Paper PS-TuP22
Investigation of Wear-Resistance Enhancement of Plasma-functionalized Carbon-nanotube Composite Polyurethane Film

Tuesday, October 31, 2017, 6:30 pm, Room Central Hall

We have investigated possible causes of mechanical enhancement for a composite polyurethane (PU) film with plasma-treated carbon nanotubes (CNTs). Wear-resistance is a main topic here in terms of mechanical property. Our preliminary result showed that wear-resistance was improved by means of making a CNT-composite PU film, in particular, in the case when the CNTs treated with the plasma, which is made with gas mixture of nitrogen and carbon dioxide, was utilized. In order to enhance such a mechanical property of PU, we considered the following two possibilities; the wear-resistance increased due to 1) a uniform spatial distribution of CNTs in a PU film and/or 2) the fact that plasma-treated CNTs gives additional wear-resistance from chemical aspects, possibly from functional groups on CNTs. In fact, it is known that isocyanate (NCO) group is sometimes utilized in order to enhance their mechanical property of PU. First, we observed our CNT composite PU films with optical microscopy. The observation showed that the spatial distribution of CNTs in a composite PU film was not really enhanced due to plasma treatment by comparing with other CNT composite PU film. The circumstance indicates that the plasma-treated CNTs enhances the wear-resistance of PU film possibly from chemical aspect. However, we know that this is still in the range of our speculation. Therefore, we have recently focused on making a direct identification of NCO groups on the plasma-treated CNTs. In this presentation, we will show our recent results whether or not our plasma-treated CNTs actually have NCO groups on CNTs, in particular more NCO groups on the CNTs treated with nitrogen and carbon dioxides than those with other plasma treatment. Here, we utilized acridine yellow (AY, C₁₅H₁₅N₃), which is a good indicator of NCO groups by using photoluminescence (PL). AY solution (2mg/L AY in tetrahydrofuran, THF, C₄H₈O) was added the solvent dispersing CNTs to attach AY and NCO groups. And then, the PL emission was observed. Our result showed that PL emission was observed from the samples relating with the CNTs exposed to the plasma made with nitrogen/carbon dioxide and only with carbon dioxide plasma. In fact, we did not expect to observe PL emission from the CNTs treated with carbon dioxide plasma because the lack of nitrogen species in this gas composition. However, the residue of air gas might have provided the species, and showing the emission. In this presentation, we will show more recent results and analysis of identification of NCO groups on CNTs.