ELECTRET PROPERTIES OF MEDICAL NONWOVENS
The paper evaluates the possibility of giving electret properties to nonwoven fabrics used in the manufacture of medical devices. The electret properties of industrial nonwovens of the SMS H40 brands manufactured by LLC "Plant Elastic" (Nizhnekamsk, Russia), SMS 35 and SMS L40 manufactured by JSC "Polymatiz" (Elabuga, Russia), Spanlace 70 and Spanlace C80 manufactured by Beuing Soonercleaning Technology Co (China) were studied. The determination of the surface density of the samples showed that they correspond to the declared ones (the figure in the designation of the brands of canvases, expressed in g/ m2) with an error of no more than 4%. It is established that the level of values of electret characteristics of samples of nonwoven fabrics of samples SMS H40, SMS L40 (lam.) and SMS L40 (non-lam.) It turned out to be quite high and stable: the surface potential is 0.15 kV and higher, the effective surface charge density is 10.04 mC/m<sup>2</sup> and higher, the electric field strength is 0.08 kV/m and higher. This is not surprising, since it was previously proved that the electret characteristics of polypropylene nonwoven fabrics directly depend on their structural parameters: the greater the surface density of the material, the higher the values of their surface potential, effective surface charge density and electric field strength [14, 15]. This is due to the fact that polypropylene is well electreted in the corona discharge. The increased values of electret properties of samples with a higher density are explained by the large amount of polypropylene in the composition of the canvases and the presence of oxygen-containing defects on the polymer surface acting as effective electronic traps. The electret properties of laminated nonwoven fabric are higher than those of non-laminated due to the presence of an additional layer of polymer electretted in the corona discharge. The values of the measured electret characteristics of Spanlace canvases are an order of magnitude lower, because crown electrets based on polar polymers, the role of the heterocarrier in which is very large, have poor electret properties. It is concluded that the level of electret characteristics of nonwoven fabrics based on polypropylene allow them to be used as a material for the creation of antibacterial medical products (clothing, masks, diapers, etc.) with increased microbial purity and reduced bacterial permeability. It is not advisable to make electret materials based on Spanlace canvases.