ISSN:
0098-1273
Schlagwort(e):
Physics
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
Low molecular weight PVC polymers of known degree of crystallinity (44% by x-ray diffraction), prepared in the presence of the chain-transfer agents n-butyraldehyde and n-butyl mercaptan, are examined by differential scanning calorimetry in order to ascertain temperatures and heats of fusion. Initial thermal scans are accompanied by large endotherms and appreciable weight losses due to the lability of the terminal groups originating from the chain-transfer agents. However, further successive scans result in approximately invariant endotherms attributable to crystalline fusion. The maximum melting point, about 265°C, exceeds the value for commercial PVC, about 210°C, but is lower than a value deduced for a hypothetical completely syndiotactic polymer, about 400°C. The average heat of fusion ΔHu is 1180 ± 90 cal/mole, and the resultant entropy of fusion is 1.1 cal/deg/bond. The present ΔHu value differs significantly from previously reported values of 660-785 and 2700 cal/mole, based on melting point depression theory, but appears to be concordant with known heats for a series of vinyl polymers.
Zusätzliches Material:
3 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1975.180130807
