Ionizing Radiation Effects on Interfaces in Carbon Nanotube-Polymer Composites

Abstract

The purpose of this research was to probe nanotube-polymer composites for evidences of radiation induced chemistry at the interface of the host polymer and the nanotube structures. Single wall carbon nanotube (SWNT) / poly (methyl methacrylate) (PMMA) composites were fabricated and exposed to gamma radiation with a Co60 source at a dose rate of 1.28 X 106 rad/hour in an air environment for a total dose of 5.9 Mrads. Neat nanotube paper and neat PMMA were also exposed. Spun coat films of SWNT/PMMA were exposed to gamma radiation with a Ce157at a dose rate of 4.46 x 103 rad/hr for a total dose of 3.86 Mrads. Both irradiated and non-irradiated samples were compared. Glass transition temperatures were characterized by differential scanning calorimetry. Dynamic mechanical analysis and dielectric analysis evidenced changes in relaxations induced by irradiation. Irradiated composites exhibited radiation induced chemistry distinct from degradation effects noted in the pure polymer. Scanning electron microscopy provided images of the SWNTs and SWNT/PMMA interface before and after irradiation. This investigation imparts insight into the nature of radiation induced events in nanotubes and nanocomposites.

Transparent Poly(methyl methacrylate)/Single‐Walled Carbon Nanotube (PMMA/SWNT) Composite Films with Increased Dielectric Constants

“…0.26 wt.-% pure SWNTs were placed in 9.5 g of de-inhibited MMA. A loading of 0.26 wt.-% was used to compare with previously studied PMMA±SWNT composites with the same loading [23,24]. The mixture was sonicated for 30 min with a Branson Sonifier 450 until the nanotubes were finely dispersed in the monomer.…”

“…Another PMMA±SWNT composite was prepared by adding CNTs to PMMA and melt blending via a previously described method [23,24]. After dissolution in methylene chloride, this composite sample exhibited visible agglomeration of CNTs resulting in non-transparent thin films.…”

“…[28] The experimental data published for polymer/SWNT composites [23,24,29,30] demonstrate an increase in permittivity for the composite samples compared with the neat samples. Permittivity data obtained in this study agrees with previously published results.…”

“…The permittivity of the non-transparent melt-blended PMMA±SWNT composite with CNT loading identical to that of the film samples also increased as compared to the neat PMMA. [23,24] Both the electronic nature of the polymer and the effect of CNTs in the composites can be understood by correlating the dielectric constant values from DEA with the refractive index. According to van Krevelan, [31] if the sample is a non-polar insulator, the dielectric constant (e¢) for low frequencies can be expressed by Maxwell's equation e¢ = n 2 ,where n is the refractive index.…”

Preparation and Physical Properties of Carbon Nanotubes–PVA Nanocomposites

“…[18 -20] A different approach is to expose the nanotube composite to gamma radiation to modify the chemistry at the interface, as in the case of SWNTs-poly(methylmethacrylate). [21] As a further example, Bubert et al found that the treatment of vapor growth carbon fibers (VGCFs) by plasma resulted in the formation of polar groups on the surface with consequent modification of surface morphology. [22] Among polymers investigated for nanocomposite fabrication poly(vinyl alcohol) (PVA) has attracted great attention.…”