4wt%. At the same ZB loading levels, ZBS and ZBM losttheir mass slower than the control coating. When theloading level further increases, mass loss of ZBS andZBM is similar or even higher than the control coating.When the loading level is fixed (e.g., 2%), mass loss ofZBM is much lower than that of the control coating. Asirradiance level increases, ZBM shows the lowest mass lossamong all samples.

When the coating decomposed and gas formed in theprocess of being heated, the fire retardant components aredehydrated and expanded to form a dense char layer whichcaptures the dispersed solid in the smoke. At small loadinglevels, the addition of ZBS or ZBM refines the char layer,leading to an increase in the mass of residual charring dueto capturing more solid particles in the smoke. As the loadinglevel increases, the occurrence of agglomeration of zincborate leads to a reduction in reaction efficiency betweenZB and fire retardant components. As a result, the formedchar layer may have a relative low density. During the com-bustion, large amount of solid particles may pass throughthe coarse char layer, resulting in the increase of mass lossrate. On the other hand, a dense char layer may be formedat a low loading level of ZB. For example, mass loss ofZBM2% is around 27%, which is lower than the control coat-ing with a 32% of mass loss. This sample also shows the low-est value of THR and SPR indicating an excellent flameretardancy. Therefore, the IFRs with a low loading level ofZB were selected for further characterisation. For a purposeof a comparison, the control coating was also examined byTGA, DTA, SEM, EDS, and FTIR.

3.6. Thermogravimetric-Differential Thermal Analysis. Thethermal degradation behavior of selected IFR coatings isinvestigated by thermal analytical techniques. The curves ofTGA and DTA are presented in Figures 14 and 15, respec-tively. The thermal analysis parameters and results are pre-sented in Table 3. The values of degradation temperatureT1% and T10% of IFR/ZB are slightly lower than those of thecontrol coating. When mass loss of IFR coatings increases,the degradation temperatures of IFR/ZB are consistentlyhigher than those of the control coating. This tendency isindependent on the size of ZB at a loading level of 2%. Incomparison with IFR/ZBS and IFR/ZBL, IFR/ZBM exhibitsthe highest thermal stability. This is demonstrated by itshigh initial degradation temperature. For example, the addi-tion of ZBM improved the initial degradation temperatureof IFR coating from 315°C to 331°C and 540°C to 630°C,corresponding to T30% and T70%, respectively. Table 3 alsopresents the mass of residual of char at elevated tempera-tures. At temperatures above 600°C, all IFR/ZB coatingsexhibit higher amount of char residue compared to the con-trol coating, indicating that ZB could reduce mass losscaused by char oxidation. Again, IFR/ZBM shows the highestamount of residual mass.

0

20

40

60

80

100

0 200 400 600 800

Wei

ght (

%)

Control IFRZBS2%

ZBM2%ZBL2%

Temperature (°C)

Figure 14: TG curves of IFR/ZB coatings (under air).

−10

−5

0

5

10

15

0 200 400 600 800

DTA

(𝜇V

)

Temperature (°C)

Control IFRZBS2%

ZBM2%ZBL2%

Figure 15: DTA curves of IFR/ZB coatings (under air).


The mass loss of a APP-PER-MEL IFR system maymainly take place in three temperature ranges. At tempera-tures below 260°C, the mass loss is attributed to the escapingwater from the coating. In the temperature range of 260 to450°C, the mass loss is attributed to the decomposition of fireretardant component and acrylic resin. At temperaturesabove 450°C, the mass loss is attributed to decompositionof char residue. In Figure 15, small endotherms at around100°C are associated with the evaporation of water from thecontrol coating. At 190°C and 390°C, the endotherms areattributed to the decomposition of APP and PER, respec-tively [23]. An endothermic peak at 420°C may be due tothe decomposition of acrylic resin. As temperature increases,a distinctive exothermic peak at 630°C is attributed to theoxidation of char. When ZB was introduced into the coatingsystem, the decomposition of acrylic resin takes place at tem-peratures below 400°C. In the temperature range of 180 to400°C, APP and PER decompose. Thus, the interaction ofAPP, PER, and acrylic resin will be promoted, leading tothe formation of a good “honeycomb” char structure. Theaddition of ZB significantly reduces the exothermic peak at630°C, indicating a better resistance to the oxidation of char.These tendencies are observed on all IFR/ZB coating at aloading level of 2%.

Fire occurs in air only in a very limited time. The com-bustion is practically performed in an oxygen-depleted envi-ronment. Therefore, TGA and DTA were also carried outunder nitrogen and the results are presented in Figures 16and 17, respectively. The thermal analysis parameters andresults are presented in Table 4. All IFR coatings (with orwithout ZB) start to decompose in nitrogen at higher temper-ature than those in air. This is agreed with results observedon polypropylene [24]. The thermal decomposition of poly-mers mainly proceeded by the action of heat. In many poly-mers, the thermal decomposition processes are acceleratedby oxidants [25]. Therefore, the minimum decompositiontemperatures are lower in air than those in nitrogen. A fur-ther examination of the decomposition temperatures showsthat the degradation temperatures of IFR/ZB are still consis-tently higher than those of the control coating. This trend isthe same as TGA results under air. A comparison of DTAcurves obtained under different atmosphere shows that theexothermic peak at 630°C is not observed in the control coat-ing tested under nitrogen. This is due to the lack of oxidationof char under nitrogen. Based on the results obtained undernitrogen, it can also be concluded that the addition of ZBincreases the initial decomposition temperature of fire retar-dant coating.

3.7. Morphologies of Char Residues. Residual char is animportant barrier for intumescent fire retardant coatings toretard the decomposition of combustible materials and pre-vent heat transfer and oxygen entry [26]. Figure 18 givesthe photo for residual char of the control coating and theIFR coatings with ZB at 2wt% of loading after cone calorim-eter tests. All specimens had formed intumescent and com-pact char layers. A comparison of char layers of differentspecimens reveals that the char layer of ZBM2% is thickand relatively dense without cracks. This char layer servesas an excellent thermal barrier, holding back the heat andoxygen. As a result, the wood treated with ZBM2% coatingexhibits the longest time to ignite during cone calorimetertests. The intumescing char residue of all these samples is fur-ther examined by SEM.

Figure 19 shows the microstructure of intumescingchars at high magnification. As can be seen from the fig-ure, intumescing chars taking from IFR/ZBs show a refine

Table 3: TGA data of IFR/ZB coatings (under air).

T1% (°C) T10% (

°C) T30% (°C) T50% (

°C) T70% (°C) W600°C (%) W700°C (%) W800°C (%)

Control IFR 51 169 315 370 540 20.98 2.57 1.01

ZBS2% 48 153 317 392 581 27.09 19.66 13.13

ZBM2% 45 160 331 394 630 30.98 26.31 19.67

ZBL2% 50 150 308 389 564 21.84 15.27 10.92

∗Note: T1%, T10%, T30%, T50%, and T70% are the temperature at which 1%, 10%, 30%, 50%, and 70% weight loss occurs, respectively.W600°C,W700°C, andW800°Care the residue of materials at 600, 700, and 800°C.

0

20

40

60

80

100

0 200 400 600 800

Wei

ght (

%)

Temperature (°C)

Control IFRZBS2%

ZBM2%ZBL2%

Figure 16: TG curves of IFR/ZB coatings (under nitrogen).

−10

−5

0

5

10

15

0 200 400 600 800

DTA

(𝜇V

)

Temperature (°C)

Control IFRZBS2%

ZBM2%ZBL2%

Figure 17: DTA curves of IFR/ZB coatings (under nitrogen).


microstructure in comparison with the control coating. Athigh magnification, the wood substrate can be clearly identi-fied in Figure 19(a). Figures 19(b), 19(c), and 19(d) presentthe SEM micrographs of intumescent chars obtained fromZBS2%, ZBM2%, and ZBL2%, respectively. The IFR/ZBsamples show a continuous and compact char structure.There is no efficient “honeycomb” char structure formedfrom IFR/ZBS. This may be attributed to the agglomerationof fine ZB particles, leading to the damage of a synergistic

effect between flame retardant additives and acrylic resin.This leads to the formation of a loose char structure withsmall holes. A homogenous char structure without visiblecavities is shown in Figure 19(c). The medium ZB particleshave a good interaction with fire retardant components, pro-moting the formation of char. At high temperature, ZB wasdecomposed into ZnO and B2O3. ZnO may take part in thechemical reaction during combustion to form more cross-linking network which reduces crack and shrinkage. Some

Table 4: TGA data of IFR/ZB coatings (under nitrogen).

T1% (°C) T10% (

°C) T30% (°C) T50% (

°C) T70% (°C) W600°C (%) W700°C (%) W800°C (%)

Control IFR 138 253 362 424 609 30.19 15.38 7.23

ZBS2% 124 256 385 427 620 30.74 25.14 17.56

ZBM2% 123 259 389 435 697 34.93 29.86 21.95

ZBL2% 134 247 359 415 533 27.76 24.15 13.42

∗Note: T1%, T10%, T30%, T50%, and T70% are the temperature at which 1%, 10%, 30%, 50%, and 70% weight loss occurs, respectively.W600°C,W700°C, andW800°Care the residue of materials at 600, 700, and 800°C.

Control IFR ZBS2% ZBM2% ZBL2%

Figure 18: Digital photos of residual char of IFR with ZB in different particle sizes.

50 𝜇m

(a)

50 𝜇m

(b)

50 𝜇m

(c)

50 𝜇m

(d)

Figure 19: SEM of (a) Control IFR, (b) ZBS2%, (c) ZBM2%, and (d) ZBL2%.


ZB particles are identified in Figure 19(d), indicating a poorinteraction between ZB and flame retardant additives. Theintumescing chars of ZBL2% show cracking due to the non-uniform shrinkage at high temperature.

The chemical compositions of char layers were deter-mined by EDS, as shown in Figure 20 and Table 5. Zn ele-ment is identified on ZBM2%, indicating that ZB wasdecomposed into ZnO and B2O3. ZnO may take part inthe chemical reaction during combustion to form morecrosslinking network in the char, leading to a dense charlayer and thus improves the performance of the coating.Compared to the control coating, ZBM2% shows a relativehigher content of P and O element. This is agreed with theresult reported in the previous study. Feng et al. [12] pro-posed that ZB could promote to remain more P and O inthe outer char layer and increase the crosslinking networkin the char layer.

3.8. Infrared Spectrum Analysis. The residual char after CCTwas collected and examined by FTIR. The spectrum curves ofthe control coating and ZBM2% are presented in Figure 21. Itcan be seen from this figure that the intensity of the absorp-tion peak of –(CH2)n– n > 4 (720 cm-1) increases when ZB

was incorporated in the IFR coating. This implies an increasein the mass of residual char, which is agreed with the TGAresult. The absorption peak at 1369 cm-1 is assigned to thebending vibration of C-H [27, 28]. The absorption peaks of–OH (1527 cm-1 and 3742 cm-1) are an indication of decom-position of PER while the absorption peak of C-NH2(3313 cm-1) is an indication of decomposition of APP [29].The absorption peak at 2417 cm-1 is associated with CO2[30] which is produced, as a result of the oxidation of char.The addition of ZB decreases the intensity of this peak. Thisagain confirms that ZBM2% has higher resistance to oxida-tion of char compared to the control coating. The stretchingvibration peaks of C=O (1778 cm-1) bond is attributed to theformation of aldehyde or ketone compounds. They are the

50 𝜇m

KCnt

8.4

6.7

5.0

3.4

1.7

0.01.00

TiO Mg P

KK

TiTi

2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00Energy-keV

C

(a) Sample Control IFR

19.1

15.3

11.5

7.7

3.8

0.01.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

Energy-keV

50 𝜇m

C Na

O

ZnTi

Ti

P

Ti Zn Zn

KCnt

(b) Sample ZBM2%

Figure 20: Energy spectrum pictures of Control IFR and ZBM2%.

Table 5: EDS results of Control IFR and ZBM2%.

Sample label Element CK OK PK TiK ZnK

Control IFRWeight% 81.56 09.83 03.09 02.03 —

Atomic% 88.76 08.03 01.30 00.55 —

ZBM%Weight% 18.95 37.02 31.84 07.93 03.77

Atomic% 30.55 44.82 19.91 03.21 01.12


intermediate nitrogen-containing production produced bythe reaction between acrylic resin and APP. The occurrenceof these intermediate products indicates the poor interactionbetween acrylic resin and APP. ZBM2% shows no stretchingvibration peaks of C=O bond. On the other hand, a new peakat 1680 cm-1 is observed on ZBM2%. This peak is attributedto water vapor, as a result of decomposition of ZB intoZnO and B2O3. Zn may be involved in the interactionbetween APP and acrylic resin, prompting the formation ofa char layer.

3.9. Effect of Particle Size on Flame Retardancy and SmokeSuppression. Figure 22 presents a schematic illustration foreffects of particle size on the performance of IFR coatings.The small particle is associated with a large surface areawhich may absorb more dispersed solid (in a smoke), as com-pared to large particles. On the other hand, the reducedsurface area (of IFR/ZBL) affects the interaction betweenZB and fire retardant components, leading to a coarse charlayer. As a result, ZBM2% exhibits better flame retardancyand smoke suppression performance compared to ZBL2%.Compared to ZBM and ZBL, ZBS has a larger surface areawhich is associated with a large surface force. However, theincrease in surface force causes agglomeration of ZB parti-cles in a mixing process. The agglomerated particles mayeven absorb less dispersed solids, as compared to large par-ticles. Therefore, the IFR/ZBS coatings show worse smokesuppression performance compared to the IFR/ZBL and

IFR/ZBM coatings. At a lower loading level, most of smallparticles are well dispersed. These particles have a good inter-action with fire retardant components, promoting the for-mation of char. The ZBS2% exhibits an increased charredresidue compared to ZBL2%. As reflected by THR and HRRvalues, the flame retardancy of IFR/ZBS coatings is higherthan that of IFR/ZBL coatings. However, due to the presen-tence of agglomerated particles, charred residue of IFR/ZBScoatings shows a relative loose structure with some smallholes on the outer char surface, declining flame retardancycompared to IFR/ZBM coatings.

4. Conclusions

In this paper, the APP-PER-MEL acrylic/IFR coatings wereprepared by the incorporation of ZB with different particlesize. Effects of particle size and loading level on fire retar-dancy and smoke suppression of the acrylic/IFR/ZB coatingwere studied. The DTA result reveals a decrease in exother-mic peak at 2417 cm-1, indicating that addition of ZBenhances the resistance of char oxidation of the IFR coating.This is believed to be due to the increased crosslinking net-work in the char layer. During the combustion, ZB decom-poses into B2O3 and ZnO. Zn is hypothesised to beinvolved in the interaction of APP, PER, and acrylic resin,promoting the reaction for char formation. As a result, adense “honeycomb” char structure was observed on the acry-lic/IFR/ZB coating. The dense and homogeneous char layer

Abso

rban

ce

4000 3000 2000Wavenumber (m−1)

1000

13691533

1533

1778

2416

2416

3313Control IFR

3313ZBM2%

3742

3742

16801369

720

720

Figure 21: Fourier infrared curve of Control IFR and ZBM2%.

Substrates

Char layer

Agg

lom

erat

ion

Smokeparticles

(a) IFR/ZBS

Substrates

Char layer

Smokeparticles

(b) IFR/ZBM

Substrates

Char layer

SmokeParticles

(c) IFR/ZBL

Figure 22: Schematic view of the effect of particle size.


holds back heat and oxygen and thus improves fire retar-dancy of the IFR coating.

The particle size of ZB shows a significant influence onfire retardancy of the IFR coating. The presence of the ZBwith a medium particle size increased the time to ignitionfrom 700 to 1200 s. This is independent on the loading levelof ZBM. The addition of ZB with a small particle sizeincreased the TTI value at the loading level up to 6wt%.As the loading level increases, the addition of ZBS shows alittle influence on the TTI value. The addition of ZB with alarge particle size also shows a little influence on the TTI,regardless of the loading levels. The result of THR andHRR is agreed with the TTI result. At all investigated load-ing levels, the addition of ZBM decreases the THR andHRR value. The lowest THR and HRR values were observedon acrylic/IFR/ZB at 2wt% of ZBM. Compared to the con-trol coating, the THR and HRR values of ZBM2% werereduced by 84.6% and 67.4%, respectively.

The smoke suppression performance of IFR coatings isexperimental investigated by both cone calorimeter test andinfrared smoke analysis. ZBM2% shows the lowest value ofTSP (determined by CCT) and smoke density (determinedby infrared smoke analysis). The toxicity reduction of IFRcoatings is investigated by monitoring CO concentrationduring the combustion. ZBM2% again exhibits the lowestCO concentration. Compared to the control coating, theTSP value and CO concentration were reduced by 77% and73.8%, respectively.

The cone calorimeter test of Control IFR, ZBS2%,ZBM2%, and ZBL2% is also conducted at a high irradiancelevel (50 kw·m-2). The results of TTI, THR, HRR, SPR, andTSP at a high irradiance level are consistent with those at alow level (25 kw·m-2). Compared with the control coatingand other IFR/ZB coatings, ZBM2% shows the best fire retar-dant and smoke suppression performance.

Data Availability

The data used to support the findings of this study are avail-able from the corresponding author upon request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

References

[1] H. Lu, L. Song, and Y. Hu, “A review on flame retardant tech-nology in China. Part II: flame retardant polymeric nanocom-posites and coatings,” Polymers for Advanced Technologies,vol. 22, no. 4, pp. 379–394, 2011.

[2] K. Huang, X. L. Cao, and H. Zhang, “Research progress andprospects of facing fire retardant coatings,” Value Engineering,vol. 10, no. 016, pp. 313-314, 2014.

[3] C. Jiao, X. Zhao, W. Song, and X. Chen, “Synergistic flameretardant and smoke suppression effects of ferrous powderwith ammonium polyphosphate in thermoplastic polyure-thane composites,” J Therm Anal Calorim, vol. 120, no. 2,pp. 1173–1181, 2015.

[4] C. Jiao, H. Wang, Z. Zhang, and X. Chen, “Preparation andproperties of an efficient smoke suppressant and flame-retardant agent for thermoplastic polyurethane,” Polymers forAdvanced Technologies, vol. 28, no. 12, pp. 1690–1698, 2017.

[5] X. Chen, Y. Jiang, and C. Jiao, “Smoke suppression proper-ties of ferrite yellow on flame retardant thermoplastic poly-urethane based on ammonium polyphosphate,” Journal ofHazardous Materials, vol. 266, pp. 114–121, 2014.

[6] L. Yan, Z. Xu, and X. Wang, “Influence of nano-silica on theflame retardancy and smoke suppression properties of trans-parent intumescent fire-retardant coatings,” Progress inOrganic Coatings, vol. 112, pp. 319–329, 2017.

[7] B. Xu, X. Wu, W. Ma, L. Qian, F. Xin, and Y. Qiu, “Synthesisand characterization of a novel organic-inorganic hybridchar-forming agent and its flame-retardant application inpolypropylene composites,” Journal of Analytical and AppliedPyrolysis, vol. 134, pp. 231–242, 2018.

[8] Y. Fang, Q. Wang, C. Guo, Y. Song, and P. A. Cooper, “Effectof zinc borate and wood flour on thermal degradation and fireretardancy of polyvinyl chloride (PVC) composites,” Journalof Analytical and Applied Pyrolysis, vol. 100, pp. 230–236,2013.

[9] X. He, X. Li, Z. Zhong et al., “The fabrication and propertiescharacterization of wood-based flame retardant composites,”Journal of Nanomaterials, vol. 2014, 6 pages, 2014.

[10] F. Zhang, P. Chen, Y. Wang, and S. Li, “Smoke suppressionand synergistic flame retardancy properties of zinc borateand diantimony trioxide in epoxy-based intumescent fire-retardant coating,” Journal of Thermal Analysis and Calorime-try, vol. 123, no. 2, pp. 1319–1327, 2016.

[11] Q. Tai, R. K. K. Yuen, W. Yang, Z. Qiao, L. Song, and Y. Hu,“Iron-montmorillonite and zinc borate as synergistic agentsin flame-retardant glass fiber reinforced polyamide 6 compos-ites in combination with melamine polyphosphate,” Compos-ites Part A: Applied Science and Manufacturing, vol. 43,no. 3, pp. 415–422, 2012.

[12] C. Feng, Y. Zhang, D. Liang, S. Liu, Z. Chi, and J. Xu, “Influ-ence of zinc borate on the flame retardancy and thermal stabil-ity of intumescent flame retardant polypropylene composites,”Journal of Analytical and Applied Pyrolysis, vol. 115, pp. 224–232, 2015.

[13] Z. Wu, Y. Hu, and W. Shu, “Effect of ultrafine zinc borate onthe smoke suppression and toxicity reduction of a low‐densitypolyethylene/intumescent flame‐retardant system,” Journal ofApplied Polymer Science, vol. 117, no. 1, pp. 443–449, 2010.

[14] X. L. Lin, H. P. Liu, J. Z. Zhang, P. Zhu, and Z. R. Liu, “Studyon zinc borate/APP-MEL-PER composites flame-retardantpolyoxymethylene,” Fire Science and Technology, vol. 37,p. 32, 2018.

[15] M. Doğan and E. Bayramlı, “Synergistic effect of boron con-taining substances on flame retardancy and thermal stabilityof clay containing intumescent polypropylene nanoclay com-posites,” Polymers for Advanced Technologies, vol. 22, no. 12,pp. 1628–1632, 2011.

[16] C. Liu, B. Xiang, Y. Liu et al., “Synthesis of aqueous andhydroxy-terminated polyurethanes:impacts of formulationparameters by orthogonal matrix design,” Progress in OrganicCoatings, vol. 90, pp. 1–9, 2016.

[17] The British Standards Institution, BS ISO 5660-1:2015Reaction-to-fire tests-heat release, smoke production and massloss rate Part 1: Heat release rate (cone calorimeter method)


and smoke production rate (dynamic measurement), BSIStandards Limited, Geneva, Switzerland, 2015.

[18] F. Carosio, J. Alongi, and G. Malucelli, “Flammability andcombustion properties of ammonium polyphosphate-/poly(-acrylic acid)- based layer by layer architectures deposited oncotton, polyester and their blends,” Polymer Degradation andStability, vol. 98, no. 9, pp. 1626–1637, 2013.

[19] F. Carosio and J. Alongi, “Flame retardant multilayeredcoatings on acrylic fabrics prepared by one-step deposition ofchitosan/montmorillonite complexes,” Fibers, vol. 6, no. 2,p. 36, 2018.

[20] C. K. Chen, Combustion Theory, China Machine Express, Bei-Jing, China, 2012.

[21] J. W. Hao, H. X.Wen, J. X. Du, R. J. Yang, and Y. X. Ou, “Studyon fire resistance and mechanism of zinc borate synergisticintumescent flame retardant epoxy coating,” Journal of BeijingInstitute of Technology, vol. 32, no. 10, pp. 1091–1095, 2012.

[22] W. Jincheng, Y. Shenglin, L. Guang, and J. Jianming, “Synthe-sis of a New-type Carbonific and Its Application in Intumes-cent Flame-retardant (IFR)/Polyurethane Coatings,” Journalof Fire Sciences, vol. 21, no. 4, pp. 245–266, 2003.

[23] Z. Wang, E. Han, and W. Ke, “Effect of acrylic polymer andnanocomposite with nano-SiO2 on thermal degradation andfire resistance of APP-DPER-MEL coating,” Polymer Degrada-tion and Stability, vol. 91, no. 9, pp. 1937–1947, 2006.

[24] D. E. Stuetz, A. H. Diedwardo, F. Zitomer, and B. P. Barnes,“Polymer flammability,” Journal of Polymer Science: PolymerChemistry, vol. 18, no. 3, pp. 967–985, 1980.

[25] M. J. Hurley, SFPE Handbook of Fire Protection Engineering(Fifth Edition), Springer-Verlag New York Inc, New York,USA, 2016.

[26] S. Gayathri, N. Kumar, R. Krishnan et al., “Influence of transi-tion metal doping on the tribological properties of pulsed laserdeposited DLC films,” Ceramics International, vol. 41, no. 1,pp. 1797–1805, 2015.

[27] Z. Huang and W. Shi, “Thermal behavior and degradationmechanism of poly(bisphenyl acryloxyethyl phosphate) as aUV curable flame-retardant oligomer,” Polymer Degradationand Stability, vol. 91, no. 8, pp. 1674–1684, 2006.

[28] W. Yang, B. Tawiah, C. Yu et al., “Manufacturing, mechan-ical and flame retardant properties of poly(lactic acid) bio-composites based on calcium magnesium phytate andcarbon nanotubes,” Composites Part A: Applied Science andManufacturing, vol. 110, pp. 227–236, 2018.

[29] F. Zhang, J. Zhang, and D. Sun, “Study on thermal decom-position of intumescent fire-retardant polypropylene byTG/Fourier transform infrared,” Journal of ThermoplasticComposite Materials, vol. 22, no. 6, pp. 681–701, 2009.

[30] R. Zhang, H. Huang, W. Yang, X. Xiao, and Y. Hu, “Effectof zinc borate on the fire and thermal degradation behaviors ofa poly(3-hydroxybutyrate-co-4-hydroxybutyrate)-containingintumescent flame retardant,” Journal of Applied Polymer Sci-ence, vol. 125, no. 5, pp. 3946–3955, 2012.


CorrosionInternational Journal of

Hindawiwww.hindawi.com Volume 2018

Advances in

Materials Science and EngineeringHindawiwww.hindawi.com Volume 2018


Journal of

Chemistry

Analytical ChemistryInternational Journal of


Scienti�caHindawiwww.hindawi.com Volume 2018

Polymer ScienceInternational Journal of



Advances in Condensed Matter Physics


International Journal of

BiomaterialsHindawiwww.hindawi.com

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of


NanotechnologyHindawiwww.hindawi.com Volume 2018

Journal of


High Energy PhysicsAdvances in

Hindawi Publishing Corporation http://www.hindawi.com Volume 2013Hindawiwww.hindawi.com

The Scientific World Journal

Volume 2018

TribologyAdvances in



ChemistryAdvances in


Advances inPhysical Chemistry


BioMed Research InternationalMaterials

Journal of


Na

nom

ate

ria

ls


Journal ofNanomaterials

Submit your manuscripts atwww.hindawi.com
https://www.hindawi.com/journals/ijc/https://www.hindawi.com/journals/amse/https://www.hindawi.com/journals/jchem/https://www.hindawi.com/journals/ijac/https://www.hindawi.com/journals/scientifica/https://www.hindawi.com/journals/ijps/https://www.hindawi.com/journals/acmp/https://www.hindawi.com/journals/ijbm/https://www.hindawi.com/journals/je/https://www.hindawi.com/journals/jac/https://www.hindawi.com/journals/jnt/https://www.hindawi.com/journals/ahep/https://www.hindawi.com/journals/tswj/https://www.hindawi.com/journals/at/https://www.hindawi.com/journals/ac/https://www.hindawi.com/journals/apc/https://www.hindawi.com/journals/bmri/https://www.hindawi.com/journals/jma/https://www.hindawi.com/journals/jnm/https://www.hindawi.com/https://www.hindawi.com/

effectsofsizeofzincborateontheflameretardantpropertiesof ...ammonium polyphosphate (app) in tpu...

Documents