Preparation and characterization of UHMWPE/HDPE/MWCNT melt-blended nanocomposites

Abstract

The nanocomposite blends of ultra-high-molecular-weight polyethylene (UHMWPE) and high-density PE (HDPE) reinforced with 1 wt% of multi-wall carbon nanotube (MWCNT) were prepared by melt mixing at different compositions in an internal mixer. Two different grades of HDPE were used in this research to improve the processability of UHMWPE. Rheological, thermal, morphological, and mechanical properties were investigated for both (UHMWPE/HDPE) blends and their nanocomposites. The results confirmed the reduction in melt viscosity and improvement in the processability of UHMWPE by the addition of HDPE. Differential scanning calorimetry (DSC) results showed a single melting and crystallization peak, and the broadness of these peaks in blends compared to pure components indicated that two components form separate crystals. The effect of incorporating MWCNT to the blend samples on mechanical properties was studied, and the samples prepared with HDPE 5218 exhibited slight improvement in mechanical properties. Incorporating MWCNT into the blend of UHMWPE (20 wt%) accelerated crystallization; but in higher contents of UHMWPE, crystallization of the composites was slightly delayed. Rheological data exhibited lower complex viscosity and storage modulus and therefore lower elasticity for UHMWPE/HDPE/MWCNT nanocomposites compared to their blends. Drop in viscosity and storage modulus as well as tensile strength of nanocomposites compared to their blends was attributed to adsorption of higher molar mass polyethylene chains onto MWCNT surface. The morphology of nanocomposites was analyzed by scanning electron microscopy (SEM) and phase separation, and probably localization of MWCNT

Evaluation of the Mechanical and Thermal Properties of Blended (HDPE/UHMWPE) Nanocomposites with Graphite Nanosheets (GNS)

“…Another sensitive parameter in such situations is the endothermic curve; Full Width at Half Maximum (FWHM) which reveals occurrences of a single cocrystal. If the FWHM is higher in pure components, it is expected that both components form separated crystals . In accordance with Table , the FHWM values for blends with 20 and 30 wt% UHMWPE are higher than for the pure polymers, and thus crystallize individually and successively in mixtures, even if only a single peak is observed .…”

“…If the FWHM is higher in pure components, it is expected that both components form separated crystals. [15] In accordance with Table 2, the FHWM values for blends with 20 and 30 wt% UHMWPE are higher than for the pure polymers, and thus crystallize individually and successively in mixtures, even if only a single peak is observed. [15] Yet, for the UH10 sample, the inverse situation occurred, exhibiting co-crystallization.…”

“…The melting peaks for the blends are observed between the melting temperatures of their HDPE and UHMWPE components. In relation to melting temperature (Tm) it was noted that the highest was for UHMWPE; this was expected since in the literature it has a higher melting temperature in a range from 130 and 140 C. [15] In the mixtures, a small decrease to the value around 131 C is seen for all the blends. For the crystallization temperatures (Tc) it was noticed that blend temperatures were greater than HDPE, that is, crystallization occurs at higher temperatures (except for the UH20 sample).…”

“…This suggests a single crystal or a co‐crystallization. Co‐crystallization occurs when chain segments of a diffuse component crystallize into lamellae of the other component . However, since the polymers present very close melting (Tm) and crystallization (Tc) temperatures (Table ), endothermic and exothermic curve overlaps occur in the thermogram.…”

“…For the crystallization temperatures (Tc) it was noticed that blend temperatures were greater than HDPE, that is, crystallization occurs at higher temperatures (except for the UH20 sample). This behavior may be attributed to the introduction of UHMWPE, which acts as a crystallization nucleus …”