Melting lowering

The order of melting transitions for the diphenyhnethane bismaleimides is surprising (Table 6) because the 4,4 -MDA-BMI melts lower (155—157°C) than the 3,3 -MDA-BMI. The tetra alkyl-4,4-MDA-BMI also melts around 150°C. The BMI based on the isomeric diphenylindane diamine (24) is very low melting because it is a complex blend of various isomers. 

A material which melts lower than the solid state reaction temperature, dissolves one or more of the components and allows material transport to the reaction zone, without entering into the solid state reaction. Preferably, the end-product should be insoluble in the flux". 

If the crude product melts lower, it contains too much tribromoaniline to permit satisfactory purification. Recrystallization effects no separation repeated fractional steam distillation is very slowly effective. 

Figure 7 Comparison of melt structure factor and single-chain structure factor for PB (upper panel, calculated as scattering from the united atoms only) and a bead-spring melt (lower panel, in Lennard-Jones units).

Chemistry. Mabery showed early in this century that paraffin wax consists mainly of normal paraffins of C23H48 to C29HM (54) This work has been amply substantiated by combined fractional distillation and fractionations (11, 26, 62, 71) and recently by urea adducting (128). Most investigators also find that commercial products contain small amounts of naphthene-containing and possibly branched-paraffin molecules (65,69-71). These types of molecules melt lower than the normal paraffins for a given boiling point. They have been called soft waxes (11, 70). 

The residual oxygen present in a copper melt can be removed by equilibrating the melt with a H20-H2 gas mixture. It is desired to keep the oxygen concentration in the copper melt lower than 0.001 wt% at 1,200°C. Calculate the ratio of H20 to H2 in the gas mixture which is in equilibrium with 0.001 wt% oxygen in the melt. The following data are given ... 

If all the acetic acid is not removed the product melts lower, ca. 138-139°... 

Note that we have reversed the temperature gradient within the furnace in 4.2.22. and that the top is cooler then the bottom, where the melt is first formed. In other variations of the Kyropoulos method, we raise the melt through the freezing point of the melt, by raising it past the baffles of the furnace. Another possible method is one where we use a single- zone fiimaee, stabilize the melt, lower the fumaee temperature to ineipient... 

DSC Differential scanning calorimetry, measurement melting temperatures, glass transition temperature and heat of melting lower temperature range than DTA. 

Injection molding. High moisture concentrations in thermoplastics that are injection molded can result in nozzle drool, foamy melt, lower melt viscosity, flow lines and silver streaks in the gate area, rough or scaly part surface, voids in the part, poor dimensional control, and reduced mechanical properties. 

Extrusion. The effects of excess moisture during extrusion may include a foamy melt, lower melt viscosity, bubbles in the extrudate, surging that results in arrow heads and wave forms in the extrudate, surface roughness, and reduced mechanical properties. 

Accumulation of metallic melts Lower spacer grid... 

The purposes of this study were to determine what chemical and physical structures are present in polyepichlorohydrin and to correlate these structures with the crystallization rates observed microscopically and dilatometrically. Crystallization rates were shown to be an extremely sensitive way of characterizing these polymers. For example, the study revealed that the crystalline polyepichlorohydrins examined consisted of isotactic sequences that can crystallize as two different kinds of spheru-lites, arbitrarily called Type I and Type II. The two types can cocrystallize. The polymers that crystallize most rapidly and that have the highest melting temperature have some optical activity. Their films contain predominantly Type II spherulites. Polymers that contain Type I spherulites melt lower and show little or no optical activity. These polymers are racemic mixtures. 

Figure 2. Efficient mixing of steel melt lower and upper voliunes by 3 DPP purging bricks...

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