Crystallizers temperatures for

Other crystallization parameters have been determined for some of the polymers. The dependence of the melting temperature on the crystallization temperature for the orthorhombic form of POX (T = 323K) and both monoclinic (T = 348K) and orthorhombic (T = 329K) modifications of PDMOX has been determined (284). The enthalpy of fusion, Aff, for the same polymers has been determined by the polymer diluent method and by calorimetry at different levels of crystallinity (284). for POX was found to be 150.9 J/g (36.1 cal/g) for the dimethyl derivative, it ranged from 85.6 to 107.0 J/g (20.5—25.6 cal/g). Numerous crystal stmcture studies have been made (285—292). Isothermal crystallization rates of POX from the melt have been determined from 19 to —50 C (293,294). Similar studies have been made for PDMOX from 22 to 44°C (295,296). 

Figure 13 Top, plot of linear growth rates of polyfethylene adipate) spherulites as a function of crystallization temperature for indicated molecular weight fractions. Spherulites shown correspond to the indicated range of temperatures. (A) Crystallization at the lower temperature range (B) at intermediate temperatures (C) crystallization at high temperatures. Reproduced with permission from Ref. [216]. Copyright 1956,...

Figure 3 shows a plot of the volume normalized nucleation time constant as a function of isothermal crystallization temperature for PEO droplets, taken from the work of Massa and Kalnoki-Veress [84]. As expected, droplets of different volumes have the same value of r V. The inset in Fig. 3 is a plot consistent with classical nucleation theory (see Eqs. 1, 4) only the last four data points correspond to the work of Massa and Kalnoki-Veress. The first... 

Fig. 4 Reported dynamic crystallization temperatures for PEO isolated spheres as a function of their volume (bottom x-axis) and diameter (top x-axis). The inset shows dynamic (symbols with vertical bars) and isothermal crystallization (vertical dashed bars) temperature ranges for PEO spheres, see text...

Fig. 5 Schematic plot showing reported crystallization temperatures for PEO in the bulk and as a component of block copolymers of varying compositions. The morphology of the PEO block is indicated on the x-axis. The filled bars are for data where isothermal crystallization measurements were performed and Avrami indexes of 1 or less were reported. The horizontal lines indicate the maximum temperature range that can be associated with PEO homogeneous nucleation, see text...

Fig. 9 Inverse of the crystallization half-time as a function of isothermal crystallization temperature for PCL11 homopolymer and for the PCL block of the indicated copolymers. All experiments were performed after the PPDX block had been previously crystallized until saturation. Solid lines are fits to the Lauritzen and Hoffman theory. (From [103]. Reproduced with permission of the Royal Society of Chemistry)...

Fig. 19 Avrami index as a function of crystallization temperature for PS-b-PE-fr-PCL and PE-fc-PS-fc-PCL triblock copolymers. (Reprinted from [94] with permission from Elsevier)...

The paraffins in diesel fuel can vary in molecular weight, concentration, and crystallization temperature. For this reason, fuels with similar physical properties may behave differently at low temperatures. This difference in behavior can be related to the low-temperature properties of the fuel paraffins present. 

From Figure 6 it is clear that whatever is crystallization temperature, 80°C or 100°C, the crystallization time should not excess 4 days. After this delay, the amorphisation of the material is completely reached, the value of the specific surface area drops sharply and no homogeneous pore size distribution is obtained. Lower crystallization temperatures, for example 60°C, should be studied. It should be noted that for a given molar ratio of decane/TMB the variation of crystallization temperature and time can lead to the formation of both MCM-41 and MCM-48 We would like to show here only the effect of crystallization temperature and time on the formation of mesoporous materials. We neglect at the moment which kind of mesoporous materials is formed at a given crystallization temperature and time This will be discussed in the following section. 

Fig. 22 Ratio of growth rates Gioo/Gno vs. crystallization temperature for extended-chain crystals of Ciggfbgg from 2% (w/v) solution in octacosane (diamonds) and for linear polyethylene from 0.05% solutions in hexane (squares). The polyethylene crystal at Tc = 70.0 °C and the C198H398 crystals above Tc = 110 °C are non-truncated lozenges these form for any Guo/ cos( /2) > G100, where cp/2 = tan 1(flo/ o) and ao, b0 are unit cell parameters (cf Fig. 10). Data for PE are from [32] (from [45])...

Fig. 24 Step initiation rate i (open symbols) and step propagation rate v (solid symbols) on the 100 faces as a function of crystallization temperature for n-C246H494 crystals growing from a 4.75% octacosane solution. Key squares, extended chain triangles, folded-chain growth (from [29])...

Figure 4 Dependence of the initial sticking coefficient vs. crystal temperature for Ag(l 0 0) and Ag(l 1 0). The curves are normalised to the value at T = 100 K for an easier comparison. For Ag( l 0 0) desorption prevails and S0 drops above T = 170 K, when the lifetime of the admolecules becomes shorter than the time constant of the uptake experiment (typically 0.3 sec). On Ag(l 1 0), on the contrary, S0 decreases smoothly with T, suggesting that dissociation must take place also at terrace sites. The values of the initial sticking coefficient of 02/Ag(l 00), estimated from the intensity of the 0/Ag(l 00) vibration at 30meV, [71], is reported in the inset for 200 K < T < 400 K. The increase with 74 s attributed to the thermal generation of active sites, identified with kinks at closed packed steps.

FIgyre 2.16 Variation of melting temperature with crystallization temperature for (O) poly(8-caprolactone) and ( ) poly(E-caprolactone) in a blend with poly(4-hydroxystyrene) (85% weight fraction of PCL). (From Ref. 15.)... 

Isothermal crystallization of the oil or fat was monitored by a Perkin Elmer DSC 7 differential scanning calorimeter. Sample sizes range from 5 to 10 mg. The oil sample is heated to a temperature of 80°C at a heating rate of 5°C/min from ambient and held at that temperature for at least 10 min in order to totally erase all past crystallization memories. The sample was then cooled at a rate of 5°C/min until the desired crystallization temperature had been reached. The sample temperature was then maintained at this crystallization temperature for 2 h to monitor the complete crystallization behavior of the sample. Partial areas under the thermal curve were determined by means of the Perkin Elmer Pyris partial area analysis software. 

Table 11-2 shows the freeze crystallization cycles for the study. Three different freeze crystallization temperatures, — IO C, — 2() C, and — 30°C, and three different levels of acetone, 10vol%, 20 vol%, and 30 vol%, were studied. The output variables were the degree of crystallization of imipenem products and the percentage of the liquid phase at the freeze crystallization temperature. For the aging time of stage 3, a value of 99.95 hours was shown in order to hold the freeze dryer shelf temperature at —40°C overnight. 

From the latter (Eq 3.49), the homogeneous crystallization temperature for each polymer could be estimated in a simple way. 

Fig. I show the DTA curves for LZS parent glass. The endothermic base line shift at 500°C indicates the glass transition temperature and the exothermic peak at about 680°C is a crystallization temperature for this system. Normally speaking, nucleation temperature was about 50°C above the transition temperature. Because the anneal temperature was 500°C, which was very close to the nucleation temperature, so the one-step heat-treatment was adopted.

Figure 2. Variation of melting temperature with crystallization temperature for atactic isotactic (O),and syndiotactic (l ) PPBA...

FIGURE 4 The rate of crystallization as a function of crystallization temperature for PHBV = 0 °C, = 146 °C), the solid circles correspond to Arrhenius equation, the... 

Figure7.11 illustrates the irreversible behavior ofthe same TCB and polyethylene, but under nonequilibrium conditions. The DSC data were collected after quenching to 354 and 388 K for crystallization. Comparing with Fig. 7.10 shows reasonable agreement for TCB. For polyethylene, crystallization at the higher temperature, 378 K, raises the eutectic and melting temperatures relative to crystalUzation at 354 K. The coohng traces, in contrast, show even lower crystallization temperatures for the polymer and at higher concentration, the TCB phase diagram is also affected. It is of particular interest that both the eutectic temperatures and the eutectic concentrations...

---