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Positron annihilation lifetime spectroscopy (PALS) is a recognized instrument for the studies of size-distribution of nanopores (intrinsic free volume holes FVH) in polymers, particularly membrane materials. The limits of this application in the case of “alien” pores, produced by swelling of poly (hexafluoro propylene) PHFP in the gas (CO2) in super-critical (sc-) state are discussed. The obtained conclusions are controlled by measurements of low temperature gas (N2) sorption (LTGS) and by comparison of the data with the results on permeation of various gases through the PHFP membrane. Attention is payed to relaxation with time of the newly created FVH in the PHFP membrane.

Objectives. To quantitatively describe the thermochromic properties of films of isotactic polypropylene, a large-tonnage polymer widely used in the production of flexible packaging for goods and foodstuffs, as well as substantiate the possibility of covert labeling of transparent packaging.Methods. Differential scanning calorimetry, polarization photometry, infrared Fourier spectrometry, gravimetry, temperature control, physical and mechanical strength testing.Results. The identified thermochromic effect of dichroism in polarized light on industrial samples of transparent biaxially oriented film of isotactic polypropylene was studied. A change in the phase composition of the film-forming composition during short-term heating during marking was established. The absence of heat shrinkage and change in transparency in non-polarized light was shown, which provides the possibility of hidden recording of information and its contrast manifestation in a passing light stream at a certain arrangement of light filters.Conclusions. The causes and optimal conditions of the thermochromic effect are established. It is proposed to use local contact heat treatment of a polypropylene film for covert recording of information and marking of product packaging in order to protect against counterfeiting.

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Brands and products counterfeiting, and falsification are global problems for the development and distribution of high‐tech industrial and food products, which affect world economies. One way to solve these problems is to develop original packaging with protection elements and labeling against counterfeiting, which excludes the possibility of replication and forgery by printing or other methods. The most reliable way to protect packaging from counterfeiting is the use of new materials with unique optical properties and constantly updated technologies for packaging manufacturing and labeling. This paper proposes a new multi‐level technology for the design, manufacture and hidden labeling of polymer packaging made from several layers of transparent polymer films. The design and marking of the multilayer films are combined with perforation, thermal treatment and heat sealing of the package. The reliability of the proposed markings is based on the characterization of optical pleochroism effects in transparent multilayer polymer materials with shape memory. The thermomechanical and optical properties of films made of bulk thermoplastics (polypropylene, polystyrene, polyvinyl chloride and polyethylene) were characterized in polarized light. The modification and combination of these films provide a high color difference and sufficient contrast of hidden markings, allowing to identify genuine products by bar codes formed from shape memory films in sealing seams of flexible polymer packaging.