Nonisothermal crystallization kinetics of polyoxymethylene/montmorillonite nanocomposite

Abstract

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.

Crystallization kinetics of polyamide 11 in the presence of sepiolite and montmorillonite nanofillers

“…At high supercooling, at temperatures slightly below about 100 °C, there is then observed a rapid increase of the crystallization rate due to a change from heterogeneous nucleation, evident at high temperature, to homogeneous nucleation, prevailing at low temperature. Note that the change of the nucleation mechanism on variation of the supercooling of the melt has been investigated in an independent study [21,22]. Most important in the context of the present work, however, is the observation of a decrease of the characteristic time of crystallization of PA 11 due to the presence of the nanofillers.…”

“…For many polymers including polypropylene [18][19][20], polyoxymethylene [21], poly(ethylene terephthalate) [22], poly(butylene terephthalate) [23], poly(butene-1) [24], but in particular polyamides [25][26][27][28][29][30][31][32][33][34], it has been shown that addition of nanofillers often enhance crystallization and even support the formation of specific crystal polymorphs. In fewer cases, however, a retardation of the crystallization process has also been reported, likely due to an immobilization of polymer chain segments at the polymer/nanofiller interface [35,36].…”

Preparation and Prospect of Polymer Nanocomposites Used in High Voltage Equipment

“…Compositing to the matrixes, not only the mechanical properties of materials prepared by this method are increased significantly, but the composite materials have many especial performance, such as thermal stability, magnetism, electricity and nonlinear optics and so on [17]. But, there are still some limitations in the application of this method, such as melt intercalation method, the nanoparticles are still difficult to be dispersed uniformly.…”

Dielectric relaxation mechanisms in polyoxymethylene/polyurethane/layered silicates hybrid nanocomposites

“…Furthermore, it exhibits low water absorption and good electrical insulation properties, rendering it as a perfect candidate for electrical and electronic applications [8]. On the other hand, the high degree of crystallinity of POM accompanied by brittleness is a limiting factor for its applications [9,10]. Blending POM with thermoplastic polyurethane (PU) is often proposed as a reliable solution for POM toughening [11][12][13].…”