Thermal behaviour of polymorphic n-alkanes: effect of cooling rate on the major transition temperatures

✍ Scribed by Ahmed Hammami; Anil K. Mehrotra

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 667 KB
• Volume: 74
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(94)p4338-3

✦ Synopsis

Both the melting and the crystallization d.s.c. thermograms for these paraffins exhibit two major peaks, a and /I, corresponding to the liquid-solid and solid-solid transitions. At the same rate of temperature change, the shape and peak height of the melting endotherms differ considerably from those of the cooling exotherms. The experimental results are explained in terms of the established crystallographic descriptions of the crystalline rotator phases for these alkanes. More importantly, the peak-to-peak temperature difference (ATpeak = T,-T,) depends on the carbon number but not on the cooling rate. The following linear relation, which is independent of cooling rate, is proposed for the variation of ATpeat with the carbon number (C): ATpeaL= 17-0.42C.