Compatibilization of polyethylene/aluminum hydroxide (PE/ATH) and polyethylene/magnesium hydroxide (PE/MH) composites with functionalized polyethylenes

Measurements, emission characteristics, and control methods of fire effluents generated from tunnel asphalt pavement during fire: a review

Tunnels are widely used in high-grade roads, particularly in mountainous areas; however, tunnel fires often result in severe economic losses and casualties. The fire effluents produced from asphalt pavement have attracted significant research attention. The main objective of this study is to assimilate information on various aspects of bituminous mixture emissions during fires. In this study, the fume emissions of bitumen and bituminous mixtures during combustion are comprehensively reviewed and summarized. First, the test methods for fire effluents produced by bitumen and bituminous mixtures after combustion are summarized. Second, the factors influencing the fume concentration and composition are determined. In addition, different methods to reduce the emission of fire effluents are compared, particularly for the suppression of toxic gas emissions. Then, reasonable suggestions are proposed to reduce the damage caused by hazardous gases to humans and the environment. This review is beneficial for comprehensively understanding the fume emission behaviour and future research on the smoke suppression of highway tunnel asphalt pavements during fires.

Enhanced Flame Retardancy in Ethylene-Vinyl Acetate Copolymer/Magnesium Hydroxide/Polycarbosilane Blends

A polymer ceramic precursor material—polycarbosilane (PCS)—was used as a synergistic additive with magnesium hydroxide (MH) in flame-retardant ethylene–vinyl acetate copolymer (EVA) composites via the melt-blending method. The flame-retardant properties of EVA/MH/PCS were evaluated by the limiting oxygen index (LOI) and a cone calorimeter (CONE). The results revealed a dramatic synergistic effect between PCS and MH, showing a 114% increase in the LOI value and a 46% decrease in the peak heat release rate (pHRR) with the addition of 2 wt.% PCS to the EVA/MH composite. Further study of the residual char by scanning electron microscopy (SEM) proved that a cohesive and compact char formed due to the ceramization of PCS and close packing of spherical magnesium oxide particles. Thermogravimetric analysis coupled with Fourier-transform infrared spectrometry (TG–FTIR) and pyrolysis–gas chromatography coupled with mass spectrometry (Py–GC/MS) were applied to investigate the flame-retardant mechanism of EVA/MH/PCS. The synergistic effect between PCS and MH exerted an impact on the thermal degradation products of EVA/MH/PCS, and acetic products were inhibited in the gas phase.

The impact of reagents concentration on the efficiency of obtaining high-purity magnesium hydroxide

The work presents the impact of reagents concentration and the drying process on the efficiency of obtaining magnesium hydroxide and its specific surface area. Magnesium sulphate(VI) within the concentration range of 0.7–2.0 mol/dm3 was used in the research as magnesium feedstock and sodium hydroxide was used as a precipitating agent within the same concentration range. The process of obtaining magnesium hydroxide was carried out with a 25% excess of the precipitating agent in relation to the reaction stoichiometry. The obtained suspension was separated by way of multi-stage sedimentation with the use of acetone and freezing samples. Depending on the concentration of reagents the efficiency of obtaining magnesium hydroxide fell within the range of 88–99%, whereas the specific surface area – within 115–609 m2/g, while the high purity of samples above 99% of magnesium hydroxide was maintained.

Effect of Ammonium Polyphosphate to Aluminum Hydroxide Mass Ratio on the Properties of Wood-Flour/Polypropylene Composites

Two halogen-free inorganic flame retardants, ammonium polyphosphate (APP) and aluminum hydroxide (ATH) were added to wood-flour/polypropylene composites (WPCs) at different APP to ATH mass ratios (APP/ATH ratios), with a constant total loading of 30 wt % (30% by mass). Water soaking tests indicated a low hygroscopicity and/or solubility of ATH as compared to APP. Mechanical property tests showed that the flexural properties were not significantly affected by the APP/ATH ratio, while the impact strength appeared to increase with the increasing ATH/APP ratio. Cone calorimetry indicated that APP appeared to be more effective than ATH in reducing the peak of heat release rate (PHRR). However, when compared to the neat WPCs, total smoke release decreased with the addition of ATH but increased with the addition of APP. Noticeably, WPCs containing the combination of 20 wt % APP and 10 wt % ATH (WPC/APP-20/ATH-10) showed the lowest PHRR and total heat release in all of the formulations. WPCs combustion residues were analyzed by scanning electron microscopy, laser Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Thermogravimetric analysis coupled with FTIR spectroscopy was used to identify the organic volatiles that were produced during the thermal decomposition of WPCs. WPC/APP-20/ATH-10 showed the most compact carbonaceous residue with the highest degree of graphitization.

Polylactic acid biocomposites: approaches to a completely green flame retarded polymer

Basic paths towards fully green flame retarded kenaf fiber reinforced polylactic acid (K-PLA) biocomposites are compared. Multicomponent flame retardant systems are investigated using an amount of 20 wt% such as Mg(OH)2 (MH), ammonium polyphosphate (APP) and expandable graphite (EG), and combinations with silicon dioxide or layered silicate (LS) nanofillers. Adding kenaf fibers and flame retardants increases the E modulus up to a factor 2, although no compatibilizer was used at all. Thus, in particular adding EG and MH decreases the strength at maximum elongation, and kenaf fibers, MH, and EG are crucial for reducing the elongation to break. The oxygen index is improved by up to 33 vol% compared to 17 vol% for K-PLA. The HB classification of K-PLA in the UL 94 test is outperformed. All flame retarded biocomposites show somewhat lower thermal stability and increased amounts of residue. MH decreases the fire load significantly, and the greatest reduction in peak heat release rate is obtained for K-PLA/15MH/5LS. Synergistic effects are observed between EG and APP (ratio 2:1) in flammability and fire properties. Synergistic multicomponent systems containing EG and APP, or MH with adjuvants offer a promising route to green flame retarded natural fiber reinforced PLA biocomposites.

Interfacial adhesion between functionalized polyethylene surface and graphene via molecular dynamic simulation

In this study, interfacial adhesion between functionalized polyethylene (PE) surfaces and graphene were examined using molecular simulation. Various functional groups including amino, carboxy, hydroxy, cyano, isocyanato, oxo, and ethylamino were used to cover the PE surface with surface densities of 0.48, 1.30, and 4.84 groups per nm(2). The interfacial adhesion between the modified PE surfaces and the graphene was quantified via calculation of work of separation (Wsep), the amount of the required work to separate two surfaces without occurring any relaxation and diffusion phenomena. Insertion of the functional groups on the PE surface decreased the amount of Wsep, except for the oxo, amino, and higher densities of the carboxy groups. Increasing the surface group density enhanced the adhesion due to decreasing the surface atomic roughness and increasing the atomic density at the interface. In addition, the effect of surface group rearrangement was investigated via calculation of the work of adhesion (Wadh) while sufficient time had been devoted to relax the interface. The surface reorganization during the relaxation process significantly enhanced adhesion due to eliminating the surface roughness and increasing the surface atomic density.

Flame Retarded PE with MH/ATH/Microencapsulated Red Phosphorous and its Toughening by Polymeric Compatibilizers

Non-halogen flame retarded polyethylene (PE) can be prepared by filling metallic hydroxides magnesium hydroxide (MH) or aluminium hydroxide (ATH), the mechanical properties of polymer composites will decline greatly when filling much more inorganic particles. Selecting microencapsulating particles, suitable synergistic agents or compatibilizers are good methods for improving the combination performance of composites. In this study, microencapsulated red phosphorous (MRP) was synthesized by using melamine-formaldehyde resin through in-situ polymerization, and used as a synergistic agent of MH and ATH, and the best proportion of three flame retardants was studied in detail. Results showed that flame retarded PE had a better combination performance when filling with 45 wt% compound flame retardants of MRP, MH and ATH under the weight ratio of 46/46/8. In order to improve the mechanical performance of composite, two polymeric compatibilizers POE-g-MAH and EPDM-g-MAH were selected to toughen the flame retarded PE composite. Results showed the flame resistance and mechanical properties of composites improved greatly with an increase of compatibilizer content, under the same condition, POE-g-MAH has a better contribution on the flame resistance and EPDM-g-MAH has a better toughening effect. The best flame retarded PE composite can be obtained by filling with 45 wt% compound flame retardants and 10 wt% EPDM-g-MAH.

Cellular Structure of EVA/ATH Halogen-free Flame-retardant Foams

Composites of etylene vinyl acetate (EVA)/aluminum trihydroxide (ATH) (up to 70 wt%) were foamed to create new materials with good fire retardancy properties and low weight, proving the feasibility of developing cellular structures when high levels of halogen-free flame retardants (HFFR) are included. An experimental study was carried out to explore the effects of chemical composition on cellular structure as well as the effect of structure on thermal stability, mechanical and combustion properties. Sample fabrication was carried out using an improved compression molding route consisting of polymer compounding, precursor preparation and foaming under pressure. The polymer matrix consisted of EVA as well as certain amount of linear low-density polyethylene-maleic anhydride as coupling agent. The inorganic filler used was ATH ranging from 0 wt% to 70 wt%. Furthermore, azodicarbonamide was used as chemical blowing agent. Foamed samples with cell sizes below 100 µm were produced. These samples showed similar fire retardancy than their solid precursors. The compatibilization was proved indispensable to achieve a good adhesion between mineral filler and polymer and to improve the cellular structure. The increase of the amount of filler has an interesting effect on the cellular structure, going from a closed-cell (up to 50 wt% of ATH) to an open-cell cellular structure (60 wt% of ATH or more). The feasibility of producing HFFR cellular materials has been demonstrated as a result of this investigation, leading to a notable reduction of material compared to the solid one and to new properties which can result in new applications.