[en] Electron-beam and gamma irradiation of polymers are widely applied in Brazil today. The main applications are: radio-induced crosslinking of wire and cable for automobile and appliance industry; heat shrinkable tubes for appliance, automobile and electronic; heat shrinkable packing for food processing industry; sterilization of medical supplies and so on. Nevertheless, there are only a few industrial facilities about 20 years old in full operation at present and there are some new low energy machines for food packing. The reason for such absence of investment in this area was studied and the relation between automobile and appliance production with radiation processing was fully demonstrated for Brazil case. In conclusion, it was shown that the industry of radiation processing of polymers is likely to experience a strong growth based on the continuous increase in the production of automobiles and appliances. The R and D activities of IPEN are an important support for developing the necessary technology and developing the necessary confidence in the radiation as tool for economical and social growth

[en] TFE is highly unstable. It can easily go through an explosive disproportionation reaction under polymerization. The present work proposes the use of ionizing radiation for the study of monomer stability by inducing the polymerization and disproportionation reactions. Radiation was used to promote the initiation of TFE polymerization with and without inhibitors. Inhibitors and TFE were irradiated by γ-rays from ⁶⁰Co. Small explosions with polymerization were observed yielding oligomer and polymer plus byproducts. It was shown that the initiation was completely inhibited by the addition of 0.1% of α-pinene, dipentene, terpinolene or its mixture 1:1:1. In conclusion, radiation is a safe, reliable and easily controllable method to study TFE stabilization

[en] The main objective of this work is to observe the most important changes that occur in the the thermo chemical properties of the polyethylene when it is submitted to different irradiation doses, to aim at its use as an insulator of wire and cables. To characterize the crosslinked PE there has been used thermogravimetric analysis (TGA) and solvent extraction. The induction time of oxidation process was measured by TGA. (author)

[en] In this study field natural rubber latex was irradiated with different doses near a ⁶⁰Co gamma source to reduce the water-soluble protein content in the final product. The protein content of the films obtained by casting method was extracted with phosphate buffer solution, pH 7 and was measured using Micro BCA Protein Assay kit. Also was measured protein in the serum samples of field NRL. The concentration of extractable proteins increased with increasing radiation dose

[en] Is well known that when polyethylene (PE) is exposed to an ionizing radiation (electron beam, gamma ray, etc) a crosslinking of polymeric chains occur, promoting a molecular weight growth that causes an increase in the thermal stability of the polymer. The main objective of this work is to observe the most important changes that occur in the thermo chemical properties of the polyethylene when it is submitted to different irradiation doses, to aim at its use as an insulator of wire and cables. To characterize the crosslinked PE there has been used thermogravimetric analysis and solvent extraction. The induction time of oxidation process was measured by TGA. (author)

[en] Published in summary form only

[en] This study compares the effects of radiation dose on the isothermal and non-isothermal crystallization of LLDPE, LDPE and HDPE by differential scanning calorimetry (DSC). It includes qualitative comparison of the non-isothermal data and quantitative calculations of Avrami parameters for crystallization rate and nucleation mode. The isothermal crystallization allowed the observation of the changes in the crystallization rate, related to the decrease in the crystallization temperature caused by the crosslinking of the polymer. It was also observed by the non-isothermal crystallization, the development of crystallites of very different sizes in the polymer

[en] Hydrogels manufactured by radio-induced crosslinking and simultaneous sterilisation of hydrogels of PVP, PEG and agar, according to the Rosiak method, have many desirable properties for using as wound dressings. However, some properties need to be improved or better controlled. The membranes need to be strong enough to be freely used. Another important property to be controlled is the capacity of absorption of exudate and the kinetics of drying. Therefore, it was necessary to understand the role of main parameters (agar, PVP, PEG concentration and dose) in the structure of the net and in the hydration and dehydration properties. The structure of the membranes was studied by sol analysis and the hydrating/dehydrating properties were studied by isothermal thermogravimetric analysis. The gel content for all samples were always in agreement with expected values considering that only PVP undergoes crosslinking. The hydrating and dehydration results did not show variation with the tested parameters. It was concluded that the network was solely composed of crosslinked PVP plasticezed by the other compounds. The properties of hydration/dehydration is related rather to diffusion than to capillarity or osmose and to the chemical retention of water in the polymeric matrix

[en] The aim of this paper is to investigate if Polypropylene (PP) modified by ionization radiation (gamma rays) in the presence of two different monomers, can be used in the food and medical area, in the last case as biomaterial. For this purpose the samples were obtained by mixture in a twin-screw extruder system with two different polyfunctional monomers. It was studied the Ethylene Glycol Dimethacrylate (EGDMA) and the Trimethylolpropane Trimethacrylate (TMPTMA) with concentration in the range of 0.5 to 5.0 mmol. After mixture they were irradiated with dose of 20kGy of gamma radiation. The structural modification of polypropylene have been analyzed, in the melt state, by measuring the melt flow rate (MFR), η^* (complex viscosity) and G' (storage modulus) in the angular frequencies range of 10^-1 to 3x10² s^-1. From the oscillatory rheology data it was possible to obtain for each sample the values of η^o (zero shear viscosity), that will be related with the molar mass. All results are discussed with respect to the crosslinkg and degradation process that occur in the post-reactor treatment to produce controlled rheology polypropylene. For investigation of any type of toxicity in these polymeric materials they were submitted to in vitro test of cytotoxicity by neutral red uptake methodology with NCTC L 929 cell line from American Type Culture Collection bank. In the first test of biocompatibility all of modified PP samples presented no cytotoxicity, indicating that these materials could be used as biomaterial and other kinds of biocompatibility test have to be done

[en] Polyvinylchloride (PVC) is under heavy attack from environmentalist groups due to the use of plasticizers and its recycling difficulties. Chloro-organics and phtalates are considered now as ubiquitous global contaminants due to their potential as weak endocrine disruptor and huge consumption. In order to make PVC acceptable for the irradiation processing industry in the long term, non-toxic plasticizers should be used. PVC was added with dioctyl phtalate (DOP) and epoxy soybean oil (ESO) and irradiated up to 50 kGy. Mechanical properties, optical properties and viscosity were measured and compared. The elongation and mechanical strength were under the usual range and they didn't show any significant change in the studied range of irradiation dose. All the samples showed a weak yellowing effect after irradiation and the molecular weight measured by viscosimetry showed only negligible changes. In conclusion, DOP and ESO were shown to be effective in stabilizing the radiolytic abstraction of HCl from PVC. Both plasticizers imparted good color stability and overall properties to the products