Melting point, crystalline

Crystalline polar polymers and solvents It has already been pointed out that at temperatures well below their melting point crystalline non-polar polymers will not interact with solvents, and similar considerations can apply to a large number of polar crystalline polymers. It has, however, been possible to find solvents for some polar, crystalline polymers such as the nylons, polyvinyl chloride and the polycarbonates. This is because of specific interactions between polymer and solvent that may often occur, e.g. by hydrogen bonding. 

The polypropylene so obtained has a high molecular weight and is crystalline.The proportion of isotactic polymer, determined by extracting with heptane for 10 h in a Soxh-let apparatus, is 98.5%. Isotactic polypropylene shows similar solubility behavior to polyethylene, but has a higher melting point (crystalline melting range 165-171 °C). 

Why is calcium fluoride, CaF2, a high-melting-point crystalline solid while stannic chloride, SnCl4, is a volatile liquid ... 

Melting point, crystalline, °C Specific gravity Refractive index nf15 Mold shrinkage, average, %... 

Of the commercially-available phenylene diamines tested, the N,N -diphenyl compound is an insoluble, high melting-point, crystalline solid, whereas the unsymmetrically substituted N-phenyl-N -(2-octyl) derivative is a liquid, readily miscible... 

It is customary to say that under the same external conditions all specimens of a particular substance have the same specific physical properties (density, hardness, color melting point, crystalline form, etc.). Sometimes, however, the word substance is used in referring to a material without regard to its state of aggregation for example, ice, liquid water, and water vapor may be referred to as the same substance. Moreover, a specimen containing crystals of rock salt and crystals of table salt may be called a mixture, even though the specimen may consist entirely of the one chemical substance sodium chloride. This lack of definiteness in usage seems to cause no confusion in practice. 

The mono-phenols are liquids or low melting-point crystalline solids, while the poly-phenols are crystalline solids only. The mono-phenols... 

High-melting point crystalline salts will generally be the most stable, in contrast to amorphous or liquid/oil salt forms. Thus amorphous ethacrynic acid and amorphous sodium ethnacrynate are less stable than the crystalline forms. ... 

The first step involves analyzing solid salts for crystallinity and melting point. Crystalline salts are usually the most desirable, because they exhibit superior processing, handling, stability, and purification properties. Low-melting salts may be relegated to a lower-priority status at this point. 

High-molecular-weight poly (thiol esters) show fiber-forming properties. This section covers the available data concerning melting points, crystallinity, solubility, and stability of this class of esters, and compares them with polyesters and polyamides. Information about spectra is also reviewed. 

CX May appear as a colorless, low-melting point (crystalline) solid or as a liquid. It has a high vapor pressure, slowly decomposes at normal temperatures it has a disagreeable, penetrating odor. 

In order to decrease the stereochemical possibilities in the final product as a result of working with racemic modifications, the acid XLIX was resolved through the quinidine salt. Both forms of the acid were obtained and a similar series of reactions was carried out using the Zei orotatory /3-methyl-5-TO-nitrobenzoylaminovaleric acid. There was thus obtained optically active l-methyl-7-ketopyrrolizidine (XXXIII) which could not consist of a mixture of more than two forms. Like the product from the racemic acid, this was an oil. When treated with hydroxylamine, however, a single, pure optically active oxime was isolated. This proved to be identical in melting point, crystalline form as observed under the microscope, and specific rotation with retronecanone oxime, and the melting points of mixtures of the two compounds showed no depression. The picrates of the aminoketoximes obtained from natural and synthetic sources were also found to be identical and showed no depression of melting-decomposition point when mixed. Likewise, the picrolonates of the oximes were identical. 

These authors have used the technique of lamellar decoration [76] which enables detailed assessment of cheu-acteristic mesophase defects and texture on a much finer scale than previously possible with conventional electron-microscopy preparations. The defects and texture existing in the polymer melt state are first retained by thermal quenching of the polymer fluid to room temperature. The glassy LCP film is then annealed above its glass transition, but below the melting point. Crystalline lamellae grow perpendicular to the local chain axis and effectively decorate the molecular director... 

Differential Scanning Calorimetry (DSC) thermal transitions oxidation onset time and temperature, melting point, crystallinity... 

Polyesteresterketone is partially crystalline polymer the thermo-stability of which depends on glassing temperature (amorphosity) and melting point (crystallinity) and increases with immobilization of macromolecules. The strong valence bonds define the high thermo-stability and longevity of mechanical and electrical properties at elevated temperature. 

For cross-linking by y rays, see Section 21.2.1. Inspection of the Gr values shows that, although styrene can be graft-copolymerized onto poly(vinyl chloride), vinyl chloride cannot be grafted onto poly(styrene). In the first case, so many radicals are produced on the polymer chain that practically no homopolymerization occurs. Above the glass transition temperature (amorphous polymers) or the melting point (crystalline polymers), the Gr values of the polymer increase because of increased chain mobility. Thus different effects can be observed by varying the temperature. 

The BMI resin is a high melting point crystalline solid and when thermally cured, the resulting networks are very brittle. Bismaleimides are rarely used alone in the solid form. In most applications, reactive comonomers (eg vinyl and allyl... 

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