Showing papers on "Cone calorimeter published in 2018"

Highly thermally conductive flame retardant epoxy nanocomposites with multifunctional ionic liquid flame retardant-functionalized boron nitride nanosheets

Abstract: The low heat dissipation efficiency and serious security issues related to polymer-based thermal management materials (TMMs) have seriously limited their practical applications. However, simultaneously improving their thermal conductivity (TC) and flame retardancy is still a challenge due to performance limitations and complicated processing. Here, non-covalent ionic liquid flame retardant-functionalized boron nitride nanosheets (ILFR-fBNNSs) were used as a multifunctional nano-additive for fabricating epoxy (EP)-based nanocomposites with both superior TC and flame retardancy. Owing to its structural uniqueness and multifunctionality, the ILFR-fBNNS triggers resin crosslinking at a given temperature, while conferring significant improvements in dispersion and interfacial adhesion, thereby forming a thermally conductive network with reduced interfacial phonon scattering and a high-efficiency nano-barrier network acting synergistically with ILFR-induced char residues during thermal degradation. Therefore, the ILFR-fBNNS not only functions as a curing agent for fabricating the nanocomposites, but also acts as a thermal conductor and flame retardant for the nanocomposites. The optimal comprehensive performances of EP/ILFR-fBNNS nanocomposite are achieved with a 12.1 vol% ILFR-fBNNS content with TC enhancement of 478%, and reductions of up to 68.9% and 42.3% by microscale combustion calorimetry (42.4% and 37.7% by cone calorimeter) in peak heat release rate (PHRR) and total heat release (THR) respectively compared to neat EP.

Constructing phosphorus, nitrogen, silicon-co-contained boron nitride nanosheets to reinforce flame retardant properties of unsaturated polyester resin

Abstract: In this work, we reported the synthesis of boron nitride nanosheets containing phosphorus, nitrogen and silicon-co-existing elements as high-performance nanofillers in unsaturated polyester resin (UPR) for the first time and precisely performed structural characterization to confirm the covalent functionalization. After incorporating 3 wt% into UPR matrix, combustion behavior of UPR nanocomposites was investigated by cone calorimeter, demonstrating the obvious reduction of 28.2% and 38.0% in PHRR and THR, respectively. TG-IR-MS coupling technique was employed to reveal thermal degradation and toxic volatiles such as CO, phenyl derivatives, hydrocarbons. On the basis of gaseous and condensed phase, we reasonably proposed the flame retardant mechanism of boron nitride with phosphorus, nitrogen and silicon elements to increase flame retardant properties of UPR. It is expected to exploit covalent functionalization of boron nitride and its nanocomposites with high flame retardance.

Preparation and characterization of flame-retardant nanoencapsulated phase change materials with poly(methylmethacrylate) shells for thermal energy storage

Abstract: In this work, flame-retardant nanoencapsulated phase change materials (NanoPCMs) containing n-octadecane as the core material and poly(methylmethacrylate) (PMMA) as the shell material were successfully fabricated by introducing diethyl bis(2-hydroxyethyl acrylate)amino methylphosphonate (DEAMP) as the crosslinking agent via miniemulsion polymerization. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses confirmed that n-octadecane was successfully encapsulated into the PMMA shell and that the NanoPCMs exhibited a regular spherical profile. The phase change properties, thermal reliability, thermal stability, and flame-retardant properties of NanoPCMs were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), cone calorimeter tests, and limiting oxygen index (LOI) measurements. The DSC results showed that the NanoPCMs possessed a relatively high encapsulation efficiency in the range of 86.5–94.0% for n-octadecane. The thermal properties and durability of the NanoPCMs were almost unchanged after the introduction of DEAMP into the NanoPCMs. The combustion test results showed that the introduction of phosphorus-based flame retardant DEAMP into the NanoPCMs significantly suppressed the heat and smoke releases and, increased the residual weight and LOI value of the EP/NanoPCM composites. In addition, a computer-aided thermal measurement system was created to investigate the thermoregulation properties of the NanoPCMs and the results showed that the addition of NanoPCMs into a gypsum board significantly improved the thermoregulation properties. In conclusion, the flame-retardant NanoPCMs showed considerable potential for thermal energy storage applications, especially in thermoregulated textile and construction fields.

Effects of intumescent flame retardant system consisting of tris (2-hydroxyethyl) isocyanurate and ammonium polyphosphate on the flame retardant properties of high-density polyethylene composites

Abstract: An intumescent flame retardant (IFR) system composed of tris (2-hydroxyethyl) isocyanurate (THEIC) and ammonium polyphosphate (APP) was used to prepare high density polyethylene (HDPE) composites, and their thermal and flammability properties were studied. The limiting oxygen index of the HDPE composite containing 30 wt% of IFR with an APP: THEIC weight ratio of 3:1 (HD31) reaches 31.5%. The cone calorimeter analysis shows that the peak and average heat release rate of HD31 are reduced by 69.5% and 58.1% respectively; while the average mass loss rate is reduced by 77.2%. The thermogravimetric analysis suggests that the IFR/HDPE composites have good char forming ability. The structural analysis of the char residue shows that the intumescent char is composed of a polyaromatic structure containing nitrogen in five or six-membered ring linked to phospho-carbonaceous structure via the P O C linkage, and some phosphorous degradation products containing P O P structure.

Zeolitic imidazolate framework-8 was coated with silica and investigated as a flame retardant to improve the flame retardancy and smoke suppression of epoxy resin

Abstract: A material (ZIF-8@SiO2) with a nuclear shell structure was synthesized to improve the flame retardancy and smoke suppression of epoxy resin (EP) through a synergetic catalytic effect. Zeolitic imidazolate framework-8 (ZIF-8) was synthesized and its surface was coated with SiO2 by hydrolyzing tetraethyl orthosilicate. Core–shell structured ZIF-8@SiO2 was obtained. Then ZIF-8@SiO2 was added to EP to explore its effect of flame retardancy and smoke suppression on the EP composite. The results of a cone calorimeter test showed that the peak heat release rate, total heat release, smoke production rate and total smoke production of the material were decreased by 75.9%, 38.9%, 51.1% and 39.8%, respectively, after 2 wt% ZIF-8@SiO2 was added to EP. Besides, through the analysis of char residue, the mechanism of ZIF-8@SiO2/EP's flame retardancy and smoke suppression was determined to be due to the physical barrier effect of SiO2 and the co-effect of SiO2 and ZnO decomposition by ZIF-8.

An Attempt to Find a Suitable Biomass for Biochar-Based Polypropylene Biocomposites

Abstract: Four biomass wastes (rice husk, coffee husk, coarse wool, and landfill wood) were added with biochar and polypropylene (PP) to manufacture biocomposites. Individual biomasses were tested for their combustion behavior using cone calorimeter. Biocomposites were analyzed for their fire/thermal, mechanical, and morphological properties. Wood had the most desirable comprehensive effect on both the mechanical and fire properties of composites. In particular, wood and biochar composite exhibited the highest values of tensile/flexural properties with a relatively low peak heat release rate. In general, application of waste derived biochar and biomasses drastically reduced the susceptibility of neat PP towards fire.

Fire reaction properties of polystyrene-based nanocomposites using nanosilica and nanoclay as additives in cone calorimeter test

Abstract: Using nanofiller additives in the polymer matrix to form nanocomposites is a potential way of reducing the flame spread and enhancing flame retardancy of polymeric materials during fire. To understand the fire reaction properties and the relative performance of flame-retardant additives in polymer during well-developed fire, neat polystyrene, polystyrene–silica and polystyrene–nanoclay (MMT) have been tested in a cone calorimeter. The neat polystyrene and the polystyrene nanocomposites have been prepared via an in situ polymerization method. An external heat flux of 50 kW m−2 was applied in the test, and parameters such as heat release rate, peak heat release rate, time to ignition, smoke toxicity, CO and CO2 yield have been investigated. Both neat polystyrene and polystyrene nanocomposites have shown the trend of a thermally thick charring polymer in the heat release rate over time data. The nanocomposites had an overall better flame retardancy than the neat polystyrene in terms of lower peak heat release rate, lower average mass loss rate and enhanced char formation. The nanocomposites had also reduced smoke emission with lower CO and CO2 yield compared to the neat polystyrene. The overall flame retardancy was enhanced as the nanofiller loading was increased for both the nanosilica and MMT nanocomposites.

Fire Phenomena of Rigid Polyurethane Foams.

Abstract: Rigid polyurethane foams (RPUFs) typically exhibit low thermal inertia, resulting in short ignition times and rapid flame spread. In this study, the fire phenomena of RPUFs were investigated using a multi-methodological approach to gain detailed insight into the fire behaviour of pentane- and water-blown polyurethane (PUR) as well as pentane-blown polyisocyanurate polyurethane (PIR) foams with densities ranging from 30 to 100 kg/m3. Thermophysical properties were studied using thermogravimetry (TG); flammability and fire behaviour were investigated by means of the limiting oxygen index (LOI) and a cone calorimeter. Temperature development in burning cone calorimeter specimens was monitored with thermocouples inside the foam samples and visual investigation of quenched specimens’ cross sections gave insight into the morphological changes during burning. A comprehensive investigation is presented, illuminating the processes taking place during foam combustion. Cone calorimeter tests revealed that in-depth absorption of radiation is a significant factor in estimating the time to ignition. Cross sections examined with an electron scanning microscope (SEM) revealed a pyrolysis front with an intact foam structure underneath, and temperature measurement inside burning specimens indicated that, as foam density increased, their burning behaviour shifted towards that of solid materials. The superior fire performance of PIR foams was found to be based on the cellular structure, which is retained in the residue to some extent.

A facile strategy to simultaneously improve the mechanical and fire safety properties of ramie fabric-reinforced unsaturated polyester resin composites

Abstract: To simultaneously improve the mechanical and fire safety properties of ramie fabric-reinforced unsaturated polyester resin (UPR) composites, a phosphorus- and nitrogen-containing silane coupling agent (TMSAP) was synthesized to be coated on surface of ramie fabrics. Then, the fabric/UPR composites were fabricated by hand lay-up/oven vacuum bag method after incorporating ammonium polyphosphate (APP) into UPR. In the vertical burning test, CF/UPR@APP10 can reach V-0 with only 10 wt% APP. Additionally, CF/UPR@APP10 composite exhibits the significant decrease on fire risks tested by cone calorimeter. For example, the significant 40.5% and 39.8% reduction in the peak heat release rate (PHRR) and total heat release (THR) values, accompanied with less toxic pyrolysis gases and more compact char layer. Moreover, compared to the neat composites, samples with TMSAP-coated fabrics show obviously enhanced tensile strength even though incorporating 10 wt% APP, implying the improved interfacial adhesion between fabrics and matrix.

The synergistic flame-retardant behaviors of pentaerythritol phosphate and expandable graphite in rigid polyurethane foams

Abstract: The flame-retardant rigid polyurethane foams (RPUFs) containing pentaerythritol phosphate (PEPA) and expandable graphite (EG) were prepared by box-foaming. The flame retardancy of RPUFs was characterized using the limiting oxygen index (LOI) and cone calorimeter. The results show that the PEPA/EG system can effectively enhance the LOI values and reduce the peak release rate of RPUFs comparing with the foams only containing PEPA or EG although the flame retardants in all the samples are same proportion. The two results imply that the PEPA/EG system form flame-retardant synergistic effect. The micromorphology and chemical structure of residues of RPUFs were also investigated by scanning electron microscope and Fourier transform-infrared instruments. During combustion, the polyphosphates and their related analogues generated by PEPA can combine with the surfaces of expanded graphite, thereby resulting in the formation of the improved char layer. The layer possessed increased barrier effect and thereby imposing the better flame retardancy to RPUFs. POLYM. COMPOS., 39:329–336, 2018. © 2016 Society of Plastics Engineers

Fabrication of ZrP nanosheet decorated macromolecular charring agent and its efficient synergism with ammonium polyphosphate in flame-retarding polypropylene

Abstract: Poor efficiency is one of the biggest challenges for halogen-free flame retardant polymer. Catalyzing the carbonization of polymer itself during combustion is proposed to be a promising way to address this issue. In this work, a novel macromolecular charring agent (MCA) decorated by zirconium phosphate nanosheet named ZrP-d-MCA was synthesized and characterized. Subsequently, it was combined with ammonium polyphosphate (APP) to reduce the flammability of polypropylene (PP). When the contents of ZrP-d-MCA and APP were 5 wt% and 15 wt%, respectively, PP/Zr-d-MCA/APP could reach a limiting oxygen index of 32.5% and achieve UL-94 V-0 rating. Moreover, the bench-scale combustion performance determined by the cone calorimeter was significantly improved. The flame-retardant mechanism of ZrP-d-MCA/APP was revealed: during combustion, ZrP nanosheet could efficiently catalyze the charring reactions of MCA to form closed micro-nano char-cages, in which the degradation products of PP would be trapped and catalyzed into thermostable graphitization char.

Preparation of Poly(phosphoric acid piperazine) and Its Application as an Effective Flame Retardant for Epoxy Resin

Abstract: A phosphorus-nitrogen containing flame retardant additive of polyphosphoric acid piperazine, defined as PPAP, was synthesized by the salt-forming reaction between anhydrous piperazine and phosphoric acid, and the dehydration polymerization under heating in nitrogen atmosphere. Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, 13C and 31P solid-state nuclear magnetic resonance measurements. The synthesized PPAP and curing agent m-phenylenediamine were blended into epoxy resin (EP) to prepare flame retardant EP thermosets. The effects of PPAP on the fire retardancy and thermal degradation behavior of cured EP/PPAP composites were investigated by limiting oxygen index (LOI), vertical burning (UL-94), thermogravimetric analysis/infrared spectrometry (TG-IR) and cone calorimeter tests. The morphologies and chemical compositions of char residues for cured epoxy resin were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The results demonstrated that the flame retardant EP thermosets successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 30.8% when incorporating 5wt% PPAP into the EP thermosets. The TGA results indicated that the synthesized PPAP flame retardant additive possessed high thermal stability and excellent charring capability. Meanwhile, the incorporation of PPAP stimulated the epoxy resin matrix to decompose and charring ahead of time due to its catalytic decomposition effect, which led to a higher char yield at high temperature. The morphological structures and the analysis results of XPS for char residues of EP thermosets revealed that the introduction of PPAP benefited the formation of a sufficient, more compact and homogeneous char layer containing phosphorus-nitrogen flame retardant elements on the material surface during combustion. The formed char layer with high quality effectively prevented the heat transmission and diffusion, limited the production of combustible gases, and inhibited the emission of smoke, leading to the reduction of heat and smoke release.

Enhancing the flame-retardant and smoke suppression properties of transparent intumescent fire-retardant coatings by introducing boric acid as synergistic agent

Abstract: A series of novel phosphorus-boron flame retardants (BPEAs) were successfully synthesized by introducing boric acid (BA) into cyclic phosphate ester acid (PEA) via the esterification and thoroughly characterized by 1H nuclear magnetic resonance spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Five kinds of transparent fire-retardant coatings applied to wood substrates were produced by thoroughly mixing amino resin with PEA and BPEAs. The effects of BA on the optical transparency, thermal stability, fire performance and smoke emission characteristics of the coatings were investigated by various analytical instruments. The transparency analysis reveals that the transparency value of the coatings gradually decreases with increasing BA loading, and MPEA4 with the highest BA content still exhibits a high degree of transparency. The results from fire protection, cone calorimeter and smoke density tests show that the introduction of BA greatly decreases the flame spread rating, mass loss, char index, heat release rate, smoke production rate, total heat release, total smoke release and specific optical density of the coatings concomitant with the increase in the residual mass and intumescent factor, which is ascribed to the formation of a more dense and continuous intumescent char judging by digital photographs and scanning electron microscope images. Thermo-gravimetric analysis indicates that the onset decomposition temperature, high-temperature stability and residual mass of the coatings greatly improve with increasing BA content. FTIR analysis shows that the introduction of BA into the coatings contributes to generate more phosphorus-rich cross-linked structures and aromatic structures and then create a compact and intumescent char layer, thereby effectively enhancing the flame retardancy and smoke suppression properties of the coatings.