Epitaxial nucleation of crystallization at polymer–filler interfaces

Abstract

SummaryIn polymer composites the interaction between polymer matrix and filler particles often results in nucleation of spherulites. The principles of polymer crystal nucleation and spherulite growth are investigated using scanning transmission electron microscopy (STEM) and microdiffraction techniques in combination with polarized light microscopy. Simultaneous diffraction patterns from the interface of the filler and the polymer were obtained. Special precautions for successful recording of the diffraction patterns were used to overcome the rapid loss of polymer crystallinity, resulting from electron beam damage. Analysis of the diffraction patterns has shown that partial epitaxial correlation between the atomic periodicity of the particle surface and the molecular periodicity of polymer chains is always present when spherulites are nucleated. STEM images show that only large particles, with well developed facets (cleavage planes), are nucleating. The nucleating efficiency of the filler is therefore dependent on the size as well as on the crystallographic orientation of the facet. Small particles, or those with no suitable facets, do not affect the crystalline structure of the polymer. It is also shown that anisotropic polymer structures can be formed by inhomogeneous dispersion of nucleating filler particles.

Nucleation mechanism of polyhydroxybutyrate and poly(hydroxybutyrate‐co‐hydroxyhexanoate) crystallized by orotic acid as a nucleating agent

“…The misfit, expressed as the deviation percentage for one period, could be accommodated by the polymer elasticity up to 15%. 35 After studying the nucleation of PHB, Barham and coworkers 36 have suggested that the nucleating effect of saccharin, ammonium chloride and BN were following this last mechanism. The efficiency of these nucleants was explained by a good lattice matching between the nucleating crystal and the b spacing of the polymer.…”

The Influence of Calcium‐Stearate‐Coated Calcium Carbonate and Talc on the Quiescent and Flow‐Induced Crystallization of Isotactic Poly(propylene)

“…While calcium carbonate only weakly nucleates iPP, with an efficiency depending on the particle properties and coating,8, 12, 13 talc is a very strong nucleating agent for iPP 6, 9–11. Its surface has a great nucleation ability, which may be due to the good fit between the surface structure and the ordering of the polymer stems which are deposited onto it during nucleation 14…”

Crystal growth in alumina/poly(ethylene terephthalate) nanocomposite films

“…5 One mechanism by which fillers alter physical properties is by causing changes in the crystallinity, spherulite size, lamellar size, and even crystal structure of semicrystalline polymers. [6][7][8] In this paper, we present the crystallization kinetics and crystalline structure of PET in 38 nm alumina/PET nanocomposite thin films. Many studies on the bulk morphology of semicrystalline polymers have shown that crystalline lamellae of the polymer chains organize into a spherulitic structure, 9 but it is also known that under geometric constraints, i.e., in thin films (<100 nm), semicrystalline polymers are not capable of growing three-dimensional (3D) spherulites.…”