Atomic Force Microscopy, thermal, viscoelastic and mechanical properties of HDPE/CaCO3 nanocomposites

Abstract

High Density Polyethylene (HDPE) and calcium carbonate (CaCO3) nanocomposites were prepared from masterbatch by melt blending in twin screw extruder (TSE). The physical properties of HDPE/CaCO3 nanocomposites samples (0, 10 and 20 wt% CaCO3 masterbatch) were investigated. The morphology, thermal, rheological/viscoelastic and mechanical properties of the nanocomposites were characterized by Atomic Force microscopy (AFM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analyzer (DMA) as well as tensile test. The AFM images showed homogeneous dispersion and distribution of nano-CaCO3 in the HDPE matrix. The DSC analysis showed a decrease in crystallinity of HDPE/CaCO3 nanocomposites with the increase of CaCO3 loading. This was due to the presence of nanofiller which could restrict the movement of the polymer chain segments and reduced the free volume/spaces available to be occupied by the macromolecules, thus, hindered the crystal growth. However, there was an increase in crystallization temperature about 1–2 °C with the addition of CaCO3. It was suggested that the CaCO3 nanoparticles acted as nucleating agent. In melt rheology study, the complex viscosities of HDPE/CaCO3 nanocomposites were higher than the HDPE matrix and increased with the increasing of CaCO3 masterbatch loading. The DMA results showed that the storage modulus increased with the increasing of nano-CaCO3 contents. The improvement was more than 40 %, as compared to that of neat HDPE. Additionally, the tensile test results showed that with the addition of CaCO3 masterbatch, modulus elasticity of nanocomposites sample increased while yield stress decreased.