Plasma assisted bio-degradation of poly-lactic acid (PLA)

Plastics are artificial synthetic organic polymers that have been used in every area of daily life. However, because of their slow degradation rate, their use is contentious. The treatment of the surface of the sample is considered necessary as enzymatic or bacterial attach is not possible, if the plastic surface environment is not ideal. The main topic of this work is the investigation of the effect of atmospheric dielectric barrier discharge (DBD) plasma on the near surface structure of polylactic acid (PLA) samples, which, in turn, can promote the adhesion of enzymes or bacteria for further biodegradation. In general, plasma processes can already be considered as inherently environmental technologies. Plasma processes enable resource saving through high energy utilization efficiency and thus, are environ-mentally friendly technologies. Atmospheric pressure discharges (APDs) are useful because of their specific advantages over low-pressure ones. They do not need expensive vacuum equipment, and generate nonthermal plasmas, which are more suitable for assembly line processes. Hence, this category of discharges has significant industrial applications. The use of a dielectric barrier in the discharge gap helps prevent spark formation. DBDs exhibit two major discharge modes: filamentary and glow (homogeneous). The glow discharge mode has obvious advantages over the filamentary one for applications such as treatment of surfaces and deposition of thin films. Glow mode discharges with average power densities comparable to those of filamentary discharges are of enormous interest for applications in which reliable control is required. Here we will present the increased adhesion of bacteria strains on DBD plasma treated PLA foils which can lead to a better degradation of the PLA. X-ray photoelectron spectroscopy (XPS) measurements of the foils prior to and after the treatment proved the changes on the polymer surface. A short discussion of the possibilities the treatment opens is given.CHANIA 2023: 10th International Conference on Sustainable Solid Waste Management Chania, Greece, 21 - 24 JUNE 202

Highly conducting poly(methyl methacrylate)/carbon nanotubes composites: Investigation on their thermal, dynamic-mechanical, electrical and dielectric properties

International audienceNanocomposites of poly(methyl methacrylate) (PMMA) containing various multi-walled carbon nanotubes (MWCNT) contents were prepared using melt mixing. Several techniques were employed to study the influence of the MWCNT addition on the thermal, mechanical, electrical and dielectric properties of the PMMA matrix. The electrical percolation threshold () was found to be 0.5 vol.% by performing AC and DC conductivity measurements. Significantly high conductivity levels () were achieved: exceeds 10 S/cm already at 1.1 vol.%, the criterion for EMI shielding ( > 10 S/cm) is fulfilled at 2.9 vol.%, and the highest loaded sample (5.2 vol.%) gave a maximum value of 0.5 S/cm. Dielectric relaxation spectroscopy measurements in broad frequency (10−10 Hz) and temperature ranges (-150 to 170 °C) indicated weak polymer-filler interactions, in consistency with differential scanning calorimetry and dynamic mechanical analysis findings. Weak polymer-filler interactions and absence of crystallinity facilitate the achievement of high conductivity levels in the nanocomposites

Semifluorinated Methacrylate Random Copolymers: Phase Transitions and Molecular Dynamics

Random copolymers of methyl methacrylate (MMA) and sermifluorinated methacrylate (sfMA), with constant side chain length (H$_{10}$F$_{10}$), as comonomers and various sfMA molar contents were studied by Dielectric Relaxation Spectroscopy (DRS) technique with respect to their phase transitions and molecular dynamics. DRS technique was proven a suitable technique for the detection of the phase transitions that take place in the systems under investigation, as it follows from the comparison with Differential Scanning Calorimetry (DSC) technique, which is traditionally used. Regarding molecular mobility, molecular motions of both the main chain and the sf side chains were followed, while different dynamics was recorded depending on the structure of the copolymers

Effects of preparation methods on producing alternative electrolyte materials for IT-SOFCs

Due to the degradation of state-of-the-art electrolyte materials from operation of SOFCs at high temperatures, research is focused to materials with high ionic conductivity and structural integrity at intermediate temperatures. Apatite-Type Lanthanum Silicates (ATLS) are promising electrolytes at IT-SOFCs as their ionic conductivity increases with doping sustaining their structural integrity. The ATLS of general formula La9.83Si6‐x‐yAlxFeyO26±δ were synthesized with mechanochemical activation (MA), sol-gel (SG) and solid state methods. Stoichiometric amounts were properly mixed for each method and the powders of each material prepared via the MA, SG and SSR methods were pressed into pellets (disks). Sintering was performed in air with temperatures up to 1600 °C and dense pellets were achieved (>95%) via uniaxial pressing and verified by archimedes method. The prepared materials were characterized using X-rays diffraction, particle size analysis by light scattering and thermal analysis (TG-DTA). The microstructure was observed by SEM and TEM. Conductivity measurements were performed in air at 600 to 850 οC. An investigation of interaction with a state of the art interconnector material CROFER-22 was also investigated in order to provide evidence of chemical compatibility for potential use in IT-SOFCs. All preparation methods provided materials with apatite structure. Mechanochemical activation technique in high energy planetary ball mills provides single–phase samples of Al or Fe–doped lanthanum silicates. The doped apatite type of materials showed significant conductivity in medium temperatures (600-800 οC) and the presence of Fe in the apatite samples seems to enhance Cr incorporation

Thermal and electrical characterization of multi-walled carbon nanotubes reinforced polyamide 6 nanocomposites

In this study composites of polyamide 6 and multiwalled carbon nanotubes (MWCNT) were prepared by diluting a masterbatch using melt mixing. Differential scanning calorimetry was employed in order to investigate the influence of nanotubes on the thermal transitions of polyamide 6. Significant changes are reported on crystallization and glass transition by the addition of nanotubes. The results are discussed in terms of polymer-filler interactions. Dielectric relaxation spectroscopy measurements were performed to study both the electrical and dielectric properties of the nanocomposites. Percolation threshold is calculated to be at 1.7 vol.% MWCNT