Polyethylene Surface Research Articles

Water contact angle as a quantitative measure of total polyethylene surface energy

A wide variety of plasma treatments was performed on polyethylene surfaces, resulting in a wide range of total surface energies. The linear correlation of with cos θ was discussed in light of the Young–Dupré equation. Hundred percent of the surface energy variation was accounted for by the polar component of surface energy; the dispersive component was not affected by surface treatment. These data show that for this polymer the contact angle of a single polar liquid can be used as a robust quantitative indicator of treatment level, and because of its excellent linear correlation with total surface energy for this system, can be used as a quantitative measure of total surface energy.

Physical mechanisms of interaction of cold plasma with polymer surfaces

Physical mechanisms of the interaction of cold plasmas with organic surfaces are discussed. Trapping of plasma ions by the CH2 groups of polymer surfaces resulting in their electrical charging is treated. Polyethylene surfaces were exposed to the cold radiofrequency air plasma for different intervals of time. The change in the wettability of these surfaces was registered. The experimentally established characteristic time scales of the interaction of cold plasma with polymer surfaces are inversely proportional to the concentration of ions. The phenomenological kinetic model of the electrical charging of polymer surfaces by plasmas is introduced and analyzed.

LDPE Surface Modifications Induced by Atmospheric Plasma Torches with Linear and Showerhead Configurations

Low density polyethylene (LDPE) surfaces have been plasma modified to improve their nanostructural and wettability properties. These modifications can significantly improve the deposition of subsequent layers such as films with specific barrier properties. For this purpose, we compare the treatments induced by two atmospheric plasma torches with different configurations (showerhead vs. linear). The modifications of LDPE films in terms of chemical surface composition and surface morphology are evidenced by X‐ray photoelectron spectroscopy, water contact angles measurements, and atomic force microscopy. A comparison between the two post‐discharge treatments is achieved for several torch‐to‐substrate distances (gaps), treatment times, and oxygen flow rates in terms of etching rate, roughening rate, diffusion of oxygen into the subsurface and hydrophilicity. By correlating these results with the chemical composition of the post‐discharges, we identify and compare the species which are responsible for the chemical surface functionalization, the surface roughening, and etching.

Cell-surface properties of Vibrio ordalii strains isolated from Atlantic salmon Salmo salar in Chilean farms.

Vibrio ordalii is the causative agent of atypical vibriosis and has the potential to cause severe losses in salmonid aquaculture, but the factors determining its virulence have not yet been elucidated. In this work, cell-surface-related properties of the isolates responsible for outbreaks in Atlantic salmon were investigated. We also briefly examined whether pathogenicity against fish varied for V. ordalii strains with differing cell-surface properties. Hydrocarbon adhesions indicated the hydrophobic character of V. ordalii, although only 4 of 18 isolates induced haemagglutination in Atlantic salmon erythrocytes. A minority of the studied isolates (6 of 18) and the type strain ATCC 33509T produced low-grade biofilm formation on polyethylene surface after 2 h post-inoculation (hpi), but no strains were slime producers. Interestingly, V. ordalii isolates showed wide differences in hydrophobicity. Therefore, we chose 3 V. ordalii isolates (Vo-LM-03, Vo-LM-18 and Vo-LM-16) as representative of each hydrophobicity group (strongly hydrophobic, relatively hydrophobic and quasi-hydrophilic, respectively) and ATCC 33509T was used in the pathogenicity studies. All tested V. ordalii strains except the type strain resisted the killing activity of Atlantic salmon mucus and serum, and could proliferate in these components. Moreover, all V. ordalii isolates adhered to SHK-1 cells, causing damage to fish cell membrane permeability after 16 hpi. Virulence testing using rainbow trout revealed that isolate Vo-LM-18 was more virulent than isolates Vo-LM-03 and Vo-LM-16, indicating some relationship between haemagglutination and virulence, but not with hydrophobicity.

Studying Magneto-Induced Iodine Sorption at Dielectric Surface

The development of new sorbents and methods of their catalytic activity increase is an important task of nuclear energy and medicine. This paper presents the investigation results on the magnetic field effect on the iodine adsorption on the polyethylene, polycarbonate, and polystyrene surfaces. The revealed effect of the sorption property improvement by the dielectric surfaces in the magnetic fields opens new possibilities for efficiency increase of radioactive materials filters. The novel technology of medical polymer modification could be developed on the basis of magneto-induced sorption effect. The goal of this technology is to decrease biodegradation degree, acquire bactericidal and antiviral properties, increase cytoreduction, and purposefully change the mechanical characteristics.

English

In the present study, we tested 83 actinomycete isolates for low density polyethylene (LDPE) degradation in the laboratory, and these isolates were previously isolated for biosurfactant production from the oil contaminated soil sample near Naval Dockyard in Visakhapatnam. Among them, 20 were positive using 2,3,5-triphenyl tetrazolium chloride (TTC) as a viability indicator and able to grow in a mineral salts medium containing LDPE as a sole source of carbon. Of these, NDYS-4 isolate showed prominent result with redox probe 2,3,5-triphenyltetrazolium chloride (TTC) as a viability indicator, which forms pink colour insoluble triphenylformazan (TPF) on mineral salts media containing emulsified polyethylene as a carbon source within five to seven days, and it was also grown prominently on mineral salt agar plates containing LDPE in comparison to other isolates, and it was selected for detailed analysis. The weight loss of polyethylene films was approximately 30% after four weeks of incubation with selected isolate. The viability and metabolic activity of this isolate growing on the polyethylene surface was confirmed using a TTC reduction test. The metabolic activity was also correlated with a concomitant increase in the protein density of the biomass on the surface of the polyethylene. The microbial degradation of LDPE was also analyzed by the change in pH of the culture media and microscopic analysis. Based on the results, this degradation may be mediated by enzymatic activity and may also involve cell-surface hydrophobicity. It was also able to grow on other polymers such as polyvinyl acetate (PVA), polycaprolactone (PCL), polyethylene oxide (PEO) and polyethylene glycol (PEG) using TTC as a viability indicator and also showed prominent growth on mineral salts agar plates containing polyethylene as a source of carbon. Based on the results of phenotypic characteristics, phylogenetic analysis, biochemical characteristics and 16S rRNA gene sequence homology, the isolate NDYS-4 was identified as Streptomyces coelicoflavus NBRC 15399T. It could be concluded that the PE degrading actinomycete selected in this study showed diverse and varying capacities to degrade polyethylene and other polymers and can be exploited for cleaning up polyethylene contaminated sites.   Key words: Biosurfactant, low density polyethylene, 2,3,5-triphenyl tetrazolium chloride, mineral salts media, hydrophobicity, sequence homology, phylogenetic analysis.

Articular congruency of the Salto Talaris total ankle prosthesis.

The Salto-Talaris polyethylene articulating surface was designed to allow, but limit accessory motion. This investigation examines surface characteristics between the polyethylene bearing and anatomic talar component in various positions of function. A Salto Talaris talar prosthesis and matching polyethylene bearing were scanned to create digital solid body models and manipulated to assess surface contact during simulated gait. With computer micromanipulation of the component positions, the surface intersections were recorded for 15 different alignments. The Salto Talaris has limited contact congruity with four points of contact in dorsiflexion, neutral, and plantarflexion. Lateral and medial translations showed only 2-point contact. The radii of curvatures between the talar component and polyethylene surfaces do not match. There was no sulcus contact yet component separation distance was small, suggesting increased loads. Surface incongruency was measured based on computer model analysis which raises a concern of increased contact pressures.

Incorporation of amine moieties onto ultra-high molecular weight polyethylene (UHMWPE) surface via plasma and UV polymerization of allylamine

Allylamine was plasma, post–irradiation grafted and UV polymerized onto UHMWPE surface to improve its cell adhesion and proliferation properties as well as to increase its wettability. For plasma polymerization, samples were coated using different process parameters. The effect of the various processes and process parameters on the physical and chemical properties of the deposited allylamine coatings was evaluated by different physical and chemical characterization techniques. Wettability, surface chemistry, thickness and surface morphology were determined. Stability and aging tests for a 7day period were also investigated. Moreover, cell tests using human foreskin fibroblasts were performed and evaluations were conducted after 1 and 7days of culturing. Different chemistries and surface morphologies were induced after each treatment and various nitrogen and oxygen functionalities were incorporated making the surface more hydrophilic. Coatings were relatively stable and cell viability was found to be significantly higher on plasma and UV treated UHMWPE compared to plain UHMWPE; this was confirmed by the overall cell morphology.

Membrane bioreactor wastewater treatment plants reveal diverse yeast and protist communities of potential significance in biofouling

The yeast community was studied in a municipal full-scale membrane bioreactor wastewater treatment plant (MBR-WWTP). The unexpectedly high diversity of yeasts indicated that the activated sludge formed a suitable environment for them to proliferate, with cellular concentrations of 2.2 ± 0.8 × 103 CFU ml−1. Sixteen species of seven genera were present in the biological reactor, with Ascomycetes being the most prevalent group (93%). Most isolates were able to grow in a synthetic wastewater medium, adhere to polyethylene surfaces, and develop biofilms of variable complexity. The relationship between yeast populations and the protists in the MBR-WWTP was also studied, revealing that some protist species preyed on and ingested yeasts. These results suggest that yeast populations may play a role in the food web of a WWTP and, to some extent, contribute to membrane biofouling in MBR systems.

Virulence phenotype, physicochemical properties, and biofilm formation of Pseudomonas aeruginosa on polyethylene used in drinking water distribution systems

Potable water piping has been demonstrated to serve as a reservoir for opportunistic pathogens bacteria such as Pseudomonas aeruginosa. In this report, we describe the characterization of P. aeruginosa strains isolated from water intended for human consumption by the presence of virulence factors. These strains expressed their suitability for adhesion and the formation of biofilms on polyethylene (PE). Also in this work, we were able to elucidate the factors intervening in adhesion and biofilm formation by showing the role of the substrate, the environment and bacteria. Strong correlation was observed between physicochemical properties especially the electron donor property and the surface percentage covered by cells. These results indicate that this property plays a crucial role in Pseudomonas aeruginosa adherence on the PE surface. In addition, if no relationship was found between the adhesion results and hydrophobicity, it means that this property was not involved in the adhesion process of Pseudomonas aeruginosa on the PE surface.

Low polarity water, a novel transition species at the polyethylene-water interface.

The bridge between water repelling and water-attracting regions is recognized here as low polarity water, a novel "neutral" form of water; its identity as a dipole-dipole water dimer is supported by spectroscopic evidence of its presence in thin films of water on a polyethylene surface. High resolution (0.5 cm(-1)), low signal energies (Sg 100) and short scans (0.1 s) are used to ensure that all peaks are detected. Thin films may be trapped between two polyethylene windows, affirming the low polarity of such water; the spectra of the trapped films ("sandwich") are similar to those from a subtraction procedure. Use of the "sandwich" is a new and useful technique in surface studies. In general, intermediate forms might bridge incompatibility between different regimes, from sets of molecules (chemistry and physics) to sets of organisms (biology and sociology). Thin films of water on polyethylene also display strong and transient peaks of water oligomers, cyclic pentamers and cyclic hexamers (chair and boat), bicyclic hexamers (books 1 and 2) and tricyclic hexamers (prism) that have been previously identified in thin films of water on a silver halide surface.

A facile approach to prepare biomimetic composite separators toward safety-enhanced lithium secondary batteries

A mussel-inspired polydopamine (PDA) coating makes radio-frequency Al2O3 sputtering a damage-free, reliable, and cost-efficient process for polyethylene (PE) surface modification for lithium secondary batteries (LIBs).

Influence of Ionizing Radiation on the Mechanical Properties of a Wood-Plastic Composite

The focus of this study was to examine the potential benefits of irradiating polyethylene (PE)-based wood-plastic composites (WPCs) in order to enhance the mechanical properties of the WPC. The PE-based WPCs were irradiated, post extrusion, at dose levels of 0, 50, 100, 150, 200, and 250 kGy with an electron beam (EB). The irradiated WPCs were then evaluated using a third point bending test (ASTM D4761) along with scanning electron microscopy (SEM). It was found that ultimate strength and modulus of elasticity (MOE) increased with increasing dose level. Examination of the fracture surfaces of polyethylene revealed a distinct difference in failure between irradiated and non-irradiated surfaces.

Adhesion of Wax Droplets to Porous Polymer Surfaces

An experimental study was done to measure the force of adhesion of molten wax droplets, 3.1 mm in diameter, dropped from heights ranging from 20 to 50 mm onto porous polyethylene and Teflon surfaces. The Teflon surface had 0.25-mm holes drilled in it and the three polyethylene surfaces had random pores with mean diameters of 35, 70, and 125 μm, respectively. The force required to remove the solidified ink from the surface was measured using a pull test. Wax splats were attached to the substrate by both adhesive and cohesive forces. The cohesive force was calculated by multiplying the ultimate tensile strength of the wax (2.2 MPa) by the cross-sectional area of the wax penetrating into surface pores. The adhesive force was obtained by multiplying the contact area between the wax and substrate by the adhesion strength per unit area, estimated to be 0.2 MPa for polyethylene and 0.1 MPa for Teflon surfaces. The contact area between splats and the substrate was typically about 60–70% of the splat area. The edges of splats lifted up, preventing complete contact.

Adhesion of Listeria monocytogenes to cutting board surfaces and removal by different sanitizers

The objective of this study was to investigate Listeria monocytogenes adhesion in new and used polyethylene cutting board surfaces and evaluate its removal using different sanitizers (peracetic acid, chlorhexidine, sodium hypochlorite and organic acids). Results showed that the number of adhered cells increased with time on both surfaces evaluated. Statistically significant differences (p < 0.05) between new and used polyethylene surfaces were observed on the adhesion of microorganism. Treatments with the peracetic acid and sodium hypochlorite sanitizers were very effective to inactivate attached L. monocytogenes on the polyethylene cutting board, avoiding the possible formation of biofilms at all contact times studied. Other sanitizers did not succeed in inhibiting completely the pathogen in the maximum concentration (2.0 %) after 24 h of bacterial growth for both surfaces (chlorohexidine), 3 h of bacterial growth on new and 6 h on used surfaces (organic acid). The results indicate that peracetic acid and a sodium hypochlorite treatment present a better method to remove microbial contamination on the surfaces of cutting boards.

Damage from unintentional metal–metal articulation of CoCrMo, TiAlV, and oxidized zirconium knee replacements following polyethylene insert failure

A small percentage of knee replacements with metal-backed tibial components experience complete polyethylene insert destruction or wear-through during in vivo service, resulting in unintentional articulation of the metal femoral bearing and tibial baseplate. Seven such explanted knee replacement sets were studied to determine the failure events that affected four combinations of unintentionally articulating metals, including both conventional CoCrMo and TiAlV, as well as surface modified oxidized zirconium (OxZr). The surface modified metal experienced local fracture at the surface when in contact with TiAlV and subsequent metal–metal wear of the substrate metal. All unintentional conventional metal–metal couples (CoCrMo–CoCrMo, TiAlV–TiAlV, CoCrMo–TiAlV, and ZrNb (substrate)–TiAlV) experienced adhesive wear processes resulting in material transfer. In mixed-metal pairs, the softer metal transferred to the harder metal (TiAlV transferred to CoCrMo and ZrNb transferred to TiAlV) during adhesion, resulting in gross dimensional change in the softer metal and roughening of the harder metal. While surface modified metals may be advantageous when articulating against polyethylene, in cases of polyethylene insert wear-through, both conventional and surface modified metals result in significant wear damage. The types of wear damage present and the extent of roughening varied across material combinations.

Self-Consistent Real Space Free Energy Calculations for Polyethylene and Isotactic Polypropylene Crystals and Interfaces

Surface free energies for (100) and (010) orthorhombic polyethylene (PE) and α1 isotactic polypropylene (iPP) are calculated with self-consistent real space quasi-harmonic lattice dynamics methods. PE is used as a model system to systematically explore the accuracy of real space calculations versus traditional reciprocal space calculations for the bulk and interfacial properties of crystalline polymers. A linear potential is added to the atomistic Hamiltonian of the crystal to minimize the free energy of crystals with interfaces. (010) iPP is found to have a lower surface free energy than (100) iPP at temperatures relevant to crystallization. PE and iPP surface free energies are found to have opposite temperature dependences, ultimately because the PE slab stem packing becomes increasingly denser than the bulk as temperature increases while the opposite is true of iPP. Real space calculations give good agreement with experimental results and reciprocal space calculations for bulk PE and iPP lattice parameters, as well as calculated surface free energies of PE, with a reasonably sized crystal supercell and simpler calculations than in reciprocal space.

Improved efficiency of reactor startup in biological aerated filter by poly(lactic acid)

The enhancement effect of polyethylene (PE) surfaces modified with poly(lactic acid) (PLA) on formation of nitrifying biofilms in biological aerated filter (BAF) was investigated in this study. X-ray photoelectron spectroscopy, scanning electron microscope, and protein absorption analysis revealed that modified PE surfaces produced active groups, including carboxyl (O═C─O), hydroxyl (C─OH), and carbonyl (C═O), increased surface roughness, and enhanced the adsorption of both the bovine serum albumin and fibrinogen. During the startup period of 33 days, the average removal rates of ammonia nitrogen (NH3-H) were 68 and 72% before and after modification which were 36 and 43% for total nitrogen, 47 and 45% for total organic carbon. The results of denaturing gradient gel electrophoresis experiments demonstrated that modified carriers adsorbed and gathered more species of bacteria on surfaces. Thus, surface modification of PE suspended carrier by PLA improved the efficiency of reactor startup for drinking water treatment.

Flame spread over electrical wire with AC electric fields: Internal circulation, fuel vapor-jet, spread rate acceleration, and molten insulator dripping

The effect of electric field on the characteristics of flame spread along a polyethylene (PE) insulated electrical wire was investigated experimentally by varying the AC frequency and voltage applied to the wire. The results showed that the flame spread rate was accelerated due to the convergence of electric flux near the end of wire, having three distinct regimes depending on applied voltage. In each regime, several subregimes could be identified depending on AC frequency. Flame shape (height and width) and slanted direction of the spreading flame were influenced differently. Fuel-vapor jets were ejected from the molten PE surface even for the baseline case without the application of an electric field; this could be attributed to the bursting of fuel vapor bubbles generated from internal boiling at the molten PE surface. An internal circulation of molten-PE was also observed as a result of non-uniform heating by the spreading flame. In the high voltage regime with a high AC frequency, excessive dripping of molten PE led to flame extinction.

Photoinduced Graft-Polymerization of Acrylic Acid on Polyethylene and Polypropylene Surfaces: Comparative Study Using IR-ATR Spectroscopy

Photoinduced graft-polymerization of acrylic acid on the surface of polyethylene and polypropylene films containing a photoinitiator pre-adsorbed from a thin layer of non-de-aerated aqueous monomer solution was investigated. Data about the monomer conversion and grafting depth as functions of the UV irradiation time and polymer nature were obtained using IR-ATR spectroscopy.