Abstract
In this work, polypropylene (PP) and graphene nanoplatelet (GNPs) composites are routed through twin screw mixing and injection moulding. Two types of GNPs with a fixed size of 25 µm with surface areas ranging from 50–80 m2/g (H25, average thickness 15 nm) and 120–150 m2/g (M25, average thickness 6–8 nm) were blended with PP at loading rates of 1, 2, 3, 4, and 5 weight%. Mechanical properties such as tensile, flexural, and impact strengths and Young’s modulus (Ε) are determined. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), field emission scanning electron microscopy (FESEM), and polarised light microscopy (PLM) techniques are used to understand the crystallisation, thermal, dynamic mechanical, and structural behaviour of the prepared composites. The improvement of mechanical strength is observed with GNP loading for both grades. Decreasing the GNP thickness decreases the impact strength and on the other hand improves the tensile and flexural strengths and Young’s modulus. Maximum tensile (≈33 MPa) and flexural (≈58.81 MPa) strength is found for the composite carrying 5 wt% M25. However, maximum impact strength (0.197 J) is found for PP-5 wt% H25. XRD analysis confirms GNPs have an induction effect on PP’s β phase crystal structure. The PP-GNP composite exhibits better thermal stability based on determining the TD (degradation temperature), T10 (temperature at 10% weight loss), T50 (temperature at 50% weight loss), and TR (temperature at residual weight). Enhancement in melt (Tm) and crystallisation temperatures (Tc) is are observed due to a heterogeneous nucleation effect. The FESEM analysis concludes that the GNP thickness has a significant effect on the degree of dispersion and agglomeration. The smaller the thickness, the better is the dispersion and the lower is the agglomeration. Overall, the use of thinner GNPs is more advantageous in improving the polymer properties.
Highlights
Graphene, a new material, has attracted considerable attention in recent scientific literature
To understand the morphology of the available Graphene nanoplatelets (GNPs), the field emission scanning electron microscopy (FESEM) images are shown in Figure 1 at different magnifications
The thermal stability of the nanocomposites was analysed by conducting thermogravimetric analysis (TGA) experiments using a Shimadzu DTG-60H apparatus made in Japan
Summary
A new material, has attracted considerable attention in recent scientific literature. High dispersibility is feasible for large-sized GNPs, thereby improving in electrical property due to reduced percolation threshold, but at an equal loading rate, GNPs with higher aspect ratios accelerate percolation within the polymer chain This is considerably important when nanoparticles of an insignificant amount are incorporated in the polymer matrix, so it is possible to use a small amount of nanofillers without causing mechanical failure. Rate up to 380% occurred with the addition of 0.01 wt% of GNPs. Their report revealed up to 11% growth of PP’s β crystals at 1 wt% loading of GNPs. limited studies are available that compare the effect of the sheet size and thickness of GNPs. The above description shows the GNP-reinforced polymer matrix improves the variety of properties and is solely dependent on its physical properties, so selecting a specific sheet size and thickness is extremely important to maximise the composite performance.
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