Chemical-exchange reactions during the compaction of glass batches

1986 ◽  
Vol 43 (2) ◽  
pp. 47-50
Author(s):  
V. G. Kalygin ◽  
V. I. Nazarov ◽  
O. S. Chekhov ◽  
B. G. Varshal ◽  
L. L. Mirskikh
Keyword(s):  
Chemical Exchange ◽  
Exchange Reactions

scholarly journals Chemical Interaction-Induced Evolution of Phase Compatibilization in Blends of Poly(hydroxy ether of bisphenol-A)/Poly(1,4-butylene terephthalate)

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1667
Author(s):  
Jing Liu ◽  
Hsiang-Ching Wang ◽  
Chean-Cheng Su ◽  
Cheng-Fu Yang
Keyword(s):  
Bisphenol A ◽  
Chemical Interaction ◽  
Chemical Exchange ◽  
Hydroxyl Group ◽  
Random Copolymers ◽  
Exchange Reactions ◽  
Butylene Terephthalate ◽  
Alcoholysis Reaction ◽  
Immiscible Blend ◽  
Hydroxy Ether

An immiscible blend of poly(hydroxy ether of bisphenol-A) (phenoxy) and poly(1,4-butylene terephthalate) (PBT) with phase separation was observed in as-blended samples. The compatibilization of phenoxy/PBT blends can be promoted through chemical exchange reactions of phenoxy with PBT upon annealing. The annealed phenoxy/PBT blends had a homogeneous phase with a single Tg that could be enhanced by annealing at 260 °C. Infrared (IR) spectroscopy demonstrated that phase homogenization could be promoted by annealing the phenoxy/PBT blend, where alcoholytic exchange occurred between the dangling hydroxyl group (–OH) in phenoxy and the carbonyl group (C=O) in PBT in the heated blends. The alcoholysis reaction changed the aromatic linkages to aliphatic linkages in the carbonyl groups, which initially led to the formation of a graft copolymer of phenoxy and PBT with an aliphatic/aliphatic carbonyl link. The progressive alcoholysis reaction resulted in the transformation of the initial homopolymers into block copolymers and finally into random copolymers, which promoted phase compatibilization in blends of phenoxy with PBT. As the amount of copolymers increased upon annealing, the crystallization of PBT was inhibited by alcoholytic exchange in the blends.

Recent 31 P n.m.r. studies of myocardium

1980 ◽  
Vol 289 (1037) ◽  
pp. 437-439 ◽  
Keyword(s):  
Mechanical Performance ◽  
Normal Values ◽  
Chemical Exchange ◽  
Exchange Reactions ◽  
Perfused Heart ◽  
Time Intervals ◽  
Non Invasive ◽  
Biochemical State ◽  
Perfused Hearts ◽  
Kinetics Of

Earlier work from this laboratory has concerned the possible use of phosphorus n.m.r. as a method to monitor, in a non-invasive manner, the biochemical state of the perfused heart as a function of its mechanical performance. We showed that a simulated coronary infarction could be detected by 31 P n.m.r. (Hollis et al 1978 a and that hypothermia and KC1 arrest could preserve the pH and the ATP levels at more nearly normal values than in a non-arrested heart during long periods (40 min) of ischaemia (Hollis et al . 1978 b ).More recently it was shown that multiple doses of KC1, given at intervals, were more effective in this respect than was a single dose (Flaherty et al . 1979). These studies essentially followed the kinetics of transitions of the heart between two or more distinct physiological states (i.e. normoxic and ischaemic, with or without KC1 arrest) by observation of the 31 P n.m.r. spectra at various time intervals over periods of up to 1 h. As described in detail and demonstrated in Dr Truman Brown’s contribution to these discussions, the rates of chemical exchange reactions occurring in a steady state can be measured by the techniques of saturation transfer in various biological systems, including perfused hearts.

Chemical Exchange Reactions in Blends of the Biodegradable Polyester with poly(hydroxy ether of bisphenol-A)

2014 ◽  
Vol 953-954 ◽  
pp. 1246-1249 ◽  
Author(s):  
Chean Cheng Su ◽  
Chern Hwa Chen ◽  
Neng Lang Shih ◽  
Yin Shuo Li
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Differential Scanning Calorimetry ◽  
Bisphenol A ◽  
Chemical Exchange ◽  
Exchange Reactions ◽  
Scanning Calorimetry ◽  
Butylene Succinate ◽  
Butylene Terephthalate ◽  
Before And After ◽  
Hydroxy Ether

Compatibilization via transreactions in blends of poly (butylene succinate-co-butylene terephthalate) [P(BS-co-BT)] with poly (hydroxy ether of bisphenol-A) (phenoxy) were investigated. Analyses were based on characterization using differential scanning calorimetry (DSC) and solid-state nuclear magnetic resonance (NMR). They revealed that the P(BS-co-BT)/phenoxy blend had a phase morphology that could be homogenized only following annealing at high temperatures. As-blended P(BS-co-BT)/phenoxy (50/50 composition) exhibited immiscible phases with two distinct Tgs, but the initially phase separated blends finally merged to form a homogeneous phase with a single Tgupon heating and annealing for 60 min at 280 °C. Chemical exchange reactions upon heat-annealing were likely to have caused the phase homogenization in the P(BS-co-BT)/phenoxy blend. NMR was performed on blend samples before and after they were heated to 280 °C, but the similarity of bonds made obtaining straight results difficult. Results of this study demonstrate phase homogenization can be brought only upon heat-annealing in the P(BS-co-BT)/phenoxy blend.

Nuclear magnetic resonance studies of ketone.BF3 complexes. I. Exchange reactions in methylene chloride solution

1968 ◽  
Vol 46 (12) ◽  
pp. 2147-2157 ◽  
Author(s):  
R. J. Gillespie ◽  
J. S. Hartman
Keyword(s):  
Chloride Solution ◽  
Methylene Chloride ◽  
Chemical Exchange ◽  
Exchange Process ◽  
Exchange Reactions ◽  
Methylene Chloride Solution ◽  
Donor Acceptor ◽  
Group 3 ◽  
Proton Resonances ◽  
Increasing Temperature

1H and 19F n.m.r. studies of BF3 adducts of some simple methyl ketones in methylene chloride solution have led to the following conclusions. (1) Only 1:1 adducts are formed which are not appreciably dissociated. (2) The down-field shifts of the proton resonances caused by complexation with BF3 are essentially independent of the ketone and depend only on the distance of the proton from the carbonyl group. (3) BF3 exchange is rapid on the n.m.r. time scale at room temperature, but the exchange process can be slowed sufficiently by lowering the temperature that separate signals due to free and complexed species can be observed. (4) Collapse of the 10B−11B isotope shift with increasing temperature showed that a second chemical exchange process, which exchanges fluorine among boron atoms, occurs in addition to the process of rapid breaking and re-forming of donor–acceptor bonds. A possible mechanism for this fluorine scrambling reaction is discussed.

scholarly journals The Effects of Acid Activation on the Thermal Properties of Polyvinylpyrrolidone and Organoclay Composites

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
F. Kooli
Keyword(s):  
Clay Mineral ◽  
Chemical Exchange ◽  
Basal Spacing ◽  
Activation Process ◽  
Acid Activation ◽  
X Ray Diffraction ◽  
Exchange Reactions ◽  
Thermal Stabilities ◽  
Stable Product ◽  
Acid Activated Clay

The thermal stabilities of polyvinylpyrrolidone-organoclays or organo-acid-activated clay composites prepared by chemical exchange reactions were assessed. The raw clay mineral was acid-activated prior to expansion by cetyltrimethylammonium surfactants. The acid activation process affected the intercalated amount of cetyltrimethylammonium cations in the resulting organoclays and, thus, the amount of polyvinylpyrrolidone in the composite. The content of cetyltrimethylammonium cations decreased with the extent of acid activation. The organophilic modification of the clay mineral was an important step in the intercalation of the polyvinylpyrrolidone molecules and, thus, in the expansion of the silicate sheets from 3.80 nm to 4.20 nm. The composites exhibited better crystalline order with intense reflections at lower angles. The thermal stability of organoclays, acid-activated clays, and composites was studied using thermogravimetric analysis andin situX-ray diffraction. The decomposition of intercalated surfactants occurred at lower temperatures relative to the neat surfactant salt, and the basal spacing of the organoclays (or acid-activated clays) shrunk to 2.0 nm at 215°C. However, the basal spacing of composites exhibited better stability and collapsed to 2.0 nm at 300°C. This type of material could offer an alternative stable product for engineering purposes in the design of new composites.

scholarly journals Variable-pressure dynamic NMR studies: effects of paramagnetic metal ions on NMR parameters in nonexchanging systems

1994 ◽  
Vol 72 (10) ◽  
pp. 2188-2192 ◽  
Author(s):  
Hideo D. Takagi ◽  
Kayoko Matsuda ◽  
Sen-Ichi Aizawa ◽  
Shigenobu Funahashi ◽  
Stephen D. Kinrade ◽  
...  
Keyword(s):  
Ligand Exchange ◽  
High Pressures ◽  
Activation Volume ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Variable Pressure ◽  
Exchange Reactions ◽  
Nmr Studies ◽  
Nmr Parameters ◽  
Paramagnetic Metal

The possible effects of paramagnetic relaxation on the apparent volumes of activation for exchange reactions in solution, as measured by NMR at high pressures, are considered. Two model paramagnetic systems that do not undergo ligand exchange on the NMR time scale were examined: tri(acetylacetonato)chromium(III) in various perdeuterated solvents, and tris(ethylenediamine)nickel(II) ion in ethylenediamine solvent. No pressure dependence was discernible up to 200 MPa for the chemical shifts of 1H (exemplifying nuclei of spin 1/2) in the Cr(III) complex, or of solvent 14N (representing quadrupolar nuclei) in the Ni(II)–ethylenediamine case. The line widths Δv1/2, however, were significantly dependent on pressure. For 1H in the Cr complex, the increase of Δv1/2 with pressure was less than expected from the theory of scalar interactions, and was small enough to imply that any contribution from this source to the observed volume of activation in exchanging systems may be neglected. For 14N in liquid ethylenediamine, the increase of Δv1/2 with pressure was significantly greater when a paramagnetic solute was present. Thus, before the observed Δv1/2 at a pressure P (in MPa) measured by the NMR of a quadrupolar nucleus can be used to obtain a chemical exchange rate for a paramagnetic solute, it should be reduced by an amount Δv1/20 exp{θ(P − 0.1)(ΔVV‡/RT + κ)}, where ΔVV‡ is the activation volume for viscous flow and κ the compressibility of the solvent, Δv1/20 is the linewidth at 0.1 MPa in the absence of chemical exchange, and θ is a scaling factor between 0 and 1. The factors Δv1/20 and θ(ΔVV‡/RT + κ) are obtainable from measurements with a chemically equivalent, nonexchanging, paramagnetic solute.

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