Exothermic interaction

A commercially important example of the special case where one monomer is the same in both copolymers is blends of styrene—acrylonitrile, 1 + 2, or SAN copolymers with styrene—maleic anhydride, 1 + 3, or SMA copolymers. The SAN and SMA copolymers are miscible (128,133,144) so long as the fractions of AN and MA are neatly matched, as shown in Figure 4. This suggests that miscibility is caused by a weak exothermic interaction between AN and MA units (128,133) since miscibility by intramolecular repulsion occurs in regions where 02 7 can be shown (143) by equation 11. 

Phosphorus trichloride detonates in contact with nitric acid. The same may occur during the highly exothermic interaction between this chloride and sodium peroxide. 

A pyrotechnic mixture of aluminium powder with potassium perchlorate, barium nitrate, potassium nitrate and water exploded after 24 h storage under water. Tests revealed the exothermic interaction of finely divided aluminium with nitrate and water to produce ammonia and aluminium hydroxide. Under the conditions prevailing in the stored mixture, the reaction would be expected to accelerate, finally involving the perchlorate as oxidant and causing ignition of the mixture. 

Bromates, chlorates or iodates ignite in contact with phosphonium iodide at ambient temperature if dry, or in presence of acid to generate bromic acid, etc. Ignition also occurs with nitric acid, and reaction with dry silver nitrate is very exothermic. Interaction with antimony pentachloride at ambient temperature proceeds explosively. 

During preparations for blasting the sulfide mineral copper pyrites, ammonium nitrate-based blasting cartridges exploded prematurely in the blast holes. This was attributed to exothermic interaction of acid ground-water with the sulfide-oxidant combination. 

Brandstrom, A., Acta Chem. Scand., 1951, 4, 1608-1610 Air must be excluded dining exothermic interaction of ethanol with sodium finely dispersed in hydrocarbons to avoid the possibility of hydrogen-air mixture explosions. 

Cotton wool sprinkled with the peroxide (used in guard tubes) will ignite a few s after exposure to moist carbon dioxide. Exothermic interaction of sodium peroxide and carbon dioxide heats the cotton which then ignites in the liberated oxygen [1], Cotton contaminated with peroxide should not be stored under any circumstances as it may ignite with atmospheric carbon dioxide [2],... 

The first two kinds of interactions are endothermic, requiring an input of energy to spread apart solvent molecules and to break apart crystals. Only the third interaction is exothermic, as attractive intermolecular forces develop between solvent and solute particles. The sum of the three interactions determines whether AHsoin is endothermic or exothermic. For some substances, the one exothermic interaction is sufficiently large to outweigh the two endothermic interactions, but for other substances, the opposite is true (Figure 11.4). 

Volume of Mixing. In general terms, exothermic interaction effects tend to diminish the volume of a mixture whereas entropic effects act in the opposite way. For miscible polymers, therefore, one expects a negative volume of mixing. This has been confirmed experimentally for different miscible polymers with LCST behavior, e.g. for miscible 50/50 blends of polystyrene and poly(2-chloro-styrene) the volume change AVM/V at 130°C has been reported to be about... 

In the case of chemisorption this is the most exothermic process and the strong molecule substrate interaction results in an anchoring of the headgroup at a certain smface site via a chemical bond. This bond can be covalent, covalent with a polar part or purely ionic. As a result of the exothermic interaction between the headgroup and the substrate, the molecules try to occupy each available surface site. Molecules that are already at the surface are pushed together during this process. Therefore, even for chemisorbed species, a certain surface mobility has to be anticipated before the molecules finally anchor. Otherwise the evolution of ordered structures could not be explained. 

A brief report has described the formation of the 1,2,4-thiadiazole ring system by the reaction of phosphorus tricyanide and sulfur dichloride their spontaneous exothermic interaction yields 3,5-dichloro-l,2,4-thiadia-zole, together with cyanuric chloride and other products.251... 

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