Nanocomposites of polyolefine matrix. Part I. Polypropylene/clay
Jolanta Janik, Grzegorz Krala, Wacław Królikowski
Quarterly No. 1, 2009 pages 34-39
DOI:
keywords: polymer nanocomposites, polypropylene, clay, montmorillonite, compatibilizer
abstract The significant amount of industrial and governmental research has been and today is being conducted on nanocomposites. The most popular polymers for research and development of nanocomposites are polyamides, polypropylene, polyethylene, styrenics, vinyls, polycarbonates, acrylics, polybutylene terephthalate, epoxies and polyurethanes as well as a variety of miscellaneous engineering resins. The most common filler is montmorillonite clay; these nanoclays are unique since they have a platy structure with a unit thickness of one nanometer or less and an aspect ratio in the 1000:1 range. Unusually low loading levels are required for property improvement. Expected benefits from nanocomposites include improvement in modulus, flexural strength, heat distortion temperature, barrier properties, and other benefits and, unlike typical mineral reinforced system, they are without the conventional trade-off in impact and clarity. Nanocomposites are a new class of composites with very low contents of nanoscale size fillers (around 5 wt. % - as a dispersion) and excellence properties. To improve dispersion, clay platelets are modified with an organic surfactant to give what is called “organo-modified” clay. Even with this chemical modification, it requires the assistance of optimized process conditions to achieve a complete dispersion of organo-clay platelets (exfoliation). In some cases, the polymer is only intercalated between clay platelets. Only well-exfoliated nanocomposites give the expected improvement in properties. This review article presents the process of preparation of nanocomposites based on polypropylene (PP) with different clays - montmorillonites (Organobentonit, Nanofil 5, 9, SE 3000) and with compatybilizer PP-g-MA (polypropylene grafted with maleic anhydride - Polybond X5104) - PP/compatybilizer/clay. The nanocomposites were compounded using a two-screw, corotating extruder, having a L/D = 32 by melt mixing PP with different concentrates - “master batch” (Polybond 60 wt. % /clay 40 wt. %) at different screw speed (100 and 300 rpm). The concentration of clays in the nanocomposites PP was kept in a range 2.5 and 5 wt. % and concentration of Polybond was kept in a range 10 wt. %. The effect of extrusion variant and the mass traction of composite components on the properties obtained (static mechanical properties, thermal and reological properties - MFR and microstructure TEM) was investigated. Experimental shows that, tensile strength m and flexural strength fm, modulus of elasticity at tensile Et and flexural Ef are the highest for nanocomposite PP/5 wt. % Nanofil 5/10 wt. % Polybond X5104 (by 300 rpm), where Et = 1679 MPa, Ef = 2050 MPa, σm = 37MPa, σfm = 59 MPa. In comparison with mechanical properties of PP it was increase by: Et by 35%, Ef by 42%, σm by 14% and σfm by 17%. TEM micrograph of ultra-thin section of nanocomposite PP/5% wt. Nanofil 5/10 wt. % Polybond X5104 shows semi-exfoliated clay platelets. Addition of compatibilizing agents and clay in a concentrate to polypropylene improve mechanical and thermal properties, reduce flammability and smoke emission in comparison with PP.