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 ISTITUZIONALEFIRE RETARDANT BEHAVIOUR OF POLYLACTIC ACID NANOCOMPOSITES / Ping W.; Bocchini S.; Di Blasio A.;Camino G.. - ELETTRONICO. - (2011). ((Intervento presentato al convegno FRPM 2011 13th European Meeting on Fireretardant Polymers tenutosi a Alessandria (Italy) nel 26-30th June 2011.OriginalFIRE RETARDANT BEHAVIOUR OF POLYLACTIC ACID NANOCOMPOSITESPublisher: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: 11583/2427778 since:Limiting oxygen index (Burning rate).Burning rate as a function of oxygen concentration is easily measured in the oxygen index test apparatus by measuring the spreadingtime of the flame between two marks at a known distance on the specimen. A Burning Oxygen Index (BOI)* can also be obtained byextrapolating BR to BR=0, which meaning is indeed similar to that of oxygen index at which the sample ignites (OC below whichignition does not occur) since it gives the OC below which burning would not occur.The plots shows that the nanocomposites have a BOI lower that PLA alone, as expected the BOI of the different nanocomposites aredirectly linked to the concentration of the different nanoparticles and their dispersion, thus it is possible to have a quantitativecorrelation between filler type, concentration and dispersion and the BOI of the different nanocomposites. Moreover in these graphsthe effect of nanoclay on fire retardacy is clearly exposed: the different nanocomposites burns at lower oxygen index but theconbustion rate is usually lower that the pure polymer thus the different clays could be considered as an additive that improves theresistance to fire but that does not work as a fire retardant if used alone.* Camino, G.; Costa, L.; Casorati, E.; Bertelli, G.; Locatelli, R. The oxygen index method in fire retardancestudies of polymeric materials Journal of Applied Polymer Science. 1988, 35, 1863-1876.MaterialsThe Poly(lactic acid), 3051D- (PLA) was supplied by Nature Works (USA). Flamestab NOR 116 a flameretardant and flame retardant synergist in polyolefin applications was supplied by Ciba specialty chemicalThe nanofillers and flame retardant used are listed in Table below:MaterialsMaterial processingThe composites were prepared via melt-processing using a leistritz co-rotating twin screw extruder (d=18mm, l/d=40). Flow with 4.0 kg/h, speed with 150 rpm were used. The residence time was about 50s.Thesamples were prepared by direct addition of the different nanofillers. Composition were listed below:Sample PLA FlamestabNOR 116 (Fl)Filler%wt %wt Type %wtPLA 100.0 - - -PLA1Fl 99.0 1.0 - -PLA25Cl 97.5 - Cl20A 2.5PLA50Cl 95.0 - Cl20A 5.0PLA25Cl30B 97.5 - Cl30B 2.5PLA50Cl30B 95.0 - Cl30B 5.0PLA50Cl30BFl 94.0 1.0 Cl30B 5.0Filler (Name) Organic modifier Filler typeCloisite 20A(Cl) MontmorilloniteClosite 30B  (Cl30B) MontmorilloniteSample FormulaFlamestab NOR 116 (Fl)CH3N+HTCH3 HTFIRE RETARDANT BEHAVIOUR OF POLYLACTIC ACID NANOCOMPOSITESW. 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, ItalyFirst applications of PLA were designed for disposable materials (e.g. packaging) or semi-durable materials (e.g. textile) where flame retardancy is not required. However because of increase of PLA for durable application, thefire retardancy issue is becoming important and it is expected that in the next future more and more scientific paper will be devoted to the subject. Actually most of the work done on PLA is on the use of traditional fire retardantsdeveloped for other polymers especially traditional polyesters such as PET or other polymers such as polycarbonate. The use of clay could help in the development of fire retardant plastics based on biopolyesters. The main goal ofthis work is to study clay nanocomposites during heating and the derived thermal and fire behavior.OHN+OH HTMorphologyAs a result of PLA melt blending with 2.5 and 5.0 wt% of (organo-modified) montmorillonite, intercalatednanocomposites were prepared by using Cloisite 20A or Cloisite 30B. There is no major modification between 2.5wt% and 5 wt% for both clays. PLA is characterized by a broad intensity with maximum approximately at 2θ=17°,indicating an amorphous structure for this sample. The interlayer spacing (d001) diffraction angle obtained by XRDmeasurements for Cl20A is equal to 2θ= 3.6°，when adding Cl20A to the PLA, , for both PLACl20Ananocomposites a sharp peak is observed at 2θ=2.6°, equivalent to a d001= 3.4 nm with an increase of the interlayerdistance of 1 nm compared with pure Cl20A, .This increase is accompanied by the appearance of a small peak at 5°due to the d002 of the dispersed Cl20A.In the case of the system of Cl30B with PLA based nanocomposites, a sharp peak shift to 2θ=2.4°, whichphenomena is similar to systems of PLA Cl20A, but the d001 increases to 3.7 nm from 1.8 nm of the original Cl30Borganoclay, interlayer distance.TEM analysesPLA based nanocomposites were further analyzed by TEM. The incorporation of Cl20A in the PLA matrix showscertain level of intercalation as well as the occurrence of exfoliated silicate layers. When correlating theseobservations with XRD results, we can conclude that the Cl20A forms partially exfoliated nanocomposites. The sameresults were obtained with Cl30B based nanocomposites. There is a certain level of intercalation but the numbers ofsilicate layers for stack are lower respect to Cl20A and higher numbers of small stacks of swollen clay layers andsingle dispersed layers can be observed in the TEM micrograph .From XRD and TEM results, it is clear that thedispersion and interaction of the Cl30B in PLA is better than that obtained with Cl20A. This can be attributed to thestronger interactions between the polymers and Cl 30B, originated from the hydrogen bonding between the carbonylgroup of PLA and the hydroxyl groups.TEM analyses of different nanocomposites A) B) PLA50Cl20A C) D) PLA50Cl30B0 5 10 15 20 25 30Intansity/CPS2Theta/degPLAPLA2.5Cl20APLA5Cl20A2.6°5.0°0 5 10 15 20 25 30Intansity/CPS2Theta/Deg2.4°5.0°PLAPLA2.5Cl30BPLA5Cl30BPLA5Cl0B1FlSample Interlayer distance d0012θ nmCl 3.60 2.4Cl30B 5.00 1.8PLA25Cl 2.60 3.4PLA50Cl 2.60 3.4PLA25Cl30B 2.43 3.7PLA50Cl30B 2.43 3.7PLA50Cl30BFl 2.43 3.7AB C DLimiting oxygen index (Self quenching time)0 20 40 60 802021222324252627  PLA PLA1FIOxygen (vol%)Self-quenching Time  (s) 0 20 40 60 80 100 120 140 160 180 200182022242628  PLA25Cl20A PLA50Cl20A PLA25Cl30B PLA50Cl30B PLA50Cl30B1FIOxygen (vol%)Self-quenching time (s)18 20 22 24 260,00,51,01,52,02,5  PLA                BOI= 21.1 PLA25Cl20A  BOI= 19.0 PLA5Cl20A    BOI= 20.4Rate (mm s-1)Oxygen (Volume%)18 20 22 24 260,00,51,01,52,02,5 PLA              BOI=21.1 PLA25Cl30B BOI=16.0 PLA5Cl30B   BOI=21.0Rate (mm s-1)Oxygen (Volume%)16 18 20 22 24 26 280,00,51,01,52,02,5 PLA                BOI=21.1 PLA5Cl30B     BOI=21.0 PLA5C30B1FI BOI=20.5 PLA1FI            BOI=21.9Rate (mm s-1)Oxygen (Volume%)For a more detailed evaluation of fire behaviour not only the limiting oxygen index number (LOI) is reported but also theburning time as a function of oxygen concentration (OC)*. The time interval between the removal of the ignition flame and theextinction of the burning specimen named “Self-Quenching Time”(SQT), is reported as a function of the oxygen concentration.The plots of PLA and PLAFl can be separated into two successive approximately linear regions which is the behaviour mostoften found for polymer materials. In the first region a large increase in oxygen concentration is required to increase the selfquenching time. The interval between the first and the second region is the change from an unstable to stable burning. In thiscase Fl works as a flame retardant because it increases of about 3 %vol the oxygen concentration in order to have a stableburning. Upon addition of nanoclays, the oxygen concentration at which PLA ignition by the external flame just becomespossible, also ensures self-sustained combustion to occur, with suppression of the unstable combustion regime observed withvirgin PLA, in other words, the oxygen index at which nanocomposites ignites and their LOI are coincident. This generallyresults in a lower LOI value for nanocomposites as compared to PLA, apart from PLA50CL20A which LOI is comparable toPLA* 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.

FIRE RETARDANT BEHAVIOUR OF POLYLACTIC ACID NANOCOMPOSITES

https://iris.polito.it/retrieve/handle/11583/2427778/54671/PLA_fire_nanocompositi.pdf

FIRE RETARDANT BEHAVIOUR OF POLYLACTIC ACID NANOCOMPOSITES

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