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Atomic force microscopy investigation of electron beam (EB) irradiated composites based on biodegradable polymers and coconut fiber*

Kodama Y., Oishi A., Nagasawa N., Nakayama K., Tamada M., Machado L. D. B.

Nukleonika

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2013

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Vol. 58, No. 4

459--468

EN

In this study, the addition of natural fibers to biodegradable PCL, PLLA blend and the effect of ionizing radiation on the surface of composites were investigated by force modulation microscopy (FMM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Hot pressed sheets were prepared using pellets of twin extruded PCL:PLLA 20:80 (w:w) blend containing 5% or 10% weight concentration of coconut fiber. In this study coconut fibers non treated chemically and acetylated ones were used. Irradiation was performed using an electron beam (EB) accelerator and an absorbed dose of 100 kGy. FMM images acquisition was obtained using a silicon cantilever, intermittent contact mode (tapping mode). Also, AFM images were obtained using tapping mode but J scanner. By FMM, it was possible to observe regions with different elasticity indicating fiber presence under the surface of the composite. Furthermore, it appears that the spherical structures size decreased on composites. This probably was induced by ionizing radiation.

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Investigation of irradiated biodegradable blends by FTIR and wide-angle X-ray diffraction

Kodama Y., Machado L. D. B., Giovedi C., de Lima N. B., Nakayama K.

Nukleonika

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2009

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Vol. 54, No. 2

107-113

EN

In the present work, twin screw extruded films of PLLA and PCL biodegradable homopolymers and 50:50 (w:w) blend were irradiated with gamma rays from Co-60 and electron beam at doses in the range of 50 to 500 kGy in order to evaluate the effect of irradiations on homopolymers and blend. The FTIR results have shown that this technique was neither sensitive enough to observe the degradation promoted by ionizing radiation of studied homopolymers and blends and, nor on the miscibility of the blends. Wide-angle X-ray diffraction (WAXD) of PCL samples, non-irradiated and irradiated showed two strongest reflections at angles 2theta = 21.4 degrees centigrade and 2theta = 23.7 degrees centigrade that have been attributed in the literature to the (110) and (200) reflections, respectively. As for extruded non-irradiated and irradiated PLLA, it was observed broad diffusion peaks corresponding to an amorphous polymer. PLLA annealed samples showed reflections at angles 2theta =16.4 degrees centigrade and 2theta =18.7 degrees centigrade previously attributed in the literature to distorted 103 (alfa-form) helices. It was possible to observe slight alteration of the crystallite size of all irradiated samples of PCL in the dose range studied.

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Development of an irradiation system for a small size continuous run multipurpose gamma irradiator

Calvo W. A. P., Rela P. R., Napolitano C. M., Kodama Y., Omi N. M., da Costa F., de Andrade e Silva L. G.

Nukleonika

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2009

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Vol. 54, No. 2

93-97

EN

The Radiation Technology Center from IPEN-CNEN/SP, Brazil, developed a revolutionary design and national technology, a small-sized continuous run and multipurpose industrial gamma irradiator, to be used as a demonstration facility for manufacturers and contract service companies, which need economical and logistical in-house irradiation system alternatives. Also, to be useful for supporting the local scientific community on development of products and process using gamma radiation, assisting the traditional and potential users on process validation, training and qualification of operators and radioprotection officers. The developed technology for this facility consists of a continuous tote box transport system, comprising a single concrete vault, where the automated transport system of products inside and outside of the irradiator utilizes a rotating door, integrated with the shielding, avoiding the traditional maze configuration. Covering 76 m2 of floor area, the irradiator design is a product overlap sources and the maximum capacity of cobalt-60 wet sources is 37 PBq. The performed qualification program of this multipurpose irradiator was based on AAMI/ISO 11137 standard, which recommends the inclusion of the following elements: installation and process qualification. The initial load of the multipurpose irradiator was 3.4 PBq with 13 cobalt-60 sources model C-188, supplied by MDS Nordion – Canada. For irradiator dose optimization, the source distribution was done using the software Cadgamma developed by IPEN-CNEN/SP. The polymethylmetacrylate (PMMA) dosimeter system, certified by the International Dose Assurance Service (IDAS) of the International Atomic Energy Agency (IAEA) was used for irradiator dose mapping. The economic analysis, performance concerning with dose uniformity and cobalt-60 utilization efficiency were calculated and compared with other commercial gamma irradiators available on the market.