高抗冲聚苯乙烯的阻燃性

Flame Retardancy and Toughening of HighImpact PolystyreneWenguang Cui,Fen Guo,Jianfeng ChenKey Lab for Nanomaterials,Institute of Chemical Engineering,Beijing University of Chemical Technology, Ministry of Education,Beijing100029,People’s Republic of ChinaFlame retardant high impact polystyrene(HIPS)was pre-pared by melt blending HIPS,nano-modified aluminum trihydrate(nano-CG-ATH),red phosphorus masterbatch (RPM),and modified polyphenylene oxide(MPPO).Sty-rene-butadiene-styrene(SBS)was used as a toughener in this research.The effects of nano-CG-ATH,RPM, MPPO,and SBS on properties of HIPS composites were studied by combustion test,mechanical tests,and ther-mogravimetric analysis.The morphologies of fracture surfaces and char layers were characterized through scanning electron microscopy(SEM).The HIPS/nano-CG-ATH/RPM/MPPO(60/6/9/25)composite and its com-bustion residues at various temperatures were character-ized by Fourier transform infrared(FTIR)spectra analysis. The results showed that the UL-94rating of the HIPS/ nano-CG-ATH/RPM/MPPO(60/6/9/25)composite reached V-0and its char layer afterflame test was integrated,but its impact strength was low.Addition of SBS improved its impact property and did not influence its thermal and flame retardant properties but lowered its tensile strength andflexural modulus to some extent.The FTIR spectra confirmed that the PÀÀOÀÀC group was present in the charred POS.,28:551–559,2007.ª2007Society of Plastics EngineersINTRODUCTIONHigh impact polystyrene(HIPS)is widely used for numerous applications in our daily life.In many applica-tions that applyfire safety regulation rules,particularly in transportation and electrical appliances,flame retardants are used to improve the ignition resistance of polymers[1]. Halogenated organic compounds in the presence of anti-mony oxide(Sb2O3)have been widely used as effective flame retardants in many polymeric systems.It is generally thought that theflame retardant effect of these additive systems is mainly due to the synergism between the halo-genated compounds and antimony oxide to form volatile antimony halides such as SbCl3and SbBr3,which act as free radical traps around theflame[2].However,the corrosive-ness and toxicity of the smoke and other emission products generated during the combustion of halogen-containing ther-moplastics have given rise to some concern[3–5].At present,extensive work has been carried out to inves-tigate theflame retardant property of halogen-freeflame retardants.In particular,some metallic hydroxidefillers have been studied in detail,which have become some of the most popular replacements for halogen-basedflame retard-ants[6–10].The effectiveness of theseflame retardants(e.g. Al(OH)3and Mg(OH)2)depends on several factors[11,12]. For instance,the endothermic decomposition of these metal-lic hydroxides and the accompanying release of water vapor are thought to withdraw heat from the substrate and dilute the fuel supply present in the gas phase and hence retard the rate of thermal degradation.In addition,the decomposed products,Al2O3and MgO may better insulate the substrate from the heat source through promotion of char formation. However,metallic hydroxide must be present at high con-centrations(usually higher than50%)in order to confer adequatefire resistance.The high loadings of metallic hydroxides in thermoplastics result in significant deteriora-tion of mechanical properties,particularly the impact strength[13].An alternative approach is the incorporation offlame retardant additives.The relatively low loadings required to achieve sufficientflame retardance,and the care-ful selection offlame retardant additives,may keep detri-mental changes to the physical and mechanical properties of the polymer to an acceptable minimum.Nano-CG-ATH is a product which is obtained from alu-minum trihydrate by chemical modification.Its thermal stability is higher than that of aluminum trihydrate,and so it can be added to the polymer materials under higher proc-essing temperature.It is well-established as a halogen-free and smoke-suppressingflame retardant.It decomposes endothermally and releases water and carbon dioxide,and so theflame retardant effect is based on cooling and dilu-tion.Highfiller loadings of nano-CG-ATH are necessary to achieve sufficientflame retardancy,which often causes a drawback in mechanical and processing properties.Red phosphorus(P r)is one of the ecologically and physi-cally harmless alternativeflame retardants,since encapsulation and the use of master batchesCorrespondence to:F.Guo;e-mail:guofen19580610@DOI10.1002/pc.20324Published online in Wiley InterScience(). V C2007Society of Plastics EngineersPOLYMER COMPOSITES—-2007cessfully to eliminate problems of handling safety and sta-bility.Theflame retardancy of P r in polymers functions pre-dominantly in the condensed phase[14].Condensed phase mechanisms of P r increase char formation,which decreases the combustible volatiles and therefore the total fuel support of theflame.Furthermore,the char can act as a barrier, decreasing the mass loss rate.The action of P r depends on the chemical structure of the polymer.Polymers with heter-oatoms,such as oxygen,are polar and adsorb water.The presence of water in a polymer is one of the most important prerequisites for condensed phase mechanisms of P r,as it was proposed for glassfiber reinforced polyamide66[15]. In nonpolar polymers,phosphorus can barely befixed by oxidation in the condensed phase.MPPO is a polymer blend of polystyrene and polypheny-lene oxide.Itsflame retardant synergistic effect with P r is favorable.Moreover,the compatibility between MPPO and HIPS matrix is good.Based on these results,the combination of advantageous properties from nano-CG-ATH,red phos-phorus masterbatch(RPM),and MPPO in HIPS is promising.In this work,flame retardant HIPS composite was ob-tained by melt blending HIPS,nano-CG-ATH,RPM,and MPPO.But addition of nano-CG-ATH,RPM,and MPPO made the impact strength of HIPS decrease to some extent. To improve the impact property,styrene-butadiene-styrene (SBS)was used to toughen the composite.Then,burning, thermal,and mechanical properties of HIPS composites were analyzed.The morphologies of fracture surfaces of the HIPS/nano-CG-ATH/RPM/MPPO(60/6/9/25)and HIPS/nano-CG-ATH/RPM/MPPO/SBS(45/6/9/25/15)were observed by scanning electron microscopy(SEM).In addition,Fourier transform infrared(FTIR)spectra before and after treatment of the HIPS/nano-CG-ATH/RPM/MPPO(60/6/9/25)at vari-ous temperatures were recorded.Detailed research and the results will be discussed in the following sections. EXPERIMENTALMaterialsHIPS(476L)was obtained from BASF.Red phosphorus masterbatch(RPM)was produced by Chenguang Research Institute of Chemical Industry,China National Blue Star. MPPO was kindly supplied by Beijing Beihua Gaoke New-Tech.Styrene-butadiene-styrene(SBS-801)was kindly sup-plied by Yueyang Petrochemical,China.Aluminum trihydrate(ATH),sodium hydroxide,CO2, and oxalic acid from Beijing Chemical Reagent were used in the preparation of nano-CG-ATH.Sample PreparationPreparation of Nano-CG-ATH.The experimental pro-cedures are as follows:(i)A certain amount of ATH raw material was pouredinto boiling sodium hydroxide solution.Then,theslurry was heated until ATH was fully dissolved toobtain raw sodium aluminate(SA)solution,whichwas subsequently diluted andfiltered to obtain clearSA solution with a desired concentration.(ii)The SA solution was carbonated by absorbing CO2 in a rotating packed bed(RPB)at room temperatureto yield nano-ATH suspension while it was forced tocirculate between the RPB and an agitating tank bya centrifugal pump.(iii)The nano-ATH suspension discharged from the RPB was aged for3h at708C,then wasfiltered andrinsed to obtain nano-ATH.(iv)The nano-ATH was redispersed into an aqueous oxalic acid solution and heated up to a temperature of130–1808C under stirring in a closed vessel for30–90minto obtain desired nano-CG-ATH suspension,whichwas subsequentlyfiltered,rinsed,and dried for futureuse.Polymer Compounding.Table1lists the compositions of all samples.These raw materials werefirst melt-mixed using a twin-screw extruder(PE-20,Keya Company Lim-ited,Nanjing,China).The temperatures of the extruder were ordinal:150,180,205,and2008C.Subsequently,the pellets were fed into a single screw extruder(SJ-30,Bei-jing Plastic Engineering,Beijing,China)to prepare the test specimens,the temperatures of which were ordinal(160, 190,205,and2008C).Combustion TestThe UL-94test was performed to evaluate theflame spread of the test specimens in air atmosphere using a CZF-1 type instrument(Nanjing Jiangning Analytical Instrument Factory,China)on sheets according to ISO1210-1992.positions of all samples.SampleHIPS(wt%)Nano-CG-ATH(wt%)RPM(wt%)MPPO(wt%)SBS(wt%) 16609250 26339250 36069250 45799250 554129250 66960250 76663250 86366250 957612250 10856900 117569100 127069150 136569200 146040000 156000400 1660150250 175469256 185169259 1948692512 2045692515552POLYMER COMPOSITES—-2007DOI10.1002/pcThermogravimetric AnalysisThermal degradation study was performed using a STA-449C thermogravimetric analyzer (Netzsch,Germany).The samples (about 15mg)were heated in air or nitrogen atmosphere from room temperature up to about 8008C at a heating rate of 108C/min.Mechanical PropertiesThe impact strength of the composites was measured by Charpy pendulum impact testing machines (XJJ-5,ChengDe JinJian Testing Machine Company,China.)at room temperature.The tensile (testing speed,50mm/min)and the flexural (testing speed,10mm/min)properties were recorded by Instron universal testing machine (Ins-tron 1185,Instron,England)at room temperature.Morphological ObservationThe morphologies of fracture surfaces after the impact test and combustion char residues were observed by scanning elec-tron microscope (SEM Hitachi LTDx-650,Japan).The mor-phology of nano-CG-ATH was observed by field-emission scanning electron microscope (FESEM,FEI XL-30,USA).Fourier Transform Infrared Spectra AnalysisThe FTIR spectra of KBr wafers were recorded using a Shimadzu FTIR-8400S infrared spectrophotometer (Japan).RESULTS AND DISCUSSION Characteristics of Nano-CG-ATHThe FESEM micrograph of nano-CG-ATH is shown in Fig.1.It can be seen from the FESEM that nano-CG-ATH has lozenge morphology and is 20–40nm in thickness,100–200nm in length,and 50–100nm in width.Figure 2presents the thermogravimetric (TG)curve of nano-CG-ATH in N 2atmosphere at the heating rate of 108C/min.Nano-CG-ATH started to decompose at $3308C and decomposed in one single step.Because of the high decomposition temperature,nano-CG-ATH can be added to the polymer materials with higher processing temperature.Flame RetardancyThe UL-94test is widely used to evaluate the flame re-tardant property of materials.The results of the UL-94test are listed in Table 2.It can be seen that the UL-94rating reached V-1after 9wt%RPM and 25wt%MPPO was added.Here,addition of 6wt%nano-CG-ATH caused the UL-94rating to increase from V-1to V-0.When the quan-tity of nano-CG-ATH and MPPO was 6and 25wt%respectively,with addition of 6wt%RPM,the UL-94rat-ing increased from HB to V-1.When 9wt%RPMwasFIG.1.FESEM micrograph ofnano-CG-ATH.FIG.2.TGA curve of nano-CG-ATH in nitrogen.TABLE 2.The results of the UL-94test.Sample Nano-CG-ATH (wt%)RPM (wt%)MPPO (wt%)SBS (wt%)UL-94109250V-1239250V-1369250V-0499250V-05129250V-0660250HB 763250HB 866250V-19612250V-0106900HB 1169100HB 1269150HB 1369200V-11440000HB 1500400HB 16150250HB 1769256V-01869259V-019692512V-020692515V-0DOI 10.1002/pc POLYMER COMPOSITES—-2007553added,the UL-94rating reached V-0.The quantity of MPPO also had a great influence on the UL-94rating.If only 6wt%nano-CG-ATH and 9wt%RPM were added,the UL-94rating was HB.But,when 20wt%MPPO was added together with 6wt%nano-CG-ATH and 9wt%RPM,the UL-94rating improved from HB to V-1.When the quantity of MPPO increased to 25wt%,the UL-94rat-ing reached V-0.In addition,when 40wt%nano-CG-ATH or 40wt%MPPO was added or 15wt%nano-CG-ATH and 25wt%MPPO were added,the UL-94rating couldnot be increased.These suggest that RPM shows a goodsynergistic effect of flame retardancy with nano-CG-ATH and MPPO.Table 2also shows that addition of SBS did not influence the UL-94rating.Figure 3shows the SEM micrographs of char layers taken from flame-tested specimens.From Fig.3b and 3c,it is evident that the HIPS/nano-CG-ATH/MPPO (69/6/25)composite and HIPS/nano-CG-ATH/RPM (85/6/9)com-posite did not form intact and strong char layers after the flame test.In contrast to Fig.3b and 3c,Fig.3a showsaFIG.3.SEM micrographs of char layers of the composites (a)HIPS/RPM/MPPO(66/9/25);(b)HIPS/nano-CG-ATH/MPPO(69/6/25);(c)HIPS/nano-CG-ATH/RPM(85/6/9);(d)HIPS/nano-CG-ATH/RPM/MPPO(60/6/9/25);(e)HIPS/nano-CG-ATH/RPM/MPPO/SBS(45/6/9/25/15).554POLYMER COMPOSITES—-2007DOI 10.1002/pcbetter char layer.In addition,it is obvious that incorpora-tion of nano-CG-ATH,RPM,and MPPO in proportion pro-moted the formation of a compact char layer in the con-densed phase during burning of HIPS,and that addition of SBS hardly affected the integrity of the char layer.A com-pact char layer can slow down heat and mass transfer between the gas and condensed phases and prevent the underlying polymeric substrate from further attack by heat flux in a flame.So,the flame retardant property of the HIPS/nano-CG-ATH/RPM/MPPO (60/6/9/25)composite and HIPS/nano-CG-ATH/RPM/MPPO/SBS (45/6/9/25/15)composite was better than that of other composites.Thermogravimetric AnalysisThe TG results in air at the heating rate of 108C/min are illustrated in Fig.4.It can be seen from Fig.4that HIPS decomposed in one single step and no residues occurred at8008C.The TG curve of Sample 6shows that when only 6wt%nano-CG-ATH and 25wt%MPPO were added,few residues appeared,in which the decomposition product of nano-CG-ATH was the maximum.For the HIPS/nano-CG-ATH/RPM (85/6/9)composite,after the main mass loss,a subsequent mass gain was observed,followed by a second mass decrease.The main mass loss corresponded to the decomposition of the composite.The mass gain was attrib-uted to the oxidation of phosphorus in the condensed phase by oxygen and water from the atmosphere.The second mass decrease corresponded to the loss of some unstable residues.Figure 4also shows that there were more residues in the sys-tem with RPM,indicating that synergistic action RPM with nano-CG-ATH and MPPO took place for the residues.Par-ticularly,in case of incorporation of nano-CG-ATH,RPM,and MPPO in proportion,the residual quantity was the larg-est.The residues can not only insulate the substrate,the heat source and oxygen,but also reduce the quantity of carbon entering the flame,and hence play a significant role in the flame retardancy.In addition,addition of SBS had little in-fluence on the decomposition and residues of the HIPS/nano-CG-ATH/RPM/MPPO (60/6/9/25)composite.FTIR AnalysisFTIR spectra recorded before and after treatment of the HIPS/nano-CG-ATH/RPM/MPPO (60/6/9/25)composite at various temperatures are shown in Fig.5.In curve (a),the absorption bands at 3,671and 1,715cm À1were attributed to the following stretching vibrations:O ÀÀH and C ¼¼O in nano-CG-ATH,respectively.The broad absorption band be-tween 2,850and 3,060cm À1was assigned to C ÀÀH stretch-ing vibration.The absorption band at 1,600cm À1was aro-matic C ¼¼C stretching vibration.Curve (b)represents the FTIR spectrum for the residues of the composite after being treated in a muffle at 4008C.In comparison with curve (a),curve (b)demonstrates weak absorption bands at 3,671and 1,715cm À1,which indicates that part of nano-CG-ATH decomposed after the composite was treated at 4008C.FIG.4.TGA in air (n ,HIPS;&,Sample 1;*,Sample 6;l ,Sample 10;*,Sample 20;*,Sample3).FIG.5.FTIR spectra;(a)the HIPS/nano-CG-ATH/RPM/MPPO (60/6/9/25)composite;(b)its combustion residues at 4008C;(c)its combustion residues at 5008C;(d)its combustion residues at 6008C.FIG.6.Variation of the impact strength and tensile strength against nano-CG-ATH content.DOI 10.1002/pc POLYMER COMPOSITES—-2007555In curve (c),O ÀÀH and C ¼¼O groups in nano-CG-ATH disappears,which reveals that nano-CG-ATH completely decomposes when the composite is treated at 5008C.C ÀÀH stretching vibration is still seen from curve (c),indicating that the composite did not completely decompose after treated at 5008C.In contrast to curves (a)and (b),aromatic C ¼¼C stretching vibration in curve (c)intensifies.Curve (c)also shows that two broad absorption bands at 3,250and 1,150cm À1assigned to phosphoric acid were gener-ated during the thermal treatment.In curve (d),the two broad absorption bands at 3,250and 1,151cm À1are strong.Moreover,a strong absorption band at 1,618cm À1appears.These indicate that more red phos-phorus is oxidized to phosphoric acid at 6008C.The absorp-tion band at 969cm À1attributed to P ÀÀO ÀÀC indicates that part of phosphoric acid reacted with resin to form a stable structure containing the P ÀÀO ÀÀC group,which was benefi-cial for the formation of a compact char layer in the con-densed phase during the burning of polymer materials.The afore-mentioned research results suggest the flame re-tardant mechanisms of the HIPS/nano-CG-ATH/RPM/MPPOcomposite.The endothermic decomposition of nano-CG-ATH,accompanied by the release of water,provides an effective heat sink mechanism,in comparison with polymer pyrolysis based on product oxidation.Beyond this effect,nano-CG-ATH acts as an inorganic filler and Al 2O 3layer as a barrier.The presence of oxygen in MPPO contributes to the for-mation of a phosphoric anhydride with increasing tempera-ture [16],leading to phosphoric acid (see Fig.5),by released water from nano-CG-ATH,and then phosphoric polyacid,causing a dehydration of HIPS and char forma-tion (Fig.3d).In addition,the solid phase oxidation of phosphorus suppresses the thermo-oxidative HIPS decom-position by oxygen consumption (see Fig.4).Fire retardancy by the char forming system works here by two mechanisms [15].On the one hand,the char acts as a barrier layer,influencing the mass and heat transfer,thus resulting in a decrease of the heat release rate.On the other hand,the char-forming process can lead to an increase of the thermally stable residue and consequently to a decrease of the total heat release,resulting from a decrease of the total amount of combustible volatileproducts.FIG.7.Variation of the flexural modulus against nano-CG-ATHcontent.FIG.8.Variation of the impact strength and tensile strength against RPMcontent.FIG.9.Variation of the flexural modulus against RPMcontent.FIG.10.Variation of the impact strength and tensile strength against MPPO content.556POLYMER COMPOSITES—-2007DOI 10.1002/pcMechanical PropertiesFigure 6shows the impact strength and tensile strength of the HIPS/nano-CG-ATH/RPM/MPPO composite with the variation of nano-CG-ATH content.As the content of nano-CG-ATH increases,the impact strength decreases.After 6wt%nano-CG-ATH was added,the impact strength decreased from 6.10to 4.36kJ/m 2,and decreased continu-ously to 3.12kJ/m 2with the addition of 12wt%nano-CG-ATH.On the other hand,the tensile strength increased with nano-CG-ATH content.When 12wt%nano-CG-ATH was added,the tensile strength increased from 29.35to 31.73kJ/m 2MPa,which indicated that nano-CG-ATH took on a strengthening effect.Figure 7shows the flexural modulus of the HIPS/nano-CG-ATH/RPM/MPPO composite with the variation of nano-CG-ATH content.It can be seen that addition of nano-CG-ATH gave an evident improvement in the flexural modulus,when its content ranged from 0to 6wt%.When nano-CG-ATH was added more than 9wt%,the flexural modulus grad-ually decreased.Variation of the impact strength and tensile strength of the HIPS/nano-CG-ATH/RPM/MPPO composite versus RPM content is shown in Fig.8.It can be seen that addi-tion of RPM resulted in a decrease in impact strength,decreasing with increasing of RPM content.When RPM was added from 0to 12wt%,the impact strength de-creased from 6.37to 4.31kJ/m 2.Figure 8also shows that as the content of RPM increases from 0to 9wt%,the tensile strength gradually increases,and then,evidently decreases with the RPM content.Variation of the flexural modulus of the HIPS/nano-CG-ATH/RPM/MPPO composite versus RPM content is shown in Fig.9.When RPM was added from 0to 9wt%,the flex-ural modulus continuously increased with the RPM content.But,when the content of RPM was more than 9wt%,the flexural modulus rapidly decreased.Figure 10shows the effect of the quantity of MPPO on the impact strength and tensile strength of the HIPS/nano-CG-ATH/RPM/MPPO composite.Figure 11shows the effect of the quantity of MPPO on the flexural modulus of the HIPS/nano-CG-ATH/RPM/MPPO composite.It can be seen that the impact strength slightly decreases with MPPO con-tent.When 25wt%MPPO was added,the impact strength only reduced 0.67kJ/m 2.On the other hand,the tensile strength and flexural modulus evidently increased with MPPO content.If 25wt%MPPO was added,the tensile strength and flexural modulus increased about 39.96%and 29.78%,respectively.These are mostly attributed to lower toughness and higher strength of MPPO.In addition,the good miscibility between MPPO and HIPS also contributes to the strengthening effect of MPPO.Figure 12shows the effect of the quantity of SBS on the impact strength and tensile strength of the HIPS/nano-CG-ATH/RPM/MPPO/SBS composite.Figure 13shows the effect of the quantity of SBS on the flexural modulus of the HIPS/nano-CG-ATH/RPM/MPPO/SBS composite.It is clear that the impact strength evidently increases with SBS content.After 15wt%SBS was added,the impact strength increased from 4.36to 10.17kJ/m 2,which increasedaboutFIG.11.Variation of the flexural modulus against MPPOcontent.FIG.12.Variation of the impact strength and tensile strength against SBScontent.FIG.13.Variation of the flexural modulus against SBS content.DOI 10.1002/pc POLYMER COMPOSITES—-2007557133.26%.This is mainly attributed to high miscibility between SBS and HIPS.In contrast to the impact strength,the tensile strength and flexural modulus decrease with SBS content.The tensile strength and flexural modulus of a com-posite depend mainly on the tensile and flexural properties of the composite components besides the factor of interfa-cial adhesion.SBS is an elastomer whose tensile strength and flexural modulus are lower than those of HIPS;there-fore,increase in the weight fraction of SBS evidently reduces the tensile strength and flexural modulus of the composite.Morphologies of Fracture SurfacesThe morphology of the fractured surface of the HIPS/nano-CG-ATH/RPM/MPPO (60/6/9/25)composite after impact test is shown in Fig.14a.It can be seen that the fractured surface of the composite is smooth and has a brit-tle nature,which suggests that cracks can propagate a long way in initial directions.It means that the material exhibits low impact strength.Figure 14b shows the morphology of the fractured sur-face of the HIPS/nano-CG-ATH/RPM/MPPO/SBS (45/6/9/25/15)composite after impact test.Since the S-block of SBS has a high miscibility with PS and the B-block is compatible with PB,the dispersion of SBS in HIPS matrix and the adhesion between SBS and the matrix are both good.Apart from the chemical structure of SBS,the size of the rubber particles plays a decisive role.Depending on the nature of the matrix polymer,the optimum diameter of the rubber particles can vary between 100nm and several micrometers [17].The mode of action of the rubber par-ticles consists generally in initiating deformation mecha-nism,which allows high dissipation of energy.During the fracture of the composite,microcracks have greater propa-gating velocities in HIPS than in SBS.When entering into SBS,microcracks will be deflected with sudden changes in propagating velocities.Such deflections causing tortuosityand complexity of the fracture surface (Fig.14b)can not only absorb fracture energy but also buffer interfacial im-pact stresses and prevent whiskers from breaking,so that the toughness of the composite is improved.CONCLUSIONIn this study,RPM showed good synergistic effect of flame retardancy with nano-CG-ATH and MPPO.The combined flame retardant system lowered the flammability of HIPS to the level of V-0class and formed a compact char layer after the flame test.The P ÀÀO ÀÀC group was beneficial for the formation of the compact char layer in the condensed phase during burning of polymer materials.The char layer was related to good flame retardant effect.However,the impact strength of the flame retardant HIPS was low.To improve its impact strength,SBS was used as a toughener.Evidently,the impact strength of the flame re-tardant HIPS increased with SBS content.On the contrary,its tensile strength and flexural modulus decreased to some extent with SBS content.In addition,addition of SBS did not influence its thermal decomposition and flame retardant property.REFERENCES1.D.Radloff,H.W.Spiess,J.T.Books,and K.C.Dowling,J.Appl.Polym.Sci.,60(5),715(1996).2.H.Sato,K.Kondo,S.Tsuge,H.Ohtani,and N.Sato,Polym.Degrad.Stab.,62(1),41(1998).3.R.Xie and B.Qu,J.Appl.Polym.Sci.,80(8),1181(2001).4.W.Von Gentzkow,J.Huber,H.Kapitza,and W.Rogler,J.Vinyl Addit.Technol.,3(2),175(1997).5.Z.Li and B.Qu,Polym.Degrad.Stab.,81(3),401(2003).6.J.T.Yeh,M.J.Yang,and S.H.Hsieh,Polym.Degrad.Stab.,61(3),465(1998).7.X.Zhang,F.Guo,J.Chen,G.Wang,and H.Liu,Polym.Degrad.Stab.,87(3),411(2005).FIG.14.SEM micrographs of fractured surfaces of the composites;(a)HIPS/nano-CG-ATH/RPM/MPPO 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