DD251904A3 - RADIATION-RESISTANT HEAT-RESISTANT FORM PARTS - Google Patents

Abstract

Radiation-resistant, heat-resistant molded parts for use in medical, nuclear, radiation and space technology with the aim of developing molded parts with improved radiation resistance and heat resistance and to find a suitable material for this purpose. The task was solved by moldings of norbornene-ethylene copolymers, which can be subjected to a limit irradiation dose of 15 MGy at an operating temperature of 373 K without the strength values dropping. Applications in medical technology are medical instruments, container and apparatus parts. In the core and blasting technique, the molded parts of norbornene-ethylene copolymers are used for housing parts, for BMSR facilities and for cladding.

Description

Object of the invention

The aim of the invention is to develop moldings with improved radiation resistance and heat resistance for use in medical, nuclear, aerospace and space technology.

Explanation of the essence of the invention

The invention has for its object to find nikeinen suitable material for moldings in the medical, nuclear, aerospace and technology. This object is achieved by radiation-resistant heat-resistant molded parts, according to the invention, the molded parts made of norbornene-ethylene copolymers. Surprisingly, these moldings can be used up to a limit irradiation dose of 15MGy at an operating temperature up to 373 K.

In medical technology, syringes, cannulas, scalpel blades, probes, parts of infusion sets, parts of equipment, bottles and containers are capable of more than 200 radiation sterilizations before the utility value characteristics drop.

On the other hand, molded parts made of polyethylene permit only a 40-times sterilization, moldings made of polyamide-6 a triple sterilization and moldings made of polypropylene only a one-time sterilization.

The use of norbornene-ethylene copolymers brings about in the nuclear and radiation technology that moldings produced therefrom can be used at higher operating temperatures and radiation exposure.

embodiments

example 1

Cans are made by injection molding copolymers of norbornene and ethylene. Radiation sterilization of the sealed canned food with 5OkGy makes it virtually unlimited shelf life. Radiation sterilization preserves the nutritional value and appetizing appearance of the food. The sterilization dose and a subsequent thermal load up to 373K in case of disaster will not damage the container.

Example 2

Inspection discs for control instruments whose scale and indicator are covered with fluorescent paint are made from copolymers of norbornene and ethylene by injection molding. The radiation exposure by the luminous color and a temperature load up to 373 K in case of emergency leads to no cracking and clouding of the lens.

Example 3

A copolymer of norbornene and ethylene is sprayed at 533 K to test bars. The exposure to nuclear radiation is simulated by gamma irradiation in air at a dose rate of 10kGy / h. After an irradiation dose of 10MGy, the tensile strength is 62 N / mm ² , the Ε-modulus 4100N / mm ² , the elongation 3% and the impact strength 1.2 kJ / m ² . The corresponding values of the starting material are 60 N / mm ² , 4000 N / mm ² , 4% and 1.2 kJ / m ² .

Example 4

Norbomene-ethylene copolymers with a Vicat-Temperaturyon 408 K are sprayed to parts of syringes (piston, cylinder, union nut).

After 200 25kGy sterilizations, there was no decrease in the utility properties of the syringes.

Example 5

The probe of an electronic monitor, which is inserted directly into the bloodstream during complicated operations, is encapsulated in a norbornene-ethylene copolymer injection molded part. Bacterial pyrogens are inactivated by gamma irradiation at a dose of 1 MGy. The probe is fully functional after 4 pyrogen inactivations by gamma irradiation. '^;

Examples, I

Oxygenators for heart-lung machines are produced by injection molding of norbornene-ethylene copolymer according to Example 4. After 150 sterilizations with a gamma irradiation dose of 25 kGy, the oxygenator is still fully functional. !

Example 7

Test bars of norbornene-ethylene copolymer according to Example 4 are exposed to a dose rate of 10 kGy / h. After a radiation dose of 6MGy, no discoloration of the material occurs. The tensile strength is 65 N / mm ² , the Ε modulus is 3.3 kN / mm ² , the elongation is 4% and the notched impact strength is 1.3 kJ / m ² . The corresponding values of the starting material are 60N / mm ² , 3.2kN / mm ² , 4% and 1.2kJ / m ² .

Example 8

Cartridges for X-ray film are made by injection molding of norbornene-ethylene copolymer. After 5 years of use, no evidence of wear from exposure to hard X-rays is observed.

Example 9

The walls of a "hot cell" for nuclear studies are lined with 4mm thick norbomene-ethylene copolymer plates, and after 10MGy cumulative exposure to radiation, the plates show slight discoloration but no cracking.

Example 10

The visor for the setting indicator and ram and gear parts of the roller counter of a servomotor for the nuclear reactor cooling circuit are made of norbornene-ethylene copolymer. After a cumulative radiation exposure of 4MGy and an operating temperature of 333 K to 373 K, the lens does not show any discoloration, the roller counter is fully functional.

Example 11

Encapsulation, screwing and stem of a spherical ionization chamber for the measurement of high gamma irradiation dose rates are made of norbornene-ethylene copolymer by injection molding. After 2500 hours of operation at operating temperatures up to 373K, the ionization chamber is fully functional and shows no cracking.

Example 12

Norbomene-ethylene copolymer with a Vicat temperature of 408 K is sprayed at 533 K to test bars and exposed in air to a gamma irradiation with a dose rate of 10kGy / h. After an irradiation dose of 10MGy, the tensile strength is 62N / mm ² , the Ε modulus is 3.2kN / mm ² , the elongation is 3%, and the notched impact strength is 1.2kJ / m ² . The corresponding values of the starting material are 60 N / mm ² , 3.2 kN / mm ² , 4% and 1.2 kJ / m ² .

Example 13

Norbomene-ethylene copolymer according to Example 12 is sprayed at 543 K to components of switching relays. After exposure to 12MGy gamma irradiation at 373K (dose rate 10kGy / h), the components showed no damage.

Claims (1)

Radiation-resistant heat-resistant molded parts, characterized in that the molded parts consist of norbornene-ethylene copolymers. Field of application of the invention The invention relates to radiation-resistant heat-resistant molded parts for use in medical, nuclear, aerospace and space technology. Characteristic of the known technical solutions Radiation sterilization of medical instruments is becoming increasingly important over heat sterilization and chemical sterilization because sterilization can be done in sealed plastic bag packaging. In the packaging, the instruments remain virtually unlimited sterile. 25kGy has become internationally accepted as a sterilization dose (W.Stolz, "Strahlensterilisation", J.Barth Verlag, Leipzig, 1972). The prerequisite for repeated use and radiation sterilization of a medical instrument is the radiation resistance of the material used. This means that the material properties must remain almost constant over a wide dose range. If plastic materials are used under the influence of ionizing radiation (gamma, beta, neutron and X-ray radiation) in radiation technology and nuclear technology, the material properties should remain nearly constant in the widest possible dose range. If the ionizing radiation leads to chain scission of the polymer, this is associated with a drop in the material properties. If crosslinking of the polymer occurs due to the ionizing radiation, the material properties remain virtually constant over a wide dose range. It is known that polymers with quaternary C atoms Γη the chain such as polytetrafluoroethylene, polymethyl methacrylate and polyvinylidene fluoride under ionizing radiation undergo a rapid structure and are therefore unsuitable for medical, nuclear and radiation engineering. Polymers with secondary and tertiary C atoms in the chain such as polyethylene, polyamides, polyvinyl chloride and polystyrene crosslink under the action of ionizing radiation; the material properties remain constant in a limited dose range (A. Henglein, "Introduction to Radiation Chemistry", Akademie-Verlag Berlin , 1969). Furthermore, it is known that polystyrene up to a limiting dose of 10MGy, polyamide up to a limiting dose of 6MGy and polyethylene (high density) up to a limiting dose of 1 MGy are suitable for use in the radiation and nuclear engineering, if their use below 348K (Perkinson, "Use of Plastics in Nuclear Radiation", Nuclear Eng. 17 [1971], 247 bis 280). , '' For use above 348K, the special plastics polyimide, polyamide-imide and aromatic polyamides are the suitable plastic materials for electrical and electronic components in radiation and nuclear technology up to an irradiation dose of about 10MGy (K. Bühler, "Spezialplaste", Akademie-Verlag Berlin , 1978). The known, under the influence of ionizing radiation crosslinking plastic construction materials such as' polystyrene and polyamide can be used under the influence of gamma irradiation to about 10MGy. The disadvantage, however, is that the operating temperature is limited to a maximum of 348K. The use of specialials such as polyimides and aromatic polyamides is limited by the high price and the difficult thermoplastic processability. The same criteria apply to the use of plastic materials under the influence of orbital radiation in space travel as in radiation and nuclear technology. It is further known that the limit load capacity for use in medical technology for polyethylene is 1 MGy, polypropylene 3OkGy, polystyrene 6MGy, polyvinyl chloride 10OkGy and polyamide-6 8OkGy. In the case of polymethyl methacrylate and polytetrafluoroethylene molding compositions, even a one-time 25 kGy sterilization leads to a sharp drop in material properties, so that these plastics can not be used for radiation-sterilizable medical devices (Van de Voorde, Effects of radiation on materials and compounds, CERN 75-5 Feb. 1970). In medical technology, polyethylene, polystyrene and polypropylene are widely used for the production of radiation sterilizable hypodermic syringes. Polystyrene, polyamide and polypropylene are suitable plastic materials for cannulas, scalpels, probes, parts of infusion sets, bottles and containers. The disadvantage of these known radiation-sterilizable plastic materials consists in the polyamide and polypropylene in the relatively low radiation resistance with repeated radiation sterilization. Polyethylene has insufficient stiffness for a number of applications.