Physical properties of biaxially oriented poly(ethylene terephtalate) irradiated at different temperatures and doses with electron beam

Fabrication of highly durable polysiloxane-zinc oxide (ZnO) coated polyethylene terephthalate (PET) fabric with improved ultraviolet resistance, hydrophobicity, and thermal resistance

Developing a universal strategy to improve the properties of polyethylene terephthalate (PET) fibers, such as UV resistance, hydrophobicity, and thermal resistance, is highly desirable in expanding the application of PET fibers. Herein, a highly durable and robust ZnO layer was deposited onto PET fabric via radiation-induced graft polymerization (RIGP) of γ-methacryloxypropyl trimethoxysilane (MAPS) and the subsequent sol-gel in situ mineralization with zinc acetate to produce wurtzite nanocrystalline ZnO. The as-obtained material, denoted as PET-g-PMAPS/ZnO. The interfacial layer consisted of Zn-O-Si and Si-O-Si covalent bonds not only leads to an improvement in adhesion between ZnO nanoparticles and its support, but it also overcomes the poor film-forming ability of inorganic particles. Most importantly, photocatalytic self-degradation of its organic support caused by the high photocatalytic activity of ZnO can be eliminated because of high bond energy of the organic-inorganic hybrid structure. PET-g-PMAPS/ZnO exhibited excellent thermal resistance, UV resistance and durability. Superhydrophobicity was achieved by simply annealing the PET-g-PMAPS/ZnO fabric at 200 °C in ambient air, and the coated fabric still retains its superhydrophobicity after 40 laundering cycles test and even stored for a few weeks. This study presents an effective method to overcome the bottle-necks in growing inorganic nanocrystals on polymeric supports surface.

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

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.