Preparation and Characterization of Flame-Retardant Melamine Cyanurate/Polyamide 6Nanocomposites by In Situ Polymerization
Zhi-Yong Wu,1,2Wei Xu,1,2Yao-Chi Liu,1Jin-Kui Xia,2Qian-Xin Wu,2Wei-Jian Xu 1
艺术活动心得1
Polymer Institute,College of Chemistry and Chemical Engineering,Hunan University,Changsha 410082,China
2
Rubber Department of Baling Petrochemical Limited Liability Company,SINOPEC,Yueyang 414000,China
Received 26May 2008;accepted 8January 2009DOI 10.1002/app.30022
Published online 24April 2009in Wiley InterScience (www.).ABSTRACT:This article focus on an improved ,improved in situ polymerization of e -caprolactam in the prence of melamine derivatives to prepare flame-retardant melamine cyanurate/polyamide 6(MCA/P
A6)nanocomposites.The chemical structures of the synthetic flame retardant composites are characterized by Fourier-transform infrared spectroscopy and X-ray diffraction.Morphologies,mechanical properties,and thermal proper-ties also are investigated by the u of transmission elec-tron microscopy,mechanical testing apparatus,differential scanning calorimetry,and thermogravimetric analysis,
respectively.Through transmission electron microscopy photographs,it can be found that the in situ -formed MCA nanoparticles with diametric size of less than 50nm are nanoscaled,highly uniformly disperd in the PA6matrix.The nanocomposites,which have good mechanical prop-erties,can reach UL-94V-0rating at 1.6-mm thickness
电饭锅做最简单的蛋糕even at a relatively low MCA loading level.V
C 2009Wiley Periodicals,Inc.J Appl Polym Sci 113:2109–2116,2009
Key words:in situ polymerization;flame retardant;
最深的海polyamide 6;nanocomposite
INTRODUCTION
Becau of its chemical stability and superior me-chanical and electrical properties,polyamide 6(usu-ally known as nylon 6,PA6)has many industrial us,such as fibers for clothing and automobiles.1,2However,in some of the fields,it is desirable to provide this material with a high level of flame retardance in addition to its inherent properties.However,this thermoplastic with low limiting oxy-gen index can easily burn.Thus,how to impart flame retarding property to PA6material becomes an important rearch topic.3–15
Among the veral common ud flame retardant additives,the s -triazine compounds,including mel-amine or its derivatives,have been widely studied during the past 20years.3–12Becau of its effi-ciency,small additive dosage,and small negative effect on the mechanical performance of the matrix resin,the class environmentally friendly flame retardants are widely ud in polyamide fields.As far as we know,most of the flame-retardant com-posites are prepared by simple molten blending.巴林是哪个国家
Becau melamine or its derivatives have poor solu-bility in PA6,it is difficult to obtain flame-retardant
polyamide 6(FRPA6)with good mechanical and flame retarding performance at a relative low flame retardant additive loading level.Kawasaki et al.said that even when MCA is pregrinded into a fine po
再也没有wder particles size of 2–3l m,it can undergo c-ondary agglomeration and changes into large par-ticles of veral tens of micrometers in the process of molten blending with PA6matrix.3Thus,the flame-retardant composites prepared by this way are usually unspinnable becau of the existence of large MCA particles.Moreover,with the lap of the time,melamine or its decomposition products could migrate from inside of the aforementioned composites to the surface,exhibiting a phenomenon called ‘‘blooming.’’3
This article relates to improved in situ polymeriza-tion for preparing synthetic MCA-bad FRPA6.First,melamine/adipic acid salt and cyanuric acid/hexane diamine salt were prepared by the reaction of melamine with adipic acid and cyanuric acid with hexane diamine at aqueous environment,respec-tively.Then,the two kinds of salts were intro-duced into the hydrolytic polymerization system of e -caprolactam to prepare MCA/PA6nanocompo-sites.In this work,the structures and mechanical and flame retarding properties of the composites were fully characterized and investigated.
Journal of Applied Polymer Science,Vol.113,2109–2116(2009)V C 2009Wiley Periodicals,Inc.Correspondence to:W.-J.Xu (polymer_).Contract grant sponsors:Baling Petrochemical Limited Liability Company of SINOPEC.
EXPERIMENTAL
Raw materials
The following materials were ud as received:e-caprolactam(chemically pure,supplied by Baling Petrochemical,Hunan Yueyang,China),melamine (chemically pure,supplied by Chengdu Kelong Chemical Plant,Chengdu,China),cyanuric acid (chemically pure,supplied by Shandong Wolan Chemical Plant,China),adipic acid and hexane dia-mine(Shenma Chemical Plant,China),PA6(with relative viscosity of3.2in98%H2SO4as granulate product supplied by Baling Petrochemical),mela-mine cyanurate(MC50,purchad from Ciba Spe-cialty Chemicals,Beijing,China).
Preparation of melamine/adipic acid salt and cyanuric acid/hexane diamine salt
Melamine/adipic acid salt was prepared by reaction of melamine with equimolecular amount of adipic acid at an aqueous environment under ambient tem-perature for an hour.The ratio of melamine/H2O by mole was chon as1:4,by orthogonal experiment results.Cyanuric acid/hexane diamine salt was treated with cyanuric acid,hexane diamine and water (molar ratio1:1:122.5),refluxing for an hour.
In situ polymerization of FRPA6
Synthetic MCA/PA6nanocomposites were prepared in the hydrolytic polymerization system of molten e-caprolactam.Heat supply was provided by an elec-tric heater and controlled by a stainless rheostat.The synthetic FRPA6prepared were summarized(Table I).For example,to synthesize P-7.34(P signifies that it was prepared by in situ polymerization;7.34 shows that it contained7.34g MCA per100g PA6) nanocomposite,62.6g of melamine/adipic acid salt, 56.4g of cyanuric acid/hexane diamine salt,24mL of deionized water,and800g of e-caprolactam were introduced into a GSH-22-L polymerization auto-clave at room temperature.Then the autoclave was heated and kept at275 C for3h.Finally,the system was cooled to245 C,keeping vacuum-pumping for
at least30min.The product was extracted with
deionized water before measurement.Molecular weight by GPC:M w¼1.87Â104,M n¼1.15Â104. P-9.52was prepared in the same way described
earlier,just changed the weight ratio of MCA with e-caprolactam.For comparison,58.7g of MC50,800 g of e-caprolactam,and appropriate amount of water were added in the GSH-22-L polymerization auto-clave to prepare P*-7.34.
Preparation of MCA/PA6blend
To prepare MCA/PA6blend of B-20.08(weight ratio of MCA/PA6is20.08/100,B signifies blending), calculated amounts of MCA and dried PA6were first mixed and dried with a high-speed mixer for10 min(model:SHR-10A,Zhangjiagang Fangfeng Ma-chinery,China).Then,they were melt-blended in a twin-screw extruder.(Five extruding region temper-ature:160,220,240,245,250 C,L/D¼40,model: SHJ-20,Nanjing Sori Chemical Equipment,China.) The extrudate and synthetic MCA/PA6nanocompo-sites werefirst cut into pellets,dried,and then injec-tion molded into various specimens forflammability and mechanical property tests.
Characterization
Infrared(IR)spectra were performed with a WQF-410Fourier transform infrared spectrometer(Beijing, China).Differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA)were performed on a Netzsch STA449C(Netzsch,Germany)at a heating rate of10 C/min under nitrogen atmos-phere.DSC was performed with a temperature rang-ing from20to300 C and sample weight of$10mg under nitrogen atmosphere.Samples,encapsulated in aluminum pans,were heated to300 C at a rate of 10 C/min and held for5min at this temperature to cancel their thermal history,then cooled to20 C at a rate of40 C/min.Finally,the sample was reheated to300 C at a rate of10 C/min.The recorded tem-peratures were calibrated by the u of indium as
TABLE I
Thermal Properties and Crystallinity of Pure PA6and Synthetic FRPA6
Sample M wÂ104M nÂ104T m a( C)T c b( C)D H f c(J/g)X c d(%)T dec e( C)T10f( C) Pure PA6 1.96 1.3621917157.925.2316389 P-7.34 1.87 1.1521617556.324.5312344 P-9.52––20617855.424.1297325
a Melting temperature.
b Temperature of crystallization peak.
c Heat of fusion.
d Percentag
e crystallinity calculated by DSC.
e Temperature at which a5%weight loss occurred in N
2with a heating rate of10 C/min.
f Temperature at which a10%weight loss occurred in N
2with a heating rate of10 C/min.
2110WU ET AL. Journal of Applied Polymer Science DOI10.1002/app
standards.Crystalline melting temperature (T m )was obtained as the maximum of the melting endotherm.Percentage crystallinity (v DSC )of products was calcu-lated via the ratio between the measured and equi-librium heats of fusion (D H f /D H 0f ).The equilibrium
heat of fusion (D H 0
f )is 230J/
g for 100%crystalline PA6.16XRD were performed on a Rigaku D/Max2500diffractometer (Ni-filtered,Cu/K a radia-tion of wavelengt
h 0.154nm)in the reflection mode over the range of diffraction angles (2y )from 5 to 45 at ambient temperature.The voltage and tube current were 40kV and 200mA,respectively.Gel permeation chromatography analysis was conducted on an Alltech (Altech Associate,Deerfield,IL),using polystyr
ene standards and m -cresol/chloroform mixed solvents as eluent and the flow rate was 1.0mL/min.The morphology of the PA6material was obrved by a Hitach
i Model-800transmission elec-tron microscope (TEM).
The vertical burning test was conducted on a CZF-3horizontal and vertical burning tester on sheet 127mm Â12.7mm Â1.6mm according to ASTM D 3801.Notched Izod impact strengths,tensile strengths,and flexural moduli were determined according to GB/T1843-1989,GB1040-1992,and GB1042-1992.
RESULTS AND DISCUSSION
Becau melamine,cyanuric acid,or MCA can hardly dissolve in molten e -caprolactam or PA6,the direct introduction of melamine and cyanuric acid into e -caprolactam hydrolytic polymerization system can only obtain micron-grade disperd composites,3who mechanical properties are detrimentally affected.In this study,melamine/adipic acid salt and cyanuric acid/hexane diamine salt were first prepared,and their solubility in molten e -caprolac-tam was much improved.Second,the two kinds of salts can lf-asmble in the aqueous polymeriza-tion system to form MCA crystallites by hydrogen bonding and polycondensation reaction occurred between the left adipic acid and hexane
diamine to form PA66chains (Scheme 1).17,18The synthesis mechanisms of the MCA/PA6nanocomposites are shown in Scheme 1.From the gel permeation chro-matography results in Table I,it can be en that the hydrolytic polymerization of e -caprolactam was almost not affected by the existence of the aforemen-tioned salts or the in situ -formed MCA at all.The detailed chemical structures,flame retarding per-formance and mechanical properties will be dis-cusd
thereinafter.
Scheme 1Synthesis mechanisms of the MCA/PA6nanocomposites.
FLAME-RETARDANT MCA/PA6NANOCOMPOSITES 2111
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Structure characterization of synthesized MCA/PA6nanocomposites FTIR analysis
Figure 1includes the FTIR spectra of pure PA6[Fig.1(a)],MCA/PA6nanocomposite by in situ polymer-ization [Fig.1(b),P-9.52],and FRPA6by molten blending [Fig.1(c),B-20.08].It can be en that they all display characteristic absorptions of pure PA6at 3298cm À1(N A H stretch vibration),1639cm À1(C ¼¼O,stretch vibration),1543cm À1(N A H deforma-tion).P-7.34and B-20.08show somewhat the same characteristic absorption bands and tho character-istic absorptions of melamine and cyanuric reported (3468cm À1,3418cm À1,stretching of A NH 2in mela-mine molecule;3027cm À1,1467–1397cm À1,vibra-tions of A OH in cyanuric acid molecule,respectively.)completely disappear,5which indicate that the lf-asmbly of melamine with cyanuric is fully complete (e also in XRD patterns in Fig.5).The band at 1464cm À1is caud by NCO and/or NCN bending coupl
ed with ring deformation.The absorption at 1732cm À1can be attributed to the vibrations of C ¼¼O group in MCA molecule.In addi-tion,becau P-7.34and B-20.08own the same FTIR spectra and we can not find ester group absorption peaks,thus it can reasonably speculate the products by in situ polymerization are just nanoscaled MCA/PA6composites,not star-type polymers.DSC analysis
To compare the thermal properties of synthetic FRPA6with pure PA6,DSC and TGA were con-ducted.The DSC heating curves are shown in Figure 2,where curves a,b,and c correspond to pure PA6,P-7.34,and P-9.52,respectively.For convenience,the
melting and crystallizing results are prented in Ta-ble I.From Figure 2,it can be en that all the three samples have only one endothermic peak,which corresponds to the melting of a type crystal of PA6.With the amount of MCA increas,T m decreas from 219 C (pure PA6)to 206 C (P-9.52),but the change of percentage crystallinity is not so signifi-cant.The factors affecting the crystallization degree can be possibly attributed to the following two aspects:(1)compatibility of MCA with PA6matrix and (2)heterogeneous nucleating effect of in situ formed MCA nanoparticles.2,19The in situ -formed nanoparticles in this rearch have strong interaction with PA6matrix (which could be en from TEM microscopy in Fig.6).Therefore,with MCA content increasing,the movement of PA6chains is restrained more greatly and the clo packing of PA6chains is interrupted,relating to m
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ore incomplete PA6crystal.Thus,in turns of this aspect,the crystallization degree of MCA/PA6nanocomposites should show a decreasing trend.However,at the same time,more MCA particles can enhance the heterogeneous nucle-ating effect,which should cau incread crystalli-zation degree.It ems that the two aspects discusd above have contrary effects on the crystal-lization degree.From the experimental results,it is speculated that the first aspect plays a more impor-tant role on the little decread trend of percentage crystallinity.
清蒸银鳕鱼
In addition,The DSC curves of pure PA6,P-7.34,and P-9.52during cooling are prented in Figure 3and the crystallization temperature (T c )are listed in Table I.Compared with pure PA6,it can be en that both samples of P-9.52and P-7.34have greater T c values.It is speculated that it is caud by the heterogeneous nucleating effect of
MCA
Figure 1FTIR spectra of pure PA6(a),MCA/PA6nano-composite by in situ polymerization (b),and MCA/PA6composite by molten blending (c).
2112WU ET AL.
Journal of Applied Polymer Science DOI 10.1002/app
nanoparticles in the composites.During cooling,the prence of MCA can make the molten PA6form crystallites at a higher temperature.
TG analysis
The thermal decomposition properties of synthetic MCA/PA6nanocomposites(P-7.34and P-9.52)were evaluated by TGA analysis in a nitrogen atmosphere at a heating rate of10 C/min(Fig.4and Table I). The decomposition temperature(T dec)of P-7.34and P-9.52did not show significant decreasing trend,but the temperature for10%weight loss(T10),which is an important criterion for evaluating thermal stabil-ity,dramatically changed.T10of P-7.34and P-9.52 are45 C and64 C lower than that of pure PA6, respectively.
Pure PA6weight loss takes place in a single region from316 C to about500 C,but the decom-position of MCA/PA6nanocomposites involve two steps:thefirst one was in the range of about300–335 C,and the cond one was from360 C to about 500 C.Thefirst weight loss region can be reasonably attributed to the thermal dissociation of MCA to melamine and cyanuric acid,becau it can be en from Figure4that the curves in thefirst degradation region shows a weight loss proportional to MCA loading level in the composites.Also,it can be attributed to the reaction of MCA with the degrada-tion products of PA6becau MCA can volatilize at a higher temperature when it was heated alone.The weight loss region from360 C to about500 C is mainly caud by the degradation of PA6to oligom-ers,caprolactam,CO,etc.;the reaction of MCA(or its degradation products)with caprolactam or oligomers.
XRD analysis
Figure5displays the XRD patterns of P-7.34(a)and pure PA6(b).For curve a,characteristic MCA dif-fraction peaks(10.8 ,11.8 ,28.1 )appear and fea-tured melamine and cyanuric diffraction peaks(2y¼13.29 ,17.88 ,19.95 ,22.22 ,26.38 ,28.97 ,and 29.92 )disappear,5indicating the lf-asmbly reac-tion becomes complete in the hydrolytic polymeriza-tion system of e-caprolactam.For curve b,pure PA6 gives two characteristic peaks of a form at2y¼20.0 and2y¼23.8 ,corresponding to
the reflections of the crystalline planes(200)and(002)þ(202), respectively.20The aforementioned analytical results are in good agreement with the FTIR
results.
减肥食物排行榜Figure4TG curves of pure PA6(a)and MCA/PA6
nanocomposites:P-7.34(b)and P-9.52(c).
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