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Polymers 2018, 10(4), 397; https://doi.org/10.3390/polym10040397

Effect of Ionizing Radiation on the Chemical Structure and the Physical Properties of Polycaprolactones of Different Molecular Weight

1
Instituto de Ciencia y Tecnología de Polímeros (CSIC), Juan de la Cierva 3, 28006 Madrid, Spain
2
Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 Ciudad de México, Mexico
3
Instituto de Física, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 Ciudad de México, Mexico
*
Author to whom correspondence should be addressed.
Received: 9 March 2018 / Revised: 30 March 2018 / Accepted: 1 April 2018 / Published: 3 April 2018
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Abstract

Polymers used in the biomedical sector can be exposed to ionizing radiation (X-ray, gamma) in vivo as implants or ex vivo for sterilization purposes (gamma, electron beam). This ionizing radiation can, at certain levels, cause degradation of the polymer. Polycaprolactones (PCL) of different molecular weights were irradiated with electron beam and the changes in their chemical structure and physical properties with the dose were evaluated. Electron beam irradiation produced crosslinking and chain scission in the PCL chain without significant predominance of one mechanism over the other. Minimum dose for gelation decreased with the increase in PCL molecular weight whereas crosslinking efficiency was almost independent of PCL molecular weight. Carboxylic groups, hydroxyl groups and new saturated hydrocarbon species were detected by proton nuclear magnetic resonance (NMR). These species were consistent with a mechanism where chain scission could take place at any bond in the PCL chain with preference in the –COO–CH2– bond. Crosslinking decreased significantly the crystallization temperature of PCL. Tensile properties decreased continuously with the increase in dose. Irradiation with gamma rays produced a faster decay in mechanical properties than electron beam. View Full-Text
Keywords: polycaprolatone; electron beam irradiation; gamma rays; mechanical properties; degradation mechanism polycaprolatone; electron beam irradiation; gamma rays; mechanical properties; degradation mechanism
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Navarro, R.; Burillo, G.; Adem, E.; Marcos-Fernández, A. Effect of Ionizing Radiation on the Chemical Structure and the Physical Properties of Polycaprolactones of Different Molecular Weight. Polymers 2018, 10, 397.

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