DETERMINATION OF BASIC CHARACTERISTICS OF PROTECTIVE LAYERS BASED ON POLYMERIC NANOFIBERS
This work focuses on a basic research in developing new class of protective layers for building materials based on polymeric nanofibers. Nonwoven nanotextiles are fibers with diameter spanned from tens to hundreds of nanometers. Thin films consisting of suitable polymer-based nanofibers were prepared using NANOSPIDER equipment. Applied technology is unable to fully guarantee quality (homogeneity, thickness, etc.) of the protective coating. Traditionally used technologies –such as painting or spraying – are not too effective and the separation of protective coating or loosing of protective properties is frequently observed.
Water-Resistance of Nanofiber Textiles
This work deals with the determination of basic waterproofing properties of nanofiber textiles with basis weights of up to 30 g/m2. Samples used in this experiment were made from nanofiber textiles based on two polymers – PVDF and PUR. Each polymer was prepared in three basis weights. All samples were not treated prior to testing. One of the key properties was the contact angle of water and the resistance to penetration of liquid water. Water-resistance of nanofiber textiles was tested according to the harmonized European standard EN 13859-1., Underlays for discontinuous roofing in pitched roof constructions are tested according to this standard. In the position of underlays there has to be some layer with low diffusion resistance of water vapor and relatively high waterproofing. We suppose such properties of nanofiber textiles. Testing of the two groups of material basis shows correlation between the contact angle and water-resistance of the nanofiber textile.
Stress equivalence in the theory of solution hardening
Basinski et al. have shown that if solid solutions of two different solutes in copper (or in silver) have the same flow stress at a given temperature, then they have the same activation volume. This result is known as stress equivalence. The activation volume may greatly exceed the volume associated with a single solute atom, and, over a tenfold range of flow stress or, is roughly proportional to 0~2/3. It is shown that these results follow naturally from Labusch’s theory of solution hardening, in which a dislocation overcomes a group of obstacles simultaneously, although the predicted stress dependence of the activation volume is about 0-1/2 At high stresses the activation volume drops sharply as a result of a change from a regime in which the two partials of a dissociated dislocation move in a coordinated manner to a regime in which the partials move independently. This transition also shows stress equivalence, as is observed. At low stresses there is a transition to Friedel statistics, in which the two partials in a coordinated manner overcome obstacles singly. The position of this transition should not show stress equivalence, and the experiments provide no evidence in this region. The activation volume in Friedel statistics should be proportional to 0-2