Materials With Improved Properties From Polymer-Ceramic Nanocomposites

Abstract

In order to link the fundamental research field of polymer crystallization with the technical important field of composite materials polymer-layered silicate nanocomposites from polyethylene (PE) are prepared and their morphology and properties are investigated. The effect of an external confinement introduced by highly anisotropic silicate layers of organically modified clay minerals on crystal growth and nanocomposite properties has been studied. The prepared nanocomposites of organically modified clay minerals and PE exhibit not only a homogeneous distribution of individual silicate layers but also of tactoids. The isothermal crystallization rate of PE in the corresponding nanocomposite at 120 °C is increased in the composite material due to the action of the silicate layers. A significant effect on crystal phase has not been observed so far but from X-ray experiments, however the crystal size seems to be influenced. The thermal stability of the nanocomposites is significantly enhanced and the decomposition mechanism has been changed due to the presence of the layered silicates within the host polymer acting as a barrier for the diffusion of small molecules like oxygen. Due to the none permanent attachment of the polymer chains to the silicate surface the thermal-mechanical properties are only moderately enhanced at low temperature while the glass transition temperature remains unaffected.

Preparation and properties of polyamide-6-boehmite nanocomposites

“…All these observations are in agreement with the behavior reported for PA6 nanocomposites [14][15][16][17]. Generally speaking, presence of an inorganic filler results in poor rearrangement of polymer molecules and thus, favors the formation of the g-phase.…”

“…By comparing the melting peaks at various boehmite concentrations, this low temperature peak appears to grow at the expense of the high melting a-peak, so that the chain arrangement is probably similar to the a-structure. As the melting point is reduced one can speculate that this a 0 -structure forms crystallites with a lower lamellar thickness [15] or involves a distorted lamellar structure arising form the curvature induced by the boehmite cylinders. This should be compared to the observation that in PA6 nanocomposites containing montmorillonite clay platelets a higher melting phase of PA6 has been observed [16]; which probably results from the stabilization of the lamellar crystals.…”

Features, Questions and Future Challenges in Layered Silicates Clay Nanocomposites with Semicrystalline Polymer Matrices

“…The improved properties of the nanocomposite are either ascribed to the polymer-clay interface, [24,25] or to the clay aspect ratio. [6,26] According to Shelley et al, [27] the enhancement of stiffness, strength and barrier properties is the consequence of the existence of a confined polymer fraction having a higher local stiffness.…”

“…Polyamide 6 [82,83] Polymerisation Epoxy [84,85] Poly(methyl methacrylate) [86,87] Poly(e-caprolactone) [88] Polyurethane [89] Polyimide [26,90] Polyamide 12 [91] Polyester [92,93] Melt compounding Polyamide 6 [29,94] Poly(propylene) [95,96] Polyethylene [24] Polyamide 66 [97] Poly(propylene) [98] Solution blending Polyethylene [99] Poly(vinylpyrrolidone) [100] Poly(vinyl alcohol) [101] Poly(ethylene oxide) [1] same metal as Mg 2þ in talcum occupies all sites, the silicate is neutral and mechanical processes can easily separate the layers. In the silicate layers of mica or smectic clay, Na þ , Ca þ or K þ act as counter charges in the gallery spacing resulting in a strong ionic bond which is hard to break.…”

On The Origins of Silicate Dispersion in Polysiloxane/Layered‐Silicate Nanocomposites

“…Confinement effects are well known and have been described elsewhere. [14][15][16] Significant alterations in crystallite morphology [11,13,[17][18][19][20][21][22][23][24][25][26] and orientation, [11,13,17,18,21,24,[26][27][28] as well as the crystalline phase(s) present, [11,13,21,[26][27][28][29][30][31][32][33][34][35][36] will also affect the materials properties. Finally, the flexible nature of these layers [37] and their propensity to align at high strains [11,13,[26][27][28][38][39][40][41] and to induce void formation at high stresses [17,…”