Breathable polymeric materials based on high-density polyethylene prepared by environmental crazing

This work addresses the preparation of breathable materials based on high-density polyethylene (HDPE) and characterization of their performance. The sustainable HDPE mesoporous materials were prepared by the tensile drawing of the HDPE films in the presence of physically active liquids (PALEs) via the mechanism of environmental intercrystallite crazing (EIC). The prepared mesoporous materials were characterized by the different physicochemical methods such as differential scanning calorimetry (DSC), atomic force microscopy (AFM), low-temperature nitrogen adsorption (LTNA), and so forth. Water vapor transmission rate (WVTR) of the breathable materials can be tailored by varying the tensile strain upon the EIC and is found to be equal to 597–1345 g m⁻² day⁻¹. The breathable HDPE-based materials are characterized by good mechanical and insulating properties as well as by high water entry pressure (~43–47 bar). Hence, the deformation of HDPE films via the EIC mechanism provides an efficient route for the preparation of mesoporous breathable materials based on the low-cost commercial polymers, which can be used as waterproof, protective, subroof, gas storage, and packaging materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48567.     

Relaxation capacity and cracking resistance of nitrous coating produced by electron-beam facing of 0.6C-24Cr-0.7N-16Mn steel powder during wear by hard abrasive under heavy loads

Specific features of the topography of friction tracks formed during the sliding of a WCo6 ball over an austenitic nitrous coating at various velocities of sliding under various loads using the ball-on-disc arrangement are studied and compared with those for the WCo6 ball-110Mn13 steel pair. It has been found that the wear resistance of nitrous austenite is due to its capacity to relax frictional stresses. The correlation between the H ₃/E ₂ parameter of the friction surface and the wear rate has been shown.     

Biodeterioration of plasticized PVC/montmorillonite nanocomposites in aerobic soil environment

The aim of this study was to assess the effect of montmorillonite nanofillers, Cloisite Na⁺ and Cloisite 30B, on the biodeterioration of PVC-based nanocomposites plasticized by means of dioctyl adipate (DOA), dioctyl phthalate (DOP) and modified poly(propylene adipate) (PPA), in the aerobic environment of soil (soil burial test, time of exposure: 198 days). Tests were carried out at 25 ± 1 °C, under moisture-controlled (55 %) and aerobic conditions. The extent of the biodeterioration process was evaluated on the basis of changes in weight, tensile strength and elongation-at-break values. Finally, analysing chemical structures using FTIR and visual observation, both macroscopic and microscopic via scanning electron microscopy assisted in the evaluation process. The results of this study suggested that plasticized PVC/montmorillonite nanocomposites have an increased susceptibility for undergoing biological deterioration in comparison with plasticized PVC. In each instance, adding Cloisite 30B resulted in reducing the resistance of PVC/montmorillonite nanocomposites to the actions of microorganisms. In the case of Cloisite Na⁺ as the filler, results cannot be clearly quantified, although a negative influence prevailed, particularly a change in colour, whose change intensity was also dependent on the type of plasticizer, increasing in the following sequence: PVC/DOA/Cloisite Na⁺ > PVC/DOP/Cloisite Na⁺ > PVC/PPA/Cloisite Na⁺. However, each sample containing Cloisite Na⁺ achieved a lower rate of degradation (by normalised weight loss and FTIR) compared with nanocomposites containing Cloisite 30B. This can be attributed to the migration and accumulation of Cloisite Na⁺ on the surface of the nanocomposites particles where the former phenomenon producing a surface barrier which caused a reduction in the permeability of the material toward water and microorganisms, during the test.     

Immobilization of silver nanoparticles on polyethylene terephthalate

Two different procedures of grafting with silver nanoparticles (AgNP) of polyethylene terephthalate (PET), activated by plasma treatment, are studied. In the first procedure, the PET foil was grafted with biphenyl-4,4′-dithiol and subsequently with silver nanoparticles. In the second one, the PET foil was grafted with silver nanoparticles previously coated with the same dithiol. X-ray photoelectron spectroscopy and electrokinetic analysis were used for characterization of the polymer surface at different modification steps. Silver nanoparticles were characterized by ultraviolet-visible spectroscopy and by transmission electron microscopy (TEM). The first procedure was found to be more effective. It was proved that the dithiol was chemically bonded to the surface of the plasma-activated PET and that it mediates subsequent grafting of the silver nanoparticles. AgNP previously coated by dithiol bonded to the PET surface much less.     

Selected Simple Natural Antimicrobial Terpenoids as Additives to Control Biodegradation of Polyhydroxy Butyrate

In this experimental research, different types of essential oils (EOs) were blended with polyhydroxybutyrate (PHB) to study the influence of these additives on PHB degradation. The blends were developed by incorporating three terpenoids at two concentrations (1 and 3%). The mineralization rate obtained from CO₂ released from each sample was the factor that defined biodegradation. Furthermore, scanning electron microscope (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) were used in this research. The biodegradation percentages of PHB blended with 3% of eucalyptol, limonene, and thymol after 226 days were reached 66.4%, 73.3%, and 76.9%, respectively, while the rate for pure PHB was 100% after 198 days, and SEM images proved these results. Mechanical analysis of the samples showed that eucalyptol had the highest resistance level, even before the burial test. The other additives showed excellent mechanical properties although they had less mechanical strength than pure PHB after extrusion. The samples’ mechanical properties improved due to their crystallinity and decreased glass transition temperature (Tg). DSC results showed that blending terpenoids caused a reduction in Tg, which is evident in the DMA results, and a negligible reduction in melting point (Tm).     

cNTnC and fYTnC2, Genetically Encoded Green Calcium Indicators Based on Troponin C from Fast Animals

NTnC-like green fluorescent genetically encoded calcium indicators (GECIs) with two calcium ion binding sites were constructed using the insertion of truncated troponin C (TnC) from Opsanus tau into green fluorescent proteins (GFPs). These GECIs are small proteins containing the N- and C-termini of GFP; they exert a limited effect on the cellular free calcium ion concentration; and in contrast to calmodulin-based calcium indicators they lack undesired interactions with intracellular proteins in neurons. The available TnC-based NTnC or YTnC GECIs had either an inverted response and high brightness but a limited dynamic range or a positive response and fast kinetics in neurons but lower brightness and an enhanced but still limited dF/F dynamic range. Here, we solved the crystal structure of NTnC at 2.5 Å resolution. Based on this structure, we developed positive NTnC2 and inverted iNTnC2 GECIs with a large dF/F dynamic range in vitro but very slow rise and decay kinetics in neurons. To overcome their slow responsiveness, we swapped TnC from O. tau in NTnC2 with truncated troponin C proteins from the muscles of fast animals, namely, the falcon, hummingbird, cheetah, bat, rattlesnake, and ant, and then optimized the resulting constructs using directed molecular evolution. Characterization of the engineered variants using purified proteins, mammalian cells, and neuronal cultures revealed cNTnC GECI with truncated TnC from Calypte anna (hummingbird) to have the largest dF/F fluorescence response and fast dissociation kinetics in neuronal cultures. In addition, based on the insertion of truncated TnCs from fast animals into YTnC2, we developed fYTnC2 GECI with TnC from Falco peregrinus (falcon). The purified proteins cNTnC and fYTnC2 had 8- and 6-fold higher molecular brightness and 7- and 6-fold larger dF/F responses to the increase in Ca²⁺ ion concentration than YTnC, respectively. cNTnC GECI was also 4-fold more photostable than YTnC and fYTnC2 GECIs. Finally, we assessed the developed GECIs in primary mouse neuronal cultures stimulated with an external electric field; in these conditions, cNTnC had a 2.4-fold higher dF/F fluorescence response than YTnC and fYTnC2 and was the same or slightly slower (1.4-fold) than fYTnC2 and YTnC in the rise and decay half-times, respectively.     

The thermal cracking of canola and soybean methyl esters: Improvement of cold flow properties

A study was performed to evaluate the use of thermal cracking to overcome cold flow and stability limitations of current biodiesel. Experiments were conducted in a batch cracking reactor system using soy methyl ester and canola methyl ester feedstocks. The amount of high-MW C₁₆–C₂₄ FAMEs was reduced from nearly 100% in the original feedstock by an order of magnitude. Yields of desirable cracking product ranged from 70 to 85% while cloud and pour points decreased around 20 °C and 15 °C, respectively. The stability of the fuel was improved by converting all of the unsaturated esters into lower-MW saturated esters. This method may lead to an attractive process to produce an improved biodiesel that is more conductive to cold temperature utilization and more stable during storage.     

A possible method of computer-aided design of materials with a highly porous matrix structure based on the method of moving cellular automata

The method of moving cellular automata was used to model a sample of ZrO₂ ceramic with a matrix structure under conditions of uniaxial compression. Studies were made of the strength and type of damage to the initial structure and its modifications. Particular attention was devoted to studying the influence of characteristics of the matrix structure on the formation and suppression of internal stress macroconcentrators. It is shown that the method of moving cellular automata can be used for the computer-aided design of matrix materials with a complex structure by specifically influencing the formation and evolution of stress macroconcentrators. Pis’ma Zh. Tekh. Fiz. 24, 71–76 (February 26, 1998)     

Modelling DNA damage induced by different energy photons and tritium beta-particles

PURPOSE: To model the production of single- and double-strand breaks (ssb and dsb) in DNA by ionizing radiations. To compare the predicted effectiveness of different energy photon radiations and tritium beta-particles. MATERIALS AND METHODS: Modelling is carried out by Monte Carlo and includes consideration of direct energy depositions in DNA molecules, the production of species, their diffusion and interactions with each other and DNA. Computer-generated electron tracks in liquid water are used to model energy deposition and to derive the initial positions of chemical species. Atomistic representation of the DNA in B form with a first hydration shell is used. Photon radiations in the energy range 70keV-1MeV and tritium beta-particles are considered. RESULTS: A tentative increase for dsb yield has been predicted for 70 keV photons and tritium compared with 137Cs. This increase is more pronounced for complex dsb. Double-strand breaks are much more prone compared with ssb to combine with additional strand breaks and base damage, which contributes to break complexity. At least half of DNA breaks are hydroxyl radical mediated. CONCLUSIONS: The developed model makes predictions compatible with features of available experimental data. Break complexity has to be addressed in biophysical modelling when the relative effectiveness of radiations in DNA damage is studied. Obtained data strongly argue against the dominance of direct radiation action in DNA damage in the cellular environment predicted by some theoretical studies.