Low-density Polyethylene Surface Research Articles

Transfer of Graphene CVD to Surface of Low Density Polyethylene (LDPE) and Poly(butylene adipate-co-terephthalate) (PBAT) Films: Effect on Biodegradation Process

Here, the influence of graphene as a coating on the biodegradation process for two different polymers is investigated, poly(butylene adipate-co-terephthalate) (PBAT) (biodegradable) and low-density polyethylene (LDPE) (non-biodegradable). Chemical vapor deposition graphene was transferred to the surface of two types of polymers using the Direct Dry Transfer technique. Polymer films, coated and uncoated with graphene, were buried in a maturated soil for up to 180 days. The films were analyzed before and after exposure to microorganisms in order to obtain information about the integrity of the graphene (Raman Spectroscopy), the biodegradation mechanism of the polymer (molecular weight and loss of weight), and surface changes of the films (atomic force microscopy and contact angle). The results prove that the graphene coating acted as a material to control the biodegradation process the PBAT underwent, while the LDPE covered by graphene only had changes in the surface properties of the film due to the accumulation of solid particles. Polymer films coated with graphene may allow the production of a material that can control the microbiological degradation, opening new possibilities in biodegradable polymer packaging. Regarding the possibility of graphene functionalization, the coating can also be selective for specific microorganisms attached to the surface.

Investigation of the factors that influence lead accumulation onto polyethylene: Implication for potable water plumbing pipes

The influence of polymer aging, water pH, and aqueous Pb concentration on Pb deposition onto low density polyethylene (LDPE) was investigated. LDPE pellets were aged by ozonation at 85 °C. ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analysis of aged LDPE surfaces showed that a variety of polar functional groups (>CO<, >CO, >COO) were formed during aging. These functional groups likely provided better nucleation sites for Pb(OH)2 deposition compared to new LDPE, which did not have these oxygen-containing functional groups. The type and amount of Pb species present on these surfaces were evaluated through XPS. The influence of exposure duration on Pb deposition onto LDPE was modeled using the pseudo-first-order equation. Distribution ratios of 251.5 for aged LDPE and 69.3 for new LDPE showed that Pb precipitates had greater affinity for the surface of aged LDPE compared to new LDPE. Aged LDPE had less Pb surface loading at pH 11 compared to loading at pH 7.8. Pb surface loading for aged LDPE changed linearly with aging duration (from 0.5–7.5 h). Pb surface loading on both new and aged LDPE increased linearly with increasing Pb initial concentration. Greater Pb precipitation rates were found for aged LDPE compared to new LDPE at both tested pH values.

Plasma‐treated polyethylene as electrochemical mediator for enzymatic glucose sensors: Toward bifunctional glucose and dopamine sensors

The application of inert and insulating low density polyethylene (LDPE) in electrochemical detection is null. However, in a recent study it was found that reactive species formed onto the surface of plasma‐treated LDPE and other polymers promote the electrocatalytic oxidation of dopamine. In this work, we examine the role of plasma‐treated LDPE as mediator in enzymatic glucose biosensors based on Glucose oxidase and glass carbon substrate. Results indicate that plasma‐induced changes facilitate the electrocommunication between the enzyme and the substrate. The chronoamperometric response of these sensors prove their bifunctionality since the oxidation of glucose to gluconolactone, which is catalyzed by the GOx, coexists with the oxidation of dopamine that is electrocatalytized by the plasma activated LDPE surface.

Tunable wettability and pH‐responsiveness of plasma copolymers of acrylic acid and octafluorocyclobutane

Novel and intelligent plasma copolymers based on hydrophilic/hydrophobic monomers with tunable wettability and pH‐responsiveness are demonstrated. A series of plasma copolymer coatings with various carboxylic acid and fluorocarbon group ratio are prepared on the low‐density polyethylene (LDPE) surfaces via capacitively coupled radio frequency plasma (CCP). The static water contact angles (SWCA) of C4F8‐co‐AA plasma polymer coatings on nanotextured LDPE surfaces tuned from 163 to 4°. These C4F8‐co‐AA plasma polymer coatings showed different pH‐responsiveness by the combined effect of the carboxylic acid to fluorocarbon group ratios and surface nanotexture. The increase of carboxylic acid groups of C4F8‐co‐AA plasma polymers shifted the reversibly switchable wettability of pH‐responsiveness towards low SWCA range. The magnifying effect of surface nanotexture on pH‐responsiveness was also observed.

Development and characterisation of chitosan or alginate-coated low density polyethylene films containing Satureja hortensis extract

This study aimed to develop novel bilayer films based on alginate, chitosan and low-density polyethylene (LDPE) containing different concentrations of summer savory extract (SSE). The cold atmospheric plasma system was used to increase the surface energy of LDPE. Initially, water contact angle, surface roughness and the functional group of LDPE before and after plasma treatment were investigated. Then physical, mechanical, optical, antioxidant and microstructure properties of plasma-treated and untreated bilayer films and antioxidant films incorporated with SSE were characterized. Results showed that plasma treatment increased oxygen-containing the polar group, surface roughness and decreased water contact angle of LDPE surface (from 90.47° to 48.73°) and in result enhanced adhesion between polysaccharide coating and LDPE. Tensile strength of both alginate and chitosan coated-LDPE increased from 10.096 to 14.372 and 11.513 to 13.459MPa, respectively after plasma pretreatment. However chitosan-based films had lower water solubility. Although, incorporation of SSE into chitosan and alginate coated-LDPE despite slight adverse effects on the physical and mechanical properties of films, it provided antioxidant activity. Chitosan coated-LDPE containing SSE had potential to use as antioxidant food packaging.

Enhanced Thermal Conductivity and Dielectric Properties of Iron Oxide/Polyethylene Nanocomposites Induced by a Magnetic Field

Iron Oxide (Fe3O4) nanoparticles were deposited on the surface of low density polyethylene (LDPE) particles by solvothermal method. A magnetic field was introduced to the preparation of Fe3O4/LDPE composites, and the influences of the magnetic field on thermal conductivity and dielectric properties of composites were investigated systematically. The Fe3O4/LDPE composites treated by a vertical direction magnetic field exhibited a high thermal conductivity and a large dielectric constant at low filler loading. The enhancement of thermal conductivity and dielectric constant is attributed to the formation of the conductive chains of Fe3O4 in LDPE matrix under the action of the magnetic field, which can effectively enhance the heat flux and interfacial polarization of the Fe3O4/LDPE composites. Moreover, the relatively low dielectric loss and low conductivity achieved are attributed to the low volume fraction of fillers and excellent compatibility between Fe3O4 and LDPE. Of particular note is the dielectric properties of Fe3O4/LDPE composites induced by the magnetic field also retain good stability across a wide temperature range, and this contributes to the stability and lifespan of polymer capacitors. All the above-mentioned properties along with the simplicity and scalability of the preparation for the polymer nanocomposites make them promising for the electronics industry.

Influence of ethanol vapor addition on the surface modification of polyethylene in a dielectric barrier discharge

In this paper, ethanol vapor up to 50% is added to an argon, air or nitrogen dielectric barrier discharge at medium pressure to profoundly investigate the effect of ethanol addition on the surface modification of low density polyethylene (LDPE). Water contact angle (WCA) and X-ray photoelectron spectroscopy (XPS) measurements show that the ethanol vapor addition effect on the LDPE surface depends on the used carrier gas. Adding ethanol to an argon plasma has no significant effect on the wettability nor on the chemical composition of LDPE compared to a pure argon plasma treatment. Ethanol addition does however slightly increase the LDPE surface roughness. Addition of small amounts of ethanol vapor to an air plasma makes it possible to incorporate additional nitrogen and oxygen groups on the LDPE surface, resulting in an extra decrease of 11% in WCA value. Moreover, the LDPE surface roughness is slightly increased due to the ethanol vapor addition. The most significant effect of ethanol addition is however observed when nitrogen is used as carrier gas. After an N2/2% ethanol plasma treatment, an 85% reduction in WCA value to 8.5° is found compared to a pure N2 plasma treatment. This very hydrophilic LDPE surface is obtained due to a significantly high incorporation of oxygen and nitrogen groups on the surface with an O/C and N/C ratio reaching 32% and 53% respectively. FTIR measurements also reveal that the observed extremely high wettability of LDPE is not the result of plasma activation but is due to plasma polymerization effects occurring on the surface resulting into the deposition of a plasma polymer containing ketones, amides as well as CN groups. In addition, ageing studies have also been conducted and these studies reveal that for all carrier gases, ethanol addition to the discharge gas significantly suppresses the ageing effect. All the above mentioned conclusions therefore indicate that ethanol vapor based plasmas can be an excellent tool to increase the surface energy of polymers.

Biodegradation of thermally treated low density polyethylene by fungus Rhizopus oryzae NS 5.

Polythene is considered as one of the important object used in daily life. Being versatile in nature and resistant to microbial attack, they effectively cause environmental pollution. In the present study, biodegradation of low-density polyethylene (LDPE) have been performed using fungal lab isolate Rhizopus oryzae NS5. Lab isolate fungal strain capable of adhering to LDPE surface was used for the biodegradation of LDPE. This strain was identified as Rhizopus oryzae NS5 (Accession No. KT160362). Fungal growth was observed on the surface of the polyethylene when cultured in potato dextrose broth at 30°C and 120rpm, for 1month. LDPE film was characterized before and after incubation by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and universal tensile machine. About 8.4±3% decrease (gravimetrically) in weight and 60% reduction in tensile strength of polyethylene was observed. Scanning electron microscope analysis showed hyphal penetration and degradation on the surface of polyethylene. Atomic force microscope analysis showed increased surface roughness after treatment with fungal isolate. A thick network of fungal hyphae forming a biofilm was also observed on the surface of the polyethylene pieces. Present study shows the potential of Rhizopus oryzae NS5 in polyethylene degradation in eco friendly and sustainable manner.

Study and characterization of LDPE/Polyolefin elastomer and LDPE/EPDM blend: effect of chlorinated water on blend performance

The free chlorine present in water which is used as a disinfectant is reported to reduce the life of the polymeric material. The objective of this work is to study the influence of chlorine concentration on low-density polyethylene (LDPE) and blends of LDPE with ethylene butene copolymer (EBC) and ethylene propylene diene terpolymer (EPDM). The LDPE blend with EBC and EPDM were tested with water containing 50, 500, and 5000 ppm chlorine under static condition for 500 h at 25 and 80 °C. It has been seen that at 5000 ppm chlorine concentration, the mechanical properties of LDPE, LDPE/EBC blend, and LDPE/EPDM blend changed drastically and a significant reduction in the elongation at break was found for LDPE, LDPE/EBC, and LDPE/EPDM blend. LDPE/EPDM shows stable modulus value for 5000 ppm as 80 °C. Chemical changes in the aged sample were studied by Fourier transform infrared spectroscopy (FTIR) where an increase in the O–H and C=O peaks were observed. The thermal characteristics of LDPE, LDPE/EBC blend, and LDPE/EPDM blends were investigated using DSC and TGA which shows that the melting temperature and crystalline melt temperature remains unchanged while percent crystallinity increases slightly. Scanning electron microscope showed that there was the formation of microcracks and cavities on the fracture surface of LDPE, LDPE/EBC blend, and LDPE/EPDM blend after exposure to a higher concentration of chlorine indicative of degradation. Furthermore, the Chlorine resistance of LDPE/EPDM blend at 5000 ppm chlorine concentration is much higher than that of pristine LDPE.

A facile route to develop hydrophilicity on the polyolefin surface for biomedical applications

In this study, the surface of low-density polyethylene (LDPE) was functionalized with maleic anhydride (MA) using solution grafting method in the presence of benzoyl peroxide (BPO), an initiator. The surface chemistry of the grafted LDPE was characterized using different characterization tools. The effect of MA grafting for analysis of bulk properties such as the change in mechanical strength and thermal properties was studied. Further, the nanoindentation study was performed to analyze the surface mechanical property after MA grafting. Biocompatibility studies were carried out using NIH-3T3 cells through MTT assay test. FTIR analysis revealed the presence of carboxylic groups on LDPE surface. The contact angle value was found to be 44 ± 3°, which confirms the development of hydrophilicity in LDPE. Cell viability was found >75% in MTT assay. These results suggested that the prepared hydrophilic LDPE is a potential candidate for biomedical applications and surface coatings with other polar polymer.

Effect of surface state on DC breakdown of LDPE films

Interface between the metal electrode and insulating material affects dielectric performance of the whole insulating system significantly. In this study, low density polyethylene (LDPE) films were treated in ozone atmosphere for different time duration to investigate the effect of interface state on breakdown performance. Fourier transform infrared spectra (FT-IR) results show that carbonyl group (C=O) is introduced into the surface of LDPE film after ozone treatment, and the amount of C=O groups increases when the ozone oxidation time extends. Surface trap distribution characterized by surface potential decay (SPD) reveals that two hole-type traps exist in the surface of LDPE and ozone treated specimens. Both trap levels become shallower and the density of deeper level traps decreases with the increasing ozone oxidation time, while that of shallower level traps increases. Space charge distribution measured by pulsed electro-acoustic (PEA) method suggests that more positive charges are injected into specimens from the anode and accumulated in the vicinity of cathode after ozone treatment. Furthermore, the dc breakdown strength declines monotonously with longer ozone treatment time, and the lowest breakdown strength of specimen occurs after 6 hours, decreasing by 26.9% compared with that of untreated LDPE. Finally, it is concluded that ozone treatment results in changing of surface chemical composition, which determines surface trap distribution (surface state), leading to the variation of charge injection and accumulation properties as well as the subsequent breakdown performance.

Surface coating of silver nanoparticles on polyethylene for fabrication of antimicrobial milk packaging films

In this study, antimicrobial packaging films were prepared by coating silver (Ag) nanoparticles onto the surface of low density polyethylene (LDPE) films modified by corona air plasma. The possibility of these films for use in the packaging of milk was studied. The influence of input power of the corona discharge treatment on the surface modification and performance of the fabricated Ag/LDPE nanocomposite films was also investigated. The prepared antimicrobial packaging films showed promising antimicrobial efficiency against micro‐organisms that are present in milk and were able to increase the microbial shelf life of the milk. Packages fabricated at corona input powers of 210, 500 and 800 W reached the maximum limit after 5, 8 and 14 days (respectively).

Time of flight-secondary ion mass spectrometry analysis of protein adsorption on a polyvinylidene difluoride surface modified by ion irradiation

We investigated the effects of nanoscopic surface modification of polyvinylidene difluoride (PVDF) and low-density polyethylene (LDPE) by plasma-based ion implantation on protein adsorption with time of flight-secondary ion mass spectrometry (ToF-SIMS) analysis. The chemical composition of the LDPE and PVDF surfaces was changed by ion irradiation. In particular, irradiation substantially decreased the number of CH and CF bonds on the PVDF surface, but only slightly decreased that of CH bonds for LDPE. These decreases may reflect a higher hydrogen recombination rate of the LDPE than the PVDF surface. An increase in oxygen was observed on both the LDPE and PVDF surfaces following ion irradiation, but was saturated after irradiation of 1×1015cm−2 on the PVDF surface. The hydrophilicity of the ion-irradiated LDPE surface was promoted with an increase of the total ion fluence. Ion irradiation also changed the surface properties of PVDF to become more hydrophilic, but the variation did not correlate with the total ion fluence presumably due to the presence of fluorine atoms and the saturation of oxidation. Both bovine serum albumin (BSA) and collagen adsorption were suppressed on the LDPE surface by ion irradiation, which may have resulted from a decrease of the hydrophobic interaction. By contrast, ion irradiation increased protein adsorption on the PVDF surface, and BSA was adsorbed more than collagen, whereas there was no difference in the adsorption between BSA and collagen on the ion-irradiated LDPE surface. Moreover, the adsorption of BSA decreased on the oxygen- and fluorine-rich PVDF surface. These results indicate that the nanoscopic composition changes on the PVDF surface affect the adsorption behavior of BSA. Specifically, ferroelectric property on the PVDF surface was changed by ion irradiation and the nanoscopic change in polarity presumably affected the protein adsorption. Our findings suggest that selective adsorption control of protein can be achieved by ion irradiation to PVDF surface.

A New Route of Fucoidan Immobilization on Low Density Polyethylene and Its Blood Compatibility and Anticoagulation Activity

Beside biomaterials’ bulk properties, their surface properties are equally important to control interfacial biocompatibility. However, due to the inadequate interaction with tissue, they may cause foreign body reaction. Moreover, surface induced thrombosis can occur when biomaterials are used for blood containing applications. Surface modification of the biomaterials can bring enhanced surface properties in biomedical applications. Sulfated polysaccharide coatings can be used to avoid surface induced thrombosis which may cause vascular occlusion (blocking the blood flow by blood clot), which results in serious health problems. Naturally occurring heparin is one of the sulfated polysaccharides most commonly used as an anticoagulant, but its long term usage causes hemorrhage. Marine sourced sulfated polysaccharide fucoidan is an alternative anticoagulant without the hemorrhage drawback. Heparin and fucoidan immobilization onto a low density polyethylene surface after functionalization by plasma has been studied. Surface energy was demonstrated by water contact angle test and chemical characterizations were carried out by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Surface morphology was monitored by scanning electron microscope and atomic force microscope. Finally, their anticoagulation activity was examined for prothrombin time (PT), activated partial thromboplastin time (aPTT), and thrombin time (TT).

Immobilization of Synthesized Silver Nanoparticles Using Mango Peel Extract on Low Density Polyethylene Surface and its Application as Biologically Active Packages

This work focuses on surface modification of polyethylene films by ammonium persulphate/ferric nitrate mixtures and coating of silver nanoparticles on the surface of treated film. For this purpose, the surface of polyethylene film was treated with ammonium persulphate/ferric nitrate mixtures and then the modified polymeric film was immersedin a solution of silver nanoparticles that was synthesized by plant extract reduction of silver salt using mango peel extract. The antimicrobial activity of silver/polyethylene nanocomposite was evaluated and then it was used as an active package to extend shelf life of strawberry during storage at 4°C. The obtained results showed that, silver/polyethylene nanocomposite film has high antimicrobial properties against Listeria monocytogenes, Pseudomonase aeroginosa and Fusarium oxysporum. Finally, the strawberry storage indicated that, strawberry rapped in silver/polyethylenenanocomposite had values of weight loss, pH and total aerobic bacteria count as well as yeast and mold count lower than other samples(unwrapped and wrapped in native polyethylene).

Macromol. Mater. Eng. 6/2016

Back Cover: A green polymer self-etching strategy for fabricating superhydrophobic surfaces exhibiting low and high adhesion is proposed by using hot-pressing and exfoliation on a pair of low-density polyethylene (LDPE) films. Hierarchical micro-/nanostructures are observed in the exfoliated LDPE surfaces and superhydrophobic vessels can be obtained. Further details can be found in the article by Zhong Xiong,* Chenglin Zheng, and Yanzhi Xia* on page 653.

Polymer Self‐Etching for Superhydrophobicity through a Green Hot‐Pressing‐Exfoliation Process: Low and High Adhesion

A green polymer self‐etching strategy for fabricating superhydrophobic surfaces exhibiting low and high adhesion is proposed by using hot‐pressing and exfoliation on a pair of low density polyethylene (LDPE) films. It is demonstrated that the hot‐pressing temperature has significant influence on the surface morphology of LDPE. Effective hot‐pressing temperature for low‐adhesive superhydrophobicity ranges from 109 to 161 °C. Bird's‐nest like micro‐/nanostructures are observed in the unzipped LDPE surfaces compressed at 109 °C, which shows excellent water repellency. LDPE surface compressed at 108 °C demonstrates superhydrophobicity with high adhesion, i.e., a water droplet cannot roll off even when the surface is turned upside down. Furthermore, superhydrophobic vessels are processed and applied to transport water and microdroplets of water losslessly. image

Biodegradation of low density polyethylene (LDPE) modified with dye sensitized titania and starch blend using Stenotrophomonas pavanii

Plastic goods including plastic shopping bags, which are generally made from low density polyethylene (LDPE), are a cause of considerable environmental nuisance. Development of a material that would degrade, due to simple factors i.e. sunlight and/or biotic factors, in the open environment, is therefore, of considerable interest. Biodegradation of photodegraded and non-photodegraded LDPE films, modified with food grade dye sensitized titania (TiO2) nanoparticles and starch blend, was evaluated under laboratory conditions. Bacterial strains were isolated from solid waste dump site using enrichment culture and two step screening procedure for their ability to degrade LDPE. Bacterial strains capable of growing in the LDPE-Titania environment were further screened for their ability to form biofilm on LDPE films, salt aggregation test (SAT) and cell surface hydrophobicity. The potential bacterial strains were then identified as Pseudomonas aeruginosa (CA9), Burkholderia seminalis (CB12), and Stenotrophomonas pavanii (CC18) (GenBank accession number KR738718, KR738720 and KR738722, respectively) based on the 16S rRNA gene sequence homology. The strain CC18 showed highest biofilm, hydrophobicity and growth rate. The LDPE films of 3 × 3 cm were incubated with CC18 in mineral salt media (MSM) for 56 days. The viability tests of the isolates grown on LDPE surface were performed which also correlated with the protein density of biomass (R2 = 0.98). LDPE films were characterized using SEM, TGA, XRD and FTIR before and after incubation. Biodegradation of LDPE was confirmed by an increase in the Keto Carbonyl, Ester Carbonyl and Vinyl Bond Index compared to control. The results conclusively demonstrated the potential of the LDPE-titania-starch blend for production of shopping bags which may easily be degraded in open environment after use.

Effect of Ar ion on the surface properties of low density polyethylene

In this paper, low-density polyethylene (LDPE) was irradiated by argon ion with different fluences up to 1015ions/cm2. The optical, chemical and hardness properties have been investigated using UV‐Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and micro-indentation tester, respectively. The results showed the ion beam bombardment induced decreases in the transmittance of the irradiated polymer samples. This change in transmittance can be attributed to the formation of conjugated bonds i.e. possible formation of defects and/or carbon clusters. The indirect optical band gap decreased from 3.0 eV for the pristine sample to 2.3 eV for that sample irradiated with the highest fluence of the Ar ion beam. Furthermore, the number of carbon atoms and clusters increased with increasing Ar ion fluences. FTIR spectra showed the formation of new bands of the bombarded polymer samples. Furthermore, polar groups were created on the surface of the irradiated samples which refer to the increase of the hydrophilic nature of the surface of the irradiated samples. The Vicker's hardness increased from 4.9 MPa for the pristine sample to 17.9 MPa for those bombarded at the highest fluence. This increase is attributed to the increase in the crosslinking and alterations of the bombarded surface into hydrogenated amorphous carbon, which improves the hardness of the irradiated samples. The bombarded LDPE surfaces may be used in special applications to the field of the micro-electronic devices and shock absorbers.

Hemocompatibility of hyaluronan-enhanced linear low-density polyethylene surfaces for heart valve leaflet applications

Hemocompatibility of hyaluronan-enhanced linear low-density polyethylene surfaces for heart valve leaflet applications