Crazing as a method for preparation of polymer blends

Abstract

Publications on the development of a new universal method for the preparation of poly mer-polymer blends are reviewed. This approach is based on the phenomenon of solvent crazing, which comes into play in the tensile drawing of polymers in the presence of adsorption active liquid media. It is important that solvent crazing is accompanied by the development of a unique fibillarporous structure, in which the dimensions of craze pores and fibrils do not exceed several tens of nanometers. Two approaches to the preparation of the polymer-polymer blends are described. According to the first approach, the nanoporous structure of the solvent crazed polymer is filled with the monomer, and its further in situ polymerization results in the polymer-polymer blends. The sec ond approach has been recently advanced by the authors of this publication; it involves direct penetra tion of macromolecules into the formed fibillar-porous structure of the solvent crazed polymer. Both approaches are capable of producing diverse polymeric blends with a high degree of mutual dispersion of the components. The above materials are shown to be characterized by specific mechanical, elec trical, and adsorption properties, which are due to the unique fibillar-porous structure of the solvent crazed polymer. The composition, structure, and properties of the prepared blends are controlled by the mechanism of solvent crazing and by the deformation conditions of the initial polymer. Several aspects of the practical application of the polymer blends prepared via the mechanism of solvent craz ing in adsorption active liquid media are reviewed. Fig. 5. Electron micrographs of nanocomposite HDPE-PMMA (tensile strain in the monomer, 200%) after the selective washing of (a) HDPE and (b) PMMA.

Cold Crystallization of Glassy Polylactide during Solvent Crazing

“…stretched via the crazing mechanism. 30,57 The effective volume porosity of such films depends on the tensile strain and may be as large as 60 vol %.…”

“…The micrograph clearly shows the pronounced alternating regions of the bulk polymer and the porous material (crazes), which is similar to those previously obtained for other amorphous glassy polymers (PET, poly­(vinyl chloride), etc.) stretched via the crazing mechanism. , The effective volume porosity of such films depends on the tensile strain and may be as large as 60 vol %.…”

“…In this work, we propose to use the solvent-crazing process − to reduce the PLA fragility and to increase its strength characteristics. Crazing of polymers is a fundamental mechanism of plastic deformation of solid amorphous and semicrystalline polymers, and it is accompanied by the formation of an oriented highly dispersed fibrillar–porous structure in local deformation zones, which are referred to as crazes. , Moreover, it is known − that crazing is considered as a method for loading polymer matrices with different thermodynamically incompatible low- and high-molecular additives, such as dyes, fire-retardant agents, odorants, bactericides, and so forth, with a simultaneous dispersion of fillers up to the nanometric level.…”