Crosslinking in metallocene ethylene-co-5,7-dimethylocta-1,6-diene copolymers initiated by electron-beam irradiation

Photocured Poly(Mannitol Sebacate) with Functional Methacrylic Monomer: Analysis of Physical, Chemical, and Biological Properties

In this work, we described the formation of polymeric networks with potential antimicrobial character based on an acrylate oligomer, poly(mannitol sebacate) (PMS), and an enzymatically synthesized methacrylic monomer with thiazole groups (MTA). Networks with different content of MTA were prepared, and further physico-chemically characterized by microhardness, water contact angle measurements, and differential scanning calorimetry. Monomer incorporation into the networks and subsequent quaternization to provide thiazolium moieties affected the mechanical behavior and the surface wettability of the networks. Moreover, the introduction of permanent cationic charges in the network surface could give antimicrobial activity to them. Therefore, the antibacterial behavior and the hemotoxicity were analyzed against Gram-positive and Gram-negative bacteria and red blood cells, respectively.

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.

Sago Starch-Mixed Low-Density Polyethylene Biodegradable Polymer: Synthesis and Characterization

This research focuses on synthesis and characterization of sago starch-mixed LDPE biodegradable polymer. Firstly, the effect of variation of starch content on mechanical property (elongation at break and Young’s modulus) and biodegradability of the polymer was studied. The LDPE was combined with 10%, 30%, 50%, and 70% of sago for this study. Then how the cross-linking with trimethylolpropane triacrylate (TMPTA) and electron beam (EB) irradiation influence the mechanical and thermal properties of the polymer was investigated. In the 2nd study, to avoid overwhelming of data LDPE polymer was incorporated with only 50% of starch. The starch content had direct influence on mechanical property and biodegradability of the polymer. The elongation at break decreased with increase of starch content, while Young’s modulus and mass loss (i.e., degradation) were found to increase with increase of starch content. Increase of cross-linker (TMPTA) and EB doses also resulted in increased Young’s modulus of the polymer. However, both cross-linking and EB irradiation processes rendered lowering of polymer’s melting temperature. In conclusion, starch content and modification processes play significant roles in controlling mechanical, thermal, and degradation properties of the starch-mixed LDPE synthetic polymer, thus providing the opportunity to modulate the polymer properties for tailored applications.