**4. Conclusions**

In this work, polymer nanocomposites consisting of CNF particles as reinforcement filler and thermoset epoxy polymer were produced by shear mixing process. The prime objective of this study is to prepare a CNF-filled thermoset polymer-based composites. CNF particles were filled up to 5 wt.% in epoxy polymer matrix. The e ffect of CNF concentration on curing tensile, DMA, TGA, and water uptake properties was evaluated. CNF addition shows positive e ffect in these properties. FTIR and curing studies shows that CNF may act as a curing catalyst during epoxy gelation and increases the cross-link density of the epoxy polymer and reduces with curing time. Well-dispersed CNF particles were obtained in this processing method. Almost comparable modulus, 10% increased tensile strength and 26% increased elongation were observed in 3 wt.% CNF-filled epoxy nanocomposite. An optimized improved onset and endset decomposition temperature was observed at 2–3 wt.% CNF-filled epoxy nanocomposite. In the DMA study, storage modulus of 2 wt.% CNF-filled epoxy nanocomposite was increased by 28%, 56%, and 48% respectively at 25 ◦C, 80 ◦C, and 100 ◦C respectively when compared with unfilled epoxy polymer. Water uptake results sugges<sup>t</sup> that the water uptake proportionally reduces in nanocomposites as concentration of CNF particles increases in matrix polymer. Maximum 47% reduction of water mass uptake was seen in 5 wt.% CNF-filled epoxy nanocomposite. Overall results sugges<sup>t</sup> that an optimum level of improvement is obtained at 2–3 wt.% CNF-filled epoxy nanocomposite. The result suggests that the CNF can be successfully incorporated in thermoset epoxy polymer matrix with improved properties and serve as a promising green nanofiller for the epoxy matrix.

**Author Contributions:** M.T.P. conducted the study, analyzed the result and wrote the paper. K.K. was project supervision and fact checking of scientific claims in the manuscript. Both the authors together formulated the objective of the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** "This research was funded by South African National Research Foundation (NRF), gran<sup>t</sup> number 119779" and "The Research & Postgraduate Directorate of Durban University of Technology, South Africa."

**Conflicts of Interest:** The authors declare no conflict of interest.
