ИСТИНА

Solvent crazing is an approach to nanoporous polymer membrane preparation. Additionally, in crazing the polymer matrices can be loaded by different organic and inorganic substances and composites with high mutual dispersity of components can be prepared. Hybrid materials with uniform nanoparticles of a filler disposition within the matrices were obtained via solvent-crazing of a polymer in the presence of filler solution in the adsorption-active media (AAM). In the work this approach was applied to silica nanoparticles’ loading into commercial films of isotactic polypropylene and high density polyethylene. Tetrahydrofuran solution of silica sol with concentration of 3-15 wt.% was used as AAM. Silica sol is nanogel obtained by intramolecular polycyclization of hyperbranched polyethoxysiloxane. Two stretching techniques were realized: 1) in a volume of liquid medium and 2) in flowing of AAM on film surfaces. Tensile strain of polymers was 200 %. In both cases solvent-crazing of polymers was found to be carried out via delocalized mechanism; the effective volume porosity of samples was 22-30 vol.%. Silica precipitation within the polymer matrices is the result of the solvent evaporation. The content of introduced silica into a polymer was detected to be 2-17 wt.%. Using the first stretching technique practically all introduced SiO2 particles are discretely distributed within a polymer matrix. Particles’ dimension is 3-10 nm. Stabilizing effect of solid filler to the high dispersed crazed structure of a polymer increases with a rise of silica sol concentration. For example, the increase of SiO2 content in a composite from 2 to 13 wt.% results in 3 time reduction of linear shrinkage of polymer matrices. Using the second stretching technique silica phase, basically, is localized onto polymer film surfaces as a layer with the width of 1.5-2 mcm. This SiO2 layer undergoes defragmentation in the perpendicular direct and contraction in the parallel direct related stretching direct of a polymer film with a relief formation. In the volume of polymer matrices SiO2 particles with a diameter of 5-15 nm are uniformly distributed. Mechanical properties of obtained polymer/silica nanocomposites were investigated. Elasticity modulus of the composite was shown to be increased with the rise of solid filler content.