Observations of a novel strengthening mechanism in HDPE nanocomposites

Abstract

Previous strengthening mechanisms described in literature for high density polyethylene (HDPE) carbon nanotubes composites are typical of those observed in fibre reinforced polymeric micro composites. Here, we present a new molecular level strengthening mechanism based on HDPE carbon nanotubes composite, which has not been reported before to the best of authors' knowledge. The HDPE nanocomposite was produced by melt intercalation technique via twin-screw extrusion. Thereafter, the samples were subjected to mechanical tensile tests and scanning electron microscope (SEM) examination. Carbon nanotubes (CNTs) were found to be disentangled from the polymer molecules after yielding and prior to breaking. SEM and optical microscopic observations revealed visible black agglomerate bands at 45 appeared after yielding and prior to the breaking of the ductile HDPE. It was observed that CNTs were pushed out from the intricate mechanical interlocking with the thermoplastic polymeric chains of HDPE during strain hardening. ARTICLE HISTORY

Carbon Nanotube Reinforced High Density Polyethylene Materials for Offshore Sheathing Applications

“…The data presented are the averages of at least five samples. As compared to neat polymer (0 wt%), the elastic moduli ( Figure 3 ) of all the unweathered nanocomposites improved (e.g., 81% for 6 wt% nanocomposites) because of the presence of CNTs, which stiffen the polymer matrix, as confirmed previously [ 9 , 10 , 23 , 25 , 29 , 30 ]. Similarly, as compared to neat polymer (0 wt%), the tensile strengths of all the unweathered nanocomposites improved (e.g., 17% for 6 wt% nanocomposites) because of the presence of CNTs.…”

Melt‐mixed carbon nanotubes/polymer nanocomposites

“…Recently, Okolo et al had focused on the mechanism of deformation of HDPE/CNTs composites and explained that during tensile stretching some of the CNTs agglomeration get disentangled that led to breakage of composites. [116] In case of PVdF/PP-g-MA/CNTs composites, it was observed by Colonna et al that CNTs preferentially get located in the PP-g-MA phase, resulting in refined cocontinuous morphology. [117] For PMMA/functionalized MWCNTs composites, the tensile strength increased up to 0.5 wt% of MWCNTs but again decreased due to higher viscosity of the PMMA/CNTs composites at higher concentration that inhibit complete dispersion of MWCNTs in PMMA matrix.…”

“…They observed that under tensile force, the polymer chains rejected the CNTs as agglomerates that appear as black bands. However, the authors have also noted the HDPE/CNTs composites showed an improvement of 30% in tensile strength upon addition of 2 wt% of CNTs to HDPE …”

“…It was mentioned earlier that CNTs are mainly acting as reinforcing agent, and thus, help in improving the tensile strength and even impact strength of the composites. Recently, Okolo et al had focused on the mechanism of deformation of HDPE/CNTs composites and explained that during tensile stretching some of the CNTs agglomeration get disentangled that led to breakage of composites . In case of PVdF/PP‐ g ‐MA/CNTs composites, it was observed by Colonna et al that CNTs preferentially get located in the PP‐ g ‐MA phase, resulting in refined co‐continuous morphology .…”

“…However, the authors have also noted the HDPE/CNTs composites showed an improvement of 30% in tensile strength upon addition of 2 wt% of CNTs to HDPE. [116] Finally, it is important to discuss the practical application of these polymer/CNTs composites. Broadly, it finds application in electronics, biomedicals, sensor, organic light-emitting diodes, and in energy storage devices.…”