Kristina Žukienė

The effect of surface properties on the adhesion of modified polychloroprene used as adhesive

The adhesion properties of polychloroprene can be improved by addition of such materials as piperylene–styrene co-polymer (PSC), VeoVa-10 polymer, VeoVa-11/methyl methacrylate/2ethylhexyl acrylate co-polymer (VeoVa-11/MMA/2EHA) and poly(vinyl acetate) waste (wPVAc). Here, the relationship between adhesion properties and surface tension of polychloroprene was investigated. Contact angle measurements have been used to study the effects of nature and content of polymeric additives on the adhesion and surface properties of polychloroprene. Low-surface-tension VeoVa-10 polymer has the tendency to migrate to the surface of polychloroprene; thus, adhesion is determined mainly by this additive property. Enrichment of polychloroprene film bottom layer by the additive was observed using high-surface-tension PSC and wPVAc. In this case, the adhesion properties of polychloroprene depend on the interactions at the interface. Adhesion properties of polychloroprene were found to depend not only on compatibility between adhesive components, but also on compatibility between the adherend and the adhesive.

Adhesion Studies on Piperylene-Styrene Copolymer Modified Polychloroprene Adhesive: Phase Morphology and Surface Composition

The effect of piperylene-styrene copolymer (PSC) content on the bulk and surface properties of polychloroprene (CR) adhesive was investigated by different methods. Addition of PSC improves adhesion and strength properties of CR. PSC slightly deteriorates thermal stability of CR. X-ray diffraction, UV, and IR spectroscopies studies showed that no chemical interaction between CR and PSC phases occurs. Distinct bulk and surface structure of modified adhesive is caused by the high surface energy difference between CR and PSC phases. By AFM force-distance curve measurements it was deduced that the differences between pull-off force values of modified CR film surfaces in contact with air and backing was related to the enrichment of the higher surface energy component at the backing/film interface. The properties and structure of boundary layers of adhesive modified by high surface energy polymeric additive are essential for the adhesion behavior.

UV-Curable Aliphatic Silicone Acrylate Organic–Inorganic Hybrid Coatings with Antibacterial Activity

The most effective means to protect against bacterial invasion and to reduce the risk of healthcare-associated infections are antibacterial components synthesis. In this study, a novel process for the synthesis of organic–inorganic hybrid coatings containing silver nanoparticles is presented. Silver nanoparticles and polymer formation proceeds simultaneously through the in situ photoreduction of silver salt to silver nanoparticles and UV-crosslinking of bifunctional aliphatic silicone acrylate. The nanocomposite films with 0.5–1.43 wt % of silver nanoparticles concentration were obtained and investigated. The formation of silver nanoparticles in polymer matrix was confirmed via UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron spectroscopy, and energy dispersive spectroscopy. Our investigations clearly show the formation of silver nanoparticles in silicone acrylate network. Direct photoreduction of silver salt by UV-radiation in the organic media produced silver nanoparticles exhibiting cubic crystal structure. The size of nanoparticles was determined to be near 20 ± 5 nm. The antibacterial activities of coatings were determined using the disc diffusion and direct contact methods. UV-curable silicone acrylate hybrid coatings exhibited antibacterial activity against harmful bacteria strains.

Properties of mechanically recycled polycaprolactone-based thermoplastic polyurethane/polycaprolactone blends and their nanocomposites

In this study, the effect of mechanical recycling process parameters on the morphology, properties, and hydrolytic degradation of polycaprolactone-based thermoplastic polyurethane/polycaprolactone waste blends (TPU-PCL/PCL) and their nanocomposites were investigated. Modification of recycled TPU-PCL/PCL was carried out using natural and organically modified montmorillonite nanoclays. Effect of reprocessing time on the structure of TPU-PCL/PCL and nanoclay separation in nanocomposites was evaluated by differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy analysis. It has been demonstrated that mechanical recycling of waste from industrial TPU-PCL/PCL only marginally changes its properties. The exfoliation of Cloisite 30B clay was not enough to enhance the properties of recycled materials. However, the structure, thermal, and mechanical properties, hydrolytic degradation of obtained recycled TPU-PCL/PCL:nanoclay nanocomposites depend on the separation level of the nanoclays.