Yushan Xing

The reuse of nonmetals recycled from waste printed circuit boards as reinforcing fillers in the polypropylene composites

The feasibility of reusing nonmetals recycled from waste printed circuit boards (PCBs) as reinforcing fillers in the polypropylene (PP) composites is studied by using both mechanical and vicat softening temperature (VST) tests. The concentration of Cu leaded from the composites is also tested. The mechanical test shows that both tensile and flexural properties of the nonmetals/PP composites can be significantly improved by adding the nonmetals into PP. The maximum increment of tensile strength, tensile modulus, flexural strength and flexural modulus of the PP composites is 28.4%, 62.9%, 87.8% and 133.0%, respectively. As much as 30 wt% nonmetals recycled from waste PCBs can be added in the PP composites without violating the environmental regulation. The VST test shows that the presence of nonmetals can improve the heat resistance of the nonmetals/PP composites for their potential applications. The optimum particle is the fine or medium nonmetals recycled from waste PCBs, and the optimum content of the nonmetals is 30 wt% basing on the comprehensive consideration. All the above results indicate that the reuse of nonmetals as reinforcing fillers in the PP composites represents a promising way for recycling resources and resolving the environmental pollutions.

A novel approach to recycling of glass fibers from nonmetal materials of waste printed circuit boards

The printed circuit boards (PCBs) contain nearly 70% nonmetal materials, which usually are abandoned as an industrial solid-waste byproduct during the recycling of waste PCBs. However those materials have abundant high-value glass fibers. In this study, a novel fluidized bed process technology for recycling glass fibers from nonmetal materials of waste PCBs is studied. The recycled glass fibers (RGF) are analyzed by determination of their purity, morphology and surface chemical composition. This process technology is shown to be effective and robust in treating with nonmetal materials of waste PCBs. The thermoset resins in the nonmetal materials are decomposed in the temperature range from 400 degrees C to 600 degrees C. And the glass fibers are collected at high purity and recovery rate by the cyclone separators without violating the environmental regulation. This novel fluidized bed technology for recycling high-value glass fibers from nonmetal materials of waste PCBs represents a promising way for recycling resources and resolving the environmental pollutions during recycling of waste PCBs.

A study of the reaction characteristics and mechanism of Kapton in a plasma-type ground-based atomic oxygen effects simulation facility

Kapton, a commonly used spacecraft material, is studied to investigate the atomic oxygen (AO) erosion effects in a plasma-type ground-based AO effects simulation facility. The samples before and after the experiments are compared in aspect, mass and surface morphology. The reaction characteristics of the material in the facility are obtained. The contribution of AO and ionic oxygen to mass loss in the sample and the reaction mechanism between the different particles and samples are analysed. It is concluded that neutral AO is the major cause of material erosion and mass loss and that the collision of energetic ions may accelerate the oxidation reaction.

Surface metallization of cenospheres and precipitators by electroless plating

This paper reports the use of a colloidal Pd0 catalysis system to metallize the surface of precipitators separated from coal fly-ash, and metals such as Cu, Ni etc. are deposited on the precipitators surface. Alternatively, according to the characteristic surface of cenospheres, an Ag coating catalysis system is adopted to first deposit Ag on the cenospheres surface, followed, if necessary, by the deposition of other metals such as Cu, Ni, etc. on the Ag coating to produce monolayer and multilayer metal-coated cenospheres. The surface characteristics and the morphologies of the metal coatings are examined in detail with scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) techniques. It can be shown that the quality of metal coatings derived from the Ag coating catalysis system, is better than that of the colloidal Pd0 catalysis system.

Influence of Spray Drying Conditions on the Properties of Ammonium Dihydrogen Phosphate Fire-Extinguishing Particles

Superfine spherical hollow ammonium dihydrogen phosphate (NH4H2PO4) fire-extinguishing particles are first produced by the spray-drying method. The particles prepared at drying gas inlet temperature ranging from 180°C to 220°C are composed of NH4H2PO4. When the proportion of FK-510 increases from 5 wt%to 10 wt%, the surfaces of the as-prepared particles become rougher, and the volume mean size of particles increases from 11.25 to 15.44 µm. When the proportion of FK-510 increases from 10 to 15 wt%, the amount of broken spherical hollow particles clearly decreases and the volume mean size of particles decreases from 15.44 to 13.5 µm. The flow rate and bulk density of the particles prepared from the solution containing the proportion of FK-510 ranging from 5 to 15 wt% decreases with an increase in the proportion of FK-510. When 15 wt% of FK-510 is added, diesel oil contact angle of particles markedly increases. In addition, water contact angle of particles decreases with an increase in the proportion of FK-510. XPS analysis suggests that the wettability of particles is attributed to the migration of FK-510 and silicone oil emulsion to the surface of particles during the spray-drying process. Diesel oil contact angles of particles agree with fluorine element concentrations on the surface of particles, while water contact angles of particles agree with silicon element concentrations.

Superfine Spherical Hollow Ammonium Dihydrogen Phosphate Fire-Extinguishing Particles Prepared by Spray Drying

Superfine spherical hollow ammonium dihydrogen phosphate fire-extinguishing particles are prepared by spray drying and modified in situ with silicon oil emulsion. The results show that the amount of rough particles increased observably when the proportion of silicon oil emulsion is increased from 9 to 15 wt%, while no significant difference is detected when the proportion of silicon oil emulsion was varied from 0 to 9 wt%. The flowability of particles is improved with an increase in the proportion of silicon oil emulsion; 9.0 wt% is the optimal proportion of silicon oil emulsion for improving the hydrophobic performance of particles. Fire-extinguishing tests show that the fire-extinguishing capability of spray-dried superfine spherical hollow ammonium dihydrogen phosphate fire-extinguishing particles is much better than the two varieties of existing superfine dry chemical fire-extinguishing agents.

Experimental Study of Vacuum Ultraviolet Radiation Effects and Its Synergistic Effects with Atomic Oxygen on a Spacecraft Material-Polytetrafluoroethylene

Abstract Polytetrafluoroethylene (Teflon), a widely used spacecraft material, is studied to investigate the vacuum ultraviolet (VUV) effects and its synergistic effects with atomic oxygen (AO) in a ground based simulation facility. The samples before and after the experiments are compared in appearance, mass, optical properties and surface composition. The reaction characteristics of Teflon are summarized and the reaction mechanisms are analyzed. The following conclusion can be drawn: at the action of VUV the Teflon sample surface is darkened for the accumulation of carbon; and when the sample is exposed to AO, the carbon is oxidized and the darkening surface is bleached; the synergistic effects of VUV and AO may cause the erosion of Teflon more severe.