Development of Polyhydroxybutyrate-Based Packaging Films and Methods to Their Ultrasonic Welding.

This study developed a technical task associated with the formation of welded joints based on biodegradable polymers and their subsequent physicochemical characterization. The primary objective was to establish the effect of the welding process and modification of natural poly(3-hydroxybutyrate) (PHB) with N,N-dibutylundecenoylamide (DBUA) as a plasticizing agent on the structure and properties of PHB-based biopolymer materials as well as the process and structure of welded joints formation using ultrasonic welding technique. The weldability of biodegradable layers based on PHB and PHB/DBUA mixture was ultrasonically welded and optimized using a standard Branson press-type installation. The effect of the DBUA plasticizer and welding process on the structure of PHB-based biodegradable material was investigated using scanning electron microscopy, X-ray diffraction, FT-IR spectroscopy, differential scanning calorimetry, and thermomechanical analysis. The results confirmed that the DBUA acted as an effective plasticizer of PHB, contributing to lower crystallinity of the PHB/DBUA mixture (63%) in relation to the crystallinity degree of pure PHB film (69%). Ultrasonic welding resulted in an additional increase (approximately 8.5%) in the degree of crystallinity in the PHB/DBUA in relation to the initial PHB/DBUA mixture. The significant shift toward lower temperatures of the crystallization and melting peaks of PHB modified with DBUA were observed using DSC concerning pure PHB. The melt crystallization process of PHB was affected by welding treatment, and a shift toward higher temperature was observed compared with the unwelded PHB/DBUA sample. The butt-welded joints of biodegradable PHB/DBUA materials made using the ultrasonic method tested for tensile strength have damaged the area immediately outside the joining surface.

Thermal transport properties of porous silicon filled by ionic liquid nanocomposite system.

This paper investigates thermal transport in a nanocomposite system consisting of a porous silicon matrix filled with ionic liquid. Firstly, the thermal conductivity and heat capacity of two imidazolium and one ammonium ionic liquids were evaluated using the photoacoustic approach in piezoelectric configuration and differential scanning calorimetry, respectively. Then, the thermal transport properties of the composite system "ionic liquid confined inside porous silicon matrix" were investigated with the photoacoustic approach in gas-microphone configuration. The results demonstrated a significant enhancement of the thermal conductivity of the composite system when compared to the individual components, i.e. (i) more than two times for pristine porous silicon and (ii) more than eight times for ionic liquids. These results provide new paths for innovative solutions in the field of thermal management, particularly in the development of highly efficient energy storage devices.

Preparation, Characterization, and Antimicrobial and Antiviral Properties of Silver-Containing Nanocomposites Based on Polylactic Acid-Chitosan.

Antimicrobial and antiviral nanocomposites based on polylactic acid (PLA) and chitosan were synthesized by a thermochemical reduction method of Ag+ ions in the PLA-Ag+-chitosan polymer films. Features of the structural, morphological, thermophysical, antimicrobial, antiviral, and cytotoxic properties of PLA-Ag-chitosan nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and antiviral, antimicrobial, and cytotoxic studies. The effects of temperature and the duration of reduction of Ag+ ions on the structure of PLA-Ag-chitosan nanocomposites were established. During the thermochemical reduction (T = 160 °C, t = 5 min) of silver palmitate ions in PLA-Ag+-chitosan polymer films, Ag nanoparticles with an average size of 4.2 nm were formed. PLA-Ag-chitosan polymer nanocomposites have strong antimicrobial activity against S. aureus and E. coli strains. In particular, for PLA-chitosan samples containing 4% Ag, the diameters of the S. aureus and E. coli growth inhibition zones were 25.8 and 25.0 mm, respectively. The antiviral activity of the nanocomposites against influenza A virus, herpes simplex virus type 1, and adenovirus serotype 2 was also revealed. The PLA-4%Ag-chitosan nanocomposites completely inhibited the cytopathic effect (CPE) of herpes virus type 1 by 5.12 log10TCID50/mL (high antiviral activity) and the development of the CPE of influenza virus and adenovirus by 0.60 and 1.07 log10TCID50/mL (relative antiviral activity). The obtained nanocomposites were not cytotoxic; they did not inhibit the viability of MDCK, BHK-21, and Hep-2 cell cultures.

Nanoporous Polymer Films of Cyanate Ester Resins Designed by Using Ionic Liquids as Porogens.

Novel nanoporous film materials of thermostable cyanate ester resins (CERs) were generated by polycyclotrimerization of dicyanate ester of bisphenol E in the presence of varying amounts (from 20 to 40 wt%) of an ionic liquid (IL), i.e., 1-heptylpyridinium tetrafluoroborate, followed by its quantitative extraction after complete CER network formation. The completion of CER formation and IL extraction was assessed using gel fraction content determination, FTIR, 1H NMR, and energy-dispersive X-ray spectroscopy (EDX). SEM and DSC-based thermoporometry analyses demonstrated the formation of nanoporous structures after IL removal from CER networks, thus showing the effective role of IL as a porogen. Pore sizes varied from ~20 to ~180 nm with an average pore diameter of around 45-60 nm depending on the initial IL content. The thermal stability of nanoporous CER-based films was investigated by thermogravimetric analysis.