Melting thermograms

Also, after determining the temporal distribution of crystallization peaks in a complete isothermal experiment, the melting thermogram of a particular polymorph can be determined. First, the sample is remelted completely, and held to erase its thermal memory. Then, the isothermal crystallization process is repeated, but only up to the time at which the polymorph of interest has completely solidified (exothermic peak fully formed). A heating scan is then performed immediately (Kawamura, 1980, 1981). 

Fig. 1. Dynamic heating (melting) thermograms (5°C/min) for sesame oil, palm stearin, and blends of palm stearin in sesame oil at different proportions. Tm is the melting temperature of the triacylglycerides (TAG) with highest melting temperature (i.e., tri-pal mitin) (adapted from Ref. 9).

Figure 3.1 DSC melting and crystallisation thermograms of palm oil. For melting thermogram, sample was cooled to — 30°C at rate of 40°C/min, held for 10 mins and heated to 80°C at 5°C/min for cooling thermogram, sample was melted to 80°C and cooled to —30°C at 5°C/min. Lm low melting fraction, Hm high melting fraction.

Cooling and melting thermograms of palm olein are illustrated in Figures 3.4 and 3.5. In contrast to the thermograms of palm oil, those for palm olein reveal only a single broad crystallisation peak. This exotherm is generally sharper in... 

The crystallisation and melting behaviour of palm stearin depends on the composition. Figures 3.6 and 3.7 show the behaviour of different palm stearins. PMF shows crystallisation exotherms which overlap into several peaks, while its melting thermogram shows one main endotherm with a shoulder, finally melting... 

Figure 3.5 Melting thermograms of palm oleins. Sample was cooled to —30°C at rate of 40°C/min, held for 10 mins and heated to 80°C at 5°C/min.

A differential scanning calorimeter is used to obtain a solidification (or melting) thermogram, from which a pore size distribution can be extracted. By comparing the solidification and melting processes, thermoporometry can also be used to determine a thermodynamic pore shape factor, which varies generally from 1 (spherical pores) to 2 (cylindrical pores). 

Differential Scanning Calorimetry (DSC) of the PPTA/ sulfuric acid system was carried out in order to establish the melting behavior of the system. Samples (5-10 mg) were sealed in gold-coated aluminum pans under N, and cooled at 10 C/min to -150 C. Subsequently the samples were heated to 100 C at 10 C/min and the melting thermograms were recorded. 

Figure 7 Melting thermogram of chocolate mousse emul sions. (From Ref 31.)...

In the following discussion, the above phenomena will be illustrated with respect to morphology, thermal history, molecular-weight distribution and structure, by means of melting thermograms. 

Melting thermograms of numerous polyamides have been determined by Ke and Sisko 221) in a qualitative fashion to determine the effects of polymer composition on mdting points (Fig. 32). 

Exceptional about the behavior of this polymer is also the insensitivity in melting point with crystallization conditions. Samples crj tallized during heating at rates between 2 and 807min exhibit surpisingly similar melt thermograms (Fig. 35). 

An example of c(q)olymer melting in which both components are present in substantial fractions is illustrated in Fig. 40 for the inter-facial adipamide-sebacamide copolymer system. When the DTA-peak temperatures were plotted against copolymer composition, a phase diagram is obtained in which the eutectic melting point of 79° corresponds to a mole fraction of 70% sebacamide. With the exception of the eutectic, the copolymer melt thermograms showed multiple peaks, which... 

The melting endotherms of PHB, EPC, and their blends are shown in Fig. 4.1. Apparently, all the first melting thermograms (except for that of EPC) show a single peak characteristic of PHB. 

Figure 2. DSC melting thermograms for (a) linear, (b) 9.65, (c) 14.1, (d) 20.6, (e) 28.6 branches/1OOOC PE aystallized at different temperatures for 30 min. The melting scans were initiated at the crystallization temperatures with a rate of 2.5°C/min.

Figure 8.32 Schematic melting thermogram of a binary linear polyethylene blend. Drawn after data presented by Rego-Lopez ei al (1988).

Fig. 26 DSC melting thermograms of irradiated PVDF films from 0 to 1200 kGy (Reprinted with permission of Elsevier) [51]...

Figure 6 Differential scanning calorimetric melting thermograms of NIE and CIE but-terfat-canola oil blends, (a) Butterfat (b) 90 10 (c) 50 50. The shaded area represents the CIE blends.

Figure 10.13 DSC melting thermograms of ethylene-propylene copolymer (EPS 3.0 mol-% ethylene), propylene-(l-bu-tene) copolymer (BPS 7.6 mol-% 1-butene), and BPS/EPS 50/50 blend after isothermal crystallization in the range of 60-110°C (heating rate 10°C/min). Reprinted from Bartczak et al. [66], Copyright 2006, with permission from Elsevier.

Melting thermograms of Ny6/PP-AA blends with polyamide as dispersed phase, isothermally crystallized from the melt, revealed also the presence of melting peaks of Ny6 at temperatures lower than the usual melting temperature of a form (221 °C), indicating the existence of a considerable amount of y form crystals (215 C). No melting peak of /phase was observed for Ny6/iPP blends at any Ny6 content. 

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