Bocchini S.

Camino G.

Di Blasio A.

Ping W.

English

BOCCHINI, SERGIO

DI BLASIO, ALESSANDRO

CAMINO, GIOVANNI

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

04 August 2020POLITECNICO DI TORINORepository ISTITUZIONALEFLAME RETARDANT AND THERMAL BEHAVIOUR OF THE PLA/EXPANDABLE GRAPHITE COMPOSITES / Ping W.;Bocchini S.; Di Blasio A.; Camino G.. - ELETTRONICO. - (2011). ((Intervento presentato al convegno FRPM 2011 13thEuropean Meeting on Fire retardant Polymers tenutosi a Alessandria (Italy) nel 26-30th June 2011.OriginalFLAME RETARDANT AND THERMAL BEHAVIOUR OF THE PLA/EXPANDABLE GRAPHITECOMPOSITESPublisher:PublishedDOI:Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2427779 since:MaterialsThe Poly(lactic acid), 3051D- (PLA) was supplied by Nature Works (USA). Flamestab NOR116 a flame retardant and flame retardant synergist in polyolefin applications was suppliedby Ciba specialty chemical.Material processingThe composites were prepared via melt-processing using a leistritz co-rotating twin screwextruder (d=18 mm, l/d=40). Flow with 4.0 kg/h, speed with 150 rpm were used。Theresidence time was about 50s.The samples were prepared by direct addition of the differentnanofillers. Composition were listed belowSamples PLA GR FI%wt %wt %wtPLA 100.0 - -PLA1FI 99.0 - 1.0PLA1GR 99.0 1.0 -PLA2.5GR 97.5 2.5 -PLA5GR 95.0 5 -PLA10GR 90.0 10.0 -PLA1GR1FI 98.0 1.0 1.0Sample FormulaFlamestab NOR 116 (Fl)FLAME RETARDANT AND THERMAL BEHAVIOUR OF THE PLA/EXPANDABLE GRAPHITE COMPOSITESW. Ping1, S. Bocchini2, A. Di Blasio2, G. Camino21 School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai, People’s Republic of China2 Polytechnic of Turin, Alessandria site, ItalyThis article describes studies on the thermal behavior and flame retardant properties of polylactide (PLA) composites with halogen-free flame retardant expandable graphite (GR). The heat releaserate (HRR) and total heat release (THR) were used to evaluate the flammability by cone. Vertical burning test (UL-94) was also successfully passed revealing non-dripping and char formation.Ignition oxygen index (IOI) and burning rate (BR) was used studied composites combustion rate in the LOI test. Monomeric N-alkoxy hindered amine (NOR116) was also discussed as the flameretardant synergist in the PLA/GR composites.Forced combustionThe cone calorimeter based on the oxygen consumption principle has been extensively used toevaluate the flammability of materials because its results correlates well with those obtained fromlarge-scale fire tests and can be used to predict the combustion behaviors of materials in real fires.The heat release rate (HRR) and especially the peak of HRR, has been found to be the mostimportant parameter to evaluate fire safety. The peak HRR and HRR of PLA composites decreasewith increasing graphite content. Compared to pure PLA, the peak HRR of composites 5wt% and 10wt% graphite shows a decrease with reduction of peak HRR about 10% and 28%. Meanwhile, thetotal heat released also distinct decreases of 33% and 20% respectively, while the loading amount ofgraphite less than 5wt%, the HRR, Peak HRR and THR do not significant decrease compared withthe pure PLA. The flame retardant capability of graphite is thus relative to the amount of graphite.These results indicate that it is necessary a complete coverage of PLA by graphite to reduce smallmolecular volatile and suppress smoke production effectively when graphite loading over 2.5wt%.Meanwhile, it prevents the heat release by promoting char formation. The char layer may act as aninsulator and mass transport barrier which slows the escape of the generated volatile products andoxygen diffusion, then slow down heat and mass transfer between the gas and condensed phase,which prevents the underlying polymeric substrate from further attack of heating which areaccordant with the results of UL-94 test.Sample TTI THE HRRAve pkHRR EHC TSR(s) (MJ/m2) (kW/m2) (kW/m2) (MJ/kg) (m2/m2)PLA 64 64 254 426 18 69PLA /1FI 67 62 242 403 17 56PLA/1GR 44 70 267 409 18 77PLA/2.5GR 42 67 253 396 18 73PLA/5GR 43 44 201 378 18 36PLA /10GR 60 52 126 307 17 32PLA/1GR/1FI 43 66 260 396 18 58The flame retardant properties of  PLA compositesThe oxygen index (OI) is the minimum concentration of oxygen in a flowing mixture ofoxygen and nitrogen that supports candle-like combustion of a specimen. The ignition andburning time is considerable at the determination of the oxygen index. For more detailedevaluation of fire behavior, the measurements of IOI (ignition oxygen index ) and increaseof BR (burning rate) with OC (ΔBR) are as to complement each other*. The presence ofsmall amount of expandable graphite additives slightly increases values of both IOI and OIin PLA/graphite composites compared with pure PLA. General, the low value OI is notgood for the flame retardancy, in fact only PLA/5GR can pass UL-94 rating V-0. Inaccordance with a low combustion rate of 0.84 and slightly high IOI. The charring withoutcracking on the top of stick was also observed. The other system on the list with UL-94rating V-2 is due to lower IOI and more fast combustion rate. For example，the system of2.5 GR, IOI is 25 and ΔBR is 0.94, while the system of 1GR, IOI is 23.5 and ΔBR is 1.46,and there are charring and dripping on the side of the stick. For the pure PLA a totalcombustion and dripping behavior from the stick was observed, the combustion rate (1.7)is larger than any other system on the list. This results show that ignition oxygen index andcombustion rate is also beneficial for the evaluation of the flame retardancy.* Camino, G.; Costa, L.; Casorati, E.; Bertelli, G.; Locatelli, R. The oxygen index method in fireretardance studies of polymeric materials Journal of Applied Polymer Science. 1988, 35, 1863-1876.0 100 200 300 400 500 6000100200300400500Heat release rate(kW/m2)Time(s) PLA PLA/1GR PLA/2.5GR PLA/5GR PLA/10GR PLA/1GR/1FISample IOI LOI BOI ΔBR UL-94V%vol %vol %vol [mm/(s OC%)]PLA 20.9 23 21.3 1.7 NCPLA1GR 23.3 23.3 22.2 1.41 V2PLA2.5GR 25 25 23 0.94 V2PLA5GR 24.5 24.5 22.5 0.86 V0PLA10GR - - - - V0PLA1GR1FI 23 23 21.6 0.81 V2The flame retardant properties of  PLA compositesPLA/expandable graphite composites have been produced by melt-blending. Expandablegraphite amount improves the flame retardancy of PLA composites when the loading ofexpandable graphite is larger than 5 wt%. The vertical burning test was successfully passedrevealing non-dripping and char formation for PLA composites with expandable graphiteamount equal and higher than 5wt%. The monomeric N-alkoxy hindered amine (NOR116),can increase thermal stability and decrease of the heat release rate as a flame retardantsynergist in PLA/expandable graphite.

FLAME RETARDANT AND THERMAL BEHAVIOUR OF THE PLA/EXPANDABLE GRAPHITE COMPOSITES

https://iris.polito.it/retrieve/handle/11583/2427779/54673/PLA_fire_grafite.pdf

FLAME RETARDANT AND THERMAL BEHAVIOUR OF THE PLA/EXPANDABLE GRAPHITE COMPOSITES

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