Fabrication of carbon nanotube/polyvinyl alcohol nanocomposites reinforced with calcined clamshells (Mactra chinensis) and their influence on physico-mechanical properties

This study is aimed to examine the impacts of incorporating increasing amount of carbon nanotubes (CNTs) into PVOH nanocomposites with different amounts of calcined clamshell. The samples of CNTs- and calcined clamshell-added PVOH nanocomposites were produced via solution casting method. The elongation at break and tensile strength for the CNTs/calcined clamshell-added PVOH nanocomposites had demonstrated a gradual increment up to 54% corresponding to higher levels of CNTs (2–3 phr) and 1 phr of calcined clamshell. However, the introduction of higher amounts of both CNT (≥ 0.4 phr) and calcined clam shells (3 phr) has adversely impacted the tensile strength of samples to drop from ~ 38 to ~ 33 MPa because the presence of CNT particles in higher amounts tended to severely agglomerate into larger aggregate particles within the polymer matrix of PVOH, as observed in SEM analysis. Additionally, the increase of CNTs amount had resulted in a decrement in d-spacing and interchain separation, which indicates the rupturing of the crystallite in the PVOH matrix, as observed in XRD analyses. However, at higher CNTs amount (≥ 0.3 phr), the calcined clamshell in the higher level of 3 phr had resulted in a slight increment in d-spacing and interchain separation, which facilitates the interlocking of CNTs in PVOH matrix. The crystallite size increased with increasing levels in calcined clam shells might be attributed to their capability to encourage an ordered chain arrangement. In FTIR analysis, the O–H stretching wavenumber was observed to reduce with the increasing amount of CNTs and calcined clamshell. This is because the lower wavenumber indicated the weakening of O–H stretching due to the presence of stronger hydrogen bonding within the polymer matrix of PVOH samples.