The nonisothermal crystallization kinetics of poly(propylene) (PP) and poly(propylene)/organic‐montmorillonite (PP/Mont) nanocomposite were investigated by differential scanning calorimetry (DSC) with various cooling rates. The Avrami analysis modified by previous research was used to describe the nonisothermal crystallization process of PP and PP/Mont nanocomposite very well. The values of half‐time and Zc showed that the crystallization rate increased with increasing cooling rates for both PP and PP/Mont nanocomposite, but the crystallization rate of PP/Mont nanocomposite was faster than that of PP at a given cooling rate. The activation energies were estimated by the Kissinger method, and the values were 189.4 and 155.7 kJ/mol for PP and PP/Mont nanocomposite, respectively. PP/Mont nanocomposite could be easily fabricated as original PP, although the addition of organomontmorillonite might accelerate the overall nonisothermal crystallization process. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 408–414, 2002; DOI 10.1002/polb.10101

ABSTRACT:In this study, three cationic surfactants (hexadecyltrimethylammonium chloride, hexadecyldimethylbenzylammonium chloride, and octadecyltrimethylammonium chloride) were used to modify montmorillonite and polyethylene (PE)/maleic anhydride grafted polyethylene (PE-g-MAH)/organic-montmorillonite (Org-MMT) nanocomposites, prepared by two blending processes (directmelt blending and solution blending). X-ray diffractometry and transmission electron microscopy were used to investigate the intercalation behavior and microstructure of composites. Mechanical properties were also tested. It was found that the intercalation effect of PE/PE-g-MAH/Org-MMT could be enhanced by increasing the content of PE-g-MMT, using the silicate modified by a cationic surfactant with a benzyl group or long alkyl chain, adopting the solutionblending method or using high-density polyethylene as matrix. The degree of crystallinity of composites and the crystalline thickness perpendicular to the crystalline plane [like (110) and (200)] decreased with increasing amounts of PEg-MAH and, under certain prescription, the crystalline thickness of the composite made by the solution method was much smaller than that made by direct-melt blending. This clearly showed that Org-MMT and PE-g-MAH had a heterogeneous nucleation effect on crystallization of PE from the melt, resulting in a decrease of crystalline thickness, and the heterogeneous nucleation effect was more evident in the nanocomposite made by the solution-blending method than in that made by the direct-melt intercalation process. The tensile strength initially increased and then decreased with increasing contents of PE-g-MAH. The maximum value in tensile strength (23.3 MPa) was achieved when the concentration of PE-g-MAH was 6 wt %. The impact strength increased concomitantly with the content of PE-g-MAH; it was 122.2 J/m when the concentration of PE-g-MAH was 9 wt %.

ABSTRACT:The nonisothermal crystallization kinetics of polyoxymethylene (POM), polyoxymethylene/Na-montmorillonite (POM/Na-MMT), and polyoxymethylene/organic-montmorillonite (POM/organ-MMT) nanocomposites were investigated by differential scanning calorimetry at various cooling rates. The Avrami analysis modified by Jeziorny and a method developed by Mo were employed to describe the nonisothermal crystallization process of POM/Na-MMT and POM/organ-MMT nanocomposites. The difference in the values of the exponent n between POM and POM/montmorillonite nanocomposites suggests that the nonisothermal crystallization of POM/Na-MMT and POM/organ-MMT nanocomposites corresponds to a tridimensional growth with heterogeneous nucleation. The values of half-time and the parameter Z c , which characterizes the kinetics of nonisothermal crystallization, show that the crystallization rate of either POM/Na-MMT or POM/organ-MMT nanocomposite is faster than that of virgin POM at a given cooling rate. The activation energies were evaluated by the Kissinger method and were 387.0, 330.3, and 328.6 kJ/mol for the nonisothermal crystallization of POM, POM/Na-MMT nanocomposite, and POM/organ-MMT nanocomposite, respectively. POM/montmorillonite nanocomposite can be as easily fabricated as the original polyoxymethylene, considering that the addition of montmorillonite, either Na-montmorillonite or organ-montmorillonite, may accelerate the overall nonisothermal crystallization process.