Surface crosslinking of polyethylene using a hydrogen glow discharge

Linear high‐density polyethylene is crosslinked by exposing it to a hydrogen glow discharge and alternatively by exposing it to a low‐pressure Hg–A ultraviolet lamp in a dry nitrogen atmosphere. For the UV lamp case, the crosslinked gel is measured as a function of the radiation dose. For the plasma case, the crosslinked gel is measured as a function of the exposure time. The two gelation curves are alternatively compared to an exponentially attenuated light theory and a diffusion theory. Excellent agreement exists between the measured gel‐versus‐dose curve and the theoretical curve based on the light theory for a monochromatic light beam at 1849 Å. The gelation curve for the hydrogen glow discharge case can be explained using the identical theory but applied to a spectrum of light covering the range from 1200 Å to 1900 Å. The different curves can be explained in terms of the different spectra. Energy transfer between the plasma and the polymer due to excited atoms, and/or charged particles, is not required to account for the different gel curves.