Formation and Properties of Thermosetting and High TgSystems

1989 ◽  
Vol 154 ◽  
Author(s):  
John K. Gillham
Keyword(s):  
Material Properties ◽  
Point Of View ◽  
Reaction Conditions ◽  
Ttt Diagram ◽  
Temperature Transformation ◽  
Polymeric Glasses ◽  
Generalized Time

AbstractA review of research in the author's laboratory on the conversion of reactive liquids to amorphous polymeric glasses is presented. Inter-relationships between reactants, reaction conditions, and subsequent material properties of thermosetting and high Tg polymers are discussed from the point of view of a generalized time-temperature-transformation (TTT) diagram.

scholarly journals The Effect of Reaction Conditions and Presence of Magnesium on the Crystallization of Nickel Sulfate

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1485
Author(s):  
Ina Beate Jenssen ◽  
Oluf Bøckman ◽  
Jens-Petter Andreassen ◽  
Seniz Ucar
Keyword(s):  
Initial Conditions ◽  
Nickel Sulfate ◽  
Industrial Process ◽  
Point Of View ◽  
Reaction Conditions ◽  
Valuable Metals ◽  
Electric Vehicle Battery ◽  
Temperature Transformation ◽  
Solid Phases ◽  
Effects Of Temperature

Recycling of valuable metals such as nickel is instrumental to meet the need from the dramatic increase in electric vehicle battery production and to improve its sustainability. Nickel required in the battery manufacture can be recovered from the hydrometallurgical industrial process streams by crystallization of nickel sulfate. Here, crystallization of nickel sulfate is studied from an industrial point of view, investigating the effects of temperature, seeding and presence of magnesium on the formation of various solid phases for the evaluation of their potential influence on the process design. Results showed that the precipitating phase was dictated both by seed amount and reaction temperature. Transformation of metastable phases both in suspension and in a dry state was observed over time. Presence of magnesium was shown to promote formation of NiSO4·7H2O in solution and increased its stability in a dry form. In their dry state, nickel sulfate that was formed in the absence of magnesium transformed towards α-NiSO4·6H2O, whereas those precipitated in the presence of high magnesium concentrations transformed towards β-NiSO4·6H2O, indicating that magnesium inhibited the phase transformation towards α-NiSO4·6H2O. Knowledge about various solid phases of varying crystal morphology and stability can be used as input to decisions for the best suited solid product type and how this relates to the initial conditions of the sidestreams.

Time-temperature-transformation (TTT) diagram of caustic calcined magnesia

CIM Journal ◽  
2015 ◽  
Vol 6 (1) ◽  
pp. 42-50 ◽  
Author(s):  
K. Ebrahimi-Nasrabadi ◽  
M. Barati ◽  
P. W. Scott
Keyword(s):  
Ttt Diagram ◽  
Temperature Transformation

scholarly journals Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. % Ga

2008 ◽  
Vol 1104 ◽  
Author(s):  
Jason R Jeffries ◽  
Kerri J. M. Blobaum ◽  
Mark A. Wall ◽  
Adam J. Schwartz
Keyword(s):  
Ttt Diagram ◽  
Optimal Conditioning ◽  
High Temperature Anneal ◽  
Conditioning Treatment ◽  
Conditioning Temperature ◽  
Δ Phase ◽  
Transformation Mechanisms ◽  
Temperature Transformation ◽  
Underlying Mechanisms ◽  
Kinetics Of

AbstractThe gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable δ phase to the gallium-containing, monoclinic α′ phase near -100 °C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation (TTT) diagram, where two nose temperatures anchoring an upper- and lower-C describe minima in the time for the initiation of transformation. The underlying mechanisms responsible for the double-C behavior are currently unresolved, although recent experiments suggest that a conditioning treatment—wherein, following an anneal at 375 °C, the sample is held at a sub-anneal temperature for a period of time—significantly influences the upper-C of the TTT diagram. As such, elucidating the effects of the conditioning treatment upon the δ⟶α′ transformation can provide valuable insights into the fundamental mechanisms governing the double-C kinetics of the transition. Following a high-temperature anneal, a differential scanning calorimeter (DSC) was used to establish an optimal conditioning curve that depicts the amount of α′ formed during the transformation as a function of conditioning temperature for a specified time. With the optimal conditioning curve as a baseline, the DSC was used to explore the circumstances under which the effects of the conditioning treatment were destroyed, resulting in little or no transformation.

General procedures in chain-growth polymerization

2004 ◽  
Author(s):  
Najib Aragrag ◽  
Dario C. Castiglione
Keyword(s):  
Free Radical ◽  
Ring Opening ◽  
Point Of View ◽  
Polymerization Process ◽  
Undergraduate Teaching ◽  
Chain Growth ◽  
Reaction Conditions ◽  
Growth Processes ◽  
Reagent Purity ◽  
Step Growth

This chapter is intended to provide a general introduction to the laboratory techniques used in polymer synthesis, by focusing on some relatively well-known polymerizations that occur by chain-growth processes. In this way some of the more commonly used procedures in polymer chemistry are described. Due to the nature of the intermediates produced, such as free radicals, carbanions, carbocations, together with a range of organometallic species, the techniques often involve handling compounds in the complete absence of oxygen and moisture. Because of this the best results may require quite sophisticated equipment and glassware; however, it is our intention to show that the general procedures are accessible to any reasonably equipped laboratory, and indeed some of the techniques are suitable for use in an undergraduate teaching laboratory. Chain-growth polymerization involves the sequential step-wise addition of monomer to a growing chain. Usually, the monomer is unsaturated, almost always a derivative of ethene, and most commonly vinylic, that is, a monosubstituted ethane, 1 particularly where the growing chain is a free radical. For such monomers, the polymerization process is classified by the way in which polymerization is initiated and thus the nature of the propagating chain, namely anionic, cationic, or free radical; polymerization by coordination catalyst is generally considered separately as the nature of the growing chain-end may be less clear and coordination may bring about a substantial level of control not possible with other methods. Ring-opening polymerizations exhibit many of the features of chain-growth polymerization, but may also show some of the features expected from stepgrowth polymerizations. However, it is probably fair to say that from a practical point of view the techniques involved are rather similar or the same as those used in chain-growth processes and consequently some examples of ring-opening processes are provided here. It is particularly instructive to consider the requirements of chain-growth compared to step-growth processes in terms of the demands for reagent purity and reaction conditions.

Synthetic and Mechanistic Studies on 2,3-Dihydrobenzo[b][1,4]-oxaselenines Formation from Selenocyanates

Synthesis ◽  
2020 ◽  
Vol 52 (11) ◽  
pp. 1643-1658
Author(s):  
Sergio H. Szajnman ◽  
Juan B. Rodriguez ◽  
María N. Chao ◽  
Mauricio Cattaneo ◽  
Jonathan Sanchez Gonzalez ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Aromatic Ring ◽  
Relevant Information ◽  
Point Of View ◽  
Cyclization Reaction ◽  
Mechanistic Studies ◽  
Reaction Conditions

An expedient preparation of selenium-containing hetero­cycles via an m-chloroperbenzoic acid-mediated seleno-annulation starting from selenocyanate derivatives is described. In spite of its significance, this cyclization reaction is virtually understudied not only from the point of view of its scope, but also from the mechanistic aspects associated to this remarkable transformation. In this sense, several selenocyanate and thiocyanate derivatives bearing an aromatic ring were evaluated as substrates under different reaction conditions of this interesting cyclization yielding important insights on its scope as well as relevant information on the reaction mechanism.

An Example of Ketone Olefination via Praseodymium-Mediated Barbier Reaction in the Presence of Diethyl Phosphite

Synlett ◽  
2019 ◽  
Vol 30 (12) ◽  
pp. 1437-1441
Author(s):  
Xu yan Cao ◽  
Fei Huang ◽  
Songlin Zhang
Keyword(s):  
Double Bond ◽  
Bond Formation ◽  
Point Of View ◽  
Diethyl Phosphite ◽  
Reaction Conditions ◽  
One Pot ◽  
Type Reaction ◽  
Mild Conditions ◽  
Allyl Halides ◽  
Barbier Reaction

The first example of carbon double-bond formation via praseodymium-mediated Barbier type reaction of ketones and allyl halides in the presence of diethyl phosphite is reported. The reaction is highly α-regioselective and conveniently carried out under mild conditions in a one-pot fashion. From a synthetic point of view, a series of conjugated alkenes were obtained in moderate to good yields in this one-pot reaction with practical reaction conditions.

Neodymium-Promoted Highly Selective Carbon–Carbon Double Bond Formation of Ketones with Allyl Halides in the Presence of Diethyl Phosphite

Synthesis ◽  
2020 ◽  
Vol 52 (22) ◽  
pp. 3446-3451
Author(s):  
Songlin Zhang ◽  
Dengbing Xie ◽  
Yiqiong Wang ◽  
Bo Yang
Keyword(s):  
Double Bond ◽  
Bond Formation ◽  
Point Of View ◽  
Diethyl Phosphite ◽  
Reaction Conditions ◽  
One Pot ◽  
Mild Conditions ◽  
Carbon Double Bond ◽  
Allyl Halides ◽  
First Time

The carbon–carbon double bond formation via neodymium-mediated Barbier-type reaction of ketones and allyl halides in the presence of diethyl phosphite is reported for the first time. The reaction is highly α-regioselective and was conveniently carried out under mild conditions in a one-pot fashion. From a synthetic point of view, a series of conjugated alkenes were obtained in moderate to good yields in this one-pot reaction with feasible reaction conditions.

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