Melting crystallization temperatur

The pressure effect on the melting/crystallization temperature of an MDPE sample, in the pressure range from 50 to 200 MPa, is illustrated in Figure 5. The isobaric temperature scans were performed at a rate of 0.833 mK s either in ascending or... 

Figure 5 Heat flow curves obtained on heating and cooling at a rate of0.833 mK s for the mercury-pressurized MDPE. The base lines were shifted for the sake of clarity on the pressure effect on the melting/crystallization temperatures...

Figure 6 Pressure effect on the temperature-induced and gas-assisted melting of tetracosane and PVDF (for more details and explanations, see refs. 26 and 29) (al) and (a2) heat rate evolution during fusion in the presence of supercritical CH and C 2 2 (VF), respectively (bl) fluid phase equilibria in the tetracosane/methane system and (b2) partial p—T phase diagram for the PVDF-VF and PVDF-N2 systems. Note the depression in the melting/crystallization temperatures in the pressure range up to 30 MPa for the tetracosane/CH and PVDF/VF systems...

C), it has been observed that its crystallization from the melt is enhanced [103-106], Melt crystallized polymers nucleated with n-s polymer-CD-ICs crystallize more rapidly, evidence greater levels of crystallinity, higher melt crystallization temperatures, and semicrystalline morphologies characterized by crystals which are smaller and more uniformly distributed than in un-nucleated pure bulk samples. 

Water whose melting/crystallization temperature and enthalpy of melting/ crystallization are not significantly different from those of normal (bulk) water is called freezing water. Those water species exhibiting large differences in transition enthalpies and temperatures, or those for which no phase transition can be observed calorimetrically, are referred to as bound water. It is frequently impossible to observe crystallization exotherms or melting endotherms for water fractions very closely associated with the polymer matrix. These water... 

Halloysite in an amount of about 0.01 to about 2 wt% increased the melt-crystallization temperature increased by at least 1 to 3°C compared to the polyethylene composition that does not contain the nucleating agent."... 

Depending upon the melt crystallization temperature 1, 2 or 3 melt endotherms occur (Fig. 28). At large supercooling, crystallization from the melt produces a small melt endotherm just above 7, presumably due to secondary crystallization of melt trapped within the spherulites... 

Fig. 13 Heat flux thermograms obtained under different pressures from 50 to 200 MPa during isobaric T scans at 0.833 mK s on heating downward exothermic peaks) and cooling upward endothermic peaks) for a Hg-pressurized MDPE sample. The base lines are shifted for the sake of clarity to show the effect of pressure on melting/crystallization temperatures...

Melt-crystallization temperature measured from DSC traces at a cooling rate of 10 °C/min. 

Sun and Woo [69] showed the optical microscopy results for SPS melt-crystalhzed at different temperatures. At lower temperatures polygon-shaped spherulites with an average size of 20 pm are observed. As melt crystallization temperature increases, the spheruhtes became coarser and turn to a sheaf-like pattern. 

Figure 9.6 depicts the optical micrographs showing tiny spherulites of SPS melt-crystallized at (a) 230 and (b) 260 °C, which contained only the a crystal. Both optical microscopy results confirmed that the crystallization kinetics of the a-crystal SPS is of a heterogeneous nucleation, which remained so regardless of the melt crystallization temperature [78]. By contrast. Figure 9.7 shows the optical micrographs for the spherulites of SPS melt-crystalhzed at (a) 230 and (b) 260 °C, which contained only p crystal [78]. 

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