Investigation of Mechanical, Thermal and Electrical Properties of Various Carbon Nanofillers Incorporated Epoxy Composites for Marine Applications-A Comparative Study

Abstract

The primary objective of this research is to investigate the mechanical, thermal and electrical properties of different carbon nanofillers such as carbon nanofibers (CNF), randomly distributed carbon nanotubes (CNT), partially aligned carbon nanotubes (ACNT), functionalised carbon nanotubes (FCNT) reinforced epoxy nanocomposite systems and the influence of water absorption in altering the overall performances of these composite materials which is yet to be published. For this purpose, three different wt.% viz., 0.5 wt.%, 0.75 wt.%, and 1 wt.% of each nanofilllers have been chosen in order to prepare the nanocomposites along with neat epoxy. Among the fabricated specimens, a batch of samples have been immersed into seawater for water absorption up to their saturation period while, another batch is kept in dry conditions. A number of characterisations like mechanical (flexural modulus, flexural strength and hardness), thermal (glass transition temperature) and electrical (electrical conductivity and shielding effectiveness) tests of both the dry i.e., unexposed as well as seawater exposed specimens have been undertaken and analysed in order to predict the extent of degradation occurred in the exposed specimens when compared to their unexposed counterparts. Moreover, in the present study, comparison and analysis among the all results obtained from different nanocomposite systems have been carried out in order to get a clear understanding about the extent of degradation occurred in each types of composite material Results demonstrate that among all the unexposed nanocomposite systems specimens of FCNT/epoxy family exhibit maximum increment in flexural modulus (40-101%), flexural strength (36-124%) and hardness (75-166%) than neat epoxy. Maximum improvement in mechanical properties for these specimens are due to the strong interfacial interaction and hence formation of improved interfaces between FCNT and epoxy polymer. Whereas; maximum improvement in glass transition temperature (Tg), electrical conductivity and shielding effectiveness (SE) than neat epoxy are recorded for the specimens of ACNT/epoxy family. For these specimens an overall increment of 23-35% in Tg values, six order increment in conductivities than neat epoxy and SE of around ~11.5–13.5 dB are observed. Attainment of maximum electrical performances of these specimens is due to formation of effective conductive pathways by the ACNT through the epoxy polymer. Obtained results of all the composite systems are further correlated and confirmed with the help of microscopic investigation using field emission scanning electron microscope (FESEM). Water absorption tests of all the specimens show that neat epoxy and FCNT/epoxy specimens exhibit the maximum water uptake, whereas; the minimum water absorptions are recorded for ACNT/epoxy specimens among all. As a consequence, in case of neat epoxy and FCNT/epoxy specimens degradation is observed to be more severe; while, the lowest reduction in mechanical, thermal and electrical properties are recorded for all the specimens of ACNT/epoxy family, when compared to their unexposed one. A reduction of 25-37% in flexural modulus, 33-40% in flexural strength, 13-26% in hardness are recorded for ACNT/epoxy specimens and thereby exhibit the lowest deterioration of mechanical properties among all. In addition, one order lessening in conductivity and 23-31% reduction in SE are observed for these specimens than their unexposed one which is also the minimum declination in electrical properties as compared to others. Degradation in overall properties for all the composites are found to be because of absorption of water by these specimens that causes plasticisation of the polymer, swelling of polymer which results in formation of weak interfacial adhesion between matrix and nanofillers inside the specimens, are further confirmed by micrographs.