Filtern
Erscheinungsjahr
- 2021 (14) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (9)
- Vortrag (3)
- Monografie (1)
- Buchkapitel (1)
Schlagworte
- Flame retardant (5)
- Weathering (4)
- Durability (3)
- Aluminum hydroxide (ATH) (2)
- Cables (2)
- EVA (2)
- Ethylene-vinyl acetate (2)
- Fire resistance (2)
- Flame retardancy (2)
- Flammschutz (2)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (14) (entfernen)
Eingeladener Vortrag
- nein (3)
Die Forderung, dass der Flammschutz von Kunststoffen nicht nur zum bei der Herstellung der jeweiligen Produkte, sondern auch über die gesamte Einsatzdauer im geforderten Maß wirksam ist, stellt eine große Aufgabe dar. Ferner ist die Anforderung für viele Produkte in der Praxis neu, da bisher vor allem der Einfluss der Flammschutzmittel auf die Stabilität der Polymerwerkstoffe, nicht aber die Stabilität des Flammschutzes untersucht wurde. Das Langzeitverhalten halogenfreier Systeme ist bis heute wenig untersucht, insbesondere weil Phosphor- und Stickstoff-basierte Systeme die oxidative Beständigkeit von Polymeren weniger zu beeinflussen scheinen als halogenhaltige FSM. Die Frage, wie zuverlässig der Flammschutz wirkt, wenn Kunststoffe einige Jahre im Innen- und Außenbereich im Einsatz sind und dabei wechselnden Beanspruchungen ausgesetzt waren, wurde bislang nur vereinzelt untersucht. Mögliche Auswirkungen von Witterungseinflüssen auf flammgeschützte Polymerwerkstoffe sind, dass die Flammschutzmittel selbst abbauen, ausgewaschen werden, oder auch durch Wechselwirkung mit den eingesetzten Additiven oder mit den Alterungsprodukten der Polymermatrix in ihrer Wirkung nachlassen. Hier bestand großer Forschungsbedarf, um an den Punkt zu gelangen, die Beständigkeit der Flammschutzeigenschaften eines Produktes über seine gesamte Lebensdauer zuverlässig garantieren zu können. Diese Fragestellung greift das durchgeführte Forschungsvorhaben auf.
Ziel war die Untersuchung der Langzeitstabilität der Flammschutzwirkung von halogenfrei flammgeschützten Polymerwerkstoffen unter diversen Witterungseinflüssen. Dazu wurden die Schädigungsmechanismen der Polymerwerkstoffe und der Flammschutzmittel sowie die auftretenden Wechselwirkungen analysiert, um ein Verständnis für die ablaufenden Prozesse zu entwickeln und Empfehlung für die Reduzierung der Alterung zu erarbeiten. Gegenstand der Untersuchungen waren anwendungsrelevante Flammschutz-Konzepte, die miteinander verglichen wurden. Die Erarbeitung von Struktur-Eigenschafts-Beziehungen ermöglichte die Beschreibung der Empfindlichkeiten und den Vergleich zwischen den Systemen. Darauf basierend wurden für die FSM spezifische Leitlinien für die Optimierung der Langzeitstabilität des Flammschutzes erstellt.
A phosphorous soybean-oil–based polyol was derived via epoxidation and ring opening reaction as an alternative to petrochemical-based polyol for the synthesis of flexible polyurethane foams (FPUFs). 5-wt.% and 10-wt.% of expandable graphite (EG) were added to further improve flame retardancy. The mechanical properties (tensile strength and compression stress) of the foams were investigated. Thermogravimetric analysis (TGA) coupled with Fourier-transform infrared (FTIR) were conducted to evaluate the pyrolysis; limiting oxygen index (LOI), UL 94 and cone calorimeter were performed to analyze the fire performance of the foams; smoke density chamber was used to investigate the smoke released during burning. When 10-wt.% of EG was used, the flame retardancy of the foams was much enhanced due to the synergistic effect between phosphorus and EG. The char yield was three times higher (54wt.%). The fire load MARHE approached 100 kWm−2, half of the value expected for a superposition. The combination of phosphorous polyols and EG is proposed as strategy for future flame retarded FPUFs.
Three novel liquid ethyl (diethoxymethyl)phosphinate derivatives (EDPs) were synthesized and incorporated into flexible polyurethane foams (FPUFs). The flame retardancy of FPUFs were evaluated by limiting oxygen index (LOI), vertical burning and cone calorimetry tests, and the results indicated the structure-flame retardancy relationship of EDPs. Among these EDPs, P-(diethoxymethyl)-N-phenylphosphonamidate (EDPPA) exhibited the best flame retardant effect, methyl 3-((diethoxymethyl)(ethoxy)phosphoryl)propanoate (EDPMA) the second, and ethyl phenyl (di-ethoxymethyl)phosphonate (EDPPO) the worst. When the incorporation of EDPPA was 10 wt%, the FPUFs could self-extinguish and pass the vertical burning test. Meanwhile, the LOI value of FPUF-PA increased to 23.6% with 20 wt% loading of flame retardant. According to the investigation of volatiles during the thermal degradation of FPUFs and the morphologies of char residues after cone test, we inferred the pos- sible flame retardant mechanism. The results indicated that EDPs could release phosphorus-containing compounds in the gas phase, which would generate phosphorus-containing radicals and play the role of radical scavenger. In the condensed phase, EDPs can promote the formation of dense, intact and thermal stably char layer on the surface of FPUFs. Moreover, we found that the structure influence on flame retardancy was attributed to the atoms linked to the central phosphorus. Our results indicate that these EDPs are promising flame retardants in FPUFs that can be applied to improve the flame retardancy of FPUFs in various practical applications.
Biomass pre-treatments for bio-oil quality improvement are mainly based on thermal and chemical methods which are costly and hence reduce the sustainability of pyrolysis-based refineries. In this paper, anaerobic digestion (AD) and dark fermentation (DF) are proposed as alternative ‘green’ pre-treatments to improve this situation. For this purpose, three seaweeds namely Sargassum polycystum, (Phaephyta), Gracilaria tenuistipitata, (Rhodophyta) and Ulva reticulata, (Chlorophyta) with high ash and oxygen contents were pre-treated to improve their composition and structure prior to pyrolysis. The results reveal that both biological pre-treatments affected, positively, the composition and structure of the seaweed biomass with AD pre-treatment reducing N and S contents by 86% and 63%, respectively. DF was more efficient in terms of ash and moisture reduction with 25% and 70%, respectively. In addition, oxygen (O) reduction by 27% was observed after DF which was evidenced by FTIR spectroscopy indicating the reduction of most oxygen-containing functional groups in the biomass. On the other hand, the carbon (C) content increased in DF pre-treated seaweeds up to 42%, almost two times higher relative content than C in the raw seaweed. The changes in the composition of pre-treated seaweeds resulted in changes in their thermal degradation and the volatile profiles produced during pyrolysis. Interestingly, anhydrosugars and furans which account for some 70% (by area) in raw seaweeds markedly declined or become undetectable after DF pre-treatment and correspondingly more acetic acid and hydrocarbons were produced while after AD more aromatics with high toluene content (ca.17%) were generated. The results indicate that biooil with profiles more similar to petroleum-based composition i.e. rich in hydrocarbons and low in anhydrosugars, N and S can be generated by AD and DF pre-treatments and opens up the possibility of these approaches to effect cost reduction in the overall generation of bio-based fuels.
Fire resistance testing of components made of carbon fibre reinforced polymers (CFRP) usually demands intermediate-scale or full-scale testing. A bench-scale test is presented as a practicable and efficient method to assess how different fire protective systems improve the structural integrity of CFRPs during fire. The direct flame of a fully developed fire was applied to one side of the CFRP specimen, which was simultaneously loaded with compressive force. Three different approaches (film, non-woven, and coatings) were applied: paper with a thickness in the range of μm consisting of cellulose nanofibre (CNF)/clay nanocomposite, nonwoven mats with thickness in the range of cm and intumescent coatings with a thickness in the range of mm. The uncoated specimen failed after just 17 s. Protection by these systems provides fire stability, as they multiply the time to failure by as much as up to 43 times. The reduced heating rates of the protected specimens demonstrate the reduced heat penetration, indicating the coatings’ excellent heat shielding properties. Bench-scale fire stability testing is shown to be suitable tool to identify, compare and assess different approaches to fire protection.
Efficient flame retardancy is often achieved only when applying multicomponent systems. Flame retardants are combined or used together with adjuvants or synergists; fibres and fillers contribute to fire properties crucially. Multicomponent systems are discussed in their capacity as general and powerful strategy for achieving and optimizing flame retardant polymeric materials.
Überblick über die Herausforderungen, Anforderungen und Lösungswege für den Flammschutz von Polyurethanwerkstoffen (thermoplastisches und elastomeres Polyurethan (TPU, PUR), PUR Hard- und Weichschäume, PIR, PUR Coatings). Die Werkstoffcharakteristika wie Pyrolyse, effektive Verbrennungswärme, Rückstandsausbeute, Verarbeitungsparameter und kg-Preis definieren die Anforderungen an Flammschutzlösungen. Der Flammschutz ist spezifisch für das Material ausgelegt, aber auch für die verschiedenen Anwendungen (Automobilbau, Schienenfahrzeuge, Bauwesen, Elektrotechnik, usw.), d.h. um spezielle Brandtests zu bestehen. Die Pyrolyse und das Brandverhalten von PUR und PUR-Schäumen sowie der flammgeschützten Varianten wird diskutiert. Die gängigen Flammschutzmittel(-kombinationen) werden zusammengefasst und mit Beispielen belegt.
A rigid aromatic phosphorus-containing hyperbranched flame retardant structure is synthesized from 10-(2,5 dihydroxyphenyl)-10H-9-oxa-
10-phosphaphenanthrene-10-oxide (DOPO-HQ), tris(4-hydroxyphenyl)phosphine oxide (THPPO), and 1,4-terephthaloyl chloride (TPC). The resulting poly-(DOPO-HQ/THPPO-terephthalate) (PDTT) is implemented as a flame retardant into an epoxy resin (EP) at a 10 wt% loading. The effects on EP are compared with those of the monomer DOPO-HQ and triphenylphosphine oxide (OPPh3) as low molar mass flame retardants. The glass transition temperature, thermal decomposition, flammability (reaction to small flame), and burning behavior of the thermosets are investigated using differential scanning calorimetry, thermogravimetric analysis, pyrolysis combustion flow calorimetry, UL 94-burning chamber testing, and cone calorimeter measurements.
Although P-contents are low at only 0.6 wt%, the study aims not at attaining V-0, but at presenting a proof of principle: Epoxy resinswith PDTT show promising fire performance, exhibiting a 25% reduction in total heat evolved (THE), a 30% reduction in peak heat release rate (PHRR) due to flame inhibition (21% reduction in effective heat of combustion (EHC)), and an increase in Tg at the same time. This study indicates that rigid aromatic hyperbranched polymeric structures offer a promising route toward multifunctional flame retardancy.
The Burning of Plastics
(2021)
The burning of a polymer is a physico–chemical process strongly influenced by the coupling of a chemical reaction – oxidation of fuel – in the gas phase with a chemical decomposition reaction – pyrolysis – in the condensed phase via heat and mass transfer. The heat and mass flux control the intensity of fire and the ablation of fuel. Indeed, the temperature profile as a function of time may be one of the most important responses of a specimen to understand its burning behavior. Further, several physical phenomena, such as the heat absorption of the materials, thermal conductivity, and also melt flow and dripping, play a major role in determining ignition, flammability, and fire behavior. The burning of a polymer is very complex. The various phenomena interact with each other, e. g., pyrolysis also influences the viscosity of the melt, and, thus, whether dripping or charring results in a protective layer, increasing the shielding effect of the residual protective layer. Only a detailed and comprehensive description opens the door to a well-founded understanding of the burning behavior of polymeric materials.