Extruder-made TPO nanocomposites. II. Effect of maleated poly(propylene)/organoclay ratio on morphology and thermal expansion behavior

• Published in: Journal of polymer science. Part B, Polymer physics Polymer physics, 2013-06, Vol.51 (12), p.952-965
• Main Authors: Tiwari, Rajkiran R., Hunter, Douglas L., Paul, Donald R.
• Format: Article
• Language: English
• Subjects: Anhydrides; Applied sciences; Automotive components; coefficient of linear thermal expansion; Composites; Dispersions; elastomer; Elastomers; Exact sciences and technology; Forms of application and semi-finished materials; Mathematical models; Nanocomposites; poly(propylene); Polymer industry, paints, wood; Polypropylenes; Technology of polymers; Thermal expansion; thermoplastic olefin
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.23289

ABSTRACT Coefficients of linear thermal expansion (CTE) for poly(propylene)/ poly(propylene)‐grafted‐maleic anhydride/montmorillonite ethylene‐co‐octene elastomer (PP/PP‐g‐MA/MMT/EOR) blend nanocomposites were determined as a function of MMT content and various PP‐g‐MA/organoclay masterbatch ratios. The nanocomposites were prepared in a twin‐screw extruder at a fixed 30 wt % elastomer, 0–7 wt % MMT content, and various PP‐g‐MA/organoclay ratio of 0, 0.5, 1.0, and 1.5. The organoclay dispersion facilitated by the maleated PP helps to reduce the size of the dispersed phase elastomer particles in the PP matrix. The elastomer particle size decreased significantly as the PP‐g‐MA/organoclay ratio and MMT content increased; the elastomer particles viewed // to flow direction (FD) are smaller and less deformed compared to those viewed // to transverse direction (TD). The elastomer particle shape based on the view along the three orthogonal directions of the injection molded sample is similar to a prolate ellipsoid. The CTE decreased significantly in the FD and TD, whereas a slight increase is observed in the normal direction in the presence of MMT and PP‐g‐MA. The Chow model based on a two population approach showed better fit to experimental CTE when the effect of MMT and elastomer are considered individually. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B Polym. Phys. 2013, 51, 952–965 The high thermal expansion of thermoplastic olefin blends makes them unsuitable for some applications especially in the automotive industry. Significant reduction in the coefficient of linear thermal expansion (CTE) is shown in the presence of montmorillonite (MMT) dispersion facilitated by polypropylene‐grafted‐maleic anhydride (PP‐g‐MA). CTE decreases in flow and transverse direction and increases in normal direction with no change in bulk CTE. Overall, stiffness and toughness improved with no change in bulk CTE in the presence of MMT and PP‐g‐MA.