Abstract
Phase transitions of polytetrafluoroethylene (PTFE) oligomers (n-perfluoroalkanes), C20F42, C24F50, and a polydispersed sample of n-perfluoroalkanes (molecular weight, MW=ca. 5000–20000), denoted by L-PTFE, were studied at atmospheric pressure by differential scanning calorimetry and under high pressure up to 600 MPa by high pressure differential thermal analysis. Their phase diagrams were determined. The phase diagram of C20F42 is quite different from that of PTFE. Below about 300 MPa, a sequence of crystal-crystal transitions denoted by Tr1 and Tr2 occurs in the isobaric heating process. In the pressure region between 300 and 400 MPa, there are two cases of crystal-crystal transitions, one case in which a pair of Tr3 and Tr4 occurs and the other case in which only Tr5 occurs. Above about 400 MPa, only Tr3 and Tr4 occur. The transition line of Tr4 has a terminal point at about 300 MPa. The phase diagram of C24F50 is also similar to that of C20F42. On the other hand, the phase diagram of L-PTFE is different from these and identical to that of PTFE.
Similar content being viewed by others
Article PDF
References
C. E. Weir, J. Res. Natl. Bur. Stand., 50 95 (1953).
S. Hirakawa and T. Takemura, Jpn. J. Appl. Phys., 8, 635 (1969).
E. S. Clark and L. T. Muus, Z. Krist., 117, 119 (1962).
P. W. Bridgman, Proc. Am. Acad. Arts Sci., 76, 55 (1948).
C. E. Weir, J. Res. Natl. Bur. Stand., 46, 207 (1951).
C. Nakafuku and T. Takemura, Jpn. J. Appl. Phys., 14, 599 (1975).
H. W. Starkweather, Jr., Macromolecules, 19, 1131 (1986).
H. Schwickert, Doctoral thesis, Universität Mainz, 1984.
J. D. Brady, U. S. Patent 3 067 262 (Dec. 4, 1962).
G. R. Strobl, J. Polym. Sci., Polym. Symp. Ed., 59, 121 (1977).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Tsubakihara, S., Yasuniwa, M. High Pressure Differential Thermal Analysis of n-Perfluoroalkanes. Polym J 24, 421–426 (1992). https://doi.org/10.1295/polymj.24.421
Issue Date:
DOI: https://doi.org/10.1295/polymj.24.421