Original Article
Synthesis and properties of a novel
high-temperature diphenyl
sulfone-bad phthalonitrile polymer
Xuegang Peng1,Haitong Sheng1,Hui Guo1,Kimiyoshi Naito2,
Xiaoyan Yu1,Huili Ding1,Xiongwei Qu1and Qingxin Zhang1
Abstract
A novel high-temperature diphenyl sulfone-bad phthalonitrile polymer is prepared from bis-[4-(3,4-dicyanophenoxy)-phenyl]sulfone(BDS)monomer synthesized with high yield by a simple nucleophilic displacement of a nitro-substituent from4-nitrophthalonitrile(NPN).The structure of BDS polymer is investigated by Fourier transform infrared spectro-scopy and wide-angle X-ray diffraction.Curing behavior of BDS monomer with1,3-bis(4-aminophenoxy)benzene(APB) is recorded by differential scanning calorimetry.The properties of BDS polymer are evaluated by thermogravimetric anal-ysis,d
ynamic mechanical analysis,and tensile test.The results reveal that the BDS polymer exhibits excellent thermal and thermo-oxidative stabilities,high glass temperature(T g¼337 C),and outstanding mechanical properties(Young’s mod-ulus:4.02GPa and tensile strength:64.16MPa).Additionally,the BDS polymer exhibits high flame retardance and low water uptake.
Keywords
Phthalonitrile polymer,high glass transition temperature,thermal stability,mechanical property
Introduction
Phthalonitrile polymers,as a new family of high-temperature and high-performance polymers propod by Keller and Griffith,1have drawn great attention for their superior ther-mal and thermo-oxidative stabilities and various other prop-erties.The interest in high-performance polymers versus metallic materials aris from the need for a reduction in weight and an enhancement in performance.2For advanced composites,the upper limit application temperature is largely determined by the glass transition temperature(T g) and the thermal decomposition temperature of the polymer matrix;thus the polymer matrix plays a vital role to achieve the best performance.
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The key to the development of high-temperature poly-mers is the incorporation of thermally stable structural units such as aromatic or heteroaromatic rings within the back-bone of a polymeric system,2and heterocyclic polymers have been proved to posss high thermal stability.3–7 Nowadays,aromatic polyimides are mainly ud in high-temperature materials becau of their high thermal stability and excellent mechanical properties.8–10How-ever,volatile by-products,such as water,inevitably yield during imidization reaction leading to the formation of void-filled fabricated components thereby conquently affecting their mechanical properties.Compared with aro-matic polyimides,the addition cure mechanism of phtha-lonitrile polymers ensures that little or no volatiles are evolved during the polymerization producing highly cross-linked,void-free network polymers with the desired structure and properties.Thermotting phthalonitrile polymers are a unique class of high-temperature materials having a number of excellent properties such as high T g s, outstanding thermal and thermo-oxidative stabilities, excellent mechanical properties,good moisture resis-tance,and superior fire resistance.2,11–18It is reported that 1Institute of Polymer Science and Engineering,School of Chemical Engineering and Technology,Hebei University of Technology,Tianjin, China
2Hybrid Materials Center,National Institute for Materials Science, Tsukuba,Japan
Corresponding author:
Xiaoyan Yu,Institute of Polymer Science and Engineering,School of Chemical Engineering and Technology,Hebei University of Technology, Tianjin300130,China.
Email:
High Performance Polymers
2014,Vol.26(7)837–845
ªThe Author(s)2014
Reprints and permission:
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DOI:10.1177/0954008314532479
phthalonitrile polymer-bad composites meet the Navy specification(MIL-STD-2031)for their usage as a poly-meric composite in the interior of a submarine.19–21 In this article,a rigid,thermotolerant and oxidation-resistant diphenyl sulfone unit was introduced into the molecular skeleton of phthalonitrile polymers in order to further improve the mechanical properties and thermal and thermo-oxidative stabilities.The diphenyl sulfone-bad phthalonitrile polymer exhibits superior thermal stability, outstanding mechanical properties,high T g,and excellent flame-retardant property,and thus it is a qualified candi-date for applications in the field of heat-resistant and high-performance materials.
Experimental ction
Materials
4-Nitrophthalonitrile(NPN;98.0%),bis-(4-hydroxyphe-nyl)sulfone(BHPS;þ98.0%),and1,3-bis-(4-aminophe-noxy)benzene(APB;þ97.0%)were supplied by Wako Chemical Industries(Japan).Pulverized anhydrous potas-sium carbonate(99%)and dehydrated dimethyl sulfoxide (DMSO)were provided by Alfa Aesar(Ward hill,Massa-chutts,USA)and Wako,respectively.All the chemicals were ud without any pretreatment.
Synthesis of BDS monomer
To a500-mL three-necked flask was added BHPS(37.51g, 0.15mol),NPN(51.92g,0.30mol),pulverized anhydrous potassium carbonate(62.10g,0.45mol),and200mL of dry DMSO.Then,the mixture was kept at80–90 C for5h under nitrogen(N2)atmosphere with continuous stirring.After cooling,the product mixture was slowly poured into hydrochloric acid solution(600mL,2M) and brown bis-[4-(3,4-dicyanophenoxy)phenyl]sulfone (BDS)monomer deposited conquently.The BDS mono-mer was collected by suction filtration and washed with plenty of distilled water until the filtrate became neutral. The filtered BDS cake was dried at80 C for24h with a yield of64.76g(86%).
Preparation of BDS prepolymer and polymer
BDS prepolymer was synthesized in a500-mL reaction ket-tle equipped with a mechanical stirrer.First,BDS monomer (30.00g,0.0597mol)was melted followed by the addition of APB(1.02g,0.0035mol)with continuous stirring at 250 C for5min,and then the BDS prepolymer was formed with a black block.The prepolymer was pulverized and fur-ther cured,namely,postcured,in an autoclave under0.70 MPa pressure with a high degree of vacuum(À0.10MPa) by a heating procedure:200 C for4h,260 C for4h,315 C for4h,and343 C for4h.The prepared BDS polymer was ma
chined into rectangular specimens(55.00Â10.00Â2.00 mm3)for dynamic mechanical analysis(DMA)experiments. Characterization
The proton nuclear magnetic resonance(1H NMR)spec-trum of BDS monomer was recorded on a Bruker300MHz NMR spectrometer(Germany)with deuterated chloroform (CDCl3)as the solvent and tetramethylsilane as the internal reference.Elemental analysis for C,H,N,and S were car-ried out on a Thermo Flash EA1112analyzer(Thermo Fisher Scientific,Waltham,Massachutts,USA).Fourier transform infrared(FTIR)spectra were recorded using a Nicolet Nexus670FTIR spectrometer(Madison,Wisconsin, USA)in potassium bromide mode for BDS monomer and attenuated total reflectance mode for BDS prepolymer and polymer.Wide-angle X-ray diffraction(WAXD)was con-ducted with a Rigaku diffractometer(model RINT2500; Rigaku Co.,Tokyo,Japan)operating at40kV and300mA with nickel-filtered copper K a radiation(l¼0.15406 nm)in reflection mode.The2y scan data were collected from2 to60 with an interval of0.02 at a scanning speed of4 minÀ1.Thermogram of the BDS monomer with APB was recorded using a TA Q10differential scanning calori-meter(New Castle,Delaware,USA)at a heating rate of 10 C minÀ1.Scanning electron microscopy(SEM)images were acquired using a JEOL6500field emission scanning electron microscope(Tokyo,Japan).The specimen was coated with gold prior to obrvation.
Thermogravimetric analysis(TGA)was performed on solid samples and pow-der samples using a TA Q50instrument at a heating rate of 20 C minÀ1under N2and in air atmospheres,respectively. The T d,5%and T d,max are defined as the temperatures at which5%weight loss occurs and the peak of the deriva-tive thermogravimetric analysis curve,respectively. Tensile tests were performed according to ASTM D-638 standard using a universal testing machine(Table top-type tester EZ-Test;Shimadzu,Tokyo,Japan)with a crosshead speed of1mm minÀ1.The rectangular speci-men was stored in a test tube filled with distilled water for more than2months at room temperature,dried with paper towel,and weighed using a balance to determine the water uptake.DMA was performed on a2980dynamic mechanical analyzer(TA Instruments)in dual cantilever mode at a frequency of1Hz and an amplitude of10m m over the temperature range of50–450 C with a heating rate of5 C minÀ1.大三元镜头
想念的诗句Results and discussion
Synthesis
It is reported that a class of phthalonitrile monomers were prepared by a simple nucleophilic displacement of a nitro substituent.1In our rearch,the diphenyl sulfone-bad
838High Performance Polymers26(7)
phthalonitrile monomer,BDS,was synthesized with high yield by the nucleophilic displacement of a labile nitro sub-stituent from NPN.The typical procedure of synthesis of BDS monomer,prepolymer,and polymer is illustrated in Figure 1.The BDS polymer was prepared via two steps.The first is the preparation of BDS prepolymer by addition of amine into BDS monomer melt at 250 C,while the cond step is the conversion of prepolymer into highly
cross-linked BDS polymer by postcuring at elevated temperatures.
FTIR spectroscopy was employed to characterize the BDS monomer,and the overlaid FTIR spectra of BHPS and BDS monomers are shown in Figure 2.The absorption peak at 3365cm À1of BHPS is due to the stretching vibration of phenolic hydroxyl (Ar–OH),while BDS monomer shows no absorption signal around 3365cm À1indicating that nucleophilic displacement reaction has taken place and all the –OH groups have been replaced by NPN.Aromatic C–H bending absorptions appear at 3097and 3043cm À1,and the out-of-plane bending absorptions are obrved at 900–700cm À1.A strong absorption peak appears around 2237cm À1corresponding to the characteristic stretching of nitrile groups (–CN)of BDS.The absorption bands within 1600–1400cm À1could be attributed to the stretching of phe-nyl rings.It is noticed that a strong absorption peak centered at 1251cm À1appears,which is ascribed to the stretching of C–O of BDS,and absorption range within 1
孔雀之舞
300–1100cm À1should be assigned to sulfone group (–SO 2–)stretching.While FTIR spectra provide information about charac-teristic groups of molecules to further confirm the structure of BDS monomer,NMR spectroscopy is employed and 1H NMR spectrum of the BDS monomer is prented in Figure 3.All signals have been assigned to protons as follows:1H NMR (300MHz,CDCl 3,d ):8.06(d,J ¼8.6Hz,4H,H1),7.80(d,J ¼8.4Hz,2H,H4),7.35(d,2J ¼2.4Hz,2H,H5),7.32(dd,1J ¼8.3Hz,2J ¼2.4Hz,2H,H3),and 7.21(d,J ¼8.6Hz,4H,H2).Moreover,the signal integrations sup-port the formulation.Calculated values for BDS monomer (C 28H 14N 4SO 4):C,66.93;H, 2.79;N,11.16;S, 6.37.Found:C,66.68;H,2.71;N,11.03;S,6.19.Elemental analysis and 1H NMR results are consistent with the FTIR spectroscopy analysis proving that the BDS monomer was successfully synthesized.
The WAXD spectrum of BDS monomer is prented in Figure 4.The cell parameters of the monomer were deter-mined by a trial and error method,and the result was further refined by a least squares procedure.The experimental and calculated cell parameters are listed in Table 1,and the
unit
Figure 1.Synthesis of BDS monomer,prepolymer,and polymer.BDS:
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bis-[4-(3,4-dicyanophenoxy)phenyl]sulfone.
Figure 2.FTIR spectra of BHPS and BDS monomer.FTIR:Fourier transform infrared spectroscopy;BHPS:bis-(4-hydroxyphenyl)sul-fone;BDS:
bis-[4-(3,4-dicyanophenoxy)phenyl]sulfone.中国五大行
Figure 3.1H NMR spectrum of BDS monomer.1H NMR:proton nuclear magnetic resonance;BDS:bis-[4-(3,4-dicyanophenoxy)phenyl]sulfone.
Peng et al.839
cell was determined to be orthorhombic with unit cell dimen-sions:a ¼26.1289A
˚,b ¼12.3071A ˚,and c ¼4.1142A ˚,with a volume of 1323.01A
˚3.Microstructure of BDS polymer
The differential scanning calorimetry (DSC)scan of the
BDS monomer with ABP (5.8mol %)is shown in Figure 5.To obtain a homogeneous mixture,BDS monomer and ABP were thoroughly mixed by stirring prior to DSC tests.As obrved,APB gives a small endothermic melting peak at 114.9 C,while the synthesized BDS monomer shows a sharp melting peak at 221.6 C indicating the high purity of BDS monomer.An exotherm peak at 259.5 C after the melting peak of BDS monomer is attributed to the reaction of the diamine with BDS,which manifests that the process-ing window is nearly 38 C as defined by the temperature difference between the melting point of the monomer and the exothermic curing temperature.17WAXD spectra of the BDS prepolymer and polymer are prented in Figure 6.The BDS prepolymer exhibits no sharp diffraction peak in addition to a noncrystalline diffraction hump centered at 20.1 ,implying that t
he BDS monomers have been con-verted into prepolymer indicated by the complete disap-pearance of the diffraction peaks of monomers.Similarly,the BDS polymer shows a noncrystalline diffraction at 20.7 .This noncrystalline hump indicates the frequent occurrence of a particular interatomic distance (R )of a polymer in a largely disordered substance and could be determined by the following expression:22
R ¼
54Âl 2sin y
¼1:25d Bragg ð1Þ
where l is the wavelength of X-ray and 2y is the diffraction angle.This equation means that the interatomic distance (R )responsible for a strong maximum in the diffraction
pattern at angle y is equal to 1.25times the d -spacing cal-culated with the aid of the well-known Bragg’s equation.This equation was ud to asss the most inten diffrac-tion for noncrystalline materials.As a result,the intera-tomic distance was determined to be 0.536nm for the BDS polymer.
FTIR spectra of the BDS prepolymer and polymer are given in Figure 7.As obrved,FTIR spectrum
of BDS prepolymer shows medium absorption bands within 1600–1100cm À1becau of the formation of BDS oligo-mer in the first stage.However,the characteristic peak of nitrile groups at 2230cm À1becomes weak in the prepoly-mer compared with that of BDS monomer,and it is much weaker in the BDS polymer,indicating that most of the nitrile groups have been polymerized during postcuring process.
It has been reported that phthalonitrile monomers might polymerize into polytriazine structures and polyisoindole structures.13,23,24A new absorption of BDS polymer at 1358cm À1is attributed to the formation of triazine rings,indicating that polytriazine structure might generate during polymerization.13In addition,there is still a weak absorp-tion of –CN groups at 2230cm À1for BDS polymer becau only half of the –CN groups participate in polytriazine ring structures due to high steric hindrance.On the other hand,the FTIR spectroscopy of the BDS polymer exhibits other two new absorptions at 1720cm À1(–C ¼N–)and 1528cm À1(pyrrole ring)implying that the polyisoindole struc-ture might form in the BDS polymer.23,24Bad on the above analysis,it is reasonable to conclude that both the polyisoindole structure and the polytriazine structure coex-ist in BDS polymer as illustrated in Figure 8.bios怎么读
Polyimides,as one of the most important high-temperature and high-performance polymer families,h
ave been mainly ud for high-tech applications where void-free property is particularly important.However,polyi-mides are extremely tedious to process and liberate volatile by-products such as water during the imidizing polymeriza-tion reaction leading to void-filled fabricated components.Although various methods have been tried to solve the void problems,microvoids have been a critical issue for broad high-temperature applications.SEM photographs of frac-ture surfaces of the BDS polymer are shown in Figure 9.As en,no voids can be obrved for the BDS polymer at low (1,000Â)and high (10,000Â)magnifications due to the abnce of solvents and the addition polymerization mechanism of BDS monomer,which proves the void-free structure of BDS polymer,and it also guarantees the out-standing thermal and mechanical properties.
Thermal and thermo-oxidative stabilities
The thermal and thermo-oxidative properties of BDS poly-mer were investigated between 25and 1000 C by TGA under N 2and in air atmospheres,respectively,as
shown
Figure 4.WAXD of BDS monomer.WAXD:wide-angle X-ray diffraction;BDS:bis-[4-(3,4-dicyanophenoxy)phenyl]sulfone.
840High Performance Polymers 26(7)
in Figure 10,and the thermal parameters are listed in Table 2.As obrved,the weight of BDS polymer in N 2exhibits only 5%loss with temperature growing up to 418 C (solid sample)and 436 C (powder sample),and it shows a rapid decrea upon further heating and reaches a maximum rate at T d,max of 476 C (solid sample)and 493 C (powder sam-ple),which indicates high thermal stabilities of BDS poly-mer.The BDS polymer retains 59wt %(solid sample)and 57wt %(powder sample)at 1000 C.While the T d,5%of BDS polymer solid sample appears at 450 C in air,and maximum decomposition takes place at three temperature ranges of 486,655,and 725 C,respectively.Analogously,the T d,5%of BDS polymer powder sample appears at 441 C in air,and maximum decomposition takes place at three temperature ranges of 492,658,and 740 C,respectively,which demonstrates the outstanding thermo-oxidative stabi-lity of BDS polymer.Bad on the above analysis,the effect of type of sample on thermal and thermo-oxidative prop-erties is little in the same atmosphere for the BDS poly-mer.It is reported that for most of the thermotting resins,thermo-oxidation process starts around 500 C and at 600 C char yield (CR)equals zero,7but the BDS polymer still exhibits significant char retention of 72%(solid sample)and 69%(powder sample)by weight at 600 C in air.
Generally,predominant factors that contribute to thermal stability in polymers are primary bond strength,rigid intra-chain structure,the degree of cross-linking,and so on.1,12,25The C–O (bond dissociation energy is 332kJ mol À1)and C–S (bond dissociation energy is 328kJ mol À1)among BDS polymer molecular chains are relatively weak;26as a result,
Table 1.Experimental and calculated cell parameters of BDS monomer.h k l d (A ˚)Experimental 2 (deg)
Calculated 2 (deg)Experimental
sin 2 Calculated sin 2 Experimental sin 2 –calculated sin 2
20013.06 6.76 6.760.0034760.003474 2.1Â10À63008.8010.0410.140.0076570.007816 1.6Â10À4400 6.4713.6613.540.0141430.013900 2.4Â10À4120 5.9314.9214.770.0168570.016525 3.3Â10À4410 5.7715.3415.340.0178140.017809 4.6Â10À6320 5.2216.9817.620.0217970.023470 1.7Â10À3420 4.4919.7419.790.0293830.029550 1.7Â10À4101 4.0821.7821.840.0356920.035895 2.0Â10À4130 3.9822.3021.900.0373950.036100 1.3Â10À3201 3.9222.6422.630.0385290.038494 3.5Â10À5211 3.7423.7423.760.0423090.0423958.6Â10À5311
3.5724.9024.970.0464780.046742 2.6Â10À4021 3.4126.0826.020.0509090.050670 2.4Â10À4321 3.2427.5227.990.0565750.058501 1.9Â10À33
3
1
2.75
32.46
32.45
0.078117
0.078064
5.2
Â10À5
BDS:
bis-[4-(3,4-dicyanophenoxy)phenyl]sulfone.
Figure 5.DSC thermogram of BDS monomer with 5.8mol%of APB.DSC:differential scanning calorimetry;BDS:bis-[4-(3,4-dicya-nophenoxy)phenyl]sulfone;APB:
1,3-bis(4-aminophenoxy)benzene.
Figure 6.WAXD of BDS prepolymer and polymer.WAXD:wide-angle X-ray diffraction;BDS:bis-[4-(3,4-dicyanophenoxy)phenyl]sulfone.
Peng et al.
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