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Polymerization and crystallization behavior of anionic nylon 6
Author(s) -
Iobst Stanley A.
Publication year - 1985
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760250708
Subject(s) - crystallization , polymerization , materials science , polymer chemistry , nylon 6 , arrhenius equation , caprolactam , anionic addition polymerization , chemical engineering , bulk polymerization , polymer , activation energy , composite material , chemistry , radical polymerization , engineering
The kinetics of the activated anionic polymerization of caprolactam to nylon 6 was studied by the adiabatic temperature rise technique. This allowed very rapid reaction conditions to be studied. The polymerization was activated by diisocyanate and catalyzed by sodium caprolactamate, produced in situ by the addition of sodium hydride. The temperature rise measurements were used to generate Arrhenius curves of the rate data. Several isocyanates were investigated, all giving similar rate curves. The reaction rate was reduced, however, when the activator concentration exceeded the catalyst concentration. To model the actual rapid molding conditions, time vs . temperature reaction profiles were measured for thin plaque castings. In these reaction profiles, two successive exotherms were observed. The first was the polymerization exotherm, and the second was determined to be the crystallization peak. This second exotherm allowed the direct observation of crystallization times within the closed molds. The crystallization times were found to depend strongly on the mold temperature and to a lesser extent on the monomer temperature. The crystallization times were minimized at a 150°C mold temperature. At higher temperatures, the crystallization rate was significantly slower, while at lower temperatures, the slow rate of polymer formation delayed the onset of crystallization. This study has demonstrated the value of using temperature monitoring as a means of studying the polymerization and crystallization behavior of nylon.