Crystallinity and the effect of ionizing radiation in polyethylene. V. Distribution of trans‐vinylene and trans,trans conjugated double bonds in linear polyethylene

Abstract

Freeze‐dried chain folded single crystals and the single crystals without amorphous surface layers (crystalline cores) of different thicknesses of linear polyethylene were irradiated with 60Co γ‐rays up to 600 Mrad. Concentration of trans‐vinylene double bonds and conjugated diene produced during irradiation of the crystals was measured by infrared. Concentrations of trans‐vinylene and of the conjugated diene were independent of thickness of crystalline core which suggest that the double bonds wer randomly distributed in the crystalline parts of the crystals. Concentrations of trans‐vinylene and of conjugated double bonds were lower in chain‐folded crystals than in the crystalline cores and this suggests that the folds (amorphous surface layers) are less preferential sites for formation of the double bonds. The zero‐order growth and first‐order decay kinetics of trans‐vinylene double bonds was studied by the equation derived by Dole et al1. The equation is strictly obeyed up to 300 Mrad and the results then deviate. Since there is the decay of trans‐vinylene double bonds and though there are no crosslinks in the crystalline cores, it has been suggested that the decay of the double bond does not result in the crosslinks.

Dose tolerance at helium and nitrogen temperatures for whole cell electron tomography

“…The contrast eVect in the membranes may be easiest to understand, since their radiation chemistry is simplest. Mass loss in alkanes, such as the membrane lipid tails, involves almost exclusively extraction of hydrogen (Patel, 1975), which would tend to accumulate in the hydrophobic region of the lipids if its diVusion were limited. It appears that fragments released from the proteins are similarly conWned within the protein in the initial stages of damage, producing the Wne texture of bubbles such as seen in Fig.…”

Effect of Irradiation and Detection of Long-Lived Polyenyl Radicals in Highly Crystalline Ultra-High Molar Mass Polyethylene (UHMMPE) Fibers

“…Much work has been published on the use of low dose rate gamma irradiation in various doses to crosslink UHMMPE fibers [6,7,8,11,22,23,24,25]. In one such paper, deBoer and Pennings [8] were successful at crosslinking the fibers, however, they observed a marked decrease in tensile strength (up to 40%) with increasing dose.…”

Stroboscopic image capture: Reducing the dose per frame by a factor of 30 does not prevent beam-induced specimen movement in paraffin

“…In the case of paraffin the predominant form of damage appears to be the introduction of trans double bonds (Patel, 1975;Patel and Keller, 1975), which clearly results in a molecular shape that no longer fits into the original crystal lattice. In a more general situation, such as proteins and other biological materials, ionization will lead primarily to bond rupture, and as a result two atoms that previously were about 0.15 nm apart will separate to a distance of about 0.35 nm.…”