Compounding and spinning of polypropylene nanocomposites with kaolinite

Isotactic polypropylene (PP) was melt compounded with the various amount of kaolinite nanoparticles (from 3% up to 30% wt). Nanofilled fibers with low and high filler amount were successfully produced by melt-spinning process through a co-rotating twin screw extruder and drawn at 145°C in air at increasing draw ratio (up to 15). The dispersion of nanoparticles enhanced the elastic modulus of PP, positively affected the stress at break, and decreased the strain at break for compositions at high nanofiller content (20% and 30% wt.). Moreover, kaolinite significantly improved the crystallinity content, acting as a nucleating agent, and it increased the thermal stability.

Fibers of high density polyethylene (HDPE)/organically modified hydrotalcite (LDH) were produced by melt intercalation in a two-step process consisting of twin-screw extrusion and hot drawing. The optimum drawing temperature was 125 degrees C at which the draw ratios up to 20 could be achieved. XRD analysis revealed intercalation with a high degree of exfoliation for the composites with 1-2% of LDH. Higher thermal stability of nanofilled fibers was confirmed by TGA analysis. DSC data indicated that dispersed LDH particles act as a nucleating agent. Crystallization kinetics of the HDPE matrix in the composite fibers is characterized by two transition temperatures, that is, for Regimes I/II at 123 degrees C and for Regimes II/III ranging between 114-119 degrees C as a function of the nanocomposite composition. Fibers with 1-2% of LDH show for the drawing ratios up to 15 a higher elastic modulus, 9.0-9.3 GPa (with respect to 8.0 GPa of the neat HDPE), maintain tensile strength of 0.8 GPa and deformation at break of 20-25%. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40277.