Key words: crazing, supercritical carbon dioxide, nanoporous structure, polyethylene, polypropylene
Peculiarities of the uniaxial stretching of partially crystalline polyolefins on the examples of high density polyethylene and isotactic polypropylene in the presence of carbon dioxide in temperature and pressure ranges 35—75 °C and 0.1—30 MPa are investigated. The formation of nanoporous structure with a pore diameter of 3—7 nm in the polymer films via the delocalized crazing mechanism is shown to start at 4—5 MPa. The increment of the sample volume at the expanse of pore formation depends on the fluid parameters (pressure, temperature, density) and the deformation degree of a polymer and can reach 30—70 %. The most efficient pore formation via the crazing mechanism occurs if the fluid is in a supercritical state at near-critical temperature (35 °C) in a pressure range of 10—30 MPa where the density of CO2 is approaching the density of liquid.
doi:10.1134/S199079311408017X