ISSN:
0449-2951
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The kinetics of propylene polymerization catalyzed by α-titanium trichloride-diethyl-aluminum chloride in heptane diluent were studied. Initiation and transfer processes were followed by using C14-labeled (C2H5)2AlCl. There was no important termination process in this system. The initial C14 activity found in the polymers gave the concentration of active ethyl groups on the surface, [C]. The propagation step was first order in [monomer] and [C], with an activation energy of 13.0 kcal. mole-1; kp at 50°C. was 0.426 ± 0.018 l. mole-1 sec.-1. There were two transfer processes: (1) Rtr1 = ktr1[C] - [(C2H5)2AlCl]1/2, with an activation energy of 18.6 kcal. mole-1, and a value of ktr1 at 50°C. of 6.54 × 10-5 mole-1/2 sec.-1; and (2) Rtr2 = ktr2 [C] [α-TiCl3], with an activation energy of 7.6 kcal. mole-1, and a value of ktr2 at 50°C. of 9.45 × 10-4 l. mole-1 sec.-1. These kinetic data were used to calculate number-average molecular weights M̄n, which agreed well with the ones obtained directly from the C14 specific activity in the polymer. Furthermore, fractionation of four polypropylene samples gave values of M̄n in agreement with those obtained above. At low temperatures, [C] is sensitive to the Al/Ti ratios. This dependence was interpreted as the result of an equilibrium between an active complex containing (C2H5)2AlCl and a much less active complex containing (C2H5)AlCl2. At higher temperatures, [C] is insensitive to the Al/Ti ratios, and polymerization to give amorphous polymers becomes important. Qualitative information was obtained about the processes which give amorphous polymers.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1963.100010138
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