Calorimetry melting temperature

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). 

Fig. 10. Differential scanning calorimetry of cellulose triacetate. Second heating at 20°C/min. glass-transition (T temperature = 177 " C crystallization on heating (T)/j) = 217 C melting temperature (Ta) = 289 C. To convert to cal, divide by 4.184.

We analyzed the embedded particles with differential scanning calorimetry to identify the property of polystyrene. As shown in Fig, 1, fhe embedded particles show a small peak around 100 °C, which is typical in atactic polystyrene [7]. It is desirable that embedding polymer has a similar melting tempeiature as the final polymer (polyethylene) because a big difference in the melting temperatures between the two polymers may cause a gel problem and poor mechanical properties. 

Table 2 Melting Temperatures and Enthalpies of Fusion for Compounds Suitable as Reference Materials in Differential Scanning Calorimetry...

Next, the thermal properties of the dye must be such that absorption of the laser energy will result in dye diffusion but not in decomposition. The melting temperature Tm, the latent heat of fusion, AH, and the specific heat for these dyes were determined by differential scanning calorimetry using a DuPont 990 Thermal Analyzer. The data are given in Table II. No thermal decomposition products for these dyes were detected upon heating to 600 °C for 20 msec. 

Fig. 8. Superheating of polyethylene extended chain crystals. Curves 1) at 421.7 K, 2) at 419.2, 3) at 417.7 K, 4) at416.7K, 5) at 414.7 K. The equilibrium melting temperature is 414.6 K. Drawn after Ref.40). "w is the weight fraction molten, obtained by isothermal calorimetry...

A study of two of the most prominent and widespread osmolytes, betaine and beta-hydroxyectoine, by differential scanning calorimetry (DSC) on bovine ribonu-clease A (RNase A) revealed an increase in the melting temperature Tm of RNase A of more than 12 K and of protein stability AG of 10.6 kj mol-1 at room temperature at a 3 M concentration of beta-hydroxyectoine. The heat capacity difference ACp between the folded and unfolded state was significantly increased. In contrast, betaine stabilized RNase A only at concentrations less than 3 M. When enzymes are applied in the presence of denaturants or at high temperature, beta-hydroxyectoine should be an efficient stabilizer. 

The melting temperature (Tm) of the biopolymer was determined from differential scanning calorimetry thermograms. The Tm value of the P (3HB) homopolymer was about 177°C and P (3HB) with 10% P(3HV) was about 150°C (Table l),but the Tm values of biopolymer extracted from E. coli HMS174 were about 166°C. The Tm of the sample was lower than that of the P (3HB) homopolymer, but higher than that of the P (3HB) with 10% P (3HV), because the P (3HV) content in the sample is only about 4.5% of the biopolymer produced. The PHV content in extracted biopolymer was low, the flexibility of extracted biopolymer was low, and different fermentation conditions should be investigated. 

Stratum corneum lipids and lanolin share an important physical characteristic in that they can coexist as solids and liquids at physiological temperatures.33 A differential scanning calorimetry thermogram of lanolin is similar to that of stratum corneum lipids, showing two broad (heterogenous) phase transitions with midpoint melting temperatures at 21.9 and 38.3°C.16 The lower temperature peak may represent the transition from a liquid crystal to a gel phase, which has also been described for lanolin alcohols.34... 

Teyssie and coworkers [86] studied the effect of macromolecular architecture on the lamellar structure of the poly(ethylene oxide) crystallizable arms in (poly tert-butyl styrene)(poly(ethylene oxide))2 [PtBuS(PEO)2] miktoarm stars by using SAXS and differential scanning calorimetry (DSC). The results were compared with the ones obtained on poly(tBuS-fe-EO) materials. At the same total molecular weight and composition the melting temperature, the degree of crystallinity and the number of folds of PEO chains were found to be lower for the branched samples. 

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