The radiation crosslinking and scission of ethylene‐propylene copolymers studied by solid‐state nuclear magnetic resonance

Abstract

Methyl groups from chain scission and H‐crosslinks have been identified by solid‐state nuclear magnetic resonance in amorphous ethylene‐propylene copolymers containing 23 and 36 mole % propylene after γ‐irradiation to 10 MGy at 30°C. G (scission) and G (crosslink) values determined from the n.m.r. spectra and by extraction are in agreement, which suggests that the crosslinks are not clustered. This may differ from the situation in polyethylene where there is a substantial crystalline content. G(S). G(X) and the ratio G(S)/G(X) increase with increasing propylene content of the copolymers.

Exploring the effect of electron beam irradiation on the properties of some EPDM‐flax fiber composites

“…Similar results have been reported in the literature by other authors . In our case, natural polymers from flax fibers (71% cellulose, 2% hemicellulose, 18.6–20.6% lignin, 2.3% pectin) can degrade under e‐beam irradiation and the polymer that will crosslink under irradiation is EPDM .…”

Effects of Electron Beam Irradiation on the Mechanical, Thermal, and Surface Properties of Some EPDM/Butyl Rubber Composites

“…By irradiation with accelerated electron beams, two processes can occur concomitantly, namely, crosslinking and chain scission. The first process appears frequently at lower electron beam irradiation doses, up to 150 kGy, while the second process leads to C–C bonds cleavage at higher doses [17,18]. The crosslinking determines the increase in tensile strength but reduces elongation, while the scission process leads to both tensile strength and elongation decrease.…”

“…The crosslinking determines the increase in tensile strength but reduces elongation, while the scission process leads to both tensile strength and elongation decrease. Because EPDM contains an aliphatic chain which has low resistance to the influence of ionizing radiation, at higher irradiation doses the degradation can be predominant as compared to crosslinking [18,19]. From Figure 1, it may be seen that the control sample (M) attained the greatest values of hardness, relatively higher than those of irradiated composites.…”

The crosslinking mechanism in gamma irradiation of polyarylsulfone: evidence for Y-links

“…This is particularly true for aromatic polymers, for which the radiation chemical yields are generally low. However, O'Donnell and Whittaker have reported quantitative determinations of the radiation chemical yields for formation of H-links in ethylene-propylene copolymers [11] and in poly(butadiene) [12] using solid-state 13 C NMR spectroscopy. Randall, Zoepfl and Silverman [13] have also reported the presence of Y-links in polyethylene irradiated to low doses, based upon solution NMR studies.…”