Premium
Radiation‐induced crystallinity changes in linear polyethylene: Influence of aging
Author(s) -
Bhateja S. K.
Publication year - 1983
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.1983.070280236
Subject(s) - crystallinity , polyethylene , high density polyethylene , irradiation , materials science , annealing (glass) , polymer , linear low density polyethylene , enthalpy of fusion , composite material , polymer chemistry , melting point , nuclear physics , physics
A previous paper described an unusual crystallinity effect observed in ultrahigh molecular weight linear polyethylene (UHMW PE) and conventional high density polyethylene (HDPE). It was discovered that upon exposure to high energy radiation, these polymers experience a significant increase in the degree of crystallinity. The present paper describes another equally unexpected and surprising phenomenon observed in irradiated UHMW PE and HDPE. It was accidentally found that the irradiated polyethylenes exhibit an aging effect; their heat of fusion and hence their degree of crystallinity increases monotonically with the aging time (since initial irradiation) at ambient conditions. Surprisingly, the aging process in irradiated polyethylenes was observed to persist even after 31 months. The magnitude of the aging effect is a strong function of the initial molecular weight of the unirradiated polymers and the irradiation dose. The aging phenomenon could not be accelerated by thermal annealing. The exact mechanisms causing the aging phenomenon remain rather elusive at the present time, but possible reasons are explored.