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An interfacial adhesion improvement between low-density polyethylene (LDPE) and aluminum (Al) foil is an important challenge in designing multilayered packaging (TetraPak packaging type) due to insufficient inherent adhesion between both untreated materials. Therefore, extra adhesive layers are often used. The hydrophobic character of LDPE is responsible for poor adhesion to Al and can result in delamination. This study deals with the comparative study of the bulk modification of LDPE with various commercially available adhesive promoters with different chemical compositions to increase LDPE's adhesive characteristics and ensure good adhesion in LDPE/Al laminates. A copolymer of ethylene and methacrylic acid; a terpolymer of ethylene, maleic anhydride, and acrylic ester; or maleated polyethylene (PE) were used as adhesive promoters, and their effect on adhesion improvement of LDPE to Al was investigated. The best adhesion improvement was observed in LDPE-modified samples with maleated PE, while 0.1 wt.% additive content significantly increased peel resistance (from zero to 105 N/m). An additional increase in additive content (0.5 wt.%) in LDPE led to stronger adhesion forces than the cohesion forces in Al foil. Adding 0.5 wt.% of maleated PE into LDPE improved the LDPE/Al laminates' adhesion and can be applied in multilayered lamination applications. [ABSTRACT FROM AUTHOR]

The wax leakage from shape-stabilized phase change materials (SSPCMs) is a limitation because it reduces their functionality. In this work, an enhancement of the compositional stability of SSPCMs formed by high-density polyethylene (HDPE) and paraffin wax blends through a lamination by aluminum (Al) foil was studied. The materials' thermal conductivity was enhanced by adding expanded graphite (EG). The lamination of SSPCMs is the simplest method of reducing leakage, but it suffers from poor adhesion between polymer-based blends and protecting layers. The improved adhesion between SSPCMs and Al foil was achieved by adding 2 wt.% of maleated polyethylene (PE) acting as an adhesion promoter into SSPCMs or by plasma treatment of both SSPCMs and Al surfaces. Microscopic, spectroscopic, and optical techniques were used to analyze the surface and adhesion properties of SSPCMs. The peel resistance of SSPCMs after plasma treatment or modification by maleated PE increased from 2.2 N/m to 7.2 N/m or 55.1 N/m, respectively. The wax leakage from the treated or modified SSPCMs was suppressed significantly. The plasma-treated or maleated PE-modified SSPCMs showed leakage of 0.5 wt.% or 0.2 wt.%, respectively, after three days of leakage test. It indicates a good potential of this treatment/modification for industrially applied SSPCMs. [ABSTRACT FROM AUTHOR]

Low-density polyethylene (LDPE) modified by atmospheric dielectric surface barrier discharge plasma in oxygen was investigated to improve surface properties and adhesion of LDPE to more polar polymers. The process of plasma modification was investigated using several methods--surface energy measurements, Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). The surface energy of LDPE increased significantly after activation by oxygen barrier plasma even at very short time of modification. The FTIR-ATR spectra manifested the presence of carbonyl functional groups on the surface of polymer pretreated by oxygen barrier plasma. It was shown by SEM, and AFM, that the topography of modified LDPE was significantly changed and the surface of modified polymer exhibited higher roughness in comparison with unmodified polymer. The surface energy of treated LDPE diminished in the course of ageing especially during the first 10 days after modification by barrier plasma. Hydrophilicity of the modified LDPE surface was stabilized by photochemical post-functionalization with 2,2,6,6-tetramethyl-piperidin-4-yl-diazoacetate. POLYM. ENG. SCI., 53:516-523, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Polyethylene exhibits many valuable bulk properties, but it has low surface energy (1, 2) which causes its poor dyeability and bondability. The modification and/or activation is necessary for improving [...]

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a polyester, produced naturally by microorganisms, with excellent biocompatibility. Corona and radio-frequency (RF) plasma treatment were applied in order to improve the degradation process of PHBV. Samples were subjected to an accelerated weathering test for 500, 1000, and 2000 h of weathering exposure and to natural weathering for one year. Various analytical, spectroscopic, and microscopic techniques have been used to analyze the degradation process. This study revealed that corona and RF plasma treatment acted as a hydrolytic and ultraviolet light (UV) degradation promoter for PHBV. Both plasma treatments chemically modify the PHBV surface resulting in better wettability contributing to the hydrolytic degradation. Microscopic analysis revealed a rougher defects-containing surface of plasma-treated PHBV in comparison with untreated PHBV after the degradation process, promoting deeper water diffusion and UV penetration. The photo- and hydrolytic degradation caused significant surface changes of plasma-treated PHBV after 2000 h of accelerated weathering and one year of natural weathering. Moreover, deterioration in mechanical properties has been more pronounced in the RF plasma-treated samples. These results demonstrate the potential use of plasma treatment on improving the degradability of PHBV. [ABSTRACT FROM AUTHOR]

Hydrophobic fibrous slippery liquid-infused porous surfaces (SLIPS) were fabricated by electrospinning polydimethylsiloxane (PDMS) and polystyrene (PS) as a carrier polymer on plasma-treated polyethylene (PE) and polyurethane (PU) substrates. Subsequent infusion of blackseed oil (BSO) into the porous structures was applied for the preparation of the SLIPS. SLIPS with infused lubricants can act as a repellency layer and play an important role in the prevention of biofilm formation. The effect of polymer solutions used in the electrospinning process was investigated to obtain well-defined hydrophobic fibrous structures. The surface properties were analyzed through various optical, macroscopic and spectroscopic techniques. A comprehensive investigation of the surface chemistry, surface morphology/topography, and mechanical properties was carried out on selected samples at optimized conditions. The electrospun fibers prepared using a mixture of PDMS/PS in the ratio of 1:1:10 (g/g/mL) using tetrahydrofuran (THF) solvent showed the best results in terms of fiber uniformity. The subsequent infusion of BSO into the fabricated PDMS/PS fiber mats exhibited slippery behavior regarding water droplets. Moreover, prepared SLIPS exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli bacterium strains. [ABSTRACT FROM AUTHOR]

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε‐caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO2) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO2 in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO2 nanocomposites. The X‐ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO2 retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO2 played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO2 were significantly reduced through weathering exposure and the incorporation of TiO2. [ABSTRACT FROM AUTHOR]

Many patients who suffer from pulmonary diseases cannot inflate their lungs normally, as they need mechanical ventilation (MV) to assist them. The stress associated with MV can damage the delicate epithelium in small airways and alveoli, which can cause complications resulting in ventilation-induced lung injuries (VILIs) in many cases, especially in patients with acute respiratory distress syndrome (ARDS). Therefore, efforts were directed to develop safe modes for MV. In our work, we propose a different approach to decrease injuries of epithelial cells (EpCs) upon MV. We alter EpCs' cytoskeletal structure to increase their survival rate during airway reopening conditions associated with MV. We tested two anti-inflammatory drugs dexamethasone (DEX) and transdehydroandrosterone (DHEA) to alter the cytoskeleton. Cultured rat L2 alveolar EpCs were exposed to airway reopening conditions using a parallel-plate perfusion chamber. Cells were exposed to a single bubble propagation to simulate stresses associated with mechanical ventilation in both control and study groups. Cellular injury and cytoskeleton reorganization were assessed via fluorescence microscopy, whereas cell topography was studied via atomic force microscopy (AFM). Our results indicate that culturing cells in media, DEX solution, or DHEA solution did not lead to cell death (static cultures). Bubble flows caused significant cell injury. Preexposure to DEX or DHEA decreased cell death significantly. The AFM verified alteration of cell mechanics due to actin fiber depolymerization. These results suggest potential beneficial effects of DEX and DHEA for ARDS treatment for patients with COVID-19. They are also critical for VILIs and applicable to future clinical studies. NEW & NOTEWORTHY Preexposure of cultured cells to either dexamethasone or transdehydroandrosterone significantly decreases cellular injuries associated with mechanical ventilation due to their ability to alter the cell mechanics. This is an alternative protective method against VILIs instead of common methods that rely on modification of mechanical ventilator modes. [ABSTRACT FROM AUTHOR]

An investigation was made of wood of the species oak (Quercus petraea), beech (Fagus sylvatica L.), maple (Acer pseudoplatanus) and ash (Fraxinus excelsior) pre-treated using radio-frequency (RF) plasma in air at reduced pressure. Physical and chemical changes for all of the wood species were determined using measurements of water contact angles and FTIR-ATR spectroscopy. The results confirmed an increase in the wood’s hydrophilicity/polarity in all cases, caused by an increase in –OH group concentration due to irradiation by RF plasma. The content of oxygen-containing functional groups after treatment by RF plasma significantly increased, and the water contact angles were diminished. FTIR-ATR spectroscopy confirmed that RF plasma modification of the surfaces of all investigated wood samples led to certain changes, which were also dependent on the time of plasma exposure. [ABSTRACT FROM AUTHOR]

This work presents electrospun nanofibers from synthetic spider silk protein, and their application as both a mechanical vibration and humidity sensor. Spider silk solution was synthesized from minor ampullate silk protein (MaSp) and then electrospun into nanofibers with a mean diameter of less than 100 nm. Then, mechanical vibrations were detected through piezoelectric characteristics analysis using a piezo force microscope and a dynamic mechanical analyzer with a voltage probe. The piezoelectric coefficient (d33) was determined to be 3.62 pC/N. During humidity sensing, both mechanical and electric resistance properties of spider silk nanofibers were evaluated at varying high-level humidity, beyond a relative humidity of 70%. The mechanical characterizations of the nanofibers show promising results, with Young's modulus and maximum strain of up to 4.32 MPa and 40.90%, respectively. One more interesting feature is the electric resistivity of the spider silk nanofibers, which were observed to be decaying with humidity over time, showing a cyclic effect in both the absence and presence of humidity due to the cyclic shrinkage/expansion of the protein chains. The synthesized nanocomposite can be useful for further biomedical applications, such as nerve cell regrowth and drug delivery. [ABSTRACT FROM AUTHOR]

Low‐density polyethylene (LDPE) and polystyrene (PS) films with hydrophilic surface were prepared by photochemical grafting of sulfobetaine‐based copolymer containing photolabile moiety, and long‐term stability of the hydrophilic nature of the surfaces in seawater was proved. The sulfobetaine‐based copolymer was prepared by copolymerization of N,N‐dimethyl‐N‐(3‐(methacryloylamino)propyl)‐N‐(3‐sulfopropyl) ammonium betaine with 2 or 5 mol% of N‐methacryloyl‐4‐azidoaniline, and the resulted polymers were grafted onto the plasma pretreated LDPE and PS films. The contact angle measurements were used to prove the modification as well as to follow the changes in the hydrophilicity during storage at room temperature under air atmosphere as well as in seawater at 32°C. The stability of the polymer layer was confirmed also by FTIR and AFM. Polysulfobetaine‐modified LDPE and PS surfaces exhibited significantly higher long‐term hydrophilicity compared with only plasma treated LDPE and PS surfaces. [ABSTRACT FROM AUTHOR]

In this paper, diffuse coplanar surface barrier discharge plasma at atmospheric pressure has been used for surface modification of polyester/cotton (PESc) fabric, which was subsequently modified by sol–gel process using suitable organofunctional silanes to enhance its hydrophobicity. Modified PESc fabric surfaces were conditioned during the gelling process to obtain the permanent hydrophobicity. The contact angle of water before washing of plasma and sol–gel pretreated PESc fabric was found to be 154° and 151° after standardized washings. It was also demonstrated that the process is applicable at the industrial scale. [ABSTRACT FROM AUTHOR]

In this study, two quaternary ammonium salts derived from l -lipoic acid were applied for self-assembled monolayers formation on rough structured gold surface. The derivatives differ in functionality since one possesses simple quaternary ammonium group whereas the other one is carboxybetaine ester containing quaternary ammonium group with pH hydrolysable ester group as a pendant. The response of surface wettability to ion exchange between Cl − and perfluorooctanoate, kinetics and gradient wettability were examined by water contact angle measurement and confirmed by X-ray photoelectron spectroscopy. Furthermore, adhesion forces related to applied counterion on the entire surface and after hydrolysis were investigated by atomic force microscopy measurement at nanometer scales. A dramatic change in wettability upon counterion exchange from superhydrophilic for Cl − to very or superhydrophobic for perfluorooctanoate in a repeatable manner was observed for both derivatives. Kinetics of counterion exchanges revealed faster hydration of simple quaternary derivate. The wettability gradient could be designed from superhydrophobic to superhydrophilic either in a reversible manner by simple immersion of the modified surface in a counterion solution modulated by ionic strength or in an irreversible manner for carboxybetaine ester derivate by time-controlled hydrolysis to charge balanced carboxybetaine. [ABSTRACT FROM AUTHOR]

Ni-B/Y2O3 composite coatings were developed through an electrodeposition process to study the effect of addition of Y2O3 particles on structure, surface, thermal, mechanical, and anticorrosion properties of Ni-B coatings. It is revealed that parent crystal structure of Ni-B matrix is preserved by addition of Y2O3, however, a noticeable improvement in crystallinity is observed. The analysis of the surface exhibits formation of dense and nodular deposits in the two types of coatings, but incorporation of Y2O3 particles in Ni-B matrix has resulted in a noteworthy change in grain size and surface roughness. Thermal analysis of the surfaces indicates that Ni-B-Y2O3 composite coatings demonstrate superior thermal stability compared to Ni-B coatings. The nanoindentation analysis shows a significant enhancement in the mechanical characteristics of the Ni-B matrix by addition of Y2O3 particles. This may be contemplated as the result of grain refinement and dispersion hardening of the Ni-B matrix by the presence of hard Y2O3 particles. A decent improvement in the corrosion protection efficiency (73.6%) is also observed by addition of Y2O3 particles into Ni-B matrix. Simultaneous improvement of mechanical and anticorrosion properties suggests potential applications of Ni-B-Y2O3 coatings in oil and gas, automobile, and many other industries. [ABSTRACT FROM AUTHOR]

Novel 2D Ti3C2Tx (MXene)-reinforced polyvinyl alcohol (PVA) nanofibers have been successfully fabricated by an electrospinning technique. The high aspect ratio, hydrophilic surfaces, and metallic conductivity of delaminated MXene nanosheet render it promising nanofiller for high performance nanocomposites. Cellulose nanocrystals (CNC) were used to improve the mechanical properties of the nanofibers. The obtained electrospun nanofibers had diameter from 174 to 194 nm depending on ratio between PVA, CNC and MXene. Dynamic mechanical analysis demonstrated an increase in the elastic modulus from 392 MPa for neat PVA fibers to 855 MPa for fibers containing CNC and MXene at 25°C. Moreover, PVA nanofibers containing 0.14 wt. % Ti3C2Tx exhibited dc conductivity of 0.8 mS/cm conductivity which is superior compared to similar composites prepared using methods other than electrospinning. Improved mechanical and electrical characteristics of the Ti3C2Tx /CNC/PVA composites make them viable materials for high performance energy applications. [ABSTRACT FROM AUTHOR]

Simple and robust methods for modifying hydrophobic polymer surfaces with zwitterionic polymers using UV irradiation were developed. Two random zwitterionic copolymers consisting of either carboxybetaine or sulfobetaine methacrylamide monomers and monomers bearing a photolabile azidophenyl group were directly photoimmobilized on polymeric surfaces (polyester, polyethylene and polystyrene) via covalent interactions in a spatially controlled manner. These copolymers were also electrospun to form self-standing mats. The modified surfaces were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, infrared spectroscopy and contact angle measurements. The electrospinning method involved the use of a trifluoroethanol solution with a copolymer concentration in the range from 2 to 10 wt.%. BHK 21 cell adhesion to both modified surfaces and mats was dramatically reduced compared to unmodified surfaces. [ABSTRACT FROM AUTHOR]