Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (23)
- Vortrag (6)
- Beitrag zu einem Sammelband (3)
- Beitrag zu einem Tagungsband (2)
- Posterpräsentation (1)
Schlagworte
- Epoxy resin (35) (entfernen)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (6)
Renewable alternatives for common thermoset resins are demanded to go for sustainability. The objective is to create a flame retarded epoxy resin from a commercial bio epoxy resin with halogen free inorganic and organic flame retardants, respectively. Alumina trihydrate, aluminum diethyl phosphinate, a DOPO-based phosphonamidate and ammonium polyphosphate seem to have promising performances. Properties are enhanced with different bio fillers: pyrolyzed cocoa shells and plant waste (provided by Otto A. Müller Recycling GmbH, thanks!), short fibers and nonwovens of the natural fiber kenaf, hydroxypropyl-ß-cyclodextrin and sulfobutylether-ß-cyclodextrin.
Fire performance is investigated by cone calorimeter examinations, LOI and UL-94 ratings. Thermal analysis is given by TG-FTIR and DSC measurements.
Combinations of flame retardants and bio-fillers lead to reduced PHRR and THR, reach V0 in UL-94 and have a significant increase in LOI of up to 37 vol.-%. 10 % ammonium polyphosphate with 10 % pyrolyzed cocoa shell performs best, builds a magnificent protective layer, and shows good intumescence.
Material solutions that meet both circular bioeconomy policies and high technical requirements have become a matter of particular interest. In this work, a prospectively abundant proteinrich waste resource for the manufacturing of flame-retardant epoxy biocomposites, as well as for the synthesis of biobased flame retardants or adjuvants, is introduced. Different biomass fillers sourced from the cultivation of the mealworm beetle Tenebrio molitor are embedded in a bioepoxy resin cured with tannic acid and investigated regarding the fire performance of the thermosets. By means of spectroscopic and thermal analysis (attenuated total reflectance FTIR spectroscopy, thermogravimetric analysis-coupled FTIR spectroscopy, and differential scanning calorimetry), the influence of the biomass microparticles on the curing and thermal degradation behavior is evaluated. The final performance of the biocomposites is assessed based on fire testing methodology (limited oxygen index, UL-94, and cone calorimetry). Providing a high charring efficiency in the specific tannic acid-based epoxy matrix, the protein-rich adult beetle is further investigated in combination with commercial environmentally benign flame retardants in view of its potential as an adjuvant. The results highlight a char forming effect of nonvegan fillers in the presence of tannic acid, particularly during thermal decomposition, and point toward the potential of protein-based flame retardants from industrial insect rearing for future formulations.
Valorizing “non-vegan” bio-fillers: Synergists for phosphorus flame retardants in epoxy resins
(2022)
Sustainable, biogenic flame retardant adjuvants for epoxy resins are receiving increased focus. Zoological products like insects, bone meal, and eggshells are available in large quantities, but remain uninvestigated as functional fillers to epoxy resins, although they are potential synergists to flame retardants. The efficacy and flame retardancy of “non-vegan” additives in combination with flame retardants is investigated and the fire behavior and thermal decomposition of bio-sourced epoxy resin composites is characterized. By comparing the fire performance of composites containing flame retardants or fillers at varying loadings (5, 10, and 20%), their role as synergists that enhance the function of organophosphorus flame retardants in bio-epoxy composites is identified and quantified. Peak heat release rates were 44% lower in composites containing both filler and flame retardant versus those containing only flame retardants, and fire loads were reduced by 44% versus the pure resin, highlighting the ability of “non-vegan” fillers to function as synergists.
Textile-reinforced concrete is currently most frequently used for non-load–bearing structures, but there is a vision for also using it in load–bearing construction elements. In recent years, this construction material has been subjected to detailed examination. Different combinations of materials for potential use in textile-reinforced concrete have been described. These differ in the type of concrete mix and the composition of the textile reinforcement. The aim of this work is to test the application of a specific textile-reinforced concrete, consisting of high-performance concrete, textile reinforcement from carbon fibers and its epoxy resin matrix, at an elevated temperature. The combination of these materials makes it possible to produce subtle load–bearing structures with excellent mechanical properties. The critical issue is the behavior of these structures when exposed to fire. A series of medium-scale fire condition experiments were carried out with a temperature load based on the ISO 834 curve, followed up by mechanical tests. The aim of these experiments was to describe critical areas of textile-reinforced concrete in fire and to propose possible solutions. In an indicative fire experiment, experimental samples displayed massive spall of concrete layers, and interaction between materials was lost due to the low temperature resistance of the epoxy resin. Concurrently, the optimal quantity of polypropylene fibers was experimentally determined. This paper presents an experimental demonstration of the problematic aspects of textile-reinforced concrete and subsequent recommendations for future work with practical application in the design of load–bearing structures.
Hyperbranched polyphosphoesters are promising multifunctional flame retardants for epoxy resins. These polymers were prepared via thiol-ene polyaddition reactions. While key chemical transformations and modes of actions were elucidated, the role of sulfur in the chemical composition remains an open question. In this study, the FR-performance of a series of phosphorus-based flame retardant additives with and without sulfur (thioethers or sulfones) in their structure are compared. The successful synthesis of thio-ether or sulfone-containing variants is described and verified by 1H and 31P NMR, also FTIR and MALDI-TOF. A decomposition process is proposed from pyrolytic evolved gas analysis (TG-FTIR, Py-GC/MS), and flame retardancy effect on epoxy resins is investigated under pyrolytic conditions and via fire testing in the cone calorimeter. The presence of sulfur increased thermal stability of the flame retardants and introduced added condensed phase action. Likely, Sulfur radical generation plays a key role in the flame-retardant mode of action, and sulfones released incombustible SO2. The results highlight the multifunctionality of the hyperbranched polymer, which displays better fire performance than its low molar mass thio-ether analogue due to the presence of vinyl groups and higher stability than its monomer due to the presence of thio-ether groups.
Most synthetic polymers have a high fire load, and as a result, they require flame retardants (FRs) to ensure their safe use. Phosphorus plays an important role in flame retardancy and has the potential to replace halogenated variants, which are assumed to be harmful to the environment and health. Among phosphorus-based FRs, there exists a trend towards polymeric, high molar mass molecules with complex molecular architectures. In this project, we synthesized a novel series of so-called phosphorus-based hyperbranched polymeric FRs and investigated their use as multifunctional additives to high-performance polymers, i.e. epoxy resins. By cleverly designing the chemical structure to contain varying amounts of P-O and P-N bonds, new insight into the chemical mechanism of flame retardancy was gained, and by comparing the hyperbranched polymers to their monomeric counterparts, a greater understanding of the role of complex architecture was won. This talk aims at presenting some of these results and proposes chemical mechanisms that illustrate what role these novel hyperbranched flame retardants play in molecular firefighting.
We synthesized a library of phosphorus-based flame retardants (phosphates and phosphoramides of low and high molar mass) and investigated their behavior in two epoxy resins (one aliphatic and one aromatic).
The pyrolytic and burning behavior of the two resins (via TGA, TG-FTIR, Hot stage FTIR, Py-GC/MS, PCFC, DSC, LOI, UL-94, Cone calorimeter) are analyzed and compared to the results of flame retardant (FR)-containing composites. A decomposition pathway incorporating the identified modes of action and known chemical mechanisms is proposed. The overlap of decomposition temperature (Tdec) ranges of matrix and FR determines the efficacy of the system. Low molar mass FRs strongly impact material properties like Tg but are very reactive, and high molar mass variants are more thermally stable. Varying PeO and PeN content of the FR affects decomposition, but the chemical structure of the matrix also guides FR behavior. Thus, phosphates afford lower fire load and heat release in aliphatic epoxy resins, and phosphoramides can act as additives in an aromatic matrix or a reactive FRs in aliphatic ones. The chemical structure and the structure-property relationship of both FR and matrix are central to FR performance and must be viewed not as two separate but as one codependent system.
The hydrogen tightness of high-pressure hydrogen storage is a Basic criterion for long-term storage. The H2 permeation coefficients of epoxy resin and a glass lacquer were determined to enable the geometric optimization of a glass capillary storage. It was found that the curing conditions have no significant influence on the H2 permeation coefficient of resin.
The H2 permeation coefficient of epoxy resin is only about three orders of Magnitude greater than that of borosilicate glass. This suggests that the initial pressure of 700 bar takes about 2.5 years to be halved in capillary array storage. Therefore, a high-pressure hydrogen storage tank based on glass capillaries is ideally suited for long-term storage in mobile applications.
A siloxane compound (MVC) and a bi-group phosphaphenanthrene/triazine compound (TGD) were employed in epoxy thermosets to explore high-efficiency flame retardant systems. With only 1wt% MVC and 3wt% TGD, an epoxy thermoset passed UL 94 V-0 rating test and achieved a limiting oxygen index value of 34.0%, exhibiting an excellent flame retardant effect. The MVC/TGD system not only decreased the peak value of heat release rate and effective heat of combustion but also imparted an improved charring ability to thermosets, thereby outstandingly reducing the flammability of 1%MVC/3%TGD/EP. Compared with the fire performance of 4%TGD/EP and 4%MVC/EP, the MVC/TGD system showed an obvious flame retardant synergistic effect, mainly depending on the general improvement of flame inhibition, charring and barrier effects of the thermoset during combustion. Evolved gas analysis combinedwith condensed-phase pyrolysis product Analysis jointly revealed the details of the changed pyrolysis mode.
The fire behaviour of carbon fibre (CF) reinforced polymers differs in comparison to polymers. Fibres behave often inert with respect to pyrolysis, they change the melt flow and dripping behaviour, the heat absorption and transfer, the amount and properties of the fire residue and so on. Flame and fire retardancy concepts are needed not only suitable for the different fire protection goals typical for each application, but also tailored for composites. This field is illuminated by examples taken from different projects carried out in the group of the author in the recent years. The examples target on different applications through achieving reduction in reaction to fire controlling the fire risks (flammability, heat release) in the beginning and development of a fire and investigating the fire stability, when a severe flame is directly applied (key property in fully developed fires). Approaches to halogen-free flame retardancy in CF reinforced thermosets are presented as well as building up a bench and an intermediate scale testing of composites in fire applying mechanical load (up to 1 MN compression) and direct flame exposure (180 kW/m2) simultaneously. Indeed, e.g. we have investigated the fire stability of stringer reinforced shell components taken out from the fuselage of an aircraft.
The understanding of fire behaviour, fire resistance, and fire retardant modes of action in composites is a promising basis for target-oriented development. The role of flame inhibition, charring, and protective layer formation is discussed. Successful concepts are presented for fire retardancy tailored for different application as well as general guidelines for future development. Different phosphorus flame retardants are proposed to achieve halogen-free flame retardancy with respect to ignition and developing fires. Different protective approaches are sketched for addressing the fire stability of composites that is the most important fire risk for the fire resistance in structural applications.