To better understand and ascertain the mechanisms of flotation reagent interaction with rare earth (RE) minerals, it is necessary to determine the physical and chemical properties of the constituent components. Seven rare earth oxides (CeO2, Er2O3, Nd2O3, Tm2O3, Yb2O3, La2O3, and Tb4O7) that cover the rare earth elements (REEs) from light to heavy REEs have been investigated using Raman spectroscopy. Multiple laser sources (wavelengths of 325 nm, 442 nm, 514 nm, and 632.8 nm) for the Raman shift ranges from 100 cm−1to 5000 cm−1of these excitations were used for each individual rare earth oxide. Raman shifts and fluorescence emission have been identified. Theoretical energy levels for Er, Nd, and Yb were used for the interpretation of fluorescence emission. The experimental results showed good agreement with the theoretical calculation for Er2O3and Nd2O3. Additional fluorescence emission was observed with Yb2O3that did not fit the reported energy level diagram. Tb4O7was observed undergoing laser induced changes during examination.
Polyurethane binder systems based on hydroxyl-terminated polybutadiene (HTPB) possess several superior properties such as superior adhesion, high solid-loading capacity, outstanding mechanical performance, etc. They have been widely used in coatings and adhesives as well as in medical and military industries. The cure reaction between hydroxyl-terminated polybutadiene (HTPB) and diisocyanates plays a key role in the properties of final products as well as the adjustment of process parameters. FT-IR spectroscopy is applied to investigate the kinetics of the curing reaction of HTPB and isophorone diisocyanate (IPDI) in the presence of a low toxic and low viscosity catalyst, stannous isooctoate (TECH). The concentrations of the isocyanate groups (NCO) characterized by FT-IR during the cure reaction with respect to time were recorded at different temperatures and at constant stoichiometric ratio R n[NCO]/n[OH] = 1.0. The kinetic parameters, i.e., activation energy (E a), pre-exponential factor (A), activation enthalpy (∆H) and activation entropy (∆S) were determined. In addition, the curing process and mechanism of the HTPB-IPDI reaction are discussed.
A polyoxometalate‐based ionic liquid‐doped sepiolite (SEP‐PIL) was prepared by electrostatically immobilizing phosphomolybdic acid (PMA) on natural sepiolite embedded with imidazolium cations (SEP‐IL), and its structural properties were fully characterized by various methods. Furthermore, a new intumescent flame‐retardant system (IFR) for high‐density polyethylene (HDPE) was constructed by adding SEP‐PIL into conventional HDPE/IFR composites. The retardant properties and thermal decomposition behaviors were comprehensively investigated. The results showed that the HDPE composite containing 24 wt% IFR and 1 wt% SEP‐PIL passed UL‐94V‐0 rating, and the limiting oxygen index increased from 17.8% (pure HDPE) to 27.6%. In addition, the HDPE/IFR/SEP‐PIL composite had lower peak heat release rate (PHRR) and total heat release (THR) compared to the HDPE/IFR composite. The thermogravimetric analysis demonstrated that the combination of SEP‐PIL with IFR could greatly promote the formation of residual chars. Dynamic rheological measurement further confirmed that the synergistic effect of SEP‐PIL and IFR could greatly improve the flame retardancy of HDPE/IFR/SEP‐PIL composites.
Castor oil and its three derivatives including methyl ricinoleate, sodium ricinoleate and ricinoleic acid were used as the raw material for alkali fusion to prepare sebacic acid. The reaction parameters including catalyst, ratio of oleochemicals/NaOH, reaction time and reaction temperature were optimized. It was found that Pb3O4 (1%) showed the best catalytic performance, and 553 K was considered as the most suitable reaction temperature. The oleochemicals/NaOH ratios of 15:14, 15:14, 15:12 and 15:14 were determined as the optimal ratio for alkali fusion of castor oil, methyl ricinoleate, sodium ricinoleate and ricinoleic acid, respectively. In addition, the optimal reaction time of alkali fusion of castor oil was 5 hours, and that of its derivatives was 3 hours. The maximum yield in sebacic acid of 68.8%, 77.7%, 80.1%, 78.6% can be obtained by using castor oil, methyl ricinoleate, sodium ricinoleate and ricinoleic acid as the raw material, respectively. High purity of sebacic acid was confirmed by GC and melting point analysis. ICP‐OES results illustrated that the content of Pb in sebcic acid was less than 1 mg kg−1. Separating glycerol from castor oil was beneficial for alkali fusion, by which, the yield of sebacic acid was increased of approximately 10%, and the reaction time was reduced from 5 to 3 hours. This study provided guiding significance for the future industrial production of sebacic acid.
A green
and environmentally friendly route of no thinning agent
was designed to prepare sebacic acid. Sodium ricinoleate was selected
as the raw material to carry out solid-phase cleavage in a tubular
furnace. The reaction parameters including catalyst, ratio of sodium
ricinoleate/KOH, reaction time, reaction temperature, and absolute
pressure were optimized to obtain a high yield of sebacic acid. A
satisfactory yield (70.2%) of sebacic acid was received in the presence
of 1% catalyst (Fe
2
O
3
) by weight (w/w), with
5:4 (w/w) ratio of sodium ricinoleate/KOH at 543 K under the absolute
pressure of 0.09 MPa in 60 min. Sebacic acid was identified by gas
chromatography analysis, and the purity (98.1%) of the product was
further assessed by its melting point (306.3 K). Alkaline enhancement
generates a better cracking effect. The yield of sebacic acid can
be improved by a certain absolute pressure as a result of avoiding
oxidation of sodium ricinoleate as well as reducing the residence
time of hydrogen.
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