Crystallisation thermogram

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.

Figure 3.7 Crystallisation thermograms of palm stearins. Sample was melted to 80°C and cooled to —30°C at 5°C/min.

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... 

In a separate study, PCL (molecular weight 15,000) was blended with poly(L-lactide) (molecular weight 10,000) by casting from solutions in chloroform and drying under vacuum at 60 °C for 24 h. DSC scans of samples heated to 200 °C and quenched showed that the Tg of poly(L-lactide) overlapped with the Tj of PCL, which rendered detailed analysis of the thermograms and assessment of polymer-polymer miscibility difficult. However, the cold-crystallisation exotherm of pure poly(L-lactide), at 131 °C, was shifted in the blends containing more than 50 wt % poly(L-lactide) to about 95 "C this shift was independent of the poly(L-lactide) content. In addition, the crystallisation rate for PCL was... 

Fig.66. DSC thermograms for PCL/SMA-14 blends after crystallisation at 35 °C for 14 days taken from [148]...

Figure 7.2 compares the DSC thermogram of the transA,4 polyisoprene crystal grown from hexane to that grown from amyl acetate. The appearance of a single peak in DSC together with the X-ray evidence indicates the crystallisation of r tn5-l,4-polyisoprene... 

Figure 7.2 DSC thermograms of a-trd s-polyisoprene crystals crystallised isothermally from hexane and amyl acetate at -20 °C. Scanning rate 10 °C/min.

The main processes which can be studied are loss of water of crystallisation, thennal decomposition, oxidation and desorption. Qualitatively, the identity of a sample can be confirmed by comparing its thermogram with that of a standard sample. In some decomposition reactions, an intermediate can be established from an inflection in the thermogram e.g. 2CUO.SO3 in the thermogram of CUSO4.5H2O. Limited quantitative analyses have been done e.g. a mixture of the oxalates of Ca, Sr and Ba which decompose at different temperatures. 

Figure 9.12 Typical DSC thermograms showing the sugar recrystal lisation exotherm for soft confectionery (chews) which have not yet reached the correct level of crystallisation.

Figure 9.17 DSC thermograms (endotherms up) showing isothermal crystallisation (left) and melting (right) of tripalmitin-tristearin blends (labelled as wt % tristearin) at (a) 62.5°C, (b) 58.5°C, (c) 54.5°C and (d) 40.5°C. The y-axis scale divisions are 1 and 10 W/g for crystallisation and remelting thermograms, respectively. This demonstrates the use of DSC in identifying the polymorphic forms of fats. (Taken from [64], Copyright (2006), with kind permission of Springer Science and Business Media.)...

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