Präsentation
Filtern
Dokumenttyp
- Vortrag (13)
- Posterpräsentation (5)
Referierte Publikation
- nein (18)
Schlagworte
- Flame retardancy (18) (entfernen)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (13)
Whereas the degradation of flame retardant polymers has been discussed since decades, only more recently, the lifetime of the flame retardancy itself becomes an important factor, e.g. for cables used as building products. In this work, several kinds of accelerated artificial ageing tests are performed simulating different environmental exposures and thus highlighting different degradation mechanisms: artificial accelerated weathering, climatic chamber, water immersion, salt spray chamber, and autoclave test. The durability is expected to be different for different flame-retardant materials. Thus, various sets of halogen-free fire-retarded polymers were investigated: ethylene vinyl acetate (EVA) with aluminum hydroxide (ATH), boehmite and synergists, ester-based and ether-based thermoplastic polyurethane (TPU) with melamine cyanurate (MC), aluminum diethylphosphinate (AlPi), and boehmite, and glass fiber reinforced polyamide 66 (PA66) with AlPi-based mixtures.
Intensive degradation of the surface was observed, e.g. yielding discoloration and yellowing, EVA showed cracking when weathered. Changes in chemical structure was investigated by ATR-FTIR. The flammability was investigated with the cone calorimeter, UL-94 classification, and oxygen index (LOI). The flame retardancy of most of the materials studied degraded only slightly for the investigated exposure times. EVA/ATH achieved an improved LOI due to flame retardants agglomeration at the surface. Sets of materials, based on EVA and TPU, were also investigated as cable jackets. While flame retarded EVA exhibited no dripping during burning, TPU flame-retarded with MC cables showed pronounced melt-dripping. Cone calorimeter tests were carried out using cable rafts as well as our self-made cable module test, simulating a vertical bundle of cables at the bench scale. The comparison of different fire tests, different exposure conditions, and different materials carved out the specific degradation phenomena with respect to each of these parameters.
Most of this work was supported by the IGF Project (18926 N) of the Fördergemeinschaft für das Süddeutsche Kunststoff-Zentrum e.V., supported by the AiF within the framework of the program “Förderung der Industriellen Gemeinschaftsforschung (IGF)” of the German Federal Ministry for Economic Affairs and Energy based on a decision of the Deutschen Bundestag.
The potential of nanocomposites, i.e. mixtures of nanoobjects with acceptable distribution in a polymer matrix, with respect to flame retardancy was discovered in an already early stage of nanocomposite reseach. Since then, a variety of nanocomposites often in combination with conventional flame retardants (FRs) and their effect on the burning behavior has been described.
Here, we show the application of this concept to enhance the flame retardancy of poly(butylene terephthalate) (PBT) and poly(butylene succinate) (PBS) using suitable phosphorus-containing polyesters as FR. The materials studied were prepared by melt compounding in a twin screw extruder using either a mixture of polymer matrix, phosphorus polymer and nanomaterial (direct compounding) or a mixture of a pre-formed batch of phosphorus polymer with nanomaterial and the polymer matrix (batch compounding). The second method has been shown to be very effective if batches prepared by in-situ nanocomposite synthesis via melt transesterification polycondensation were employed. Modified organoclay (montmorillonite, OMMT) as well as multiwalled carbon nanotubes were used as nanoobjects.
Organic modification of MMT resulted in better exfoliation and distribution within the poylmer matrix than observed with pure sodium MMT. However, modification with phosphorus-containing modifiers dis not support exfoliation due to high interaction between modifier and clay.
Analysis of the in-situ prepared nanocomposites of OMMT (Cloisite 30B) with the phosphorus polyester PET-P-DOPO by thermogravimetry, FTIR and pyrolysis-GC/MS showed that OMMT did not alter the principal decomposition pathway of the polyester, but shifted the onset of decomposition to lower temperature (due to the fast decomposition of the tertiary ammonium compound) and increased the amount of char. The fire behavir as observed by microscale combustion calorimetry (MCC) was altered and resulted in significant decrease of heat release capacity.
In-situ prepared batches of the phosphorus polyester PET-P-DOPO with 20 wt.-% OMMT and with MWCNT (1 wt.-%) were blended with PBT in the ratio 25/75 wt/wt to achieve a phosphorus concentration of 1.5 wt.-%. The nanocomposites were injection molded into plates for cone calorimeter measurements and examined using 50 kW/m2. In all samples, a reduction of toral heat evolved and total heat evolved/total mass loss (THE/TML) was observed. Addition of OMMT improved the char, which was even more pronounced in combination with PET-P-DOPO as illustrated in Figure 1. Blends containing PET-P-DOPO additionally showed intumescence. In all cases, a significant reduction of FIGRAmax was obtained. The addition of nanomaterials (both OMMT and MWCNT) to PBT/PET-P-DOPO reduced the effective heat of combustion (THE/TML) from 1.7 to 1.5 MJ/m2.
Solid-state NMR Identifying the Chemistry in Multicomponent Flame-retarded Polyolefin Systems
(2017)
Understanding of the interaction in multicomponent flame-retarded polymeric system is crucial to obtain the best performance at the possible lowest load of additives. In this work, polyolefine based systems are investigated by solid state NMR and cone calorimetry. As a polymer matrix thermoplastic elastomer based on styrene (TPE-S) was chosen. Different combination of additives was investigated in order to identify the chemistry occurring during the pyrolysis. As additives aluminium diethylphosphinate (AlPi), ammonium polyphosphate, zinc borate (ZB), poly(phenylene oxide) (PPO), magnesium hydroxide (MH) and dimethyl- methylvinyl siloxane (Si) were used. Fire residues remained after the cone calorimeter test were analyzed by solid state NMR (31P, 27Al, 13C, 11B, 29Si). The formation of different phosphates and aluminates was identified, indicating the chemical interaction between the additives. Detailed investigation delivered meaningful insights into the chemistry controlling flame retardancy.
Leather is a widely used material for thousands of years and in modern days it is produced on industrial scale. This production produces high amounts of organic waste during the tannery process. These fibers can become a resource and act as a multi-functional bio-filler in flame retardant composites.
This project investigates two leather fibers towards their ability to enhance the flame-retardancy in different composites. These composites use ammonium polyphosphate (APP) or aluminum trihydroxide (ATH) as flame retardants. Different silicon based synergists support polymers with ATH to reduce the load of flame retardant. The different modes of action (charring, gas phase activity, barrier effect) can be quantified of each composite.
The new composites form a stable char layer resulting in an increase in residue, lower peak heat release rates (pHRR) and higher limiting oxygen index (LOI). In addition, the ratings in the UL94-classification increased up to V-0.
Leather is a widely used material for thousands of years and in modern days it is produced on industrial scale. This production produces high amounts of organic waste during the tannery process. These fibers can become a resource and act as a multi-functional bio-filler in flame retardant composites.
This project investigates two leather fibers towards their ability to enhance the flame-retardancy in different composites. These composites use ammonium polyphosphate (APP) or aluminum trihydroxide (ATH) as flame retardants. Different synergists support polymers with ATH.
The new composites form a stable char layer resulting in an increase in residue, lower peak heat release rates (pHRR) and higher limiting oxygen index (LOI). In addition, the ratings in the UL94-classification increased up to V-0.
Revolutionizing our polymer industry for adaption to a sustainable carbon circular economy has become one of today’s most demanding challenges. Exploiting renewable resources to replace fossil-fuel—based plastics with biopolymers such as poly(lactic acid) (PLA) is inevitable while using waste streams as a raw material resource at least is promising. When it comes to using PLA as technical polymer, its high flammability must be addressed by flame retardants compatible with the thermoplastic processing of PLA and its compostability. This study proposes microalgae enriched with phosphorus from wastewater (P-Algae) as an elegant way towards a kind of sustainable organophosphorus flame retardant. The concept is demonstrated by investigating the processing, pyrolysis, flammability, and fire behavior of PLA/P-Algae, while varying the P-Algae content and comparing P-Algae with four alternative bio-fillers (phosphorylated lignin, biochar, thermally treated sewage sludge, and metal phytate) with different P-contents as meaningful benchmarks.
Products and by-products of the invertebrate and vertebrate farming, respectively, are shown to be promising bio-based flame retardant adjuvants in epoxy thermosets. While the addition of bone meal results in the formation of an inorganic shield, protein-based powders from insects provide an intumescent behavior under forced flaming conditions. Combining the latter with a common flame retardant such as ethylene diamine phosphate, the charring efficiency and self-extinguishing properties can be further enhanced.
The transfer of flame-retardant epoxy resin formulations to composites for structural and lightweight applications in the energy and transport sector can be complex and requires systematic investigation. Here, uncoated and silane-coated ammonium polyphosphate (APP, Si-APP) intumescent compounds are transferred to prepregs using a Bisphenol A diglycidyl ether (DGEBA) resin matrix to 0/90o bidirectional glass fibers with an aerial weight of 600 g/m2. Inorganic silicates (InSi) are added to improve the fire residues of the composites after combustion and the total amount of flame retardants in the resin formulations was 10% by weight. The prepregs' fiber volume content (FVC) is corroborated using in-process measurements and thermogravimetric analysis. This was found to be approximately 60% for the composites containing APP, which is ideal for load-bearing applications with high mechanical strength. However, the Si-APP containing prepregs showed an inconsistent FVC potentially due to interactions with the commercial sizing of the glass fibers. The composites subsequently prepared are analysed for potential filtration effects of the additives via SEM after immobilization in a cured resin and platinum sputtering. The inter-laminar shear strength and the mechanical strength of the composites are compared via three-point bending tests. Additionally, the fire performance of the composites is analysed using cone calorimetry. It was found there was minimal impact of the loading of the flame retardants on the delamination of the composites and the flexural strength. However, the high density of the glass fibers possibly results in a suppression of the mode of action of the flame retardants in the composites. Therefore, the fire residues of the composites are further compared using SEM, and the flame-retardant modes of action upon transfer are investigated.
The demands for modern flame retardants are higher than ever: a flame retardant must function effectively in a certain polymer matrix and avoid critical alterations to the material’s properties. Ideally, a flame retardant additive should be easily miscible and show no sign of leaching or blooming from the matrix. Additionally, the flame retardant should be non-toxic, non-accumulating and biocompatible. Hyperbranched polymers are a promising group of multifunctional flame retardants which fulfill these demands: their complex shape enables high miscibility and avoids leaching or blooming, while their high molecular weight potentially increases biocompatibility and lowers accumulation and toxicity. Moreover, they exhibit a low impact on polymer properties and a good flame retardant performance.
This work examines the efficacy and mode of action of phosphorus-based hyperbranched polymeric flame retardants in bisphenol A-based epoxy matrices. To investigate the effect of the complex shape, the hyperbranched polymers are compared to their corresponding monomeric variants. Furthermore, the materials are synthesized to contain systematically varying oxygen-to-nitrogen ratios, allowing for new insight into what role the chemical surrounding of phosphorous plays in flame retardant efficacy.
Using a multi-methodical approach, including thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (FTIR), hot stage FTIR, micro combustion calorimetry, differential scanning calorimetry, oxygen index (LOI), UL-94 tests and cone calorimetry experiments, the decomposition mechanisms and the flame retardant modes of action of these flame retardants in epoxy resins are investigated, shedding new light on the chemistry of flame retardancy.