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Diffusion of stabilizers in polymers. II. 2‐hydroxy‐4‐octoxybenzophenone in polyolefins
Author(s) -
Johnson M.,
Westlake J. F.
Publication year - 1975
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1975.070190624
Subject(s) - polymer , polyethylene , polypropylene , low density polyethylene , materials science , tacticity , high density polyethylene , polymer chemistry , diffusion , substituent , stabilizer (aeronautics) , analytical chemistry (journal) , chemistry , composite material , organic chemistry , thermodynamics , polymerization , mechanical engineering , physics , engineering
Abstract The migration of radioactively labeled 2‐hydroxy‐4‐octoxybenzophenone in a number of polyolefins was investigated over the temperature range 36–75°C. The rates of diffusion in the polymers studied were found to decrease in the order low‐density polyethylene > high‐density polyethylene ∼ isotactic polypropylene, the activation energies being approximately 17, 36, and 24 kcal/mole, respectively. The results of the present study were found to be in qualitative agreement with those previously determined for the same stabilizer/polymer systems, quantitative differences being attributed to the different methods of sample preparation and the resulting differences in the morphological structures of the test specimens. The calculated solubilities of the substituted 2‐hydroxybenzophenone in the various polymers were substantially higher, at a particular temperature, than the corresponding values previously determined for 2,4‐dihydroxybenzophenone, being 1.4, 0.4, and 0.8 wt‐% for low‐density polyethylene, high‐density polyethylene, and polypropylene, respectively at 75°C. Studies to determine the rate of loss of the stabilizer from polymer samples immersed in water resulted in extremely low rates of extraction, in contrast to those found for 2,4‐dihydroxybenzophenone, as a result of the octoxy substituent and the resulting increase in compatibility between the stabilizer and polymer.