Paraffin, secondary crystallization

Secondary Crystallization of Paraffin Solidified on a Cooled Plane Surface... 

Procedure for Primary Crystallization of Molten Paraffin. After die crystallizer was dipped in molten paraffin for a finite time, it was quickly taken out from the molten paraffin and detached from the coolant line. Then the coolant within the crystallizer was drained, and the crystal layer formed on its wall surface was kept at 2 K. The primary crystallization conditions are summarized in Table 1. The coolant temperature at the inlet was varied from 274.2 to 304.8K. The thickness of solidified paraffin crusted on the crystallizer surface was measured at 60 different points, and the mean value of the measurements was used for the estimation of the layer thickness L at a finite dipping time. When the observation of these items was over, the crystal layer was removed from the crystallizer and cut into about four pieces of 12 x 15x3-5 mm in size for the secondary crystallization treatment. 

Secondary Crystallization of Solidified Paraffin. The cut pieces were set in a plastic case in order to avoid direct contact between the layer surface and the case, and stored at a finite temperature within 0.1K by the thermostat bath. After the pieces were kept for a given time, they were taken out from the case and used for X-ray measurement to examine the structural change of the paraffin layer during the progress of the secondary crystallization. When 5ie X-ray measurement was over, the samples were returned to their storage location and were kept at the same temperature. In all tests, the storage temperature was varied from 277.2 to 305.7K. 

For pure primary secondary explosives (except for border-line HE such as Ammonium Nitrate or Ammonium Perchlorate) dcr decreases as p0 increases until p0 approaches very close single crystal density when dcr may increase drastically. Thus if we limit ourselves to p0 < 0.9pcrySt, increases in p0 (according to Eq 8) should result in a greater sensitivity to impact. This is quite the opposite of what is found for shock initiation and will be examined more closely later on. At a fixed density, dcr increases as p. increases (see A B, p 90). This increase is fairly pronounced at small p (<0.2 mm) but levels off becomes almost asymptotic at large p (>0.4mm, except for cast TNT or TNT with 1% paraffin oil). Thus an increase in p, as expected, leads to a decrease... 

The primary goal of solvent dewaxing is to make the pour and cloud point requirements. This is accomplished by paraffin separation by solubility of non-paraffins in cold solvent, fractional crystallization, and filtering the solid paraffins from the slurry. This may be done in ketone units which use MEK, MEK/MIBK, MEK/Toluene solvents or in propane units which use liquefied propane as the solvent. Secondary effects include viscosity increase, density increase, sulfur increase, and reduction in VI. 

---