Virginija Jankauskaitė

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.

Holograms recording with pulsed laser on diazonaphthoquinone-novolac-based photoresists and their nanocomposites

Abstract. Direct write digital holography technique (DWDH) using a single 440-nm pulsed laser exposure has been proposed to record master holograms on commercially available positive-tone photoresist systems based on a mixture of diazonaphthoquinone and novolac resin (DNQ-novolac) of different thicknesses. The DNQ-novolac nanocomposite doped with copper nanoparticles (CuNPs) films was also used. The method for numerical evaluation of hologram quality based on reflected beam diffraction intensity measurements was proposed and verified. It was found that all investigated photoresist nanocomposites were sensitive enough to record holographic structures at low single pulse laser exposures (from 3.3 to 18.0  mJ/cm2). Moreover, doping DNQ-novolac nanocomposite with CuNPs s increases its sensitivity to pulsed laser exposure by more than 30%. The potential of single pulsed laser exposures to record high quality master holograms on commercially available and metal nanoparticles doped photoresists with at least five times lower exposures values as compared to the continuous-wave laser exposures usually used to expose photoresist materials in holographic applications, opens the possibility to use pulsed lasers for quick master-originals origination for embossed holograms applying a DWDH technique or analog methods.

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.

Comparison of diffraction patterns exposed by pulsed and CW lasers on positive-tone photoresist

Two different grating formation geometries for recording onto the positive-tone photoresist with pulsed laser and continuous-wave sources are analyzed and compared. Diffraction efficiency measurements and atomic force microscopy (AFM) examination have been performed in order to investigate the optical and topographical properties of the recorded structures. Gratings patterned by a continuous-wave laser and by a pulsed laser working in the single pulse and multipulse regimes showed different surface roughness and optical properties. The possible reasons for surface roughness and effective exposure differences between gratings created with pulsed and continuous-wave laser radiations are discussed. The processing schemes for diffractive structures patterned by pulsed laser onto positive-tone photoresist for commercial hologram production are analyzed and presented in this work.

Characterization of tissue engineered cartilage products: Recent developments in advanced therapy.

Legislative requirements for the quality of pharmacological agents underwent certain evolution when new type of therapies emerged. This relates to cell based medicines, such as tissue engineered cartilage products (TECP) which are increasingly developed as new modalities for widely prevalent orthopaedic disorders. Although quality measures for TECP are subject to the same general regulatory quality requirements, combination of cellular and scaffold substances requires definition of specific characteristics in vitro that are highly relevant to potency and efficacy of the newly designed medicinal product. One of the specific issues in designing cell based medicines is the fact that the biological activity of active substance, or cells, usually is altered after seeding them on a three-dimensional scaffold. Newly acquired features of the TECP are influenced by chemical, physical and mechanical characteristics of the scaffolds. A vast array of analytical methods has been employed to measure efficacy and potency of TECP in cartilage regeneration studies in vitro. Designing specific physical characteristics of scaffolds may become essential part influencing pharmacological activity of cell based medicinal products, and discern TECP from typical pharmacological products. As an example, increasingly growing popularity of three-dimensional printing that utilizes direct laser writing technique provides an opportunity to improve efficacy of the final TECP. This review is intended to provide brief summary of current approaches used to characterize cells and scaffolds in vitro before and after combination into TECP. Validating TECP as pharmacological agents with unique biological and physical characteristics may broaden their clinical application.

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.

Influence of the Structure of Footwear Upper and Lining Materials on Their Electrical Properties

Protective footwear for occupational use conducts static electricity through the upper, linings, insole and outsole into the ground. Footwear must be made from appropriate material to reduce the possibility of electrocution and other electricity-related incidents. In this study the influence of footwear materials for the upper and lining components’ structure on their electrical properties was investigated. For investigations leather and various textile laminates were chosen. The thickness of leather coating, composition of textile laminates, the upper-lining system, and relative humidity of the environment on electrical resistivity changes were evaluated. Leather shows antistatic properties at standard humidity, but its electrical conductivity greatly increases at high humidity due to the presence of polar groups in the leather structure. Textile lining laminates composed of natural and synthetic fibres are insulators, but their systems with leather at high humidity show resistivity values close to antistatic materials. Leather acrylic coating decreases the electrical conductivity of materials.