[en] This work deals with the effect of ionizing radiations on polymers. On particular are described: - the different types of ionizing radiations used, the chemical effects induced and the industrial equipments used to produce ionizing radiations; - the reticulation of polymers by ionizing radiations (which type of polymers are concerned, the alterations of their properties: chemical stability - mechanical resistance - heat resistance, the application sectors); - the grafting of polymers by ionizing radiations (principle of radio-grafting, factors influencing the radio-grafting, advantages, industrial implementation and applications). (O.M.)

[en] The industrial use of ionizing radiations (beta and gamma), initially for the sterilization of medico-surgical instruments and for the preservation of food products, has led to the development of the chemistry of polymers under radiations. Ionizing radiations can initiate chemical reactions (chain cutting, poly-additions, polymerization etc..) thanks to the formation of free radicals. The main applications concerns the degradation of plastics, the reticulation of plastics and of woods impregnated with resin, and the grafting of polymers. The processing of plastic materials was initially performed with low energy electron accelerators (0.1 to 3 MeV), allowing only surface treatments, while recent high energy accelerators (10 MeV) and gamma facilities allow the treatment in depth of materials (from few cm to 1 m). This article describes the industrial treatments performed with such high energy facilities: 1 - action of ionizing radiations on plastic materials: different types of ionizing radiations, action of beta and gamma radiations, chemical changes induced by beta and gamma radiations; 2 - reticulation of plastic materials submitted to beta and gamma radiations: radio-'reticulable' polymers and reticulation co-agents, modification of the properties of reticulated plastic materials under beta and gamma radiations; 3 - industrial aspects of reticulation under beta and gamma radiation: industrial irradiation facilities, dosimetry and radio-reticulation control, applications; 4 - conclusion. (J.S.)

[en] Complete text of publication follows. Poly (vinylidene fluoride) is characterized by high intrinsic properties associated with the presence of a strong CF bond, responsible for its good chemical and thermal stability and its low surface energy. These properties provide a wide range of applications, from the medical field to the energy one. However, for some specific applications, excellent physicochemical affinity with a given liquid medium as well as a conservation of the dimensional integrity is required. These antagonist properties can be insured by crosslinking the material through an irradiation process such as the used of γ-ray. Compared to traditional methods which consist in a prior chemical modification of the polymers, this strategy can be applied on materials already processed. The mechanisms of the homopolymer radiolysis are relatively well known and involve free radical species which nature and concentration can be measured by ESR. The main scope of this work is to study and improve the crosslinking of PVDF-based polymers induced by γ-radiation. The macroscopic behavior of the irradiated material is related to the ability of the polymer to form crosslinking density can be evaluated from rheological measurements. Finally, a part of the study is focused on the increase of crosslinking efficiency. For this purpose, a chemical crosslinker which is sensitive to free radical reactions was incorporated into the polymer matrix. Thus, a significant improvement in properties is revealed. Moreover, the impact of radiation dose, crosslinker concentration or type of atmosphere during the radiation process is evaluated and their impact on mechanical properties is elucidated.

[en] Complete text of publication follows. Synthetic polymeric membranes have gained interest in separation science, engineering and technology. Fluoropolymers and especially poly(vinylidene fluoride) (PVDF) are used for such applications. Indeed they are well-known for their good properties in terms of chemical, thermal and electrical stabilities, inertness to acids, solvents and oils, and high resistance to ageing and oxidation. However, the high hydrophobicity of the PVDF membrane could limit its application when the fluid phases to be treated are dispersed in an aqueous medium. Therefore there is a need for the development of new surface modification processes, which renders the membrane more hydrophilic and which are clean and robust enough to be used in industrial field. This work focuses on the γ-ray induced grafting of different hydrophilic monomers onto a PA-reinforced PVDF membrane. These polymers are known to be radio-sensitive, and radicals can be generated on both components and their relative proportion determined by ESR. The influence of various parameters was evaluated, related either to the radiation process or the polymerization step, and a global methodology based on thermal properties, viscosimetry and spectroscopic techniques was used to point out the highly selective modification of the PVDF component of the membrane only. Finally, the surface properties of the membrane were evaluated and confirmed the membrane modification.

[en] The beta and gamma irradiation of elastomers makes easier the handling of the reticulation process in room temperature conditions and in adequate depth inside the material. The irradiation generates free radicals along the polymer chains, these radicals by combining form new chemical bonds (reticulation reaction). The irradiation of an elastomer is featured by the formation of covalent carbon-carbon type bonds while sulfur vulcanization leads to chain bridging based on sulfur-sulfur bonds. The reticulation process entails a rise of the ramification rate of the polymer. These modifications confer to the irradiated material a higher dimensional stability in high temperature conditions and in aggressive environment that may lead, in certain conditions to no need for the usual extra coating. The gamma irradiation facilities of the Ionisos company allow the treatment of molded plastic materials directly in their packaging and in bulk quantity. (A.C.)

[en] Biopolymers have received in recent years an increasing interest for their potential applications in the field of biomedical engineering. Among the natural polymers that have been experimented, chitosan is probably the most promising in view of its exceptional biological properties. Several techniques may be employed to sterilize chitosan-based materials. The aim of our study was to compare the effect of common sterilization treatments on the degradation of chitosan-based materials in various physical states: solutions, hydrogels and solid flakes. Four sterilization methods were compared: gamma irradiation, beta irradiation, exposure to ethylene oxide and saturated water steam sterilization (autoclaving). Exposure to gamma or beta irradiation was shown to induce an important degradation of chitosan, regardless of its physical state. The chemical structure of chitosan flakes was preserved after ethylene oxide sterilization, but this technique has a limited use for materials in the dry state. Saturated water steam sterilization of chitosan solutions led to an important depolymerization. Nevertheless, steam sterilization of chitosan flakes bagged or dispersed in water was found to preserve better the molecular weight of the polymer. Hence, the sterilization of chitosan flakes dispersed in water would represent an alternative step for the preparation of sterilized chitosan solutions. Alternatively, autoclaving chitosan physical hydrogels did not significantly modify the macromolecular structure of the polymer. Thus, this method is one of the most convenient procedures for the sterilization of physical chitosan hydrogels after their preparation.

[en] Highlights: • High dose of Gamma rays (Co"6"0) causes chain scissionof PVdF based separators. • Irradiated membranes with different cross-linkig coagents [(Triallylisocyanurate (TAIC) and a macromonomer of ethylene oxide- propylene oxide (MEP)] showed enhanced mechanical properties compared to a pristine membrane. • The utilization of coagents is limited to 2–5% per weight in order not to produce brittle membranes. • Porous structure of PVdF was not destroyed by irradiation. • This reinforcement technique allows producing thinner membranes with good mechanical properties and with low ohmic contribution to the resistivity. -- Abstract: Macroporous poly(vinylene fluoride) (PVdF) separators were prepared by phase inversion method and introduced to a gamma (γ) radiation with and without cross-linking agents. Triallyl isocyanurate (TAIC) and a macromonomer of ethylene oxide- propylene oxide (MEP) were used as a cross-linking agent. The resulting membranes were characterized in terms of thermal and mechanical properties. Ionic conductivities were determined in a molar solution of tetraethylammonium tetrafluoroborate (TEABF_4) in acetonitrile (AN) and propylene carbonate (PC). Excellent mechanical properties (250 MPa at 25 °C) and conductivities (14 mS cm"−"1) were obtained for the cross-linked separator prepared with TAIC