The preparation and evaluation mechanism of mesoporous spherical silica/porous carbon-filled polypropylene composites obtained from coal gasification fine slag

Coal gasification fine slag is a by-product of the entrained-flow gasifier, which has caused some environmental pollution. Through acid dissolution and calcination at different temperatures, mesoporous spherical silica/porous carbon composite filler was prepared using coal gasification fine slag. The particle size and specific surface area of the composite filler decreased with the decrease of unburned carbon content. The analysis of X-ray photoelectron spectroscopy (XPS) indicated the decrease of oxygen-containing functional groups and the increase of C-C groups with the decrease of the content of carbon. The effects of mesoporous spherical silica/porous carbon with different carbon content on the comprehensive properties of filled polypropylene (PP) were studied. The tensile strength and interface interaction increased at first and then decreased with the decrease of carbon content, due to the synergistic effect of mesoporous spherical silica and rough amorphous carbon. The scanning electron microscope showed that the composite filler with the carbon content of 14.47 wt.% at the calcination temperature of 450 °C had the best compatibility with the matrix. Thermodynamic analysis of the PP composites indicated that thermal insulation properties and thermal stability improved with the incorporation of the composite filler. Differential scanning calorimetry (DSC) testing indicated the highest crystallinity of the matrix corresponding to the best comprehensive performances of the composites. XRD patterns revealed that the cooperation of fillers brought characteristic peaks and did not change the primary crystal structure of PP. Simultaneously, heavy calcium powders (CC) were used as comparative fillers, and the overall properties of the PP composites filled with the composite filler were better compared to those of the CC-filled PP composite. The results illustrated that mesoporous spherical silica/porous carbon particles can completely replace CC used in the PP composites, which can be used in auto bumpers, plastic pipes, display cases, and car air deflectors. The CGFS can be processed into a plastic filler for substituting heavy calcium powder particles, which can solve the environmental pollution caused by the accumulation of solid waste.

Flame Retardation of Natural Rubber: Strategy and Recent Progress

Natural rubber (NR) as a kind of commercial polymer or engineering elastomer is widely used in tires, dampers, suspension elements, etc., because of its unique overall performance. For some NR products, their work environment is extremely harsh, facing a serious fire safety challenge. Accordingly, it is important and necessary to endow NR with flame retardancy via different strategies. Until now, different methods have been used to improve the flame retardancy of NR, mainly including intrinsic flame retardation through the incorporation of some flame-retarding units into polymer chains and additive-type flame retardation via adding some halogen or halogen-free flame retardants into NR matrix. For them, the synergistic flame-retarding action is usually applied to simultaneously enhance flame retardancy and mechanical properties, in which some synergistic flame retardants such as organo-montmorillonite (OMMT), carbon materials, halloysite nanotube (HNT), etc., are utilized to achieve the above-mentioned aim. The used flame-retarding units in polymer chains for intrinsic flame retardation mainly include phosphorus-containing small molecules, an unsaturated chemical bonds-containing structure, a cross-linking structure, etc.; flame retardants in additive-type flame retardation contain organic and inorganic flame retardants, such as magnesium hydroxide, aluminum hydroxide, ammonium polyphosphate, and so on. Concerning the flame retardation of NR, great progress has been made in the past work. To achieve the comprehensive understanding for the strategy and recent progress in the flame retardation of NR, we thoroughly analyze and discuss the past and current flame-retardant strategies and the obtained progress in the flame-retarding NR field in this review, and a brief prospect for the flame retardation of NR is also presented.

Silane-functionalized Flame-retardant Aluminum Trihydroxide in Flexible Polyurethane Foam

Flexible polyurethane (PU) foams are easily ignitable and show a high burning velocity, mainly due to their high surface area-to-mass ratio and high air permeability. Consequently, flame retardants such as halogenated compounds are applied. However, the use of halogenated flame retardants is not considered beneficial in transport applications, for example, aviation or automobile, in part due to the high smoke generation. Solid nonhalogenated flame retardants, for example, aluminum trihydroxide (ATH), are known as smoke suppressants. The application of ATH in flexible (PU) foam has not yet been reported in the literature. In this study, the application of different types and amounts of ATH and the resulting structure—property relationship in the foam are investigated. The increase in the viscosity of the filled raw materials during the foaming process and the negative effects of the filler on the mechanical properties of the final foam pose particular problems in the application of ATH. To pass the FMVSS 302 test, high amounts of ATH are necessary. To overcome the mentioned drawbacks, ATH particles are functionalized by 3-aminopropyltriethoxysilane under different conditions. The synthesized products were characterized by Fourier transform infrared, energy-dispersive X-ray fluorescence analysis, and 29Si and 1H solid-state nuclear magnetic resonance spectroscopy. The silane-treated ATH particles show a significant decrease in viscosity of the ATH—polyol system of more than 20% at ATH contents of up to 60 phpp. Values of the rising behavior during foaming and the burning velocity are not affected by this silane treatment. However, the compression test of PU foams with the silane-treated ATH particles show a decrease in compression strength of up to 20% compared to untreated ATH particles in the flexible PU foam. At higher ATH contents, no effect of silanization is observed.