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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Flame retardancy of polybutylene succinate by multiple approaches / Retard de flamme du polybutylène succinate par multiples méthodes

Hu, Chi 15 November 2018 (has links)
Cette étude a focalisé sur le retard de flamme du polybutylène succinate (PBS) qui est un polymère bio-sourcé et biodégradable et qui a des bonnes propriétés mécanique par multiple méthodes. Dans ce contexte, modification d’isosorbide a été réalisé pour obtenir des retardateurs de flamme bio-sourcé. Puis, isosorbide et poly(isosorbide)carbonate (PIC) a été extrudé avec PBS et des retardateur de flamme intumescent. Cela a montré l’augmentation des propriétés retard de flamme dans la phase condensé qui a une augmentation de taux de char et diminution de pHHR et THR. Un retardateur de flamme conventionnel, DOPO, a présenté des super propriétés de retard de flamme pour PBS dans la phase gazeuse. Il a montré une grande augmentation de temps d’ignition de 119 s à 410 s dans MLC test quand il est incorporé 10 wt% dans du PBS. Une UL-94 instrumentation original a été désigné pour l’investigation de ses mode d’action pendant un scénario de feu. Ces études ont fourni des informations pour les futurs travaux sur le retard de flamme des polymères bio-sourcés. / This study was dedicated to the development of flame retarded polybutylene succinate (PBS), a bio-based polymer, which possess good mechanical properties and biodegradability, by various different approaches. In this context, modifications of isosorbide were achieved to obtain bio-based flame retardants. Then isosorbide and poly(isosorbide) carbonate (PIC) were blended with PBS and APP to form intumescent flame retardant system acting as carbonization agent. It shows the improvement of the flame retardant properties in the condensed phase where the yield of residual char was increased and the pHRR and THR were decreased. A conventional flame retardant, DOPO, showed some super flame retardant property for PBS in the gaseous phase. It had an improvement of the ignition time from 119 s to 410 s in MLC test when 10 wt% of DOPO was incorporated in PBS. An original UL-94 instrumentation was designed to investigate its mode of action during a fire scenario. These studies have provided the information for the future works on flame retardancy of bio-based polymers.
2

Effect of infill density on mechanical and fire properties of polylactic acid composites produced by FDM 3D-printing technology

Aronsson Edström, David, Lundberg, Oskar January 2022 (has links)
3D-printing is a new and upcoming manufacturing technique that can significantly reduce time and material losses in production. Fused deposition modeling (FDM) is one of the most commonly used 3D-printing methods for processing conventional thermoplastic polymers. To reduce the printing time and usage of material via FDM technology, a user typically specifies infill density. Therefore, it is important to understand how this printing parameter affects the fire and mechanical properties of the 3D-printed object.  This study aims to investigate the effect of various infill densities on mechanical and fire properties of polylactic acid (PLA) composites produced by FDM 3D-printing technology. PLA composites of five different infill densities were 3D-printed: 20%, 40%, 60%, 80% and 100%. The samples for all tests were designed in AutoCAD and then imported into the slicing software, Ultimaker Cura. The 3D-printer used for printing was the Ultimaker S3 which uses FDM technology. To test the fire and mechanical behavior of 3D-printed PLA composites three tests were conducted: cone calorimeter test, tensile test and UL-94 flammability test. The cone calorimeter testing was done using the incident radiation of 35 kW/m2. The results showed that the trend of HHR curves of all infill densities are akin to each other, though the peak heat release rate and total heat released increases with higher infill density. Time to ignition was also longer for samples with higher infill density. Tensile testing was conducted according to the ASTM D638 standard. The results showed that with increasing infill density mechanical properties improved, with 100% infill density having the highest tensile strength (58.15 MPa) and elastic modulus (1472.1 MPa). From the UL-94 test results no difference in flammability could be observed. Every sample had no rating, which implies that PLA specimens of all infill densities are very flammable, with long afterflame and heavy flammable dripping. The study concludes that among the examined infill densities, no ideal percentage of infill density could be found. Requirements based on application will determine what infill density is most appropriate. Nevertheless, the data collected can hopefully provide a useful reference in designing and manufacturing 3D-printed PLA composites.
3

Novel phosphorus containing poly(arylene ethers) as flame retardant additives and as reactant in organic synthesis

Satpathi, Hirak 13 August 2015 (has links) (PDF)
Due to their outstanding properties, poly(arylene ethers) are useful as toughness modifiers in epoxy resins (EP). Furthermore, these polymers show rather low intrinsic fire risks. According to recent research it has been incorporated that poly(arylene ether phosphine oxides) [PAEPO’s] can further improve the fire behavior. Increasing phosphorous content of the PAEPO can influence the fire behavior too. Fire retardants containing phosphorus – regardless of whether an additive or reactive approach is used – show different mechanisms in the condensed and gas phase. In the present study PSU Control (BPA based polysulfone) with four different PAEPO’s and their corresponding blends with an EP were investigated. All poly(arylene ether phosphine oxides) were synthesized by nucleophilic aromatic polycondensation. The polymers obtained covered a wide range of weight average molar masses (6,000 – 150,000 g/mol) as determined by size exclusion chromatography with multi-angle light scattering detection (MALLS). FTIR, NMR spectroscopy and MALDI-TOF revealed formation of the desired polymer structure of the linear poly(arylene ethers). All polymers were easily soluble in common organic solvents, thus enabling processing from solution.The pyrolysis and the fire retardancy mechanisms of the polymers and blends with epoxy resin (EP) were tackled by means of a comprehensive thermal analysis (thermogravimetry (TG), TG-evolved gas analysis) and fire tests [PCFC, limiting oxygen index (LOI), UL-94, cone calorimeter]. The Mitsunobu reaction of Dimethyl-5-hydroxyisophthalate and a long chain semifluorinated alcohol requires triphenyl phosphine as a reactant. Identical, in some case higher yield was obtained in the usual conditions, with triphenyl phosphine and with trivalent phosphorus containing polymers, which was prepared in solvent free bulk (melt) polymerization technique from trivalent phosphorus monomer and a silylated diphenol in presence of CsF. Purification and the recovery of the final product which is always a big challenge in case of Mitsunobu reaction, was far more easier using polymer compared to triphenyl phosphine. During polymerization there was a possibility to have polymer having repeating unit containing both trivalent phosphorus and phosphine oxide. The trivalent phosphorus content of the polymer can be varied using different molar concentration of CsF.
4

Novel phosphorus containing poly(arylene ethers) as flame retardant additives and as reactant in organic synthesis

Satpathi, Hirak 08 June 2015 (has links)
Due to their outstanding properties, poly(arylene ethers) are useful as toughness modifiers in epoxy resins (EP). Furthermore, these polymers show rather low intrinsic fire risks. According to recent research it has been incorporated that poly(arylene ether phosphine oxides) [PAEPO’s] can further improve the fire behavior. Increasing phosphorous content of the PAEPO can influence the fire behavior too. Fire retardants containing phosphorus – regardless of whether an additive or reactive approach is used – show different mechanisms in the condensed and gas phase. In the present study PSU Control (BPA based polysulfone) with four different PAEPO’s and their corresponding blends with an EP were investigated. All poly(arylene ether phosphine oxides) were synthesized by nucleophilic aromatic polycondensation. The polymers obtained covered a wide range of weight average molar masses (6,000 – 150,000 g/mol) as determined by size exclusion chromatography with multi-angle light scattering detection (MALLS). FTIR, NMR spectroscopy and MALDI-TOF revealed formation of the desired polymer structure of the linear poly(arylene ethers). All polymers were easily soluble in common organic solvents, thus enabling processing from solution.The pyrolysis and the fire retardancy mechanisms of the polymers and blends with epoxy resin (EP) were tackled by means of a comprehensive thermal analysis (thermogravimetry (TG), TG-evolved gas analysis) and fire tests [PCFC, limiting oxygen index (LOI), UL-94, cone calorimeter]. The Mitsunobu reaction of Dimethyl-5-hydroxyisophthalate and a long chain semifluorinated alcohol requires triphenyl phosphine as a reactant. Identical, in some case higher yield was obtained in the usual conditions, with triphenyl phosphine and with trivalent phosphorus containing polymers, which was prepared in solvent free bulk (melt) polymerization technique from trivalent phosphorus monomer and a silylated diphenol in presence of CsF. Purification and the recovery of the final product which is always a big challenge in case of Mitsunobu reaction, was far more easier using polymer compared to triphenyl phosphine. During polymerization there was a possibility to have polymer having repeating unit containing both trivalent phosphorus and phosphine oxide. The trivalent phosphorus content of the polymer can be varied using different molar concentration of CsF.

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