SYNOPSISThe stabilization of polypropylene-disposable medical syringes against the y-ray-induced degradation has been the subject of active research during the last decade due to the largescale use of y-irradiation for sterilization purposes. Ethylene-propylene (EP) copolymers have been suggested as suitable alternatives to polypropylene for these purposes. In this article, we investigated the effect of irradiation dose and postirradiation time on the melt index and mechanical properties of an EP copolymer. We also determined the chemical changes occurring during irradiation and storage using IR spectroscopy and have made an attempt to co-relate the changes in chemical structure to the changes in mechanical properties and melt index measurements.

Cryo-electron microscopy of cryofixed samples is a well-established and accepted technique for imaging liquid-containing specimens without removing water and other volatile components. There are many steps between cryofixation and cryo-observation in the microscope, during which the sample and sample holder need to be handled. One such major step is the loading of the specimen onto the sample holder and the fixing of the sample holder onto the transfer mechanism. During this handling, the specimen is often exposed (mostly inadvertently) to moisture in the atmosphere, which results in frost deposition. The new specimen loader described here is designed to overcome the traditional tedious handling and to achieve ease in specimen loading. The modifications made are mainly towards allowing movement of the liquid freon cup, eliminating the need for a lock-screw and improving the shape of the stage holder, which makes the mounting of the specimen holder easy, thereby permitting smooth specimen loading without too much handling and with consequent reduced frost deposition.

Disposable medical supplies are currently made of polypropylene, which are conveniently sterilized by exposure to g-rays. However, the homopolymers (HP) and random copolymer (CP) of polypropylene, when exposed to high-energy g-irradiation, undergo oxidative degradation and loss in mechanical properties. In the current article, a comparative study of the effect of g-irradiation at different irradiation doses and the postirradiation oxidation on both the polymers is reported. The loss in mechanical properties was monitored by the bend angle and tensile measurements. The yellowness index measurements were carried out as a function of the irradiation dose and postirradiation storage time. The changes in the molecular weight (MW) and molecular weight distribution (MWD) were monitored using melt index (MI) measurements. The changes in chemical structure was determined using infrared spectroscopy.

The stabilization of polypropylene‐disposable medical syringes against the γ‐ray‐induced degradation has been the subject of active research during the last decade due to the large‐scale use of γ‐irradiation for sterilization purposes. Ethylene–propylene (EP) copolymers have been suggested as suitable alternatives to polypropylene for these purposes. In this article, we investigated the effect of irradiation dose and postirradiation time on the melt index and mechanical properties of an EP copolymer. We also determined the chemical changes occurring during irradiation and storage using IR spectroscopy and have made an attempt to co‐relate the changes in chemical structure to the changes in mechanical properties and melt index measurements. © 1996 John Wiley & Sons, Inc.

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