China
Africa
Explore chapters and articles related to this topic
Using Green Solvents to Fabricate Membrane Distillation Membranes
Published in Kang-Jia Lu, Tai-Shung Chung, Membrane Distillation, 2019
Organic solvents are very commonly used in many steps of membrane fabrication. Many of these solvents are toxic and pose threat to human health and the environment, but it is hard to replace them because of their broadly satisfactory properties such as solubility, viscosity, polarity, and boiling points (Figoli et al., 2014; Xing et al., 2014). Common solvents to prepare polyvinylidene fluoride (PVDF) membranes for membrane distillation (MD) are dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP). For example, Tomaszewska used DMF and DMAc to cast flat sheet membranes with a permeation flux of about 10 kg/m2 h (Tomaszewska, 1996). Hou et al. employed DMAc to fabricate single-layer hollow fiber membranes with a permeation flux of about 20 kg/m2 h (Hou et al., 2009). Wang et al. utilized NMP to produce dual-layer hollow fiber membranes with a permeation flux over 40 kg/m2 h (Wang et al., 2011). However, all these three solvents are very toxic and can cause many diseases. Table 9.1 briefly summarizes their hazard statements and linked diseases (Casarett et al., 2001; Regulation (EC) No. 1272/2008, 2008). In contrast, triethyl phosphate (TEP), for example, is a much safer solvent (Byrne et al., 2016; Capello et al., 2007). It is only harmful when being swallowed. In this case, not only can workers be better protected, the treatment of waste effluent can also be simplified.
Physical Constants of Organic Compounds
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Ethanol, 2,2'-[1,2-ethanediylbis(oxy)]bis-, dinitrate 10361 Triethylene glycol monoethyl 2-[2-(2-Ethoxyethoxy)ethoxy]ether ethanol 10362 Triethylenephosphoramide Tris(1-aziridinyl)phosphine, oxide 10363 Triethylenethiophosphoramide Thiotepa 10364 1,3,5-Triethylhexahydro-1,3,5triazine 10365 Triethyl phosphate Ethyl phosphate 10366 Triethylphosphine 10367 Triethylphosphine oxide 10368 Triethylphosphine sulfide 10369 Triethyl phosphite
Flame Retardancy of Synthetic Fibers
Published in Asim Kumar Roy Choudhury, Flame Retardants for Textile Materials, 2020
Czech-Polak et al. (2016) prepared new compositions of PUR foams with reduced flammability containing environmentally friendly flame retardants. Specimens of rigid PUR foams were manufactured in the hot pressing process using a press which is part of the tooling in long fiber injection (LFI) process. At the first step, the polyol component was mechanically mixed for 5 min with selected flame retardant additives. Then, the modified polyol component and the isocyanate were stirred together for 25 s. In the final step, the PUR mixture was poured into a mold heated to 65°C. The mold was closed under the pressure of 50 MPa, for 360 s. The same method was used to prepare the reference polyurethane sample without flame retardant. As flame retardants, the following compounds were used: Ammonium polyphosphate (APP)Melamine pyrophosphate (MPYP)Triethyl phosphate (TEP)Expanded or expandable graphite (also known as intumescent flake graphite),a synthesized intercalation compound of graphite that expands or exfoliates when heated, and is produced by treatment of flake graphite with various intercalation reagents that migrate between the graphene layers in a graphite crystal and remain as stable speciesBentonite modified benzyl(hydrogenated tallow alkyl) dimethyl ammonium chlorideBentonite from Russian deposits modified with butyl(triphenyl) phosphonium chlorideAll prepared PUR foams containing flame retardants are characterized by acceptable resistance to flame. Burning time values obtained during the UL 94 HB test lead to the conclusion that the foam containing flame retardants in liquid form (triethyl phosphate) has the best flame resistance, most likely due to the easier and better homogenization of flame retardant additives and polyol. Modification of polyurethane foams using suitably selected composition of flame retardants may also improve the transparency of the fumes released during the combustion of the material. In this test, the highest values were obtained for the foam containing melamine pyrophosphate and expanded graphite. The addition of flame retardant caused only slight worsening of the tensile strength of the investigated polyurethane foams. The utilizing of suitably selected flame retardants for PUR foams allows manufacturing lightweight foam materials characterized by high flame resistance with satisfying mechanical properties. Analysis of all tests leads to the conclusion that the best is a composition marked as 1.9% bentonite modified butyl(triphenyl) phosphonium chloride, 4.0% ammonium polyphosphate, and 3% expanded graphite. This PUR foam was characterized by increased fire resistance and decreased smoke density with only a small decrease in mechanical properties.
Fabrication and characterization of freeze dried strontium-doped bioactive glasses/chitosan composite scaffolds for biomedical engineering
Published in Journal of Asian Ceramic Societies, 2021
Chao-Kuang Kuo, Hsiang-Wei Huang, Liu-Gu Chen, Yu-Jen Chou
In this work, Sr-BG powder was synthesized using the spray drying technique. Composition of 58S (SiO2: CaO: P2O5 = 60: 35: 5 (mol%)) was used in order to achieve better bioactivity. Initially, the precursor solution was prepared by adding 76.52 g tetraethyl orthosilicate (Si(OC2H5)4, 99.9%, Showa, Japan), 50.60 g calcium nitrate tetrahydrate (Ca(NO3)2.4H2O, 98.5%, Showa, Japan), 11.15 g triethyl phosphate ((C2H5)3PO4, 99.0%, Alfa Aesar, UK), and 3.40 g strontium nitrate (Sr(NO3)2, 99.0%, Sigma-Aldrich, United States) into 120.00 g ethanol as the foundation of SiO2, CaO, P2O5, and SrO, respectively. The precursor solution was stirred at 25°C for 1 h for complete dissolution of precursors, then de-ionized water was added till 1000 mL and stirred again for 24 h to ensure solution homogeneity. For the spray drying process, the precursor solution was dispersed into small droplets with high speed rotating disc set at 20,000 rpm. A flow rate of 50 ml/min was used to spray into the spray drying machine (SD DD-03, IDTA machinery Co., Taiwan). The chamber was set at 200°C to dry and form the initial powder. The powder was then calcined at 600°C for 1 h with a heating rate of 1°C/min to form the final Sr-doped BG powder.
From Cells to Residues: Flame-Retarded Rigid Polyurethane Foams
Published in Combustion Science and Technology, 2020
M. Günther, A. Lorenzetti, B. Schartel
As raw materials for the foams’ formulation, two polyester polyols were used (Isoexter 4530 and 4537) with nOH of 510 and 350 mgKOH/g, respectively, and one polyether polyol (Isoter 842G) with nOH of 160 mgKOH/g, all supplied by Coim (Italy). For all formulations, the weight ratio of 2:2:1 was kept constant. As polymeric methane diphenyl diisocyanate (MDI), Voranate M600 (Dow Chemicals) with NCO% = 30.5, average functionality = 2.8 and viscosity at 25°C = 600 mPa*s was used. Dimethyl cyclohexylamine (DMCHA, Polycat 8) and pentamethyl diethylenetriamine (PMDETA, Polycat 5) were chosen for PUR polymerization; the surfactant was Tegostab B 8469. The catalysts as well as the surfactant were kindly supplied by Evonik (Germany). Distilled water was used as the blowing agent, with different amounts used to obtain different densities within the range from 30 to 100 kg/m3. Additionally, flame-retarded PUR foams were prepared by using 7 wt.-% of triethyl phosphate (Fyrol TEP, supplied by ICL-IP) as a flame retardant. In order to prevent problems in terms of dimensional stability of the samples, a higher amount of TEP cannot be used due to its plasticizing effect in PUR. (Prociak et al. 2001)
Low-carbon hydrocarbon fracturing fluid with fast cross-linking rate based on n-hexane/n-octane: synthesis and properties
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Chao Ma, Shuo Wang, Alain Pierre Tchameni, Yalan Zhang, Peng Zhang, Zhe Wang
polyphosphate intermediate, and then n-butanol reacted with n-octanol and dodecanol to prepare a dialkyl phosphate (gelling agent). The optimal reaction condition for the phosphoric acid monoester is as follows: The molar ratio of triethyl phosphate to phosphorus pentoxide is 1.25:1, the reaction temperature is 90°C, the reaction time is 7 h; the optimum reaction conditions for dialkyl phosphate esters were: the mass fraction of n-butanol, n-octanol, and dodecyl alcohol were 7.78%, 33.51%, and 58.71%, respectively. The reaction temperature is 98°C, and the reaction time is 8 h. A composite iron salt formulation with an excellent gelation time and gelation