PROCESS FOR PRODUCING POLYMER MATERIALS

Abstract

This invention relates to the radiation chemistry and high-energy chemistry technologies for the production, by heat-and-radiation treatment of workpieces, of enhanced-performance polymer materials, in particular, of polytetrafluoroethylene (PTFE) and other sorts of fluoroplastics used in various industries. Specifically, it relates to treating workpieces by high-energy ionizing radiation at a temperature strictly higher than the polymer crystalline phase melting point in an anoxic environment. The treatment is done via a pulsed linear electron accelerator generating ionizing radiation until an absorbed dose of 0-500 kGy is achieved. During the irradiation process, the polymer temperature is reduced by not more than 0.5 C./10 kGy, and subsequent to the ionizing radiation treatment, the polymer is heat treated. Alpha radiation, gamma radiation, electron radiation, irradiation with high-energy protons and neutrons, radiation from natural sources are used for the treatment. By this treatment method, physical and mechanical properties of the material are improved and consistency and programmability of the physical and mechanical characteristics are provided. 7 sub-claims.

Claims

1. A method for heat-and-radiation treatment of fluoroplastic-based products comprising polytetrafluoroethylene-based products, wherein workpieces are treated by high-energy ionizing radiation at a temperature strictly higher than the polymer crystalline phase melting point in an anoxic environment, the polymer being treated via a pulsed linear electron accelerator generating ionizing radiation until an absorbed dose of 0.5 to 500 kGy is achieved, wherein the polymer temperature is reduced by not more than 0.5 C./10 kGy in the course of irradiation, and subsequent to the ionizing radiation treatment, the polymer is heat treated.

2. The method of claim 1, wherein alpha radiation is used as the high-energy ionizing radiation.

3. The method of claim 1, wherein gamma radiation is used as the high-energy ionizing radiation.

4. The method of claim 1, wherein electron radiation is used as the high-energy ionizing radiation.

5. The method of claim 1, wherein irradiation with high-energy protons and neutrons is used as the high-energy ionizing radiation.

6. The method of claim 1, wherein radiation from natural sources is used as the high-energy ionizing radiation.

7. The method of claim 1, wherein the workpiece is treated at a temperature above 327, but not higher than 380 C.

8. The method of claim 1, wherein after the irradiation is terminated, additional heat treatment of the workpiece in the heating/cooling mode is done at temperatures ranging from the treated polymer crystallization onset temperature to 380 C./h.

Description

DETAILED DESCRIPTION

Most Preferred Embodiments of the Invention

[0012] The step-by-step implementation of the claimed heat-and-radiation treatment method: A polymer material is prepared in accordance with standard technical specifications for fluoropolymer material processing (extrusion, casting, sinter molding).

[0013] The resulting polymer material workpieces are then delivered to a preparation area and placed into the RHC. In the RHC, oxygen is pumped out until a residual pressure is reached, and then the chamber is filled with inert gas (argon, nitrogen) until a gauge pressure is reached.

[0014] In the RHC, the polymer material workpieces are heated to a temperature above the crystalline phase melting point from 327 C. and not higher than 380 C. at a rate of 60 C./h or lower and subjected to thermostating at a temperature substantially higher than the crystalline phase melting point (but not higher than 380 C.), thus making it possible to carry out a complete polymer crystalline phase melting process, while preventing potential degradation of polymer areas due to a presence of hard crystalline areas prone to severe degradation when irradiated.

[0015] At the next step, the workpieces are delivered to an irradiation area. Specifically, the polymer material workpieces are treated by ionizing braking gamma radiation from the pulsed linear accelerator at a rate of 0-1000 Gy/s. The irradiation is continued until an absorbed dose of 0.5-500 kGy (or energetically equivalent coherent high energy radiation) is achieved, while reducing the product temperature in the course of treatment by not more than 0.5 degrees/10 kGy. After the irradiation is terminated, due to potential rapid accumulation of the necessary irradiation dose and the specifics of the polymer material workpieces' structure and, therefore, physical and mechanical characteristics, changing mechanism, additional heat treatment in the heating/cooling mode is to be done at temperatures ranging from the treated polymer crystallization onset temperature to 380 C./h to normalize and stabilize its properties.

[0016] At the final treatment step, the treated polymer material workpieces are cooled to a room temperature at a rate not higher than 60 C./h.

[0017] Workpieces may also be treated with radiation other than the above braking gamma radiation, i.e. by alpha radiation, gamma radiation, electron radiation, high-energy protons and neutrons, radiation from natural sources.

[0018] The invention provides substantial improvement in the quality of resulting polymers with various sets of properties as required for various applications.