Papers by Keyword: Wollastonite

Abstract: This paper reports a study on novel geopolymers, focusing on chemically bonded composites, by incorporating wollastonite and recycled mixed plastics. Magnesium oxide and monopotassium phosphate were used as binders; while the recycled mixed plastics consisted of high-density polyethylene and polystyrene at different volume ratios. The effects of molar ratio (magnesium-to-phosphorus ratio), wollastonite-to-binder ratio and recycled mixed plastics content were investigated. The performance of geopolymers was evaluated based on their setting time and water absorption, compressive and flexural strengths as well as thermal properties.

Abstract: Wollastonite is one type of inorganic filler. The effects of wollastonite loading on tensile properties of wollastonite (WS) filled high density polyethylene (HDPE)/Natural Rubber (NR) composites was studied. The HDPE/NR/WS composites were prepared by using Brabender EC Plus at a temperature of 180 °C with rotor speed of 50 rpm for 10 min. It was found that the increasing of wollastonite loading had decreased the tensile strength and elongation at break, whereas the Young’s modulus of the HDPE/NR/WS composites had increased with the increasing of wollastonite loading.

Abstract: In the research, Polytetrafluoroethene (PTFE) is applied in a newly elastic composite cylindrical roller bearing, i.e. PTFE is modified into the traditional hollow cylindrical roller bearing so as to improve the vibration, wearing properties and life span of the roller bearing. The results show that bearing capacity of the same dimension of WF/PTFE composite materials is higher than that of WP/PTFE composite materials. Small dimension of WF-PTFE composite materials has the best wearing properties under light load conditions; large dimension of WF-PTFE composite materials has better bearing capacity and wearing properties than small dimension of WF filler under heavy load conditions. Compare to traditional method, Rolling stress improves by filler PTFE materials using our method reduces by 17.1% under light load conditions and reduces by 27.7% under heavy load conditions. The research provides basis for the modified material of the elastic composite cylindrical roller bearing.

Abstract: In general, wood-polymer composites are vulnerable to weathering factors such as UV radiation, moisture, freeze-thaw action. Weathering can cause discoloration, chalking, dimensional change, and loss of mechanical properties of wood-polymer composites. This comparative study was focused on weatherability of wood–polypropylene composites made with and without pigments. Two types of inorganic pigments were applied: carbon black master-batch and synthetic iron oxide. Wood-polypropylene composite made without pigment was used as a reference. Also, composites prepared with addition of wollastonite were tested. The composite samples were exposed to outdoor weathering and in a parallel the accelerated UV weathering was conducted in xenon weathering chamber for the 2000 hours. The colour change was estimated by spectrophotometric method, and the change of Charpy impact strength after weathering was determined. The surface morphology was studied with scanning electron microscopy (SEM). The addition of pigments decreased the lightness of non-weathered composites. The change of lightness and total colour change of weathered composites were affected a lot by type of pigment and method of weathering. As, expected wood-polypropylene composite made with carbon black showed the best results in colour stability of composites exposed to weathering. SEM showed that accelerated weathering in the xenon chamber caused more significant changes in the morphology of the polymer surface layer of the composites than outdoor weathering. Charpy impact strength of all studied composites was found to retain after 2000 hours of outdoor weathering, although accelerated weathering caused significant reduction of Charpy impact strength of these composites.

Abstract: In this paper, wollastonite nanopowder were successfully synthesized by the surfactants modified-calcined method using calcium silicate residue of potassium feldspar after extraction of potassium and alumina. The effects of modifier and calcined temperature on the phase composition, morphology and microstructure were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the phase of samples with different modifier processing is wollastonite-2M, while CTAB as modifier can avoid preferred orientation growth. The obtained wollastonite powder is spherical in morphology and well dispersed with the particle size of approximately 150nm.

Abstract: Use calcium carbonate, sodium carbonate and barium carbonate as blowing agent, polyethylene glycol as binder,Cr₂O₃ as nucleating agent,TiO₂ as nucleating agent,CaF₂ as a flux in glass powder, we can produce porous glass-ceramics, and after above research, the apparent density, powder density, porosity, the main phase, microscopic characteristics and thermal performance of the samples would be test. The results show that: considering the physical and mechanical performance of porous glass-ceramics, the froth effect of sodium carbonate is most ideal. When the dosage is 6%, the apparent density is minimum, the porosity is maximum and the thermal conductivity is maximum and the main phase is wollastonite.

Abstract: Various types of intumescent fire retardant coatings (IFRCs) have been used to protect the substrates exposed to fire. In current study, high temperature filler Wollastonite (W) filler was used to improve fire performance of intumescent fire retardant coating. The basic ingredients of the coating were ammonium poly-phosphate (APP) as acid source, expandable graphite (EG) as carbon source, melamine (MEL) as blowing agent in epoxy binder, boric acid as additive and hardener as curing agent. In this study a range of coating formulations were developed by using different weight percentages of Wollastonite filler. The coated steel substrate samples were tested for fire performance using Bunsen burner and char expansion was measured using furnace fire test. Composition of the char was determined by X-ray diffraction (XRD) technique. The char morphology was studied using field emission scanning electron microscopy (FESEM). Results showed that Intumescent coating with addition of Wollastonite filler enhanced anti-oxidation of the char. Presence of phosphorus, calcium and silicon in char layer further improved the thermal stability of char.

Abstract: Batch modification with low-enthalpy raw materials is the effective approach for reducing the glass melting energy. In the previous study, it was found that introducing wollastonite (CaSiO₃) as a source of CaO instead of calcium carbonate (CaCO₃) in the soda-lime glass batch can fasten the melting process. It is because the modified batch with CaSiO₃ has lower chemical heat demand, ΔH^o_chem, which is equivalent to the standard heat of batch-to-melt conversion. In order to investigate the kinetic property of the modified batch, the melting behaviour of 2 kg modified batch was studied. The results showed that the temperature of the modified batch increased at a faster rate than the original batch. The properties of the glass from the modified are also similar to the original batch.

Abstract: Wollastonite filled natural rubber (NR) compounds were prepared using a laboratory two-roll mill. The filler was loaded into NR at different loading, i.e., 0, 10, 20, 30 and 40 part per hundred of rubber (phr). The effect of wollastonite on curing characteristic, tensile and morphology properties has been studied. Results indicated that the cure time (t₉₀), scorch time (t₂), tensile strength and elongation at break of the NR compounds decrease with increasing wollastonite loading but the maximum torque, tensile modulus M100 (stress at 100% elongation), M300 (stress at 100% elongation) increase with increasing wollastonite loading. The fracture surface morphology of the NR compounds was investigated with a scanning electron microscope (SEM). More filler detachment from NR surface was observed with increasing wollastonite loading.

Abstract: The crystal structure of wollastonite is triclinic. Electronic structures and optical properties of wollastonite were studied using a quantum mechanical first principles approach. The geometric parameters, electric and optical properties of wollastonite are investigated by using the plane-wave ultrasoft-pseudopotential method (PWP).The equilibrium lattice constants are in good agreements with experimental data. The electronic structures reveal that wollastonite has a indirect band (5.4eV) gap and a direct band (5.5eV).Optical properties have been studied and the calculated optical dielectric constant (ε_op) is about 2.68.