Low-density Polyethylene Surface Research Articles

Influence of Structure of Chemically Grafted onto Polyethylene Surface Two-Component Titanium-Phosphoroxide Nanostructures on the Properties of Composite Material

Nanostructures with different mutual arrangement of phosphorus and titanium oxide groups were synthesized on the surface of low-density polyethylene (LDPE) films using the molecular layering technology by treatment in a different predetermined sequence with TiCl4, POCl3 and H2O vapors. Based on the data of atomic force microscopy, differential thermal analysis, as well as the assessment of the energy characteristics of the surface by the value of the contact angle, it is shown that the sequence of formation of elemental oxide structures has a significant effect both on the chemical composition of surface nanostructures and on the surface morphology and thermal oxidation resistance of polyethylene. Depending on the sequence of introduction of additives, their concentration and ratio in grafted nanostructures change, surface energy increases by 30–50%, and the amounts of polar and dispersion components in its composition largely depend on the moisture content of the environment. It has been found that chemical modification with elemental oxide groups results in a smoothing of the matrix surface, and local destruction of the polymer is observed during the synthesis of two-component nanostructures. The presence of modifiers leads to an increase in the thermal-oxidative resistance of the composition by 50–110°, depending on its structure and composition, in comparison with the original LDPE. Therewith titanium is the most active inhibitor of polymer oxidation.

Investigate the role of biofilm and water chemistry on lead deposition onto and release from polyethylene: An implication for potable water pipes

In this study, the influence of biofilm presence and water chemistry conditions on lead (Pb) deposition onto low density polyethylene (LDPE) surface was examined. The results demonstrated that biofilm presence on LDPE surfaces strongly and significantly enhanced Pb uptake, with the 13-fold greater equilibrium Pb surface loading when biofilm was present (1602 μg/m2) compared to the condition when it was absent (124 μg/m2). The kinetics of Pb adsorption onto LDPE surface when biofilm was present is best described by Pseudo 2nd order kinetic model. Pb adsorption onto new LDPE surfaces was significantly reduced from 1101 μg/m2 to 134 μg/m2 with increased aqueous solution’s ionic strength from 3 × 10−6 M to 0.0072 M. The presence of chlorine residual (2 mg/L) significantly reduced Pb adsorption onto LDPE surfaces by possible oxidation of Pb2+ to Pb4+ species. The kinetics of Pb release from LDPE surfaces was investigated under static and dynamic conditions through immediate exposure of Pb accumulated LDPE pellets to the synthetic water at pH 5.0 and 7.8. The results demonstrated a greater Pb release (86 %) at pH 5.0 compared to the pH 7.8 (58 %). An enhanced Pb release into the contact water was found under dynamic conditions compared to static conditions.

Enhancement of DC breakdown performance of LDPE films based on silver nanoparticle surface modification of biomimetic dopamine technology

Low density polyethylene (LDPE) film samples with the surface treatment by silver nanoparticles based on the biomimetic dopamine technology are obtained and the influence of the treatment on the space charge behavior as well as DC breakdown performance of the selected insulating system is studied. The results obtained by the energy dispersive spectrometer and the scanning electron microscope indicate that Ag particles with nanoscale or larger size form and distribute uniformly on the surface of LDPE modified in the dopamine solution, silver nitrate solution (AgNO3) and dopamine solution in sequence. Space charge profile measured by the pulsed electro-acoustic method shows that homo-charge injection is suppressed with proper surface treatment. DC breakdown strength increases initially and then decreases with the increase of the size of Ag particles. The electrical breakdown strength of the specimen D6-Ag1-D24 is the highest, which increases by 9.5% compared with that of untreated LDPE. Finally, it is considered that the treatment of LDPE based on the biomimetic dopamine technology changes the chemical and physical properties of the surface through forming a three-layer structure, which plays a similar role as the nano-dielectrics. Such treatment can impact the space charge injection and accumulation, and further the corresponding DC breakdown strength, which provides a novel method to optimize the dielectric strength of the polymeric insulating materials.

Degradation of low-density poly ethylene (LDPE) by Enterobacter cloacae AKS7: a potential step towards sustainable environmental remediation.

Plastics composed of polyethylene are non-biodegradable and are mostly harmful to the environment. Literature studies documented that the extent of microbial degradation of low-density polyethylene (LDPE) seems to be insufficient and the underlying mechanisms of such degradation remain unexplored. In the present study, efforts were given to degrade LDPE by a recently isolated bacteria Enterobacter cloacae AKS7. Scanning electron microscopic (SEM) image, tensile strength, and weight loss analysis confirmed the efficient degradation of LDPE by AKS7. To investigate the mechanism, it was observed that with the progression of time, the extent of microbial colonization got increased considerably over the LDPE surface. It was also observed that the organism (AKS7) gradually increased the secretion of extracellular polymeric substances (EPS) suggesting the formation of efficient biofilm over the LDPE surface. Furthermore, to comprehend the role of cell-surface hydrophobicity towards biofilm formation, two mutants of AKS7 were screened that showed a considerable reduction in cell-surface hydrophobicity in contrast to its wild type. The result showed that the mutants revealed compromised LDPE degradation than wild-type cells of AKS7. Further investigation revealed that the mutant cells of AKS7 were incapable of adhering to LDPE in contrast to wild-type cells. Thus, the results demonstrated that the cell-surface hydrophobicity of AKS7 favors the development of microbial biofilm over LDPE that leads to the enhanced degradation of LDPE by AKS7. Therefore, the organism holds the assurance to be considered as a promising bio-remediating agent for the sustainable degradation of polythene-based hazardous waste.

Cucumis metuliferus Fruit Extract Loaded Acetate Cellulose Coatings for Antioxidant Active Packaging.

A new active coating was developed by using Cucumis metuliferus fruit extract as antioxidant additive with the aim of obtaining an easy way to functionalize low-density polyethylene (LDPE) films for food packaging applications. Thus, an extraction protocol was first optimized to determine the total phenolic compounds and the antioxidant activity of CM. The aqueous CM antioxidant extract was then incorporated into cellulose acetate (CA) film-forming solution in different concentrations (1, 3 and 5 wt.%) to be further coated in corona-treated LDPE to obtain LDPE/CA-CM bilayer systems. CA and CA-CM film-forming solutions were successfully coated onto the surface of LDPE, showing good adhesion in the final bilayer structure. The optical, microstructural, thermal, mechanical and oxygen barrier performance, as well as the antioxidant activity, were evaluated. The active coating casted onto the LDPE film did not affect the high transparency of LDPE and improved the oxygen barrier performance. The antioxidant effectiveness of bilayer packaging was confirmed by release studies of Cucumis metuliferus from the cellulose acetate layer to a fatty food simulant. Finally, the LDPE/CA-CM active materials were also tested for their application in minimally processed fruits, and they demonstrated their ability to reduce the oxidation process of fresh cut apples. Thus, the obtained results suggest that CA-CM-based coating can be used to easily introduce active functionality to typically used LDPE at industrial level and enhance its oxygen barrier, without affecting the high transparency, revealing their potential application in the active food packaging sector to extend the shelf-life of packaged food by prevention of lipid oxidation of fatty food or by prevention fruit browning.

Impact of γ-rays on constructional, optical and thermal behavior of alkaline and non alkaline low density polyethylene

ABSTRACT In this study, we investigated the graft copolymerization of methyl methacrylate (MMA) onto low-density polyethylene (LDPE) in the presence of aniline as an inhibitor by gamma radiation. An alkaline treatment was carried out for the prepared graft copolymer. The structural properties of the prepared samples were examined via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD peaks were slightly shifted, indicating an interaction between MMA and the polyethylene matrix. The morphology of the samples confirmed the homogenous grafted phase scattered onto the LDPE surface. Analysis of the absorption spectra indicated an allowed indirect transition mechanism. The Urbach energy (EU) results showed that the value of the EU for grafted LDPE was found to be higher than that of pure LDPE—up to 15 kGy irradiation dose, although this value decreases upon grafting. However, the value of the EU for alkaline-treated grafted films decreases systematically by increasing the degree of grafting. The thermogravimetric analysis (TGA) of the sample indicated that the thermal stability of LDPE samples is significantly changed by grafting MMA onto it. Horowitz and Metzger's models were utilized to measure the activation energy of the thermal decomposition of all samples.

Using diffuse reflectance spectroscopy (DRS) technique for studying biofilm formation on LDPE and PET surfaces: laboratory and field experiments.

Biofilm formation on plastic debris needs to be further investigated, because microorganisms attached to plastics are transferred in all three dimensions to new regions by ocean currents. The current study aims to investigate biofilm formation on plastic strips in aquatic ecosystems using a simple physicochemical method commonly used to characterize solid surfaces, namely, the diffuse reflectance UV-Vis spectroscopy (DRS) method. Using virgin polymers that have not being exposed to the environment as a reference, DRS peaks can be attributed to the microorganisms attached to the polymer surface with time. The polymers tested were low-density polyethylene (LDPE) and polyethylene terephthalate (PET). For LDPE strips for all sampling times in the field, the development of the peaks among 10 similar samples was rather uniform in terms of peak wavelength with time. For PET strips during the early sampling time, the development of the peaks among 10 similar samples was rather uniform in terms of peak wavelength but varied in terms of intensity. This last observation phased out with longer exposure times that the peaks had similar distribution in terms of peak wavelength and intensity. Similar experiments were run for longer exposure times both in an oligotrophic laboratory bioreactor and in the marine environment. In both cases, the biofilm on PET samples seems to reach a steady state faster than LDPE with similar peaks found on both samples DRS proved to be a robust and useful tool to study the formation of biofilm on plastic samples without any pretreatment and without sample destruction. Graphical abstract.

Competitive heavy metal adsorption onto new and aged polyethylene under various drinking water conditions

The study goal was to identify factors that influence copper (Cu), iron (Fe), lead (Pb), manganese (Mn), and zinc (Zn) loading on new and aged low-density polyethylene (LDPE) under various drinking water conditions. The applied aging procedure increased LDPE surface area, hydrophilicity and the number of oxygen containing functional groups. Aged LDPE adsorbed up to a 5 fold greater metals than the new LDPE: Cu > Pb, Zn > Mn. Water pH (5.5 to 10.5) significantly altered LDPE surface metal loading. The organic carbon leached from plastic pipes inhibited Cu adsorption (−43.8%), but other metals were less impacted (−5.7% to −9.1%). The addition of free chlorine and corrosion inhibitor retarded metal adsorption to suspended LDPE materials. Overall, by changing water conditions total metal loadings (i.e., Cu, Mn, Pb and Zn) were altered 20.1 to 35.4%. When Fe was present, Cu (−4.0%) and Pb (−4.5%) loadings were reduced, while lesser impacts were found for Mn and Zn. Cu2+, Pb2+ and Zn2+ hydroxides and oxides were identified as the major metal deposit forms on the LDPE surface by XPS. To better predict metal fate in plastic piping systems, plastic surface characteristics, dissolved organics, water pH, hydraulic conditions and microbial growth should be considered.

Layered Co-Immobilization of β-Glucosidase and Cellulase on Polymer Film by Visible-Light-Induced Graft Polymerization.

Exploring a suitable immobilization strategy to improve catalytic efficiency and reusability of cellulase is of great importance to lowering the cost and promoting the industrialization of cellulose-derived bioethanol. In this work, a layered structure with a thin PEG hydrogel as the inner layer and sodium polyacrylate (PAANa) brush as the outer layer was fabricated on low density polyethylene (LDPE) film by visible-light-induced graft polymerization. Two enzymes, β-glucosidase (BG) and cellulase, were separately coimmobilized onto this hierarchical film. As supplementary to cellulase for improving catalytic efficiency, BG was in situ entrapped into the inner PEG hydrogel layer during the graft polymerization from the LDPE surface. After graft polymerization of sodium acrylate on the PEG hydrogel layer was reinitiated, cellulase was covalently attached on the outer PAANa brush layer. Owing to the mild reaction condition (visible-light irradiation and room temperature), the immobilized BG could retain a high activity after the graft polymerization. The immobilization did not alter the optimal pH and temperature of BG or the optimal temperature of cellulase. However, the optimal pH of cellulase shifts to 5.0 after immobilization. Compared with the original activity of single cellulase system and isolated BG/cellulase immobilization system, the dual-enzyme system exhibited 82% and 20% increase in catalytic activity, respectively. The dual-enzyme system could maintain 93% of carboxymethylcellulose sodium salt (CMC) activity after repeating 10 cycles of hydrolysis and 89% of filter paper activity after 6 cycles relative to original activity, exhibiting excellent reusability. This layer coimmobilization system of BG and cellulase on the polymer film displays tremendous potential for practical application in a biorefinery.

Preparation of Progressive Antibacterial LDPE Surface via Active Biomolecule Deposition Approach.

The use of polymers in all aspects of daily life is increasing considerably, so there is high demand for polymers with specific properties. Polymers with antibacterial properties are highly needed in the food and medical industries. Low-density polyethylene (LDPE) is widely used in various industries, especially in food packaging, because it has suitable mechanical and safety properties. Nevertheless, the hydrophobicity of its surface makes it vulnerable to microbial attack and culturing. To enhance antimicrobial activity, a progressive surface modification of LDPE using the antimicrobial agent grafting process was applied. LDPE was first exposed to nonthermal radio-frequency (RF) plasma treatment to activate its surface. This led to the creation of reactive species on the LDPE surface, resulting in the ability to graft antibacterial agents, such as ascorbic acid (ASA), commonly known as vitamin C. ASA is a well-known antioxidant that is used as a food preservative, is essential to biological systems, and is found to be reactive against a number of microorganisms and bacteria. The antimicrobial effect of grafted LDPE with ASA was tested against two strong kinds of bacteria, namely, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), with positive results. Surface analyses were performed thoroughly using contact angle measurements and peel tests to measure the wettability or surface free energy and adhesion properties after each modification step. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the surface morphology or topography changes of LDPE caused by plasma treatment and ASA grafting. Surface chemistry was studied by measuring the functional groups and elements introduced to the surface after plasma treatment and ASA grafting, using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). These results showed wettability, adhesion, and roughness changes in the LDPE surface after plasma treatment, as well as after ASA grafting. This is a positive indicator of the ability of ASA to be grafted onto polymeric materials using plasma pretreatment, resulting in enhanced antibacterial activity.

PLASMA-ETCHING AND MODIFICATION OF POLYETHYLENE FOR IMPROVED SURFACE STRUCTURE, WETTABILITY AND OPTICAL BEHAVIOR

In the present paper, the surface modification of low-density polyethylene (LDPE) polymer is done by plasma-etching to tune its surface structure, wettability and optical behavior to make it useful for technical applications. For this purpose, two gasses (N[Formula: see text] and (O[Formula: see text] are used as the discharge precursors in a home-built plasma reactor. The plasma-treated LDPE surface etch-rate (control other surface properties) is high at the beginning and slows down as the treatment time increases due to surface restructuring. The etched surfaces are analyzed by scanning electron microscopy (SEM), which indicate greater surface changes due to O2plasma compared to that of N2. Also, the surface hardness is slightly low at the first treatment time and increases rapidly at higher exposure durations. Besides, the friction coefficient is significantly changed by plasma treatment, suggesting the formation of cohesive surface skin. The obtained X-ray diffraction (XRD) patterns show that the plasma-treated LDPE samples suffer disordering and structural changes which increase with raising the treatment duration. Surface restructuring is attributed to the combined effects of active species (from plasma) bombardments and surface oxidation. Also, the surface chemistry changes are evaluated using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy which reveals chain scission after N2plasma treatment. Whereas, the O2plasma-treated samples suffer surface oxidation and formation of polar groups which offer some surface oxidation coatings. Furthermore, the surface wettability has been determined by the sessile drop method and shows enhancement upon plasma treatment due to the combined influence of surface chemistry and morphology. Also, the surface free energy (SFE) and adhesion are found to increase with the plasma exposure time due to surface activation. The optical behavior of LDPE is studied using ultraviolet–visible (UV–Vis) spectrophotometer which indicates that the optical bandgap performance depends on the amorphous or crystalline nature of the polymer. Also, the conjugated carbon atoms were examined and correlated to the reduced bandgap. In conclusion, the studied home-built glow discharge plasma reactor could be utilized efficiently to tune polymer surface properties to be used in high technology applications.

Microbial biofilm formation and community structure on low-density polyethylene microparticles in lake water microcosms

The occurrence of microplastics (MPs) in the environment has been gaining widespread attention globally. MP-colonizing microorganisms are important links for MPs contamination in various ecosystems, but have not been well understood. To partially address this issue, the present study investigated biofilm formation by microorganisms originating from lake water on low-density polyethylene (LDPE) MPs using a cultivation approach and the surface-related effects on the MP-associated microbial communities using 16S rRNA high-throughput sequencing. With the addition of nonionic surfactants and UV-irradiation pretreatment that changed the surface properties of LDPE MPs, more microorganisms were colonized on LDPE surface. Microbial community analysis indicated that LDPE MPs were primarily colonized by the phyla Proteobacteria, Bacteroidetes and Firmicutes, and the surface roughness and hydrophobicity of MP were important factors shaping the LDPE MP-associated microbial community structure. Half of the top 20 most abundant genera colonizing on LDPE were found to be potential pathogens, e.g., plant pathogens Agrobacterium, nosocomial pathogens Chryseobacterium and fish pathogens Flavobacterium. This study demonstrated rapid bacterial colonization of LDPE MPs in lake water microcosms, the role of MPs as transfer vectors for harmful microorganisms in lake water, and provided a first glimpse into the effect of surface properties on LDPE MP-associated biofilm communities.

Removal of impurities from low-density polyethylene using supercritical carbon dioxide extraction

Recently, extraction of impurities such as oligomers, solvent residues, and side products that are present during the production of polyethylene (PE) have attracted attention. These impurities increase the toxicity of PE and may even contaminate the packed products. Therefore, polymer industries put an increasing effort to remove them. In recent times, supercritical carbon dioxide (SCCO2) extraction has gained much attention because CO2 is considered to be cleaner, less expensive, and more environment-friendly than other materials used in the conventional methods. In the present study, aliphatic hydrocarbons such as eicosane, tetracosane, nonadecane, that are present on the surface of low-density polyethylene (LDPE) were extracted using SCCO2. Extraction condition of 22 MPa at 60 °C for 4 h was demonstrated to have better extracting capabilities than Soxhlet extraction. Thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) demonstrated that LDPE properties were not altered.

Higher polythionic acids – the precursors for formation of thallium sulphide layers on polyethylene surface

The method of thallium sulphide thin films deposition on low density polyethylene (LDPE), based on applying solutions of higher polythionic acids (H2SnO6, n = 21, 33, 45), was developed and investigated. The concentration of sulphur in the LDPE film increases with the increase of temperature of higher polythionic acid solution and its sulphurity, as well as the duration of retention of LDPE in its solution is prolonged. The sulphur concentration in the PE film under the same duration of sulphurisation and repetition of treatment cycles insignificantly changes. When the sulphurised LDPE was treated with a thallium Tl(I) salt solution, sulphur present in the polymer reacts with thallium ions and the layers of thallium sulphides, TlxSy, of different composition are formed. The stoichiometric composition of the layer changes from Tl0.1S to Tl2.6S. The amount of thallium increases in the sulphide layers when the number of the cycles of LDPE sulphurisation in the H2S33O6 solution and treatment of sulphurised polymer with the Tl(I) salt solution is increased. The stoichiometric composition of TlxSy coats of one treatment cycle samples changes from Tl0.5S to Tl1.1S. The X-ray diffraction analysis of the polyethylene, treated with the solution of higher polythionic acid, H2S33O6, and then with the Tl(I) salt solution, confirmed the premise that on the LDPE surface the layers of thallium sulphides, TlxSy, were formed. Five phases of thallium sulphides were identified: TlS, Tl2S, Tl2S2, Tl4S3 and Tl2S5. The TlS phase prevailed in diffractograms. The chemical and phase composition of the TlxSy layers surface (up to 1 nm depth) is identified by X-ray photo-electronic spectroscopy analysis. The analysis data confirmed that the compounds of TlS, Tl2S, Tl2SO4, Tl(OH)3, S8 and Tl2O3 were formed on the surface of the layers. The morphology of thallium sulphide layers and the mechanism of their formation are determined by means of scanning atomic force and electronic microscopy. Two processes take place during the formation of the layer: desorption of sulphur and reaction of thallium ions from the thallium(I) salt solution with sulphur present on the LDPE surface. The layer of thallium sulphides is formed on the surface of the sulphur layer. Deposition of thallium sulpfide films from the solution of higher polythionic acid on the LDPE films is not homogeneous, it has the separated island type morphology. The identified regularities let purposively choose the conditions for sulphurisation of LDPE films by using the solution of higher polythionic acid as the agent of polymer sulphurisation in order to compose the layers of thallium sulphides, TlxSy, of the desired chemical and phasic composition on the surface of this polymer by means of the sorption–diffusion method.

Biodeterioration of plasma pretreated LDPE sheets by Pleurotus ostreatus.

Low-density polyethylene (LDPE) waste generates an environmental impact. To achieve the most suitable option for their degradation, it is necessary to implement chemical, physical and biological treatments, as well as combining procedures. Best treatment was prognosticated by Plackett-Burman Experimental Design (PB), evaluating five factors with two levels (0.25 mM or 1.0 gL-1 glucose, 1.0 or 2.0 mM CuSO4, 0.1 or 0.2 mM ABTS [2, 20-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)], pH 4.5 ± 0.2 or 7.0 ± 0.2 and 30 or 90 day incubation), which was reproduced for 150 days. Therefore, PB identified a sequential treatment (plasma followed by fungus) for partial LDPE biodeterioration. Sheets were pretreated with glow discharge plasma (O2, 3.0 x 10−2 mbar, 600 V, 6 min.), followed by Pleurotus ostreatus biodeterioration. Fungus growth, colonization percentage, and pigment generation followed. Laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP) activities were appraised. Additionally, contact angle (CA), functional group presence and changes and carbonyl and vinyl indices (Fourier transformed infrared spectroscopy) were evaluated. LDPE surface changes were assessed by Young’s modulus, yield strength, scanning electronic microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Plasma discharge increased hydrophilicity, decreasing CA by 76.57% and increasing surface roughness by 99.81%. P. ostreatus colonization was 88.72% in 150 days in comparison with untreated LDPE (45.55%). After this treatment carbonyl groups (C = O), C = C insaturations, high hydrophilicity CA (16 ± 4) °, and low surface roughness (7 ± 2) nm were observed. However, the highest Lac and LiP activities were detected after 30 days (Lac: 2.817 U Lac g-1 and LiP: 70.755 U LiP g-1). In addition, highest MnP activity was observed at day 120 (1.097 U MnP g-1) only for P. ostreatus treated LDPE. Plasma favored P. ostreatus adsorption, adherence, growth and colonization (88.72%), as well as partial LDPE biodeterioration, supported by increased hydrophilicity and presence of specific functional chemical groups. The approximate 27% changes in LDPE physical properties support its biodeterioration.

Evaluation of surface properties of low density polyethylene (LDPE) films tailored by atmospheric pressure non-thermal plasma (APNTP) assisted co-polymerization and immobilization of chitosan for improvement of antifouling properties

This work describes the development of antifouling functional coatings on the surface of low density polyethylene (LDPE) films by means of atmospheric pressure non-thermal plasma (APNTP) assisted copolymerization using a mixture of acrylic acid and poly (ethylene glycol). The aim of the study was to investigate the antifouling properties of the plasma copolymerized LDPE films and the same was carried out as a function of deposition time with fixed applied potential of 14 kV. In a second stage, the plasma copolymerized LDPE films were functionalized with chitosan (CHT) to further enhance its antifouling properties. The surface hydrophilicity, structural, topographical and chemistry of the plasma copolymerized LDPE films were examined by contact angle (CA), X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Coating stability was also studied in detail over a storage time of 15 days by storing in water and air. The antifouling properties of the plasma copolymerized LDPE films were examined via protein adsorption and platelet adhesion studies. CA study showed significant changes in surface wettability after the coating process. XPS and FTIR analysis proved the presence of a dense multifunctional coating and an efficient immobilization of CHT. Substantial amendments in surface topography were observed, positively enhancing the overall surface hydrophilicity. Finally, in-vitro analysis showed excellent antifouling behavior of the surface modified LDPE films.

Permeability and thermal properties of PDMS/LDPE multilayer composite membranes

ABSTRACTThis work reports on the preparation and properties of polydimethylsiloxane (PDMS)/low‐density polyethylene (LDPE) multilayer composite polymer membranes (MCPM) for gas separation applications. The membranes were produced by combining sequential coating with melt‐extrusion/salt leaching techniques. In particular, the gas sorption and permeation properties at different pressure (40–90 psig) and temperature (27–55 °C) are reported with morphology and thermogravimetric properties. The results show that a 20 μm PDMS layer was able to penetrate the microporous LDPE surface layer substrate leading to improved interfacial adhesion. Based on the different gases (CO2, CH4, and C3H8) solubility, permeability, and diffusivity obtained, these membranes are seen as good candidates for industrial gas separations. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1045–1052

Photochemical grafting of polysulfobetaine onto polyethylene and polystyrene surfaces and investigation of long‐term stability of the polysulfobetaine layer in seawater

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.

Physicochemical and Biological Activity Analysis of Low-Density Polyethylene Substrate Modified by Multi-Layer Coatings Based on DLC Structures, Obtained Using RF CVD Method

In this paper, the surface properties and selected mechanical and biological properties of various multi-layer systems based on diamond-like carbon structure deposited on low-density polyethylene (LDPE) substrate were studied. Plasma etching and layers deposition (incl. DLC, N-DLC, Si-DLC) were carried out using the RF CVD (radio frequency chemical vapor deposition) method. In particular, polyethylene with deposited N-DLC and DLC layers in one process was characterized by a surface hardness ca. seven times (up to ca. 2.3 GPa) higher than the unmodified substrate. Additionally, its surface roughness was determined to be almost two times higher than the respective plasma-untreated polymer. It is noteworthy that plasma-modified LDPE showed no significant cytotoxicity in vitro. Thus, based on the current research results, it is concluded that a multilayer system (based on DLC coatings) obtained using plasma treatment of the LDPE surface can be proposed as a prospective solution for improving mechanical properties while maintaining biocompatibility.

Potential of bacteria isolated from landfill soil in degrading low density polyethylene plastic

Plastic is an important material and used for many purposes. It is returned to the environment as a waste which is recently considered as the second largest solid waste. The persistency of plastic in the environment has been attracted researchers from a different point of view. The study of the degradation of plastic using bacteria isolated from local landfill soil was conducted. Low density polyethylene (LDPE) plastic was used as tested material. Potential isolates were obtained by culturing the candidates in mineral salt medium broth containing LDPE powder. Two of ten exhibited better growth response in the selection media and were used in degradation study. Results showed that isolate SP2 and SP4 reduced the weight of LDPE film significantly to a weight loss of 10.16% and 12.06%, respectively after four weeks of incubation. Scanning electron micrograph analyses showed the surface of LDPE changed compared to the untreated film. It looked rough and cracked, and bacteria cells attached to the surface was also noticed. Fourier transform infrared spectroscopy analyses confirmed the degradation of LDPE film. These results indicated that bacteria isolated from landfill might play an important role in degrading plastic material in the landfill.