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Melting Process and the Equilibrium Melting Temperature of Polychlorotrifluoroethylene (Record no. 1160)

MARC details
042 ## - AUTHENTICATION CODE
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.
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General note /pmc/articles/PMC5327738/
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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.
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Language note en
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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
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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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