Polyamide 11 Composites with Surface-Activated Intact Mica Structures for Advanced Applications

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The present study explores the potential improvement of the mechanical properties of bio-based polyamide 11 (PA11) for demanding industrial application using natural and surface-treated mica at 1, 2 and 5 wt%. Suppressed water uptake by up to 4% was revealed with an unfavorable effect of the surface treatment. Impact strength decreased with filler content from 39.6 kJ m−2 to between 22–10 kJ m−2, while stiffness and resistance towards deformation improved: flexural modulus rose from 518.5 MPa to 596 MPa at 5 wt%-treated small particle, and elastic modulus changed from 542.7 MPa to 705.6 MPa. Particle size dependent trends were observed in crystallinity by Differential Scanning Calorimetry (DSC). Surface treatment promoted the presence of a mesophase form, which was also presented by Scanning Electron Microscopy (SEM). Dynamic Mechanical Analysis (DMA) revealed increased internal friction, temperature-dependent modifications in the elastic properties and a glass transition temperature of 36.6 °C. X-ray Diffraction (XRD) proved an unusual decrease in basal spacing of mica from 9.92 to 9.82 Å due to silanization; however, the compounding process provoked some increase again up to 10.03 Å. Results highlight a viable pathway to modify the properties of PA11 with a primarily role in the filler concentration and dimensions over the surface characteristics.