on the positron annihilation spectroscopy and tensile behavior of cooh-mwcnt/epoxy nanocomposites

Positron annihilation lifetime spectroscopy (pals) is sensitive to the material voids/free volume on the atomic scale. for this reason, this method has been used as a unique technology to measure the free volume and structural defects in polymers in recent years. in the present study,  epoxy-matrix nanocomposites with different carboxylic acid functionalized multiwalled carbon nanotubes (cooh-mwcnts) loadings (0.1-0.7 wt% at a step of 0.2) were fabricated, and the influence of cooh-mwcnts loading on the prepared nanocomposites’ free volume properties and tensile behavior were explored. the measurement of positron annihilation lifetime was done using a conventional synchronization system based on a 22na radioactive source with 7 μci activity. the detectors used in this work were fast plastic scintillators (type: nt-850) with ns time response. the results demonstrated that the tensile strength of the nanocomposites decreased with the increase in the lifetime of the ortho-positronium annihilation (increase in the radius and free volume) in the samples. the 0.3 wt% cooh-mwcnts/epoxy nanocomposite showed the maximum tensile strength. overall, the results of this work clearly revealed that there was a strong relationship between the tensile strength and free volume in the polymer nanocomposites.