Improving γ‐radiation stability of pvc—a review

Abstract

WC has a significant tendency to degrade under y irradiation. Therefore, considerable efforts have been made to improve its y-radiation stability. The purpose of this review is to summarize recent results in this area, with a special emphasis on the improvement of color stability of WC-based materials used in medical applications.

Principles of Stabilization

“…[308][309][310] Studies of Irganox 1076 and 1011 show that 30-40% antioxidant becomes inactive when a dose of 10 kGy is applied; when the dose was increased to 50 kGy, the loss of antioxidant increased to 61-66%. The major use is polymerization, but also some formulations used in medical applications may contain antioxidants.…”

“…Figure 11.39 shows that only small quantities of costabilizer are necessary to obtain substantial improvement in color retention. 308 The stabilizing effect was enhanced when hydrotalcite was used as an acid scavenger. 308 The stabilizing effect was enhanced when hydrotalcite was used as an acid scavenger.…”

Analytical Methods

“…• several mechanisms of degradation were developed with support of ESR data: polaron mechanism of thermal degradation, 123 mechanism of PVC stabilization by tin stabilizers, 124 mechanism of chain branching explaining role of HCl, 125 unimolecular mechanism of HCl splitting of, 126 post-irradiation aging, 127 peroxy-radical formation during thermal degradation, 128 • identification of polyenyl radicals, 129 • understanding of UV degradation and stabilization, 122,130 • measurement of nitroxyl radical concentration, 131,132 • plasticizer diffusion and distribution, 133 The methods of measurement are standard techniques which permit determination of paramagnetic species. In some studies, HCl evolution was measured directly in ESR tube in addition to ESR studies.…”

Commodity Thermoplastics

“…29 Effect of norbornene concentration on the glass transition temperature of the cyclic olefin copolymer.…”