rs

polycarbonate/acrylonitri

Eliza Wawrzyn a, Bernhard SchaUlrike Braun a, Manfred Dring b

aBAM Federal Institute for Materials Research and Tesb Institute of Technical Chemistry, KIT Karlsruhe Instituc Leibniz Institute of Polymer Research Dresden, Hohe

Bisphenol A bis(diphenyl phosphate) (BDP) and resor-cinol bis(diphenyl phosphate) (RDP) are effective halo-gen-free ame retardants for bisphenol A polycarbonate/acrylonitrilebutadienestyrene (PC/ABS) blends [15].Oligomeric aryl phosphates combine gas-phase and

cross-linking reactions within the pyrolysis zone [9,10]. Itwas pointed out that the increasing decompositiontemperature of commercially available aryl phosphatessuch as triphenyl phosphate (TPP), RDP and BDP increasestheir activity in the condensed phase of PC/ABS/polytetra-uoroethylene (PC/ABSPTFE) blend [11]. Increasing theoverlap between decomposition temperature ranges in-creases the probability for reactions between the ame

0014-3057/$ - see front matter 2012 Published by Elsevier Ltd.

Corresponding author. Tel.: +49 30 81041021.E-mail address: bernhard.schartel@bam.de (B. Schartel).

European Polymer Journal 48 (2012) 15611574

Contents lists available at SciVerse ScienceDirect

European Poly

elsehttp://dx.doi.org/10.1016/j.eurpolymj.2012.06.015PTFE

enhancing the cross-linking of PC, whereas BEP shows worse performance because itprefers cross-linking with itself rather than with PC. As to its re behavior, PC/ABSPTFE +TMC-BDP presents results very similar to PC/ABSPTFE + BDP; the blend PC/ABSPTFE + BEPshows lower ame inhibition and higher total heat evolved (THE). The UL 94 for the mate-rials with TMC-BDP and BDP improved from HB to V0 for specimens of 3.2 mm thicknesscompared to PC/ABSPTFE and PC/ABSPTFE + BEP; the LOI increased from around 24% up toaround 28%, respectively. BEP works as the strongest plasticizer in PC/ABSPTFE, whereasthe blends with TMC-BDP and BDP present the same rheological properties. PC/ABSPTFE +TMC-BDP exhibits the best mechanical properties among all ame-retarded blends.

2012 Published by Elsevier Ltd.

1. Introduction condensed-phase modes of action [68]. They act as ascavenger of H or OH radicals in the ame and initiatea r t i c l e i n f o

Article history:Received 27 April 2012Received in revised form 22 June 2012Accepted 25 June 2012Available online 3 July 2012

Keywords:Polycarbonate (PC)Aryl phosphateFlame retardancyPyrolysisPC/ABSlebutadienestyrene blends?

rtel a,, Michael Ciesielski b, Bernd Kretzschmar c,

ting, Unter den Eichen 87, 12205 Berlin, Germanyte of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, GermanyStr. 6, 01069 Dresden, Germany

a b s t r a c t

The reactivity of the ame retardant and its decomposition temperature control the con-densed-phase action in bisphenol A polycarbonate/acrylonitrilebutadienestyrene/poly-tetrauoroethylene (PC/ABSPTFE) blends. Thus, to increase charring in the condensedphase of PC/ABSPTFE + aryl phosphate, two halogen-free ame retardants were synthesized:3,3,5-trimethylcyclohexylbisphenol bis(diphenyl phosphate) (TMC-BDP) and bisphenol Abis(diethyl phosphate) (BEP). Their performance is compared to bisphenol A bis(diphenylphosphate) (BDP) in PC/ABSPTFE blend. The comprehensive study was carried out usingthermogravimetry (TG); TG coupled with Fourier transform infrared spectrometer (TG-FTIR); the Underwriters Laboratory burning chamber (UL 94); limiting oxygen index(LOI); cone calorimeter at different irradiations; tensile, bending and heat distortion tem-perature tests; as well as rheological studies and differential scanning calorimeter (DSC).With respect to pyrolysis, TMC-BDP works as well as BDP in the PC/ABS blend byphosphate) in halogen-free ame-retarded

Are novel aryl phosphates competito

journal homepage: www.for bisphenol A bis(diphenyl

mer Journal

vier .com/locate /europol j

action of phosphates depends on the reactivity of the com-

ABSPTFE and compared to each other using thermal analysis

were provided by Bayer MaterialScience AG (Dormagen,Germany). The extruder has a screw diameter of 27 mmand a length of 36 D. The pellets of PC/ABSPTFE were pre-dried for 3 h at 373 K and fed into the hopper. The liquidTMC-BDP and BEP, heated up to 383 K, were introducedinto barrel 4 at 14 D length at 523 K. Gravimetric dosingsystems were used in both cases. The following processingparameters were applied: an increasing temperature pro-gram from 503 K to 523 K, a screw speed of 200 rpm anda throughput of 10 kg/h. The extruded strands were pellet-ized after cooling in a water bath.

The cone calorimeter specimens were manufacturedfrom pellets using an Allrounder 420 C 1000-250 injection

sample molding was done according to CAMPUS condi-

1562 E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574(TG), ammability (LOI, UL 94), re behavior (cone calo-rimeter at different external heat uxes), mechanical tests(tensile test, bending test and heat distortion temperaturetest) as well as rheological test and differential scanningcalorimeter (DSC). TMC-BDP is proposed as an interestingalternative to BDP.

2. Experimental section

2.1. Synthesis of aryl phosphates

All materials and reagents used for the reactions werepurchased from Aldrich and used without any furtherpurication. 1H and 31P nuclear magnetic resonance spec-troscopy (NMR) spectra were obtained using a BrukerAC-250 Spectrometer at 250 MHz. Tetramethylsilane andtrimethyl phosphate, respectively, were used as internalstandards. Samples were analyzed in deuterated DMSO.The melting point was measured using the melting pointapparatus Bchi B-545 at heating rate of 3 K min1. Theelemental analysis was carried out using a Vario EL III fromElementar Analysensysteme GmbH. The purity of obtainedaryl phosphate was studied by means of high-performanceliquid chromatography (HPLC) using HP 1100 HewlettPackard. The mobile phase consisted of acetonitrile/water,ow rate was 1 ml/min and the monitoring wavelengthwas 254 nm.

2.2. Preparation of the blends

The synthesized aryl phosphates and BDP were incorpo-rated into PC/ABSPTFE using a co-rotating twin-screw extru-der Micro 27 (Leistritz, Nuremberg). PC/ABSPTFE and BDPpound used [12]. More reactive aryl phosphates increasethe activity in the condensed phase due to more cross-link-ing with PC.

The aim of this work was to enhance charring in thecondensed phase of PC/ABSPTFE + aryl phosphate. To reachthis goal two approaches were proposed:

(1) increasing the decomposition temperature of thearyl phosphate beyond the decomposition tempera-ture of BDP,

(2) using aliphatic derivatives of bisphenol A phosphateto increase the cross-linking activity due to the earlyscission of the aliphatic groups.

Thus, so far only two patents [13,14] mentioned novelame retardants were synthesized: 3,3,5-trimethylcyclo-hexylbisphenol bis(diphenyl phosphate) (TMC-BDP) andbisphenol A bis(diethyl phosphate) (BEP), showing a higherdecomposition temperature and higher char yield, respec-tively. TMC-BDP, BEP and BDP were incorporated in PC/retardant and PC decomposition products [11]. In otherwords, correspondence between the decompositiontemperature range of aryl phosphate and the PC/ABSPTFEdecomposition is a prerequisite for enhanced charring inthe condensed phase. Additionally, the ame retardingtions. An increasing temperature program up to 523 Kwas used, the injection speed was 40 mm/s and the moldtemperature was set at 353 K.

The composition of studied blends is given in Table 1.All investigated samples consisted of unbranched polycar-bonate based on bisphenol A. PTFE masterbatch was addedas an antidripping agent in the ratio 1:1 of styreneacrylo-nitrile (SAN) copolymer and neat PTFE. The ABS ratio was21:13:66 and its particles were embedded within thehomogenous PC matrix phase. The ABS exhibited a coreshell structure, since butadiene rubber particles weregrafted with SAN. The molecular weight of BDP, if consist-ing of one repeating unit, was MwBDP = 696.6 g/mol. Theoligomeric BDP investigated had an average repeating unitof n = 1.1 and contained about 2.5% of TPP. For the ame-retarded PC/ABSPTFE blends the same amount of aryl phos-phate was always applied (10 wt.%). This means that theblends had different phosphorus content (Table 1).

2.3. Characterization

The pyrolysis experiments were performed using TG ona TGA/SDTA 851 (Mettler Toledo, Germany) under nitrogenand a heating rate of 10 K min1. The sample mass was10 mg for each measurement. FTIR spectrometer Nexus470 (Nicolet, Germany) was coupled with TG to analyze

Table 1Composition of investigated blends in wt.% (remaining wt.% is otheradditives).

PC/ABSPTFE PC/ABSPTFE +BDP

PC/ABSPTFE +TMC-BDP

PC/ABSPTFE +BEP

PC 81.14 73 73 73ABS 17.14 15.42 15.42 15.42PTFE 0.52 0.46 0.46 0.46BDP 10TMC-BDP 10BEP 10P-content 0 4.3 3.9 7.7molding machine (Arburg, Germany) with a cylinder diam-eter of 35 mm and clamping force of 1000 kN. The speci-mens for LOI and UL 94 and the multipurpose testspecimens (ISO 3167 type A) for the mechanical tests weremolded using a machine Ergotech 100/420-310 (Demag,Germany) with cylinder diameter of 30 mm and clampingforce of 1000 kN and a two-cavity mold. In both cases,

phases were extracted with 1 N solution of sodium hydrox-

E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574 1563the pyrolysis gases. The temperature of the transfer linewas held constant at 523 K and that of the gas cell at533 K during each measurement.

The forced aming behavior of the blends was investi-gated using cone calorimeter (FTT, UK) following ISO5660 under three irradiations: 35, 50 and 70 kWm-2. Thesample size was (100 100 4) mm. The specimens werewrapped in aluminum foil and placed horizontally in theframe under the cone heater at a distance of 35 mm. Theammability (reaction to the small ame) was determinedaccording to the UL 94 test for the ammability of plasticsby vertical (V2, V1, V0) and horizontal (HB) classicationsfollowing IEC 60695-11-10, and according to LOI followingISO 4589-2. The dimensions of the specimens for the UL 94test were (120 12.5 1.6) mm and (120 12.5 3.2)mm; those for LOI test were (127 6.5 3.2) mm.

For rheological investigations the rheometer Anton PaarPhysica MCR 301 was used, with plateplate geometry, agap of 1 mm and a plate diameter of 25 mm. Isothermalmeasurements were conducted in the frequency sweepmode at the following temperatures: for PC/ABSPTFE andPC/ABSPTFE + BDP at 473 K, 498 K, 543 K and 588 K; forPC/ABSPTFE + BEP at 473 K, 498 K and 543 K; for PC/ABSPT-FE + TMC-BDP at 498 K, 543 K and 588 K. The frequencywas varied between 100 Hz and 0.1 Hz and a small defor-mation (gamma = 0.5%) was chosen. All measurementswere taken in a nitrogen environment. The master-curvesof the materials were determined with the referencetemperature of 498 K.

The glass transition temperature (Tg) was determinedusing the differential scanning calorimeter (DSC) per-formed on a DSC 7020 (Mettler Toledo, Germany). The fol-lowing parameters were applied: the temperatureprogram between 203 K and 523 K, three times heatingand two times cooling, both at a rate of 10 K min-1, and anitrogen ow of 50 ml min-1. The sample mass was 5 mg.

The mechanical properties were determined usingtensile, bending and heat distortion temperature tests.For tensile tests a Zwick UPM 1456 universal testing ma-chine (Zwick Ulm, Germany) was used; bending tests wereconducted on a UPM zwicki 2,5 (Zwick Ulm, Germany)according to ISO 527 and ISO 178, respectively. The charpyimpact strength tests were carried out on PSW 25 J testingequipment (WPM Leipzig GmbH, Germany) with respect toISO 179 and the heat distortion temperature was deter-mined using HDT 3/Vicat (CEAST, Italy) according to ISO75 under 0.45 MPa load. The tests were carried out at roomtemperature and the data obtained represented the aver-age value from 10 test specimens.

The determination of phosphoric acid content of neataryl phosphates as well as the molecular weight distribu-tions of PC/ABSPTFE + aryl phosphate blends were carriedout using gel permeations chromatography (GPC) with aPSS SDV column (5 lm, ID 8.0 mm x 300 mm), dichloro-methane as an eluent at a ow rate of 1.0 ml/min. ThisGPC system was operated at 296 K using a PSS SECcurity1200 HPLC pump and a PSS SECcurity 1200 DifferentialRefractometer RID detector. The concentration of thesample solutions was about 5.0 mg/ml. The samples werecompletely dissolved by stirring at about 313 K overnight.The calculation of the average molecular weights and theide (NaOH, 3 100 ml) and with water (1 100 ml). Theremaining organic layer was dried with magnesium sulfate(MgSO4), ltered off and evaporated. Next, the crude prod-uct was dissolved in CH2Cl2 (182 ml) and extracted oncemolecular weight distribution of the samples was carriedout by the so-called slice by slice method based on thepolystyrene (PS) calibration.

3. Results and discussion

3.1. Synthesized ame retardants

Two ame retardants were synthesized: TMC-BDP andBEP. TMC-BDP were obtained in two-step reactions(Fig. 1a and b), and BEP in one step (Fig. 1c).

3,3,5-trimethylcyclohexylbisphenol (TMC; Fig. 1a):Phenol (1000 g, 10.64 mol), dodecylthiol (35.8 g, 0.18mol) and dihydroisophorone (3,3,5-trimethylcyclohexan-1-one) (248 g, 1.77 mol) were placed in a stirring appara-tus, equipped with a stirrer, thermometer, reux con-denser and gas inlet pipe. The system was heated to301 K and dry hydrogen chloride (HCl) gas was addedslowly while stirring over a period of 5 h at a temperatureof 301303 K. The mixture was left to react overnight atroom temperature. Then it was stirred again for 1 h at atemperature of around 303 K. Next the water (1.5 l) wasadded to the reaction mixture and a pH value of 6 was ad-justed by adding a 45% solution of sodium hydroxide(NaOH). The system was stirred again for 1 h at 353 Kand afterwards cooled down to room temperature. Theresulting crude product was ltered off and washed threetimes with hot water (353 K). Then the residue was hot-ex-tracted with hexane and twice with methylene chloride(CH2Cl2). The product was recrystallized from xylene andleft to dry under air at ambient temperature. The yieldwas 77%. Using this procedure a total of around 900 gTMC was obtained. The white product had a melting pointof 482485 K (literature: 482485 K [15]) and was usedwithout further purication. TMC was characterized with1H NMR (Fig. 2a). Spin multiplicity is indicated: singlet, du-plet, triplet, quartet and multiplet. The chemical shifts inTMC are given in the following: 1H NMR (DMSO, ppm):d = 0.31 (s, 3H), 0.92 (overlapped signals: s, 6H and m,2H), 1.29 (d, 1H), 1.71 (d, 1H), 1.86 (m, 1H), 2.41 (d, 1H),2.58 (d, 1H), 6.59 (dd, 4H), 7.03 (dd, 4H), 9.06 (bs, 2H).

TMC-BDP (Fig. 1b): TMC (200 g, 0.65 mol) and tetrahy-drofuran (THF, 364 ml) were lled into a three-neckedround-bottomed ask equipped with a stirrer, thermome-ter, inert gas pipe and dropping funnel. When TMC wasdissolved, the triethylamine (182 ml) was added and thereaction mixture was cooled down to 278 K using an icewater bath. Then, diphenyl chlorophosphate (364 g,1.35 mol) was fed into the reaction mixture via a droppingfunnel over a period of 5 h in an inert atmosphere in thetemperature range from 278 K to 282 K. After introducingdiphenyl chlorophosphate, the reaction system was stirredovernight at ambient temperature. The obtained triethyl-ammonium chloride was ltered off and washed withtert-butyl methyl ether (3 90 ml). The combined organic

1564 E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574more with 1 N of NaOH (3 100 ml) and with water(1 100 ml) in order to thoroughly remove impurities.The organic phase was dried, ltered and evaporated. Theproduct yield was 73%. Using this procedure a total ofaround 2240 g of TMC-BDP was obtained. The purity of iso-lated TMC-BDP was over 98% and was established by HPLCdetection in which the main peak was eluted at 23.273 min(data not shown). TMC-BDP was characterized with 1HNMR (Fig. 2b) and with 31P NMR. 1H NMR (DMSO, ppm):d = 0.29 (s, 3H), 0.94 (overlapped signals: s, 6H and m,2H), 1.31 (d, 1H), 1.83 (overlapped signals: d, 1H and m,1H), 2.57 (d, 1H), 2.78 (d, 1H), 7.05-7.48 (overlapped sig-nals, 28H); 31P NMR (DMSO): d = 15.93 ppm. Elementalanalysis of TMC-BDP gave the following results: C68.71 wt.%, H 5.67 wt.%. P 7.86 wt.%; Calculated: C

Fig. 1. Synthesis route of (a) TMC76.25 wt.%, H 5.97 wt.%, P 8.74 wt.%. The molecular weightof TMC-BDP, if consisting of one repeating unit, wasMwTMC-BDP = 712.4 g/mol. The oligomeric TMC-BDP investi-gated had an average repeating unit of n = 1.1. The elugramshowed before the main TMC-BDP peak a small signal fromlarger oligomer. The obtained TMC-BDP is free of byprod-ucts and impurities, particularly no phosphoric acid wasfound using GPC measurements.

The synthesis of BEP (Fig. 1c) was performed similar tothe synthesis of TMC-BDP, at a temperature of 278282 Kusing bisphenol A (45.6 g, 0.2 mol) and diethyl chlorophos-phate (70 g, 0.4 mol) as reagents and THF (122 ml) as thesolvent. Triethylamine (56 ml) was applied as an auxiliarybase. Diethyl chlorophosphate was introduced into thereaction mixture over a period of 1.52 h at a temperature

, (b) TMC-BDP and (c) BEP.

E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574 1565between 278 K and 282 K, and afterwards the system wasleft to react overnight at room temperature while stirred.The resulting residue was washed with tert-butyl methylether (3 25 ml). An organic layer was extracted with1 N solution of NaOH (3 30 ml) and with water

Fig. 2. 1H NMR of (a) TMC, (b(1x30 ml). The product layer was separated and dried withMgSO4. The MgSO4 was ltered off and the solvent was re-moved by heating to around 373 K at reduced pressure.The extraction procedure was not repeated. The yieldwas 81%. In this way around 700 g of BEP was obtained.

) TMC-BDP and (c) BEP.

1.7% of phosphoric acid. The elugram showed before themain BEP peak a small signal from larger oligomer.

Fig. 3. Mass and mass loss rate of BDP (stars), TMC-BDP (triangles) and BEP (circles), under N2, heating rate = 10 K min1.

Table 2Thermal analysis of BDP, TMC-BDP and BEP (under N2, heating rate

-1

1566 E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574The purity of BEP was over 90% and BEP was eluted at7.337 min using HPLC (data not shown). BEP was charac-terized with 1H NMR (Fig. 2c) and with 31P NMR. 1H NMR(DMSO, ppm): d = 1.25 (t, 12H), 1.61 (s, 6H), 4.12 (q, 8H),

31

10 K min ).

BDP TMC-BDP BEP

T2wt% /2 K 592 644 512Tmax /2 K 735 759 582Weight loss/1 wt.% 96.1 97.3 82.2Residue/1 wt.% 3.9 2.7 17.87.01 (d, 4H), 7.23 (d, 4H); P NMR (DMSO): d = 5.04 ppm.Elemental analysis of BEP gave the following results: C54.68 wt.%, H 6.77 wt.%. P 12.24 wt.%; Calculated: C57.77 wt.%, H 5.85 wt.%, P 12.84 wt.%. The molecularweight of BEP, if consisting of one repeating unit, wasMwBEP = 500.4 g/mol. The oligomeric BEP investigated hadan average repeating unit of n = 0.95 and contained about

Fig. 4. Mass and mass loss rate of PC/ABSPTFE (line), PC/ABSPTFE + BDP (stars), Pheating rate 10 K min1.The other characteristic of the synthesized ame retar-dants was achieved using thermogravimetry. The TG re-sults of BDP, TMC-BDP and BEP are shown in Fig. 3 andTable 2. All of the aryl phosphates decomposed in singledecomposition step with the maximum mass loss rate(Tmax) at 735 K for BDP, 759 K for TMC-BDP and 582 K forBEP. Additionally, for BEP a broad shoulder was observedbefore (500550 K) and after (600650 K) the decomposi-tion step. BEP began decomposing rst and left 17.8 wt.%of residue. BDP decomposed at 592 K and yielded 3.9 wt.%of residue, whereas TMC-BDP started to decompose at644 K and its residue was 2.7 wt.%. TMC-BDP was morestable than BDP. According to the rst approach of thisstudy, TMC-BDP in PC/ABSPTFE increases the overlap of bothdecomposition areas, possibly enabling stronger interac-tions between ame retardant and the rearranged PCstructure. BEP showed the enhanced charring action incomparison to both BDP and TMC-BDP. With respect toC/ABSPTFE + TMC-BDP (triangles) and PC/ABSPTFE + BEP (circles) under N2,

the second motivation, more reactive BEP increases theprobability of networking with PC during decomposition.

showed an additional minor step originating from BEPdecomposition before the two major decomposition steps

Table 3Thermal analysis of PC, ABS, PC/ABSPTFE, PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BDP and PC/ABSPTFE + BEP (under N2, heating rate 10 Kmin-1).

PC ABS PC/ABSPTFE PC/ABSPTFE + BDP PC/ABSPTFE + TMC-BDP PC/ABSPTFE + BEP

T2wt%/2 K 752 655 675 665 657 582Mass loss proceeds from BEP decompositionTmax/2 K - - - - - 585Weight loss/1.0 wt.% - - - - - 6.91st main decomposition: ABSTmax/2 K 688 715 700 700 703Weight loss/1.0 wt.% 97.3 25.6 25.0 22.4 26.92nd main decomposition: PCTmax/2 K 798 - 770 794 785 798Weight loss/1.0 wt.% 72.2 - 55.2 51.2 55.9 43.7Residue at 1000 KMass/1.0 wt.% 27.8 2.7 19.2 23.8 21.7 22.5Calculated residueMass/1.0 wt.% 17.7 17.6 19.1

E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574 15673.2. Pyrolysis of PC/ABSPTFE+aryl phosphate: Mass loss

Three aryl phosphates were blended with PC/ABSPTFEand compared with each other and with non-ame-re-tarded PC/ABSPTFE blend. Thermal analysis of PC/ABSPTFE,PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BDP, PC/ABSPTFE + BEPis shown in Fig. 4 and Table 3. Additionally Table 3 pre-sents thermogravimetry results of neat PC and ABS. PCand ABS decomposed in single step with the maximumdecomposition temperature (Tmax) at 769 K and 688 K,respectively. PC yielded 27.8 wt.% residue and ABS2.7 wt.%. Compared to PC and ABS, for PC/ABSPTFE the ABSdecomposition is shifted to higher and the PC to lowertemperatures indicating interactions between the compo-nents and resulting in a strong overlap of the decomposi-tion ranges [6], whereas adding aryl phosphate increasesthe separation of the decomposition ranges of the twocomponents again due to the interaction between the arylphosphates and PC. Nevertheless, the blends PC/ABSPTFE,PC/ABSPTFE + BDP and PC/ABSPTFE + TMC-BDP decomposedin principle in only two more or less overlapping decompo-sition steps dominated by the ABS and the PCdecomposition, respectively, whereas PC/ABSPTFE + BEPFig. 5. FTIR spectra at the minor decomposition step (580 K) of PC/ABSPTFE + BEfrom diethyl hydrogen phosphate, ethylene, bisphenol A.occur. Furthermore, the mass loss after the minor decom-position step from PC/ABSPTFE + BEP is lower than the totalcontent of ame retardant in this blend. It means that BEPdid not decompose and vaporize completely. For all inves-tigated blends, the rst main decomposition step wasattributed to ABS decomposition and the second main stepto PC decomposition.

The blend with BEP began decomposing much earlier(582 K) than other investigated blends, whereas the fol-lowing materials decomposed in the similar temperaturerange of 657675 K: PC/ABSPTFE, PC/ABSPTFE + BDP and PC/ABSPTFE + TMC-BDP. All ame-retarded blends shifted theABS decomposition step to lower temperatures than PC/ABSPTFE. However, the PC decomposition step for ame-re-tarded blends was stabilized compared to PC/ABSPTFE. Inthermal analysis, addition of the ame retardants to PC/ABSPTFE led to higher residue than that of single PC/ABSPTFEblend. The residue increased in the following order: PC/ABSPTFE < PC/ABSPTFE + TMC-BDP < PC/ABSPTFE + BEP < PC/ABSPTFE + BDP. For ame-retarded blends the residues werehigher than residues calculated on the basis of superim-posing the char yields of the individual ame retardants(BDP, TMC-BDP and BEP) and simple PC/ABSPTFE. All inves-tigated ame retardants work at least partly in theP with the characteristic bands used for product identication originating

1568 E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574condensed phase by enhancing char formation. The differ-ence between experimental and calculated residue forame-retarded blends showed that BDP increased thecharring of PC/ABSPTFE by around 6 wt.%, TMC-BDP byaround 4 wt.% and BEP by 3.4 wt.%. In fact, BDP and TMC-BDP showed the same enhancement of charring, takinginto account the 10 wt.% lower phosphorus content forTMC-BDP in comparison to BDP, and the margin of uncer-tainty (1 wt.%). Besides BEP being more reactive than BDP(and having a much higher phosphorus content), itenhanced PC charring less than did BDP and TMC-BDP inPC/ABSPTFE blend. Considering the residue obtained forneat BEP, it is proposed that BEP release and self-charringcompete with the reactions with PC in PC/ABSPTFE + BEPblend.

3.3. Pyrolysis of PC/ABSPTFE+aryl phosphate: Volatile products

The TG-FTIR analysis of the volatile pyrolysis gases ofPC/ABSPTFE, PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BDP, PC/ABSPTFE + BEP is presented in Figs. 5 and 6.

Fig. 6. (a) FTIR spectra of the rst main decomposition step of PC/ABSPTFE, PC/ABSbands used for product identication originate mainly from ABS. (b) FTIR spectrPC/ABSPTFE + TMC-BDP and PC/ABSPTFE + BEP with characteristic bands used for pMinor mass loss from BEP decomposition in PC/ABSPT-FE + BEP blend (585 K = 29 min, Fig. 5) showed absorptionbands such as P = O from phosphate at 1239 cm-1, POCat 1045 cm-1 and POH at 1285 cm-1. These vibrations,together with stretching vibrations from aliphatic groups(CH2, CH3) between 2950 and 2880 cm-1, correspondwell to phosphate derivatives created during decomposi-tion of BEP (Fig. 7). One of decomposition products fromBEP is diethyl hydrogen phosphate whose FTIR spectrum(taken from database) ts well to vibrations observed atminor decomposition step from PC/ABSPTFE + BEP. Further-more, the FTIR analysis of the PC/ABSPTFE with BEP detectedabsorptions of hydrogen attached to unsaturated carbonatom (C = CH2) in the range between 3150 and 2990 cm-1

for stretching vibrations and at 19501820, 1443, 1420,and at 1005890 cm-1 for deformation vibrations. Thoseabsorptions t well with the values for ethylene (Fig. 5).Additionally, the following stretching vibrations are ob-served: at 1597 and 1495 cm-1 from CAr = CAr, at 3652 cm-1 from CArOH, at 1168 cm-1 from CArO and at 3070 cm-1

from the aromatic ring CArH. These absorptions originated

PTFE + BDP, PC/ABSPTFE + TMC-BDP and PC/ABSPTFE + BEP with characteristica of the second main decomposition step of PC/ABSPTFE, PC/ABSPTFE + BDP,roduct identication originate from PC.

decom

E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574 1569from phenol derivatives like bisphenol A (Fig. 5). Theresults conrmed that BEP decomposed to bisphenol A,ethylene and various phosphate derivatives, which mayfurther undergo decomposition releasing ethylene (Fig. 7).

At the rst main decomposition step (between 700 and715 K = 4042 min) the analysis of pyrolysis gases via FTIRof PC/ABSPTFE, PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BDP,

Fig. 7. Evolved gases observed in FTIR spectra at the minorPC/ABSPTFE + BEP (Fig. 6a) showed stretching and deforma-tion vibrations of aliphatic components RCH2R, RCH3between 29502880 cm-1 and at 1447 cm-1, respectively,stretching vibrations of styrene derivatives at 3070 and3029 cm-1 by the aromatic ring CArH, at 1630 cm-1 bythe unsaturated side groups H2C = CH, at 1597 and1495 cm-1 by the the aromatic ring CAr = CAr, and at 760,870, 910, 982 cm-1 from deformation vibrations by the aro-matic ring CArH. The particular absorption band of butenewas given at 912 cm-1 [16], and overlapped with the defor-mation vibration of CArH. These results corresponded tothe literature, where it is reported that ABS mainly decom-poses into aliphatic compounds originating from butadieneand styrene monomers and its derivatives, such as dimers,trimers, methyl styrene and toluene [17,18]. Additionally,at the rst main decomposition step of all investigatedblends absorptions from PC decomposition were observedsuch as vibrations at 3650, 1244, and 1167 cm-1 of CArOHfrom phenol derivatives, at 1747 cm-1 of the carbonylgroup C = O, at 2361 and 669 cm-1 vibrations of carbondioxide (CO2). These results conrmed that at the rstmain decomposition step of PC/ABSPTFE, PC/ABSPTFE + BDP,PC/ABSPTFE + TMC-BDP and PC/ABSPTFE + BEP, the ABSdecomposed and PC started decomposing as well.

The major decomposition products monitored for thesecond main decomposition step of all investigated blends(between 770 and 798 K = 4750 min) (see Fig. 6b) wereCO2 (2361 and 669 cm-1), methane (CH4, 3015 and1305 cm-1), carbon monoxide (CO, 2178 cm-1) and phenolderivatives (3650 cm-1 from CAr-OH, 1597 and 1495 fromCAr = CAr, 1240 and 1175 cm-1 from CArO), which t verywell with the decomposition products of PC described inthe literature created via hydrolysis of carbonate linkageand chain scission of isopropylidene linkage [1921]. For

position step during thermal analysis of PC/ABSPTFE + BEP.PC/ABSPTFE, PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BDP andPC/ABSPTFE + BEP the FTIR spectra of the second maindecomposition step revealed the decomposition of PC.

3.4. Pyrolysis: Enhancement of PC charring

The main decomposition pathways for PC during pyro-lysis are KolbeSchmitt and Fries rearrangements, chainscission of isopropylidene linkages and hydrolysis of car-bonate linkage [22,23]. PC is a charring polymer [11]. Selfcross-linking of PC stabilized the polymer and promotescharring [23,24]. ABS decomposed with only a very smallamount of residue, which did not contribute to charring.Combining PC with BDP, TMC-BDP and BEP in PC/ABSPTFEblends induced additional charring by cross-linking thosearyl phosphates with PC (Fig. 8). Supported by the presenceof PTFE, BDP, TMC-BDP and BEP created hydrogen arylphosphates which reacted with rearranged PC via transe-sterication reaction; consequently charring is enhancedand improved. Improvement of PC charring was relatedto the changed chemical structure of the residue of PC/ABSPTFE + aryl phosphate in comparison to PC/ABSPTFE.BDP and TMC-BDP underwent similar cross-linking reac-tions with PC and increased PC charring equally, takingthe different phosphorus content into account. Thesituation for BEP was different. BEP decomposed to variousphosphate derivatives, which was observed in the gas

phase (Figs. 5 and 7). However, not all phosphates wereevolved. Some of it rapidly underwent polycondensation,creating hydrogen polyphosphate. Self cross-linking ofBEP in PC/ABSPTFE was estimated to be the major reactionof this ame retardant in the condense phase. Lesscross-linking of BEP to PC was detected, due to the factthat the highly reactive BEP decomposed much earlier thanPC.

3.5. Fire performance: Forced-aming behavior andammability

Fig. 9 displays the heat release rate (HRR) of thePC/ABSPTFE blends with and without ame retardants atan external heat ux of 50 kWm-2. The HRR patterns forPC/ABSPTFE, PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BDP andPC/ABSPTFE + BEP were typical for charring and deformation

BDP,

1570 E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574Fig. 8. Transesterication reactions between PC and (a) BDP, (b) TMC-ABSPTFE + aryl phosphate; R1 and R2 = H, CH2CH3, C6H5.(c) BEP in the condensed phase during thermal decomposition of PC/

materials with the maximum HRR (pHRR) after the initialincrease when a char layer is formed [25,26]. The HRRcurves for PC/ABSPTFE + BDP and PC/ABSPTFE + TMC-BDPshowed no differences within the margin of uncertainty.Among all ame-retarded blends, the material with BEPhas less good char. Char decomposition began earlier forPC/ABSPTFE + BEP than for PC/ABSPTFE + BDP and PC/ABSPT-FE + TMC-BDP. All investigated blends showed strongdeformation phenomena during cone calorimeter tests,which resulted in high margin of error in pHRR for all

The pHRR determines re propagation. The highestpHRR was observed for the blend PC/ABSPTFE at all appliedirradiations, because of the lack of gas-phase action andless effective char formation. The addition of the ameretardants to PC/ABSPTFE blend reduced the pHRR. Ingeneral, similarly strong reductions are observed for theblend with BDP and TMC-BDP up to around 39% and 36%,respectively. For the blend with BEP, the pHRR wasreduced to around 24% for the highest heat ux in compar-ison to the non-ame-retarded blend.

Total heat evolved (THE), which is the total heat re-leased at ame-out, was reduced for ame-retarded blendsin comparison to PC/ABSPTFE at the highest irradiation. Thehighest reduction was observed for the blend with BDP(around 24%) and TMC-BDP (around 21%). Adding BEP toPC/ABSPTFE blend reduced the THE by around 12.5%(70 kWm-2). The materials with BDP and TMC-BDP yieldedvery similar THE for all heat uxes applied, whereas theblend with BEP showed worse results than other ame-re-tarded blends.

The residue of all blends investigated in cone calorime-ter for 35, 50 and 70 kWm-2 lay in the same range consid-ering uncertainty. However, the blend PC/ABSPTFE + BEPtends to give the lowest residue among all investigatedblends, and the blend PC/ABSPTFE + BDP tends to higher res-idue formation than PC/ABSPTFE, PC/ABSPTFE + TMC-BDP andPC/ABSPTFE + BEP.

Fig. 9. Heat release rate (HRR) of PC/ABSPTFE (squares), PC/ABSPTFE + BDP(triangles), PC/ABSPTFE + TMC-BDP(stars), PC/ABSPTFE + BEP (circles)(irradiation = 50 kWm2).

olved,time

TFE + B

E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574 1571external heat uxes and time to ignition (tig) for35 kWm-2.

The characteristic values of forced-aming behaviorwere determined using the cone calorimeter at differentexternal irradiations and are summarized in Table 4.

Table 4Cone calorimeter results (at ame out) and ammability (THE = total heat evsmoke release, TSR/ML = smoke yield, pHRR = peak of heat release rate, tig =

PC/ABSPTFE PC/ABSP

Cone calorimeter (irradiation = 35 kWm2)pHRR/57 kWm2 519 335THE/5 MJ m2 86.4 74.2Residue/5 wt.% 26.3 26.3THE/ML/0.1 MJ g-1 m-2 2.5 2.1

-1TCOP/ML/0.01 gg 0.06 0.10TSR/ML/6 g-1 97 129

Cone calorimeter (irradiation = 50 kWm2)pHRR/110 kWm2 593 414THE/1 MJ m2 92.6 77.9Residue/7 wt.% 22.6 21.4THE/ML/0.1 MJ g1m2 2.5 2.1TCOP/ML /0.01 gg-1 0.06 0.10TSR/ML /8 g1 98 129

Cone calorimeter (irradiation = 70 kW m2)pHRR/42 kWm2 762 463THE/1 MJ m2 97.9 74.2Residue/1 wt.% 17.8 21.8THE/ML/0.1 MJ g1 m-2 2.5 2.0TCOP/ML/0.01 gg1 0.06 0.09TSR/ML/3 g-1 101 141

FlammabilityLOI/1% 23.9 27.9UL 94 (3.3 mm) HB V0UL 94 (1.6 mm) HB V0Total heat evolved (THE) divided by mass loss (ML) is aneffective heat of combustion (THE/ML) and allows the gas-phase activity to be determined by means of ame inhibi-tion. Phosphorus ame retardants create the several typesof phosphorus radicals that react with highly reactive H orOH radicals during combustion [9,27]. This strongly limits

ML = mass loss, TCOP = total CO production, TCOP/ML = CO yield, TSR = totalto ignition).

DP PC/ABSPTFE + TMC-BDP PC/ABSPTFE + BEP

382 42674.8 87.226.3 19.62.1 2.30.10 0.08125 111

485 49079.9 89.318.6 18.72.0 2.30.10 0.08129 113

488 58277.1 85.718.1 16.42.0 2.20.10 0.09138 116

26.5 23.5V0 HBV1 HB

phenyl rings with four aliphatic groups, the reduced num-ber of arylaryl interactions and the larger disturbance ofthe molecular structure as opposed to BDP and TMC-BDP.The enhanced dynamics contribute to the obvious decreasein apparent viscosity in Fig. 10. Nevertheless, the differentorder can indicate additional effects playing a role for theviscosity, in particular for PC/ABSPTFE + BEP.

Table 5Glass transition temperatures (Tg1 originates from the ABS-Rich phase andTg2 Originates from the PC-rich phase) of PC/ABSPTFE, PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BDP, PC/ABSPTFE + BEP.

Tg1 /2 K Tg2 /2 K

PC/ABSPTFE 384 418PC/ABSPTFE + BDP 371 389PC/ABSPTFE + TMC-BDP 376 396PC/ABSPTFE + BEP 367 385

1572 E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574the oxidation process and yields a lower heat release as aconsequence. The lower the THE/ML in comparison tonon-ame-retarded material is, the higher the ame inhi-bition of the ame retardant in the gas phase. For all blendsthe THE/ML remained constant within the margin of errorfor three applied external heat uxes. The highest THE/ML,obviously, was obtained for the non-ame-retarded blendPC/ABSPTFE. The lowest effective heat of combustion wasobserved for the two blends PC/ABSPTFE + BDP and PC/ABSPTFE + TMC-BDP. BDP and TMC-BDP reduced the THE/ML by around 20% in comparison to simple PC/ABSPTFE,which indicated efcient ame inhibition in the gas phase.This ame inhibition is independent of the irradiation, andthus constitutes the re retardancy. The blend with BEPgave intermediate results, yielding a THE/ML higher thanthe blends with BDP and TMC-BDP but lower than theblend PC/ABSPTFE. The blend PC/ABSPTFE + BEP reduced theTHE/ML by around 12% compared to the non-ame-re-tarded blend. BEP worked worse than BDP and TMC-BDPby means of ame inhibition.

The results for effective heat of combustion t well withthe results for effective carbon monoxide production(TCOP/ML) and effective smoke release (TSR/ML). Carbonmonoxide (CO) and smoke are the products of incompletecombustion. The lowest TCOP/ML and TSR/ML were ob-tained for PC/ABSPTFE blend. The highest TCOP/ML wasyielded by the blends PC/ABSPTFE + BDP and PC/ABSPT-FE + TMC-BDP; hence the oxidation process for thoseblends was strongly depleted. A similar trend was ob-served for TSR/ML.

The ammability results of both LOI and UL 94 for twodifferent thicknesses are presented in Table 4. The blendsPC/ABSPTFE and PC/ABSPTFE + BEP gave the same LOI results,and neither passed the vertical burning test for two samplethicknesses. Due to a long burning time they achieved HBclassication in UL 94. Adding BDP and TMC-BDP to PC/ABSPTFE led to an LOI enhanced by around 4% andgave the best UL 94 results (V0) for 3-mm specimens.The 1.6-mm specimen of the blend with TMC-BDP gave aV1 ratio, whereas the specimen of the blend with BDPachieved the V0 class. Combining PC/ABSPTFE with BDP andTMC-BDP led to a similar improvement in ammability.Adding BEP to PC/ABSPTFE did not improve ammabilityresults compared to the non-ame-retarded blend.

3.6. Rheological properties, glass transition temperature andmechanical properties

Not only the re retardancy of PC/ABSPTFE + aryl phos-phate blends was investigated, the processing andmechanical data were also determined using the rheologi-cal test, DSC and mechanical tests. The inuence of ameretardants on the rheological properties of PC/ABSPTFEblend is shown in Fig. 10. On this graph the shear stressof four investigated materials was plotted as the functionof angular frequencies. All of the materials investigatedshowed a ow limit due to the presence of PTFE in eachblend. The addition of PTFE to PC/ABS blends preventsmaterial from dripping [6]. Additionally, BDP, TMC-BDPand BEP worked as plasticizers in PC/ABSPTFE blend. Theblends PC/ABSPTFE + BDP and PC/ABSPTFE + TMC-BDP hadthe same viscosity, whereas the blend with BEP exhibiteda stronger reduction in viscosity. The plasticizing effect ofthe aryl phosphates is well known and constitutes a benetfor thermoplastic processing such as speeding up extrusionand injection molding.

The results from rheological measurements correspondto some extent with the results for the glass transitiontemperatures (Tg) of the investigated materials (Table 5).PC/ABSPTFE is a two-phase blend, showing two, clearlyseparated glass transition temperatures. The rst Tg (Tg1)originated from an ABS-rich phase; the second Tg (Tg2)from a PC-rich phase. When 10 wt.% of ame retardantswas added to PC/ABSPTFE blend, both the Tg1 and Tg2decreased in the following order: PC/ABSPTFE > PC/ABSPTFE + TMC-BDP > PC/ABSPTFE + BDP > PC/ABSPTFE + BEP.The smallest reduction in Tg1 and Tg2 was observed for PC/ABSPTFE + TMC-BDP, since the TMC-BDP shows the highestmolecular weight of the investigated aryl phosphates anda reduced molecular exibility due to the exchange ofthe bisphenol A by 3,3,5-trimethylcyclohexylbisphenol.The greatest reduction in Tg1 and Tg2 was observed forPC/ABSPTFE + BEP and was most probably caused by the en-hanced dynamics of the BEP achieved by replacing four

Fig. 10. Rheological characteristics (shear stress as a function of angularfrequency) of PC/ABSPTFE (squares), PC/ABSPTFE + BDP (triangles), PC/ABSPTFE + TMC-BDP (stars), PC/ABSPTFE + BEP (circles).

observed for the material with BEP, whereas the blendsPC/ABSPTFE + TMC-BDP and PC/ABSPTFE + BDP gave similarresults. The results for the HDT correspond roughly withthe glass transition temperatures.

Mechanical tests showed that incorporation of TMC-BDP, BDP and BEP decreased the toughness of PC matrixin PC/ABSPTFE + aryl phosphate blends. In general, the bestresults among all ame-retarded blends were obtained

P, PC

.60.06.6.0

E. Wawrzyn et al. / European Polymer Journal 48 (2012) 15611574 1573The mechanical properties of all investigated materialswere studied by means of tensile, bending and heat distor-tion temperature (HDT) tests. Addition of ame retardantsto PC/ABSPTFE blend changed the mechanical properties assummarized in Table 6.

Upon incorporation of 10 wt.% of ame retardants in PC/ABSPTFE blend, the tensile modulus is increased around12%. Taking into account the uncertainty there is no signif-icant difference between adding the different aryl phos-phates. The bending modulus increased in the order: PC/ABSPTFE < PC/ABSPTFE + TMC-BDP < PC/ABSPTFE + BDP < PC/ABSPTFE + BEP. Nevertheless, the increase (1013%) whenadding 10 wt.% aryl phosphates is clearly more signicantthan the differences between the different aryl phosphates.Elongations at both the yield and the break decreased forame-retarded blends in comparison to PC/ABSPTFE. Amongame-retarded blends the best results were obtained forthe blend with TMC-BDP, which reduced the elongationat yield to around only 18% and elongation at break toaround 26% compared to the non-ame-retarded blend.The highest reduction was observed for the blend withBEP (31% reduction for elongation at break and 96% reduc-tion from 109.5% to 4.6% for elongation at yield), indicatingthat this material became very brittle compared to otherinvestigated blends. The reason for this extreme increasein brittleness for PC/ABSPTFE + BEP was hardly only due todisturbing the molecular structure and reducing interac-tions between matrix and BEP molecules through partlyreplacing phenyl by aliphatic groups. A signicant reduc-tion in molecular weight of PC was proposed that is alsohold responsible for the viscosity change beyond the phys-ical plasticizing effect of BEP. The molecular weight of theused PC was Mw = 27 000 Da. It is well known that a reduc-tion in molecular weight to less than Mw = 22 000 Daresults in pronounced reduction in melt viscosity of PC[28]. A reduction below Mw = 20 000 Da cuts in halfelongation to break and for Mw = 18 100 Da reduction in

Table 6Mechanical properties of PC/ABSPTFE, PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BD

TENSILE

Modulus (GPa) Elongation (%)

at Yield at Break

PC/ABSPTFE 2.16 0.11 5.1 0.1 109.5 1PC/ABSPTFE + BDP 2.51 0.09 4.1 0.1 60.6 4PC/ABSPTFE + TMC-BDP 2.37 0.16 4.2 0.1 81.4 3PC/ABSPTFE + BEP 2.40 0.16 3.5 0.4 4.6 3elongation to break was reported to 4.7% accompanied bya slight increase in modulus for PC [29], very similar as re-ported here for PC/ABSPTFE + BEP. In Table 7 Mw and Mn forthe polymer components the GPC signals for the ameretardants occurred clearly separated and were not takeninto account for the data shown in Table 7 of the inves-tigated blends are shown. The molecular weight distribu-tions of the polymer components were asymmetric, butdid not show any multimodal characteristics itself for theinvestigated blends. The molecular weight averages forthe blends are much higher than for the PC mainly dueto the ABS and the SAN/PTFE masterbatch contribution.Nevertheless the ranking as well as the order of magnitudeof the reduction in molecular weight prove the assump-tion. It is concluded that in contrast to PC/ABSPTFE + TMC-BDP and PC/ABSPTFE + BDP signicant degradation of PCwas caused in PC/ABSPTFE + BEP by the phosphoric acid leftin the synthesized BEP during processing.

The Charpy impact strength test determines the amountof energy per unit area that is absorbed by the materialduring fracture. The results are analogous to the results dis-cussed before for the viscosity, tensile investigation andbending modulus. The unnotched specimens did not crackat all except PC/ABSPTFE + BEP. The notched ame-retardedspecimens absorbed less energy during fracture than thePC/ABSPTFE. The blends with TMC-BDP and BDP gave similarclear reduction compared to PC/ABSPTFE in Charpy impactstrength tests, but in particular the blendwith BEP requiredvery low energy to break.

The heat distortion temperature was reduced for theblends with aryl phosphates in comparison to non-ame-retarded blends. The strongest reduction in HDT was

/ABSPTFE + BEP (HDT = heat distortion temperature, NB = No break).

BENDING HDT

Modulus (GPa) Charpy Impact Strength (kJm-2) (K)

Unnotched Notched

2.42 0.02 NB 65.3 4.4 380 12.68 0.01 NB 19.2 2.0 363 12.62 0.02 NB 19.5 1.1 364 12.74 0.02 198 82 7.5 1.9 353 1

Table 7Molecular mass distribution (Mw and Mn) of the main polymer peak of PC/ABSPTFE, PC/ABSPTFE + BDP, PC/ABSPTFE + TMC-BDP and PC/ABSPTFE + BEP.

Mn (Da) Mw (Da)

PC/ABSPTFE 22 400 47 900PC/ABSPTFE + BDP 21 300 47 700PC/ABSPTFE + TMC-BDP 20 600 44 400PC/ABSPTFE + BEP 18 500 39 600for the material with TMC-BDP, whereas the material withBEP became much more brittle.

4. Conclusion

The replacement of BDP in PC/ABSPTFE blend with thesynthesized aryl phosphates was studied in order toenhance charring in the condensed phase of PC/ABSPTFE + aryl phosphate by means of thermal analysis,ammability, re behavior, mechanical tests, rheologicaltest and differential scanning calorimeter. Thus, two sofar only in patents mentioned novel ame retardants were

synthesized: TMC-BDP and BEP. Although TMC-BDP wasmore stable than BDP and BEP yielded much more residuein comparison to BDP, their incorporation into PC/ABSPTFEblend did not enhance the ame retardancy in comparisonto PC/ABSPTFE + BDP.

All investigated ame retardants worked in the con-densed phase of PC/ABSPTFE + aryl phosphate blends byenhancing char formation and changing its structure.Taking the different phosphorus content into account,TMC-BDP worked as well as BDP in the PC/ABSPTFE blend;both TMC-BDP and BDP reacted via transesterication be-

Acknowledgements

The authors thank Bayer MaterialScience AG, Germany,in particular Dr. V. Taschner, Dr. M. Jung, Dr. T. Eckel, andDr. D. Wittmann for providing the PC/ABSPTFE master batchand BDP as well as for nancial support. Special thanks goto H. Bahr, D. Neubert, F. Kempel for supporting us withinthe cone calorimeter, DSC and rheological measurements,respectively.

References

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