Flammability studies on biopolymers and their blends
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Date
2016
Authors
Mngomezulu, Mfiso Emmanuel
Journal Title
Journal ISSN
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Publisher
University of the Free State
Abstract in other languages 𝘚𝘤𝘳𝘰𝘭𝘭 𝘥𝘰𝘸𝘯 𝘧𝘰𝘳 𝘈𝘧𝘳𝘪𝘬𝘢𝘢𝘯𝘴, 𝘚𝘦𝘚𝘰𝘵𝘩𝘰 𝘢𝘯𝘥 𝘐𝘴𝘪𝘡𝘶𝘭𝘶
Abstract in other languages 𝘚𝘤𝘳𝘰𝘭𝘭 𝘥𝘰𝘸𝘯 𝘧𝘰𝘳 𝘈𝘧𝘳𝘪𝘬𝘢𝘢𝘯𝘴, 𝘚𝘦𝘚𝘰𝘵𝘩𝘰 𝘢𝘯𝘥 𝘐𝘴𝘪𝘡𝘶𝘭𝘶
Abstract
𝑬𝒏𝒈𝒍𝒊𝒔𝒉
The effect of commercial expandable graphite (EG) on the flammability and thermal decomposition characteristics of two systems based on poly(lactic acid) (PLA) and poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) blend was investigated. Furthermore, the morphology, structure, melting and crystallization behaviour as well as the dynamic mechanical properties of flame retardant PLA/EG and PLA/PCL/EG composites were also studied. The flame retardant PLA/EG and PLA/PCL/EG composites were prepared by melt-mixing using the Brabender-Plastograph and were melt-pressed using the electrical hydraulichot melt press. The samples were characterized for their flammability performance and thermal stability via cone calorimeter and thermogravimetric analyser (TGA), respectively. They were also characterized for their volatile pyrolysis products during thermal degradation using simultaneous TGA-Fourier transform infrared spectroscopy (TGA-FTIR). The char residues obtained after combustion by cone calorimeter were further analysed with environmental scanning electron microscopy (ESEM). Furthermore, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to elucidate the structure and morphology of the flame retardant PLA/EG and PLA/PCL/EG composite systems. Their thermal behaviour (i.e. melting and crystallization) as well as their thermo-mechanical properties were respectively analysed by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques. For the PLA/EG composite system, the thermal decomposition stability of the composites was improved in the presence of EG. However, the char content was less than expected as per the sum of the wt.% EG added into PLA and % residue of PLA after thermal decomposition.
The flammability performance of the PLA/EG composites was improved, especially at 15 wt.% EG content, due to a thick and strong worm-like char structure. The peak heat release rate (PHRR) was improved by 74%, the total smoke production (TSP) was improved by 40% and the specific extinction area (SEA) by 55%. These improvements were due to the ability of EG to exfoliate at increased temperatures during which three effects occurred: i) cooling effect due to an endothermic exfoliation process; ii) dilution effect due to the release of H2O, SO2 and CO2 gases and iii) formation of a protective intumescent char layer. However, both the CO and CO2 yields were found to be unfavourably high due to the presence of EG. The graphite layers still existed in an aggregate structure with poor filler dispersion and lack of interfacial adhesion between EG and the PLA matrix. The presence of EG micro-particles: i) did not favour the crystallization of PLA, ii) increased the glass transition temperature and iii) showed a reduction in the crystallinity of the composites. The composites showed enhanced storage and loss moduli, especially at high EG contents (i.e. 10 and 15 wt.%). The glass transition from the loss modulus and damping factor varied inconsistently with the EG content. The use of commercial expandable graphite as filler in PLA could preserve the thermal properties of injection molding grade Cereplast PLA, while improving the fire resistance of PLA/EG flame retardant composites. In the case of PLA/PCL/EG flame retardant composite system, the thermal degradation stability of the composites was improved and the char content was found to have increased. Although the char content of the composites increased generally with EG loadings, the combined % residue from both the blend and wt.% EG initially added into the blend was higher than the observed % residue because of the thermal degradation mechanism that favoured the formation of CO and CO2 volatile gases rather than carbon.
The flammability performance results indicated that the PLA/PCL blend was successfully modified with the EG micro-filler that resulted in fire resistant composites, especially at high filler loadings, due to the formation of intumescent carbonaceous char. This was confirmed by reductions of up to 64% in both the peak heat release rate (PHRR) and the total smoke release (TSR) and 54% in the specific extinction area (SEA). This was due to the EG acting mainly through a physical mode by cooling and fuel dilution and through the formation of an intumescent char layer. However, the effective heat of combustion (EHC) and carbon monoxide (CO) yields did not favourably improve. It was found that the melt mixing process could not separate the graphite layers, which existed as aggregate structures (i.e. EG layered stacks and/or lumps). In the composites, PCL was favoured to crystallize mainly on the surface of the microspheres and EG. The PLA/PCL blend showed an immiscibility feature, even in the presence of EG filler. Incorporation of EG in PLA/PCL blend influenced the melting and crystallization behaviour of PCL than that of the PLA component. Both the PCL and EG hindered the crystallization of the PLA component. From DSC and DMA, the glass transition of the composites occurred at high temperatures, suggesting that PLA polymer chains were immobilized in the presence of EG micro filler. The storage and loss moduli values were low for the composites when compared to PLA/PCL. The results suggest that the PLA/PCL/EG flame retardant composites have low thermal and thermo-mechanical properties due to the aggregation of EG and lack of interfacial adhesion between EG lumps and the polymer blend matrix.
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𝑨𝒇𝒓𝒊𝒌𝒂𝒂𝒏𝒔 Die effek van kommersiële uitbreibare grafiet (EG) op die vlambaarheid en termiese ontbindingseienskappe van twee stelsels is ondersoek, gebaseer op ’n mengsel van poli(melksuur) (PLA) en poli(melksuur)/poli(ε-kaprolaktoon) (PLA/PCL). Verder is die morfologie, struktuur, smelt- en kristallisasiegedrag, sowel as die dinamiese meganiese eienskappe van vlamvertragende PLA/EG- en PLA/PCL/EG-samestellings ook bestudeer. Die vlamvertragende PLA/EG en PLA/PCL/EG-samestellings is voorberei deur smeltmenging met behulp van die Brabender-Plastograph en is smeltgepers met behulp van die elektriese hidroulichot-smeltpers. Die monsters is gekarakteriseer volgens hul vlambaarheidsprestasie en termiese stabiliteit via onderskeidelik die kegelkalorimeter en termogravimetriese analise (TGA). Hulle is ook gekarakteriseer volgens hul vlugtige piroliseprodukte tydens termiese degradasie deur gebruik te maak van die gelyktydige TGA Fourier Transform-infrarooispektroskopie (TGA-FTIR). Die verkoolresidu verkry ná verbranding deur die kegelkalorimeter is verder ontleed met omgewingskanderingselektronmikroskopie (ESEM). Verder is X-straaldiffraksie (XRD) en skandeerelektronmikroskopie (SEM) gebruik om die struktuur en morfologie van die vlamvertragende PLA/EG en PLA/PCL/EG saamgestelde sisteme toe te lig. Hul termiese gedrag (d.w.s. smelting en kristallisasie), sowel as hul termomeganiese eienskappe, is onderskeidelik deur die differensiële skanderingkalorimetrie (DSC) en dinamiese meganiese analise (DMA) tegnieke ontleed. Vir die PLA/EG saamgestelde sisteem is die termiese ontbindingstabiliteit van die samestellings verbeter in die teenwoordigheid van EG. Maar die kool(char)-inhoud was minder as wat verwag is volgens die som van die gew.% EG wat by PLA gevoeg is en die % residu van PLA ná termiese ontbinding. Die vlambaarheidsprestasie van die PLA/EG-samestelling is verbeter, veral by 15 gew.% EG-inhoud, as gevolg van 'n dik en sterk wurmagtige verkoolstruktuur. Die piek hittevrystellingtempo (PHRR) is met 74% verbeter, die totale rookproduksie (TSP) is met 40% verbeter en die spesifieke uitsterwingsgebied (SEA) met 55%. Hierdie verbeterings was te danke aan die vermoë van EG om by verhoogde temperature af te skilfer waartydens drie effekte plaasgevind het: i) verkoelende effek as gevolg van 'n endotermiese afskilferingsproses; ii) verdunningseffek as gevolg van die vrystelling van H2O, SO2 en CO2 en iii) vorming van 'n beskermende opwellende houtskoollaag. Daar is egter gevind dat beide die CO- en CO2-opbrengste ongunstig hoog is as gevolg van die teenwoordigheid van EG. Die grafietlae het steeds bestaan in 'n aggregaatstruktuur met swak vulstofdispersie en 'n gebrek aan grensvlakadhesie tussen EG en die PLA-matriks. Die teenwoordigheid van EG mikro-partikels: i) het nie die kristallisasie van PLA bevoordeel nie, ii) het die glasoorgangstemperatuur verhoog en iii) het 'n vermindering in die kristalliniteit van die samestellings getoon. Die samestellings het verbeterde bergings- en verliesmoduli getoon, veral by hoë EG-inhoude (d.w.s. 10 en 15 gew.%). Die glasoorgang vanaf die verliesmodulus en dempingsfaktor het inkonsekwent gewissel met die EG-inhoud. Die gebruik van kommersiële uitbreibare grafiet as vuller in PLA kan die termiese eienskappe van spuitgietgraad Cereplast PLA behou, terwyl dit die brandweerstand van PLA/EG vlamvertragende samestellings verbeter. In die geval van PLA/PCL/EG-vlamvertragende samestellings, is die termiese degradasie-stabiliteit van die samestellings verbeter en daar is gevind dat die kool(char)-inhoud toegeneem het. Alhoewel die kool(char)-inhoud van die samestellings oor die algemeen toegeneem het met EG-ladings, was die gekombineerde % residu van beide die mengsel en gew.% EG wat aanvanklik by die mengsel gevoeg is, hoër as die waargenome % residu as gevolg van die termiese degradasiemeganisme wat die vorming van CO bevoordeel het en CO2-vlugtige gasse, eerder as koolstof. Die resultate van die vlambaarheidsprestasie het aangedui dat die PLA/PCL-mengsel suksesvol gemodifiseer is met die EG-mikrovuller wat gelei het tot brandbestande samestellings, veral by hoë vulstofladings, as gevolg van die vorming van opbrandende, koolstofhoudende kool (char). Dit is bevestig deur verlagings van tot 64% in albei die piek hittevrystellingstempo (PHRR) en die totale rookvrystelling (TSR) en 54% in die spesifieke uitsterwingsgebied (SEA). Dit was as gevolg van die EG wat hoofsaaklik deur 'n fisiese modus deur verkoeling en brandstofverdunning en deur die vorming van 'n opbrandende verkoollaag opgetree het. Die effektiewe hitte van verbranding (EHC) en koolstofmonoksied (CO) opbrengste het egter nie gunstig verbeter nie. Daar is gevind dat die smeltvermengingsproses nie die grafietlae, wat as aggregaatstrukture (d.w.s. EG-lae, -stapels en/of -klonte) bestaan het, kon skei nie. In die samestellings is PCL verkies om hoofsaaklik op die oppervlak van die mikrosfere en EG te kristalliseer. Die PLA/PCL-mengsel het 'n onmengbaarheidskenmerk getoon, selfs in die teenwoordigheid van die EG-vuller. Inkorporering van EG in PLA/PCL-mengsel het die smelt- en kristallisasiegedrag van PCL as dié van die PLA-komponent beïnvloed. Beide die PCL en EG het die kristallisasie van die PLA-komponent belemmer. Die glasoorgang van die samestellings het by hoë temperature plaasgevind, wat daarop dui dat PLA polimeerkettings geïmmobiliseer is in die teenwoordigheid van die EG-mikrovuller. Die stoor- en verliesmoduliwaardes was laag vir die samestellings in vergelyking met PLA/PCL. Die resultate dui daarop dat die PLA/PCL/EG vlamvertragende samestellings lae termiese en termomeganiese eienskappe het as gevolg van die aggregasie van EG en gebrek aan grensvlakadhesie tussen EG-klonte en die polimeermengselmatriks. ___________________________________________________________________
𝑺𝒆𝑺𝒐𝒕𝒉𝒐 Sekgahla sa graphite (EG) sa kgwebo se ka atoloswang mabapi le matshwao a ho tuka le ho senyeha ha ditshebetso tse pedi tse theilweng ho poly(lactic acid) (PLA) le motswako wa poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) di ile tsa fuputswa. Ho feta mona, sebopeho sa dikarolwana esita le sebopeho ka kakaretso, ho qhibidiha le ho thatafala ho ba lehakwe esita le disebediswa tse ding tsa phediso ya malakabe le metswako ya PLA/EG le PLA/PCL/EG le tsona di fupuditswe. Sethibelamalakabe sa metswako ya PLA/EG le PLA/PCL/EG se ile sa hlophiswa ka ho tswakwa ka ho qhibidihiswa ka ho sebedisa Brabender-Plastograph mme sa hatellwa ka seqhibidihisi ka ho sebedisa sehatelli sa motlakase sa hydraulichot. Disampole di ile tsa hlakiswa bakeng sa tshebetso ya tsona ya ho tuka le botsitso ba thermal ka ho sebedisa cone calorimeter le thermogravimetric analyser (TGA), ka ho latelana. Tsena di ne di bile di tsejwa ka dihlahiswa tsa tsona tse hlwahlwa tsa pyrolysis nakong ya thermal degradation ka ho sebedisa ka nako e le nngwe TGAFourier transform infrared spectroscopy (TGA-FTIR). Masalla a ho tjha a fumanweng kamora ho tjha ka cone calorimeter a ile a sekasekwa hape ka ho sebedisa scanning electron microscopy (ESEM). Ho feta mona, X-ray diffraction (XRD) le scanning electron microscopy (SEM) di ile tsa sebediswa ho hlakisa sebopeho le sebopeho sa dikarolwana sa sethibelalelakabe PLA/EG le PLA/PCL/EG le tshebetso e hokahaneng. Boitshwaro ba thermal (ke ho re, ho qhibidiha le ho thatafala) esita le dikarolwana tse ding tsa yona tsa thermo-mechanical le tsona di ile tsa hlahlojwa ka hloko ka scanning calorimetry (DSC) esita le mekgwa e meng ya dynamic mechanical analysis (DMA). Bakeng sa tshebetso ya PLA/EG, botsitso ba thermal decomposition ba tse ka hare, bo ile ba ntlafala ka lebaka la ho ba teng ha EG. Leha ho le jwalo, dikateng tsa mashala di ne di le ka tlase ho feta kamoo di neng di lebeletswe ka teng ho ya ka palo ya wt.% EG e ekeditsweng ho PLA le % ya masala a PLA kamora thermal decomposition. Bokgoni ba ho tuka ha metswako ya PLA/EG bo ile ba ntlafatswa, haholoholo ka dikateng tsa 15 wt.% EG, ka lebaka la worm-like char structure. Tekanyetso e phahameng haholo ya motjheso (PHRR) e ile ya ntlafatswa ka 74%, tlhahiso e phahameng ka ho fetisisa ya mosi (TSP) e ile ya ntlafatswa ka 40% mme karolo e ikgethileng ya ho tima (SEA) ka 55%. Dintlafatso tsena di bile teng ka lebaka la bokgoni ba EG le ho thakgoha ka thempheretjha e ekeditsweng nakong eo ditlamorao tse tharo di etsahetseng: i) ditlamorao tsa ho phola ka tshebetso ya endothermic exfoliation; ii) ditlamorao tsa ho hlabollwa ka lebaka la ho lokollwa ha digase tsa H2O, SO2 le CO2 le iii) ho thehwa ha karolo ya tshireletso ya intumescent char. Leha ho le jwalo, ditlhahiso ka bobedi tsa CO le CO2 di fumanwe di phahame ka tsela e kgotsofatsang ka lebaka la ho ba teng ha EG. Dikarolo tsa graphite di nnile tsa ba teng ka sebopeho se bohareng le ka ho fokola ha setlatsetsi se kwahelang le ho hlokeha ha kopano pakeng tsa EG le PLA matrix. Ho ba teng ha dikarolwana tse nyenyane tsa EG: i) ha ho a dumellana le ho theha mahakwe a PLA, ii) ho ekeditse phetoho ya thempheretjha ya galase, le iii) ho bontsha phokotso ya sebopeho sa mahakwe sa metswako kapa dikarolwana. Dikarolwana di bontshitse ho eketseha ha polokeho le loss moduli, haholoholo boemong ba dikateng tse phahameng tsa EG (ke ho re, 10 le 15 wt.%). Phetoho ya galase e tswang ho loss modulus le mongobo di fapane ka tsela e sa tsepamang le ho kgema le dikateng tsa EG. Tshebediso ya graphite ya kgwebo e sarolohang e le filara ho PLA e ne e ka boloka matshwao a thermal a ente ka ho enta molding grade Cereplast PLA, ha e ntse e ntlafatsa thibelo ya mollo ya dikarolwana tsa PLA/EG flame retardant. Mabapi le tshebetso ya thibelo ya malakabe ya PLA/PCL/EG, botsitso ba thermal degradation ba dikarolwana bo ntlafetse mme dikateng tsa char tsa fumanwa di ntlafetse mme dikateng tsa char di eketsehile. Le hoja dikateng tsa char tsa dikarolwana di eketsehile ka kakaretso ka ho kenywa EG, masalla a % a tswang ho metswako ka bobedi esita wt.% EG ka bobedi e ekeditsweng esale pele ka hara motswako e ne e phahame ho feta masalla a hlokometsweng ka lebaka la thermal degradation mechanism e ileng ya thusa bakeng sa ho theha digase tse bohale tsa CO le CO2 ho na le khabono. Diphetho tsa tshebetso ya ho tuka di totobaditse hore motswako wa PLA/PCL o fetotswe ka katleho ka EG micro-filler e qetelletseng ka ho ba dikarolwana tse thibelang ho tuka ha mollo, haholoholo ha ho ekeditswe haholo mollo haholo, ka lebaka la ho thehwa ha intumescent carbonaceous char. Hona ho tiisitswe ke ho fokotswa ho fihlang ho 64% ho tekanyetso ya motjheso o phahameng haholo o hlahiswang (PHRR) le mosi o mongata haholo o hlahiswang (TSR) le 54% ho sebaka se ikgethang sa ho tima mollo (SEA). Hona e ne e le ka lebaka la EG e sebetsang ka sebopeho se tshwarehang ka ho phodisa le ho hlabolla petrolo esita le ka ho theha sebaka sa intumescent char layer. Leha ho le jwalo, bohlwahlwa ba motjheso (EHC) le carbon monoxide (CO) ha bo a hlahisa ntlafalo e kaalo. Ho fumanehile hore tshebetso ya ho qhibidihisa ha e kgone ho arola graphite, e bileng teng e le dipopeho tse bohareng (ke ho re, EG layered stacks le/kapa lumps). Ho dikarolwana, PCL e kgothaleditswe ho theha mahakwe haholoholo hodima sebaka se bataletseng sa microspheres le EG. Motswako wa PLA/PCL o hlahisitse sebopeho sa ho hana ho kopana, esita le ha ho se ho na le setswaki sa EG. Kgokahano ya EG ho motswako wa PLA/PCL e bakile ho qhibidiha le ho tiya ha PCL ho feta karolwana ya PLA. Ka bobedi PCL le EG di sitisitse ho tiya ha karolwana ya PLA. Ho tswa ho DSC le DMA, ho fetoha ha galase ha dikarolwana ho etsahetse boemong ba thempheretjha e phahameng haholo, mme hona ho bolela hore PLA polymer chains di ne di kginnwe le hoja ho na le EG micro filler. Poloko le makgabane a loss moduli di ne di le tlase bakeng sa dikarolwana ha di bapiswa le PLA/PCL. Diphetho di hlahisa hore dikarolwana tse thibang malakabe tsa PLA/PCL/EG di na le dikarolwana tse tlase tsa thermal and thermomechanical ka lebaka la papiso ya EG le ho hlokeha ha kgomarelano pakeng tsa dipokellano tsa sekgahla sa EG le polymer blend matrix. ___________________________________________________________________
𝑰𝒔𝒊𝒁𝒖𝒍𝒖 Umthelela wecommercial expandable graphite (EG) ekuvutheni kalula nokuhlephuka okwenziwa ukushisa kwamasistimu amabili asuselwe kwipoly(lactic acid) (PLA) kanye nepoly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) inhlanganisela uye waphenywa. Ngaphezu kwalokho, imofoloji, ukwakheka, ukuncibilika kanye nokuziphatha kwecrystallization kanye nezakhiwo eziguquguqukayo zemishini yezinhlanganisela zePLA/EG kanye ne-PLA/PCL/EG ezibuyisela amalangabi nazo zafundwa. Izinhlanganisela ze-PLA/EG ne-PLA/PCL/EG ezibuyisela ilangabi zalungiswa ngokuxuba okuncibilikayo kusetshenziswa iBrabender-Plastograph futhi zacindezelwa kusetshenziswa umshini wokuncibilikisa wehydraulichot kagesi. Amasampuli ayephawulwe ngokusebenza kwawo okuvutha nokusimama kokushisa ngecone calorimeter kanye nethermogravimetric analyzer (TGA), ngokulandelanayo. Baphinde baphawuleka ngemikhiqizo yabo yepyrolysis eguquguqukayo ngesikhathi sokuwohloka kokushisa kusetshenziswa kanyekanye iTGAFourier iguqule i-infrared spectroscopy (TGA-FTIR). Izinsalela zechar ezitholwe ngemva kokushiswa yicone calorimeter zabuye zahlaziywa nge-electronic scanning microscopy (ESEM). Ngaphezu kwalokho, iX-ray diffraction (XRD) kanye ne-electron microscopy (SEM) yokuskena (SEM) yasetshenziswa ukuze kucaciswe ukwakheka nokuma kweflame retardant PLA/EG kanye nePLA/PCL/EG izinhlelo eziyinhlanganisela. Ukuziphatha kwabo okushisayo (okungukuthi ukuncibilika kanye nokucwebezela) kanye nezici zabo zethermo-mechanical zahlaziywa ngokulandelana kwedifferial scanning calorimetry (DSC) kanye nezindlela zokuhlaziya idynamic mechanical (DMA). Ngohlelo lwenhlanganisela ye-PLA/EG, ukuzinza kokuhleleka okudalwa ukushisa kwezinhlanganisela kwathuthukiswa phambi kwe-EG. Kodwa-ke, okuqukethwe kwechar bekungaphansi kwalokho obekulindelekile ngokwesamba sewt.% EG engezwe kuPLA kanye no-% wezinsalela zePLA ngemva kokuhlephuka okudalwa ukushisa. Ukusebenza kokuvutha kwezinhlanganisela ze-PLA/EG kuye kwathuthukiswa, ikakhulukazi kokuqukethwe kwe-EG okungamaphesenti ayi-15 wt., ngenxa yesakhiwo sechar esiwugqinsi nesiqinile. Izinga eliphakeme lokukhishwa kokushisa (PHRR) lenziwe ngcono ngamaphesenti angama-74, isamba sokukhiqizwa kwentuthu (TSP) senziwe ngcono ngamaphesenti angama-40 kanye nendawo ethile yokushabalala (SEA) ngamaphesenti angama-55. Lokhu kuthuthukiswa kube ngenxa yekhono le-EG lokuzikhipha emazingeni okushisa anyukile lapho kwenzeke khona imiphumela emithathu: i ) umphumela wokupholisa ngenxa yenqubo yokukhishwa kwe-endothermic; ii) umphumela wokuhlanjululwa ngenxa yokukhishwa kwamagesi e-H2O, SO2 kanye ne-CO2 kanye iii) nokwakheka kongqimba lwe-char intumescent oluvikelayo. Kodwa-ke, kokubili isivuno se-CO ne-CO2 sitholakale siphezulu ngokungafanele ngenxa yokuba khona kwe-EG. Izendlalelo zegraphite zazisekhona esakhiweni esihlanganisiwe esinokuhlakazwa kahle kwesigcwalisi kanye nokuntuleka kokunamathelana phakathi kwe-EG ne-PLA matrix. Ukuba khona kwamamicro-particles e-EG: i ) akuzange kuthande ukukhishwa kwe-crystallization ye-PLA, ii) kwandise izinga lokushisa lokuguqulwa kwengilazi futhi iii) kubonise ukunciphisa i-crystallinity yezinhlanganisela. Izinhlanganisela zibonise ukugcinwa okuthuthukisiwe kanye nemoduli yokulahlekelwa, ikakhulukazi kokuqukethwe kwe-EG ephezulu (okungukuthi 10 kanye no-15 wt amaphesenti). Ukuguqulwa kwengilazi kusuka kumoduli yokulahlekelwa kanye nento yokudambisa ihluke ngokungahambisani nokuqukethwe kwe-EG. Ukusetshenziswa kwegraphite enwebekayo kwezohwebo njengesigcwalisi ku-PLA kungagcina izakhiwo ezishisayo zebanga lokubumba iCereplast PLA, kuyilapho kuthuthukisa ukumelana nomlilo kwezinhlanganisela ze-PLA/EG ze-flame retardant. Esimeni sesistimu yenhlanganisela ye-PLA/PCL/EG yeflame retardant, ukuzinza kokuwohloka kokushisa kwezinhlanganisela kwathuthukiswa futhi ikhontenti yechar yatholakala ukuthi inyukile. Nakuba ikhontenti yechar yezinhlanganisela ikhuphuke ngokuvamile ngokulayishwa kwe-EG, okuhlanganisiwe okungu-% okusele okuvela kukho kokubili ukuhlanganiswa kanye ne-wt.% EG ekuqaleni eyengezwe enhlanganisela yayiphezulu kunensalela ye-% ephawuliwe ngenxa yendlela yokuwohloka kokushisa eyayivumela ukwakheka kwe- CO. kanye namagesi ashintshashintshayo e-CO2 kunekhabhoni. Imiphumela yokusebenza kokuvutha ibonise ukuthi inhlanganisela ye-PLA/PCL ilungiswe ngempumelelo nge-EG micro-filler ephumele ekuhlanganiseni ukumelana nomlilo, ikakhulukazi ekulayishweni okuphezulu kokugcwalisa, ngenxa yokwakheka kwe-intumescent carbonaceous char. Lokhu kuqinisekiswe ukuncishiswa okufika kumaphesenti angama-64 kukho kokubili izinga eliphezulu lokukhululwa kokushisa (PHRR) kanye nesamba sokukhishwa kwentuthu (TSR) kanye namaphesenti angama-54 endaweni ethile yokuqothulwa (SEA). Lokhu kwakungenxa yokuthi i-EG isebenza ikakhulukazi ngemodi engokoqobo ngokupholisa nokuhlanjululwa kukaphethiloli nangokwakheka kongqimba lwe-char ye-itumescent. Kodwa-ke, ukushisa okusebenzayo kokuvutha (EHC) kanye necarbon monoxide (CO) akubanga ngcono kahle . Kutholwe ukuthi inqubo yokuhlanganisa ukuncibilika ayikwazanga ukuhlukanisa izendlalelo zegraphite, ezikhona njengezakhiwo ezihlanganisiwe (okungukuthi izitaki ezinengqimba ye-EG kanye/noma izigaxa). Kuma-composites, i-PCL yayithanda ukuba icwebezele ikakhulukazi ebusweni be-microspheres ne-EG. Inhlanganisela ye-PLA/PCL ibonise isici sokungaguquki, ngisho nalapho kukhona isigcwalisi se-EG. Ukufakwa kwe-EG kunhlanganisela ye-PLA/PCL kube nomthelela ekuncibilikeni nasekuziphatheni kwekristalu kwePCL kunaleyo yengxenye ye-PLA. Kokubili i-PCL ne-EG kuvimbe ukufakwa kwekristalu kwengxenye ye-PLA. Kusuka ku-DSC ne-DMA, ukuguqulwa kwengilazi yezinhlanganisela kwenzeka emazingeni okushisa aphezulu, okuphakamisa ukuthi amaketanga e-PLA polymer ayenganyakazi lapho kukhona i-EG micro filler. Amanani emoduli esitoreji nokulahlekelwa abephansi kuzinhlanganisela uma eqhathaniswa ne-PLA/PCL. Imiphumela iphakamisa ukuthi izinhlanganisela ze-PLA/PCL/EG zokubuyiswa komlilo zinezakhiwo eziphansi ezishisayo nezishisayo ngenxa yokuhlanganiswa kwe-EG nokuntuleka kokunamathela kobuso phakathi kwezigaxa ze-EG kanye ne-polymer blend matrix. ___________________________________________________________________
𝑨𝒇𝒓𝒊𝒌𝒂𝒂𝒏𝒔 Die effek van kommersiële uitbreibare grafiet (EG) op die vlambaarheid en termiese ontbindingseienskappe van twee stelsels is ondersoek, gebaseer op ’n mengsel van poli(melksuur) (PLA) en poli(melksuur)/poli(ε-kaprolaktoon) (PLA/PCL). Verder is die morfologie, struktuur, smelt- en kristallisasiegedrag, sowel as die dinamiese meganiese eienskappe van vlamvertragende PLA/EG- en PLA/PCL/EG-samestellings ook bestudeer. Die vlamvertragende PLA/EG en PLA/PCL/EG-samestellings is voorberei deur smeltmenging met behulp van die Brabender-Plastograph en is smeltgepers met behulp van die elektriese hidroulichot-smeltpers. Die monsters is gekarakteriseer volgens hul vlambaarheidsprestasie en termiese stabiliteit via onderskeidelik die kegelkalorimeter en termogravimetriese analise (TGA). Hulle is ook gekarakteriseer volgens hul vlugtige piroliseprodukte tydens termiese degradasie deur gebruik te maak van die gelyktydige TGA Fourier Transform-infrarooispektroskopie (TGA-FTIR). Die verkoolresidu verkry ná verbranding deur die kegelkalorimeter is verder ontleed met omgewingskanderingselektronmikroskopie (ESEM). Verder is X-straaldiffraksie (XRD) en skandeerelektronmikroskopie (SEM) gebruik om die struktuur en morfologie van die vlamvertragende PLA/EG en PLA/PCL/EG saamgestelde sisteme toe te lig. Hul termiese gedrag (d.w.s. smelting en kristallisasie), sowel as hul termomeganiese eienskappe, is onderskeidelik deur die differensiële skanderingkalorimetrie (DSC) en dinamiese meganiese analise (DMA) tegnieke ontleed. Vir die PLA/EG saamgestelde sisteem is die termiese ontbindingstabiliteit van die samestellings verbeter in die teenwoordigheid van EG. Maar die kool(char)-inhoud was minder as wat verwag is volgens die som van die gew.% EG wat by PLA gevoeg is en die % residu van PLA ná termiese ontbinding. Die vlambaarheidsprestasie van die PLA/EG-samestelling is verbeter, veral by 15 gew.% EG-inhoud, as gevolg van 'n dik en sterk wurmagtige verkoolstruktuur. Die piek hittevrystellingtempo (PHRR) is met 74% verbeter, die totale rookproduksie (TSP) is met 40% verbeter en die spesifieke uitsterwingsgebied (SEA) met 55%. Hierdie verbeterings was te danke aan die vermoë van EG om by verhoogde temperature af te skilfer waartydens drie effekte plaasgevind het: i) verkoelende effek as gevolg van 'n endotermiese afskilferingsproses; ii) verdunningseffek as gevolg van die vrystelling van H2O, SO2 en CO2 en iii) vorming van 'n beskermende opwellende houtskoollaag. Daar is egter gevind dat beide die CO- en CO2-opbrengste ongunstig hoog is as gevolg van die teenwoordigheid van EG. Die grafietlae het steeds bestaan in 'n aggregaatstruktuur met swak vulstofdispersie en 'n gebrek aan grensvlakadhesie tussen EG en die PLA-matriks. Die teenwoordigheid van EG mikro-partikels: i) het nie die kristallisasie van PLA bevoordeel nie, ii) het die glasoorgangstemperatuur verhoog en iii) het 'n vermindering in die kristalliniteit van die samestellings getoon. Die samestellings het verbeterde bergings- en verliesmoduli getoon, veral by hoë EG-inhoude (d.w.s. 10 en 15 gew.%). Die glasoorgang vanaf die verliesmodulus en dempingsfaktor het inkonsekwent gewissel met die EG-inhoud. Die gebruik van kommersiële uitbreibare grafiet as vuller in PLA kan die termiese eienskappe van spuitgietgraad Cereplast PLA behou, terwyl dit die brandweerstand van PLA/EG vlamvertragende samestellings verbeter. In die geval van PLA/PCL/EG-vlamvertragende samestellings, is die termiese degradasie-stabiliteit van die samestellings verbeter en daar is gevind dat die kool(char)-inhoud toegeneem het. Alhoewel die kool(char)-inhoud van die samestellings oor die algemeen toegeneem het met EG-ladings, was die gekombineerde % residu van beide die mengsel en gew.% EG wat aanvanklik by die mengsel gevoeg is, hoër as die waargenome % residu as gevolg van die termiese degradasiemeganisme wat die vorming van CO bevoordeel het en CO2-vlugtige gasse, eerder as koolstof. Die resultate van die vlambaarheidsprestasie het aangedui dat die PLA/PCL-mengsel suksesvol gemodifiseer is met die EG-mikrovuller wat gelei het tot brandbestande samestellings, veral by hoë vulstofladings, as gevolg van die vorming van opbrandende, koolstofhoudende kool (char). Dit is bevestig deur verlagings van tot 64% in albei die piek hittevrystellingstempo (PHRR) en die totale rookvrystelling (TSR) en 54% in die spesifieke uitsterwingsgebied (SEA). Dit was as gevolg van die EG wat hoofsaaklik deur 'n fisiese modus deur verkoeling en brandstofverdunning en deur die vorming van 'n opbrandende verkoollaag opgetree het. Die effektiewe hitte van verbranding (EHC) en koolstofmonoksied (CO) opbrengste het egter nie gunstig verbeter nie. Daar is gevind dat die smeltvermengingsproses nie die grafietlae, wat as aggregaatstrukture (d.w.s. EG-lae, -stapels en/of -klonte) bestaan het, kon skei nie. In die samestellings is PCL verkies om hoofsaaklik op die oppervlak van die mikrosfere en EG te kristalliseer. Die PLA/PCL-mengsel het 'n onmengbaarheidskenmerk getoon, selfs in die teenwoordigheid van die EG-vuller. Inkorporering van EG in PLA/PCL-mengsel het die smelt- en kristallisasiegedrag van PCL as dié van die PLA-komponent beïnvloed. Beide die PCL en EG het die kristallisasie van die PLA-komponent belemmer. Die glasoorgang van die samestellings het by hoë temperature plaasgevind, wat daarop dui dat PLA polimeerkettings geïmmobiliseer is in die teenwoordigheid van die EG-mikrovuller. Die stoor- en verliesmoduliwaardes was laag vir die samestellings in vergelyking met PLA/PCL. Die resultate dui daarop dat die PLA/PCL/EG vlamvertragende samestellings lae termiese en termomeganiese eienskappe het as gevolg van die aggregasie van EG en gebrek aan grensvlakadhesie tussen EG-klonte en die polimeermengselmatriks. ___________________________________________________________________
𝑺𝒆𝑺𝒐𝒕𝒉𝒐 Sekgahla sa graphite (EG) sa kgwebo se ka atoloswang mabapi le matshwao a ho tuka le ho senyeha ha ditshebetso tse pedi tse theilweng ho poly(lactic acid) (PLA) le motswako wa poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) di ile tsa fuputswa. Ho feta mona, sebopeho sa dikarolwana esita le sebopeho ka kakaretso, ho qhibidiha le ho thatafala ho ba lehakwe esita le disebediswa tse ding tsa phediso ya malakabe le metswako ya PLA/EG le PLA/PCL/EG le tsona di fupuditswe. Sethibelamalakabe sa metswako ya PLA/EG le PLA/PCL/EG se ile sa hlophiswa ka ho tswakwa ka ho qhibidihiswa ka ho sebedisa Brabender-Plastograph mme sa hatellwa ka seqhibidihisi ka ho sebedisa sehatelli sa motlakase sa hydraulichot. Disampole di ile tsa hlakiswa bakeng sa tshebetso ya tsona ya ho tuka le botsitso ba thermal ka ho sebedisa cone calorimeter le thermogravimetric analyser (TGA), ka ho latelana. Tsena di ne di bile di tsejwa ka dihlahiswa tsa tsona tse hlwahlwa tsa pyrolysis nakong ya thermal degradation ka ho sebedisa ka nako e le nngwe TGAFourier transform infrared spectroscopy (TGA-FTIR). Masalla a ho tjha a fumanweng kamora ho tjha ka cone calorimeter a ile a sekasekwa hape ka ho sebedisa scanning electron microscopy (ESEM). Ho feta mona, X-ray diffraction (XRD) le scanning electron microscopy (SEM) di ile tsa sebediswa ho hlakisa sebopeho le sebopeho sa dikarolwana sa sethibelalelakabe PLA/EG le PLA/PCL/EG le tshebetso e hokahaneng. Boitshwaro ba thermal (ke ho re, ho qhibidiha le ho thatafala) esita le dikarolwana tse ding tsa yona tsa thermo-mechanical le tsona di ile tsa hlahlojwa ka hloko ka scanning calorimetry (DSC) esita le mekgwa e meng ya dynamic mechanical analysis (DMA). Bakeng sa tshebetso ya PLA/EG, botsitso ba thermal decomposition ba tse ka hare, bo ile ba ntlafala ka lebaka la ho ba teng ha EG. Leha ho le jwalo, dikateng tsa mashala di ne di le ka tlase ho feta kamoo di neng di lebeletswe ka teng ho ya ka palo ya wt.% EG e ekeditsweng ho PLA le % ya masala a PLA kamora thermal decomposition. Bokgoni ba ho tuka ha metswako ya PLA/EG bo ile ba ntlafatswa, haholoholo ka dikateng tsa 15 wt.% EG, ka lebaka la worm-like char structure. Tekanyetso e phahameng haholo ya motjheso (PHRR) e ile ya ntlafatswa ka 74%, tlhahiso e phahameng ka ho fetisisa ya mosi (TSP) e ile ya ntlafatswa ka 40% mme karolo e ikgethileng ya ho tima (SEA) ka 55%. Dintlafatso tsena di bile teng ka lebaka la bokgoni ba EG le ho thakgoha ka thempheretjha e ekeditsweng nakong eo ditlamorao tse tharo di etsahetseng: i) ditlamorao tsa ho phola ka tshebetso ya endothermic exfoliation; ii) ditlamorao tsa ho hlabollwa ka lebaka la ho lokollwa ha digase tsa H2O, SO2 le CO2 le iii) ho thehwa ha karolo ya tshireletso ya intumescent char. Leha ho le jwalo, ditlhahiso ka bobedi tsa CO le CO2 di fumanwe di phahame ka tsela e kgotsofatsang ka lebaka la ho ba teng ha EG. Dikarolo tsa graphite di nnile tsa ba teng ka sebopeho se bohareng le ka ho fokola ha setlatsetsi se kwahelang le ho hlokeha ha kopano pakeng tsa EG le PLA matrix. Ho ba teng ha dikarolwana tse nyenyane tsa EG: i) ha ho a dumellana le ho theha mahakwe a PLA, ii) ho ekeditse phetoho ya thempheretjha ya galase, le iii) ho bontsha phokotso ya sebopeho sa mahakwe sa metswako kapa dikarolwana. Dikarolwana di bontshitse ho eketseha ha polokeho le loss moduli, haholoholo boemong ba dikateng tse phahameng tsa EG (ke ho re, 10 le 15 wt.%). Phetoho ya galase e tswang ho loss modulus le mongobo di fapane ka tsela e sa tsepamang le ho kgema le dikateng tsa EG. Tshebediso ya graphite ya kgwebo e sarolohang e le filara ho PLA e ne e ka boloka matshwao a thermal a ente ka ho enta molding grade Cereplast PLA, ha e ntse e ntlafatsa thibelo ya mollo ya dikarolwana tsa PLA/EG flame retardant. Mabapi le tshebetso ya thibelo ya malakabe ya PLA/PCL/EG, botsitso ba thermal degradation ba dikarolwana bo ntlafetse mme dikateng tsa char tsa fumanwa di ntlafetse mme dikateng tsa char di eketsehile. Le hoja dikateng tsa char tsa dikarolwana di eketsehile ka kakaretso ka ho kenywa EG, masalla a % a tswang ho metswako ka bobedi esita wt.% EG ka bobedi e ekeditsweng esale pele ka hara motswako e ne e phahame ho feta masalla a hlokometsweng ka lebaka la thermal degradation mechanism e ileng ya thusa bakeng sa ho theha digase tse bohale tsa CO le CO2 ho na le khabono. Diphetho tsa tshebetso ya ho tuka di totobaditse hore motswako wa PLA/PCL o fetotswe ka katleho ka EG micro-filler e qetelletseng ka ho ba dikarolwana tse thibelang ho tuka ha mollo, haholoholo ha ho ekeditswe haholo mollo haholo, ka lebaka la ho thehwa ha intumescent carbonaceous char. Hona ho tiisitswe ke ho fokotswa ho fihlang ho 64% ho tekanyetso ya motjheso o phahameng haholo o hlahiswang (PHRR) le mosi o mongata haholo o hlahiswang (TSR) le 54% ho sebaka se ikgethang sa ho tima mollo (SEA). Hona e ne e le ka lebaka la EG e sebetsang ka sebopeho se tshwarehang ka ho phodisa le ho hlabolla petrolo esita le ka ho theha sebaka sa intumescent char layer. Leha ho le jwalo, bohlwahlwa ba motjheso (EHC) le carbon monoxide (CO) ha bo a hlahisa ntlafalo e kaalo. Ho fumanehile hore tshebetso ya ho qhibidihisa ha e kgone ho arola graphite, e bileng teng e le dipopeho tse bohareng (ke ho re, EG layered stacks le/kapa lumps). Ho dikarolwana, PCL e kgothaleditswe ho theha mahakwe haholoholo hodima sebaka se bataletseng sa microspheres le EG. Motswako wa PLA/PCL o hlahisitse sebopeho sa ho hana ho kopana, esita le ha ho se ho na le setswaki sa EG. Kgokahano ya EG ho motswako wa PLA/PCL e bakile ho qhibidiha le ho tiya ha PCL ho feta karolwana ya PLA. Ka bobedi PCL le EG di sitisitse ho tiya ha karolwana ya PLA. Ho tswa ho DSC le DMA, ho fetoha ha galase ha dikarolwana ho etsahetse boemong ba thempheretjha e phahameng haholo, mme hona ho bolela hore PLA polymer chains di ne di kginnwe le hoja ho na le EG micro filler. Poloko le makgabane a loss moduli di ne di le tlase bakeng sa dikarolwana ha di bapiswa le PLA/PCL. Diphetho di hlahisa hore dikarolwana tse thibang malakabe tsa PLA/PCL/EG di na le dikarolwana tse tlase tsa thermal and thermomechanical ka lebaka la papiso ya EG le ho hlokeha ha kgomarelano pakeng tsa dipokellano tsa sekgahla sa EG le polymer blend matrix. ___________________________________________________________________
𝑰𝒔𝒊𝒁𝒖𝒍𝒖 Umthelela wecommercial expandable graphite (EG) ekuvutheni kalula nokuhlephuka okwenziwa ukushisa kwamasistimu amabili asuselwe kwipoly(lactic acid) (PLA) kanye nepoly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) inhlanganisela uye waphenywa. Ngaphezu kwalokho, imofoloji, ukwakheka, ukuncibilika kanye nokuziphatha kwecrystallization kanye nezakhiwo eziguquguqukayo zemishini yezinhlanganisela zePLA/EG kanye ne-PLA/PCL/EG ezibuyisela amalangabi nazo zafundwa. Izinhlanganisela ze-PLA/EG ne-PLA/PCL/EG ezibuyisela ilangabi zalungiswa ngokuxuba okuncibilikayo kusetshenziswa iBrabender-Plastograph futhi zacindezelwa kusetshenziswa umshini wokuncibilikisa wehydraulichot kagesi. Amasampuli ayephawulwe ngokusebenza kwawo okuvutha nokusimama kokushisa ngecone calorimeter kanye nethermogravimetric analyzer (TGA), ngokulandelanayo. Baphinde baphawuleka ngemikhiqizo yabo yepyrolysis eguquguqukayo ngesikhathi sokuwohloka kokushisa kusetshenziswa kanyekanye iTGAFourier iguqule i-infrared spectroscopy (TGA-FTIR). Izinsalela zechar ezitholwe ngemva kokushiswa yicone calorimeter zabuye zahlaziywa nge-electronic scanning microscopy (ESEM). Ngaphezu kwalokho, iX-ray diffraction (XRD) kanye ne-electron microscopy (SEM) yokuskena (SEM) yasetshenziswa ukuze kucaciswe ukwakheka nokuma kweflame retardant PLA/EG kanye nePLA/PCL/EG izinhlelo eziyinhlanganisela. Ukuziphatha kwabo okushisayo (okungukuthi ukuncibilika kanye nokucwebezela) kanye nezici zabo zethermo-mechanical zahlaziywa ngokulandelana kwedifferial scanning calorimetry (DSC) kanye nezindlela zokuhlaziya idynamic mechanical (DMA). Ngohlelo lwenhlanganisela ye-PLA/EG, ukuzinza kokuhleleka okudalwa ukushisa kwezinhlanganisela kwathuthukiswa phambi kwe-EG. Kodwa-ke, okuqukethwe kwechar bekungaphansi kwalokho obekulindelekile ngokwesamba sewt.% EG engezwe kuPLA kanye no-% wezinsalela zePLA ngemva kokuhlephuka okudalwa ukushisa. Ukusebenza kokuvutha kwezinhlanganisela ze-PLA/EG kuye kwathuthukiswa, ikakhulukazi kokuqukethwe kwe-EG okungamaphesenti ayi-15 wt., ngenxa yesakhiwo sechar esiwugqinsi nesiqinile. Izinga eliphakeme lokukhishwa kokushisa (PHRR) lenziwe ngcono ngamaphesenti angama-74, isamba sokukhiqizwa kwentuthu (TSP) senziwe ngcono ngamaphesenti angama-40 kanye nendawo ethile yokushabalala (SEA) ngamaphesenti angama-55. Lokhu kuthuthukiswa kube ngenxa yekhono le-EG lokuzikhipha emazingeni okushisa anyukile lapho kwenzeke khona imiphumela emithathu: i ) umphumela wokupholisa ngenxa yenqubo yokukhishwa kwe-endothermic; ii) umphumela wokuhlanjululwa ngenxa yokukhishwa kwamagesi e-H2O, SO2 kanye ne-CO2 kanye iii) nokwakheka kongqimba lwe-char intumescent oluvikelayo. Kodwa-ke, kokubili isivuno se-CO ne-CO2 sitholakale siphezulu ngokungafanele ngenxa yokuba khona kwe-EG. Izendlalelo zegraphite zazisekhona esakhiweni esihlanganisiwe esinokuhlakazwa kahle kwesigcwalisi kanye nokuntuleka kokunamathelana phakathi kwe-EG ne-PLA matrix. Ukuba khona kwamamicro-particles e-EG: i ) akuzange kuthande ukukhishwa kwe-crystallization ye-PLA, ii) kwandise izinga lokushisa lokuguqulwa kwengilazi futhi iii) kubonise ukunciphisa i-crystallinity yezinhlanganisela. Izinhlanganisela zibonise ukugcinwa okuthuthukisiwe kanye nemoduli yokulahlekelwa, ikakhulukazi kokuqukethwe kwe-EG ephezulu (okungukuthi 10 kanye no-15 wt amaphesenti). Ukuguqulwa kwengilazi kusuka kumoduli yokulahlekelwa kanye nento yokudambisa ihluke ngokungahambisani nokuqukethwe kwe-EG. Ukusetshenziswa kwegraphite enwebekayo kwezohwebo njengesigcwalisi ku-PLA kungagcina izakhiwo ezishisayo zebanga lokubumba iCereplast PLA, kuyilapho kuthuthukisa ukumelana nomlilo kwezinhlanganisela ze-PLA/EG ze-flame retardant. Esimeni sesistimu yenhlanganisela ye-PLA/PCL/EG yeflame retardant, ukuzinza kokuwohloka kokushisa kwezinhlanganisela kwathuthukiswa futhi ikhontenti yechar yatholakala ukuthi inyukile. Nakuba ikhontenti yechar yezinhlanganisela ikhuphuke ngokuvamile ngokulayishwa kwe-EG, okuhlanganisiwe okungu-% okusele okuvela kukho kokubili ukuhlanganiswa kanye ne-wt.% EG ekuqaleni eyengezwe enhlanganisela yayiphezulu kunensalela ye-% ephawuliwe ngenxa yendlela yokuwohloka kokushisa eyayivumela ukwakheka kwe- CO. kanye namagesi ashintshashintshayo e-CO2 kunekhabhoni. Imiphumela yokusebenza kokuvutha ibonise ukuthi inhlanganisela ye-PLA/PCL ilungiswe ngempumelelo nge-EG micro-filler ephumele ekuhlanganiseni ukumelana nomlilo, ikakhulukazi ekulayishweni okuphezulu kokugcwalisa, ngenxa yokwakheka kwe-intumescent carbonaceous char. Lokhu kuqinisekiswe ukuncishiswa okufika kumaphesenti angama-64 kukho kokubili izinga eliphezulu lokukhululwa kokushisa (PHRR) kanye nesamba sokukhishwa kwentuthu (TSR) kanye namaphesenti angama-54 endaweni ethile yokuqothulwa (SEA). Lokhu kwakungenxa yokuthi i-EG isebenza ikakhulukazi ngemodi engokoqobo ngokupholisa nokuhlanjululwa kukaphethiloli nangokwakheka kongqimba lwe-char ye-itumescent. Kodwa-ke, ukushisa okusebenzayo kokuvutha (EHC) kanye necarbon monoxide (CO) akubanga ngcono kahle . Kutholwe ukuthi inqubo yokuhlanganisa ukuncibilika ayikwazanga ukuhlukanisa izendlalelo zegraphite, ezikhona njengezakhiwo ezihlanganisiwe (okungukuthi izitaki ezinengqimba ye-EG kanye/noma izigaxa). Kuma-composites, i-PCL yayithanda ukuba icwebezele ikakhulukazi ebusweni be-microspheres ne-EG. Inhlanganisela ye-PLA/PCL ibonise isici sokungaguquki, ngisho nalapho kukhona isigcwalisi se-EG. Ukufakwa kwe-EG kunhlanganisela ye-PLA/PCL kube nomthelela ekuncibilikeni nasekuziphatheni kwekristalu kwePCL kunaleyo yengxenye ye-PLA. Kokubili i-PCL ne-EG kuvimbe ukufakwa kwekristalu kwengxenye ye-PLA. Kusuka ku-DSC ne-DMA, ukuguqulwa kwengilazi yezinhlanganisela kwenzeka emazingeni okushisa aphezulu, okuphakamisa ukuthi amaketanga e-PLA polymer ayenganyakazi lapho kukhona i-EG micro filler. Amanani emoduli esitoreji nokulahlekelwa abephansi kuzinhlanganisela uma eqhathaniswa ne-PLA/PCL. Imiphumela iphakamisa ukuthi izinhlanganisela ze-PLA/PCL/EG zokubuyiswa komlilo zinezakhiwo eziphansi ezishisayo nezishisayo ngenxa yokuhlanganiswa kwe-EG nokuntuleka kokunamathela kobuso phakathi kwezigaxa ze-EG kanye ne-polymer blend matrix. ___________________________________________________________________
Description
Thesis (Ph.D.(Chemistry))--University of the Free State, 2016
Keywords
Biopolymers, Polylactic acid -- Thermal properties, Polymers -- Biodegradation, Polymeric composites -- Thermal properties