Estimates of Molecular Weights of Low Molecular Weight Linear Polyethylenes via Differential Scanning Calorimetry

✍ Scribed by C.M. Feng; M.S. Delaney

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 233 KB
• Volume: 48
• Category: Article
• ISSN: 0026-265X
• DOI: 10.1006/mchj.1993.1093

✦ Synopsis

The van der Wyk equation, (1 / T_{\mathrm{f}}=a+b / Z) (where (T_{\mathrm{f}}) is the melting point in (\mathrm{K}, Z) is the number of carbons in the alkane and (a) and (b) are constants), for the prediction of melting points of straight chain alkanes up to 60 carbons has been reexamined. The original van der Wyk equation had (a=0.002395) and (b=0.0171). Reexamination has found (a=) 0.0023675 and (b=0.017407). Modifications of the van der Wyk equation have also been made to estimate the molecular weight of linear low molecular weight polyethylenes of low polydispersities made by such methods as anionic polymerization. Estimates of (M_{n}) (number weight molecular average) ( (\pm 17 %)) may be made when (a=0.002414) and (b=0.01433). Estimates of (M_{\mathrm{w}}) (weight average molecular weight) ( (\pm 19 %) ) may be made when (a=) 0.002435 and (b=0.01736). Estimates of peak molecular weight ( (\pm 13 %) ) may be made when (a=0.002440) and (b=0.01285). Factors which contribute to error in the estimates are also discussed. 1993 Academic Press, Inc.