Melting Process and the Equilibrium Melting Temperature of Polychlorotrifluoroethylene (Record no. 1242)
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042 ## - AUTHENTICATION CODE | |
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Authentication code | dc |
100 10 - MAIN ENTRY--PERSONAL NAME | |
Personal name | Hoffman, John D. |
Relator term | author |
245 00 - TITLE STATEMENT | |
Title | Melting Process and the Equilibrium Melting Temperature of Polychlorotrifluoroethylene |
260 ## - PUBLICATION, DISTRIBUTION, ETC. | |
Name of publisher, distributor, etc. | [Gaithersburg, MD] : U.S. Dept. of Commerce, National Institute of Standards and Technology, |
Date of publication, distribution, etc. | 1962. |
500 ## - GENERAL NOTE | |
General note | /pmc/articles/PMC5327738/ |
520 ## - SUMMARY, ETC. | |
Summary, etc. | A new method of estimating the equilibrium melting temperature, T(m), of a polymer is described, and applied to polychlorotrifluoroethylene (PCTFE). Experimentally determined values of the so-called observed melting point, [Formula: see text] , are plotted as a function of the isothermal crystallization temperature, T(x). When freed of secondary effects, such as recrystallization, the data fit a straight line of positive slope on a [Formula: see text] versus T(x) plot, T(x) being the abscissa. This line is then extrapolated to its intersection with the line [Formula: see text]. The temperature at this intersection is T(m). This intersection is at 224 °C for PCTFE, and T(m) is quoted as 224 ± 1 °C. (The highest melting point actually attained for a specimen was 218.2 °C.) The value of T(m) estimated using the extrapolation procedure is compared with that estimated using the customary method of slow stepwise warming. A theoretical justification is given for making the type of plot mentioned above. The most important assumption used in the theory is that one of the dimensions of the growing crystal retains a value rather close to that of the appropriate growth nucleus during an isothermal crystallization, the other two dimensions being large in comparison. Combination of this with the fact that the relevant dimension of the growth nucleus will vary as the reciprocal of the degree of supercooling leads to the prediction of melting points that increase linearly with crystallization temperature. The assumption that one of the dimensions of the crystal retains a value fairly close to that of a growth nucleus can readily be justified on the basis of polymer crystal growth with chain folds. Its justification in the case of the customary bundlelike mode of crystallization is less clear. It is demonstrated experimentally that even the largest detectible crystals in PCTFE are only about 70 percent thicker than a primary nucleus, when secondary effects are minimized. The application of the theory to systems other than PCTFE is discussed briefly, and some preliminary measurements on polyethylene mentioned. Some points relating to the shape of the melting curves of highly crystalline polymers are also brought out. |
540 ## - TERMS GOVERNING USE AND REPRODUCTION NOTE | |
Terms governing use and reproduction | |
540 ## - TERMS GOVERNING USE AND REPRODUCTION NOTE | |
Terms governing use and reproduction | https://creativecommons.org/publicdomain/zero/1.0/ |
540 ## - TERMS GOVERNING USE AND REPRODUCTION NOTE | |
Terms governing use and reproduction | The Journal of Research of the National Bureau of Standards Section A is a publication of the U.S. Government. The papers are in the public domain and are not subject to copyright in the United States. Articles from J Res may contain photographs or illustrations copyrighted by other commercial organizations or individuals that may not be used without obtaining prior approval from the holder of the copyright. |
546 ## - LANGUAGE NOTE | |
Language note | en |
690 ## - LOCAL SUBJECT ADDED ENTRY--TOPICAL TERM (OCLC, RLIN) | |
Topical term or geographic name as entry element | Article |
655 7# - INDEX TERM--GENRE/FORM | |
Genre/form data or focus term | Text |
Source of term | local |
700 10 - ADDED ENTRY--PERSONAL NAME | |
Personal name | Weeks, James J. |
Relator term | author |
9 (RLIN) | 324 |
786 0# - DATA SOURCE ENTRY | |
Note | J Res Natl Bur Stand A Phys Chem |
856 41 - ELECTRONIC LOCATION AND ACCESS | |
Uniform Resource Identifier | <a href="http://dx.doi.org/10.6028/jres.066A.003">http://dx.doi.org/10.6028/jres.066A.003</a> |
Public note | Connect to this object online. |
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