Processing and characterization of unidirectional thermoplastic nanocomposites
The manufacture of continuous fibre-reinforced thermoplastic nanocomposites is discussed for the case of E-Glass reinforced polypropylene (PP) matrix and for E-Glass reinforced Polyamide-6 (Nylon-6), with and without dispersed nanoclay (montmorillonite) platelets. The E-Glass/PP nanocomposite was manufactured using pultrusion, whereas the E-Glass/Nylon-6 nanocomposite was manufactured using compression molding. Mechanical characterization of nanocomposites were performed and compared with traditional microcomposites. Compressive as well as shear strength of nanocomposites was improved by improving the yield strength of the surrounding matrix through the dispersion of nanoclay. Significant improvements were achieved in compressive strength and shear strength with relatively low nanoclay loadings. Initially, polypropylene with and without nanoclay were melt intercalated using a single-screw extruder and the pultruded nanocomposite was fabricated using extruded pre-impregnated (pre-preg) tapes. Compression tests were performed as mandated by ASTM guidelines. SEM and TEM characterization revealed presence of nanoclay in an intercalated and partially exfoliated morphology. Mechanical tests confirmed significant improvements in compressive strength (~122% at 10% nanoclay loading) and shear strength (~60% at 3% nanoclay loading) in modified pultruded E-Glass/PP nanocomposites in comparison with baseline properties. Uniaxial tensile tests showed a small increase in tensile strength (~3.4%) with 3% nanoclay loading. Subsequently, E-Glass/Nylon-6 nanocomposite panels were manufactured by compression molding. Compression tests were performed according to IITRI guidelines, whereas short beam shear and uni-axial tensile tests were performed according to ASTM standards. Mechanical tests confirmed strength enhancement with nanoclay addition, with a significant improvement in compressive strength (50% at 4% nanoclay loading) and shear strength (~36% at 4% nanoclay loading) when compared with the baseline E-Glass/Nylon-6. Uni-axial tensile tests resulted in a small increase in tensile strength (~3.2%) with 4% nanoclay loading. Also, hygrothermal ageing (50 °C and 100% RH) of baseline and nanoclay modified (4%) E-Glass/Nylon-6 were studied. It was observed that the moisture diffusion process followed Fickian diffusion. E-Glass/Nylon-6 modified with 4% nanoclay loading showed improved barrier performance with a significant reduction (~30%) in moisture uptake compared to baseline E-Glass/Nylon-6 composites. Significant improvement in mechanical properties was also observed in hygrothermally aged nanocomposite specimens when compared with the aged baseline composite.