MaterialsandDesign31(2010)

999–1002

ContentslistsavailableatScienceDirect

MaterialsandDesign

journalhomepage:www.wendangwang.com

s

ShortCommunication

Chemicalrecyclingofcarbon bersreinforcedepoxyresincompositesinoxygeninsupercriticalwater

YongpingBaia,ZhiWangb,*,LiqunFenga

ab

SchoolofChemicalEngineeringandTechnology,HarbinInstituteofTechnology,Harbin150001,ChinaCenterforCompositeMaterials,HarbinInstituteofTechnology,Harbin150001,China

articleinfoabstract

Thecarbon bersincarbon bersreinforcedepoxyresincompositeswererecoveredinoxygeninsuper-criticalwaterat30±1MPaand440±10°C.Themicrostructureoftherecoveredcarbon berswasobservedusingscanningelectronmicroscopy(SEM)andatomforcemicroscopy(AFM).Theresultsrevealedthatthecleancarbon berswererecoveredandhadhighertensilestrengthrelativetothevirgincarbon berswhenthedecompositionratewasabove85wt.%,althoughtherecoveredcarbon bershavecleansurface,theepoxyresinonthesurfaceoftherecoveredcarbon berswasreadilyobserved.Asthedecompositionrateincreasedtoabove96wt.%,noepoxyresinwasobservedonthesurfaceofthecarbon bersandtheoxidationoftherecoveredcarbon berswasreadilymeasuredbyX-rayphotoelectronspectroscopy(XPS)analysis.Thecarbon berswereideallyrecoveredandhaveoriginalstrengthwhenthedecompositionrateswerebetween94and97wt.%.Thisstudyclearlyshowedtheoxygeninsuper-criticalwaterisapromisingwayforrecyclingthecarbon bersincarbon bersreinforcedresincomposites.

Ó2009ElsevierLtd.Allrightsreserved.

Articlehistory:

Received29June2009Accepted30July2009

Availableonline3August2009

1.Introduction

Carbon bersreinforcedresinmatrixcompositesareaclassofadvancedmaterialsthathavebeendevelopedforavarietyofappli-cationsinhigh-technology elds,suchastheaerospaceandauto-mobileindustries,aswellasinsportinggoods[1–5].Sincemostcarbon bersareutilizedwithepoxymatrixintheformofcompos-ites,ahighscraprateandsigni cantamountsofoff-cutsandre-jectsaregeneratedduringthemanufactureofthesethermosetcompositesincontrasttothemanufacturingofthermoplasticcom-posites[5,6].Carbon bersreinforcedresinmatrixcompositesthatweredestroyedinthecourseofusewillbecomewaste.Togetherwithendoflifecomponents,theamountofwastecarbon bersreinforcedresinmatrixcompositeshasreachedasigni cantlevel.Atpresenttime,thewastecompositesaremostlydisposedofinland llbecausethereisnoeconomicmeansofrecyclingthewastecomposites.Thisresultsintheincreaseinthenon-degradablewastesandalsothelossofhighvaluecarbon bers.Aneffectiverecyclingprocessisthereforehighlydesirableinordertoreclaimthehighvaluecarbon bersandreducethepressureonthesur-roundingenvironment.Recyclingthethermosetresinmatrixcompositeshasbeenextensivelystudied.Forexample,thecarbon bersreinforcedresinmatrixcompositesweredegradedbypyro-lysisintheabsenceofoxygen[7–9],bychemicalmethodandby

*Correspondingauthor.Tel/fax:+8645186413711.E-mailaddress:wangzhi1780@126.com(Z.Wang).

0261-3069/$-seefrontmatterÓ2009ElsevierLtd.Allrightsreserved.doi:10.1016/j.matdes.2009.07.057

usingcatalyststoformamixtureoforganiccompositions[10,11].Unfortunately,theabove-mentionedmethodsresultintheformationofthelayercharornon-decomposedresinmatrixontherecoveredcarbon bers.

Supercritical uidsandespeciallysupercriticalwater(T>647.3K,P>22.1MPa)arealsopotentialmediafortherecy-clingof bersandresinsincetheycanbeinexpensivereactionmedia,recyclable,non-toxicandrelativelyeasytohandle[12].Thesupercriticalwateralsopossessesaninterestingcombinationofpropertiessuchaslowviscosity,highmasstransportcoef -cients,highdiffusivityandsolvationpower.Furthermore,thesupercriticalwaterhasahighsolubilityfororganiccompoundandoxygen,especiallyoxygenandwatercanformasingleandhomogeneousphase,whichallowsoxidationtoproceedrapidlybyaneliminationofthepotentialinterfacemasstransportlimita-tions.Thesepropertiesallowusingwaterasreactionmediumin-steadofhazardousvolatileorganicsolvents[13].

Althoughextensiveresearchhasbeenperformedonthedecom-positionofthecarbon bersreinforcedresinmatrixcompositesandtheapplicationsofthesupercriticalwaterinindustry,thereareafewoftheliteratureonthesupercriticalwaterdecompositionofthecarbon bersreinforcedresinmatrixcomposites.

Inthepresentwork,theoxygenwasaddedintowaterinordertoincreasethedecompositionabilityofthesupercriticalwater.Thecarbon bersreinforcedresinmatrixcompositewasdecom-posedbytheoxygeninsupercriticalwater.Thesurfacemicrostruc-tureoftherecoveredcarbon berswasinvestigatedusingatomic