Low-density Polyethylene Films Research Articles

Plastic film packaging for the postharvest quality of fresh hop inflorescence (Humulus lupulus) cv. Cascade

Hop is an essential raw material for beer production, but, after harvest, the inflorescences have a very short shelf life. For this reason, the aim of this research was to study the effect of 4 different plastic films packaging on quality and shelf-life of fresh hops inflorescence. LDPE (low density polyethylene), LP280 (low density polyethylene-metallocene low density polyethylene-ethylene vinylic alcohol), MF (microperforated low density polyethylene-linear low density polyethylene) and HDPE (high density polyethylene-metallocene low density) plastic films, after a week of a great reduction in O2 and increase of CO2, were able to maintain O2 between 4 and 12 kPa and CO2 between 10 and 18 kPa during 28 d of storage at 3 °C. In these atmospheres, hop inflorescence chlorophyll decreased less than in MF film as well as α-acid and β-acid, while carotenoids increased but without significant difference among plastic films. MF did not produce any atmosphere different from the air but, in the 1st week, limited the negative effect (reduction of polyphenols and antioxidant properties) of atmosphere stress condition (very low O2 and high CO2), due to the high inflorescence respiration inside the low and very low permeability plastic films. Thus, to store hop inflorescences for one week, MF film is sufficient but, for a longer period, the atmosphere created by LDPE, LP280, and HDPE films, could be a good solution, before processing.

Biodegradation of LDPE (low density polyethylene) using bacterial strain

The applications of polyethylene are enormous and they are popular because of their relatively low cost, lack of difficulty in manufacture, adaptability and durability. In the past decade, the increase in the utilization of plastics and the accumulation of polyethylene in the environment all around the globe has drawn the attention of environmentalists and scientists. The plastic materials are commonly derived from petrochemicals extracted from coal and natural gas. They are produced in a wide range in synthetic, semi synthetic organic polymers. The degradation of LDPE film was determined by residual dry weight loss of the LDPE films. The potent strain showed 42.5% degradation ability in 90 d. Degradation of LDPE results in the breakdown of the polymer backbone chain producing CO2 which was checked by gravimetric analysis. Enzyme kinetic studies showed the production of three ligninolytic extracellular enzymes- lignin, laccase and manganese peroxidase by bacterial strain AJ01 in LDPE degradation. Degradation of LDPE strips followed first order kinetics model with a rate constant (R2) of 0.9783 d-1. Estimation of protein from post treated LDPE using bacterial isolate showed a total concentration of 0.440mg/0.1mL and 0.703mg/0.2mL. LDPE degradation was confirmed by using analytical techniques such as SEM which showed changes in the surface topology of LDPE strips and FTIR analysis showed changes in complex chemical structure of LDPE post 90 d of degradation using microorganisms thereby reducing carbonyl index (CI) value.

Peculiarity of the Mechanism of Early Stages of Photo-Oxidative Degradation of Linear Low-Density Polyethylene Films in the Presence of Ferric Stearate.

Ferric stearate (FeSt3) is very efficient in accelerating polyethylene (PE) degradation, but there is a lack of exploration of its role in accelerating the early stages of polyethylene photo-oxidative degradation. This study aimed to investigate the effect of FeSt3 on the photo-oxidative degradation of PE films, especially in the early stages of photo-oxidative degradation. The results show that FeSt3 not only promotes the oxidative degradation of PE but also contributes significantly to the early behavior of photo-oxidative degradation. Moreover, the results of the density functional theory (DFT) calculations proved that the C-H in the FeSt3 ligand was more easily dissociated compared with the PE matrix. The generated H radicals participate in the coupling reaction of the primary alkyl macro radicals leading to the molecular weight reduction, thus significantly increasing the initial rate of molecular weight reduction of PE. Meanwhile, the transfer reaction of the dissociation-generated C-centered radicals induced the PE matrix to produce more secondary alkyl macroradicals, which shortened the time to enter the oxidative degradation stage. This finding reveals the mechanism by which FeSt3 promotes the degradation of PE at the early stage of photo-oxidative degradation. It provides guiding significance for the in-depth study of the early degradation behavior in photo-oxidative degradation on polyolefin/FeSt3 films.

Comparison study on low-density polyethylene film biodegradation potential of Achoria grisella and Galleria mellonella larvae

Aim: The current research investigates biodegradation of Low-Density Polyethylene (LDPE) facilitated with and without gut microbiota in Galleria mellonella and Achoria grisella. Methodology: A batch of 50 larvae of Galleria mellonella and Achoria grisella administered with antibiotics (A group) along with larvae not fed with antibiotics (WA group) were exposed to LDPE film. After biodegradation, the weight loss of degraded LDPE film, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Thermogravimetric Analysis, and Gas Chromatography-Mass Spectroscopy analysis were performed to confirm the plastic biodegradation potential of selected insects. Results: In a and WA groups, the post-biodegradation for a selected species of wax moth exhibited weight loss of 2.763%, 0.789%, 5.403% and 1.481%, respectively. The SEM images revealed that both A and WA groups were capable of LDPE film disintegration. The FTIR of biodegraded film confirmed the deterioration of LDPE by indicating a change in the typical peaks of C−H and H−C−H bonds that points out the biodegradation of polyethylene.Further, the thermogravimetric analysis showed a substantial mass loss in the LDPE flakes consumed by the insects, demonstrating a decline in the thermal stabilities of disintegrated polymers. GC-MS of frass validated the presence of many component groups, including alkanes, alcohols, esters, ethers and acids, which confirmed the biodegradation of LDPE. Interpretation: Wax worms possess the capacity to biodegrade LDPE, independent of gut microbiota Key words: Achoria grisella, Antibiotic, Galleria mellonella, Low-density polyethylene

Aging rate, environmental risk and production efficiency of the low-density polyethylene (LDPE) films with contrasting thickness in irrigated region

Physical thickness of low-density polyethylene (LDPE) films might determine the release rate of phthalic acid esters (PAEs) & structural integrity and affect production efficiency. However, this critical issue is still unclear and little reported. Aging effects were evaluated in LDPE films with the thickness of 0.006, 0.008, 0.010 and 0.015 mm in a maize field of irrigation region. The Scanning electron microscope (SEM) results showed that the proportion of damaged area (Dam) to total area of LDPE films was massively lowered with increasing thickness after aging. The highest and lowest Dam was 32.2% and 3.5% in 0.006 and 0.015 mm films respectively. Also, the variations in peak intensity of asymmetric & symmetrical stretching vibrations (ASVI & SSVI) were detected using Fourier transform infrared spectrum (FTIR), indicating that the declines in peak intensity tended to be slower with thickness. Interestingly, the declines in physical integrity were tightly associated with increasing exhalation rate of PAEs. Average releasing rate of PAEs was 38.2%, 31.4%, 31.5% and 19.7% in LDPE films from 0.006 to 0.015 mm respectively. Critically, thicker film mulching can lead to greater soil water storage at plough layer (SWS-PL) and better thermal status, accordingly harvesting higher economic benefit. Therefore, LDPE film thickening may be a solution to reduce environmental risk but improve production efficiency in arid region.

Thymol@activated Carbon Nanohybrid for Low-Density Polyethylene-Based Active Packaging Films for Pork Fillets’ Shelf-Life Extension

Τhe replacement of food packaging additives and preservatives with bio-based antioxidant/antibacterial compounds has been a common practice in recent years following the trend of bioeconomy and nanotechnology. Such bio-additives are often enclosed in nanocarriers for a controlled release process. Following this trend in this work, a thymol (TO)-rich activated carbon (AC) nanohybrid was prepared and characterized physicochemically with various techniques. This TO@AC nanohybrid, along with the pure activated carbon, was extruded with low-density polyethylene (LDPE) to develop novel active packaging films. The codenames used in this paper were LDPE/xTO@AC and LDPE/xAC for the nanohybrid and the pure activated carbon, respectively. X-ray diffractometry, Fourier-transform infrared spectroscopy, and scanning electron microscopy measurements showed high dispersity of both the TO@AC nanohybrid and the pure AC in the LDPE matrix, resulting in enhanced mechanical properties. The active film with 15 wt.% of the TO@AC nanohybrid (LDPE/15TO@AC) exhibited a 230% higher water/vapor barrier and 1928% lower oxygen permeability than the pure LDPE film. For this active film, the highest antioxidant activity referred to the DPPH assay (44.4%), the lowest thymol release rate (k2 ≈ 1.5 s−1), and the highest antibacterial activity were recorded, resulting in a 2-day extension of fresh pork fillets’ shelf-life.

Computer-aided discovery of a novel thermophilic laccase for low-density polyethylene degradation

Polyethylene (PE) and industrial dyes are recalcitrant pollutants calling for the development of sustainable solutions for their degradation. Laccases have been explored for removal of contaminants and pollutants, including dye decolorization and plastic degradation. Here, a novel thermophilic laccase from PE-degrading Lysinibaccillus fusiformis (LfLAC3) was identified through a computer-aided and activity-based screening. Biochemical studies of LfLAC3 indicated its high robustness and catalytic promiscuity. Dye decolorization experiments showed that LfLAC3 was able to degrade all the tested dyes with decolorization percentage from 39% to 70% without the use of a mediator. LfLAC3 was also demonstrated to degrade low-density polyethylene (LDPE) films after eight weeks of incubation with either crude cell lysate or purified enzyme. The formation of a variety of functional groups was detected using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Damage on the surfaces of PE films was observed via scanning electron microscopy (SEM). The potential catalytic mechanism of LfLAC3 was disclosed by structure and substrate-binding modes analysis. These findings demonstrated that LfLAC3 is a promiscuous enzyme that has promising potential for dye decolorization and PE degradation.

Influence of Different Protected Environments and Reflector Material on Cultivated Oiti (Licania tomentosa[Benth.] Fritsch) Seedlings

Abstract Background Oiti (Licania tomentosa[Benth.] Fritsch) is an option for urban forestation and rural environments that require shading by plants, so studying the plant environment to obtain quality seedlings is essential. The present study aimed to evaluate oiti seedlings in different protected environments with or without reflective material on a cultivation bench. Methods The following protected environments were evaluated: an agricultural greenhouse covered with a low-density polyethylene film and a thermo-reflective screen with 42%/50% shading under the film; an agricultural screenhouse with an aluminized screen with 35% shading; an agricultural screenhouse with a black screen with 30% shading; and an agricultural screenhouse with a black screen with 18% shading. Production systems with and without photosynthetically active radiation-reflecting material (aluminized screen, Aluminet®) on the cultivation bench were assessed in each protected environment. Results There was no interaction between the environmental factors; however, the environments influenced height, stem diameter, root dry matter, and total biometric relationships and growth rates. The reflective material did not improve the quality of oiti seedlings. The ratio of shoot and root dry matter was, on average, 71% for the shoots and 29% for the roots. The photosynthetically active radiation received by oiti seedlings ranged from 600 to 1,100 μmol m−2s−1. Conclusions The greenhouse with 42%/50% shading screen under the film and the black screen with 30% shading were the best environments for the formation ofLicania tomentosaseedlings. The reflective material on the cultivation bench did not result in better quality oiti seedlings.

Cold Plasma Surface Modification of PLA and LDPE Polymer Plastics

Low-density polyethylene (LDPE) and polylactic acid (PLA) plastic films were subjected to modification using different plasma sources. Argon, nitrogen, air and oxygen were used as a gas phase throughout the process, and their impact on the material's surface properties was verified. The surface activation rate was measured via atomic force microscopy regarding the porosity factor and using the water contact angle technique. The last method – being feasible, agile and of high sensitivity to alternating physicochemical surface character – was utilised to verify the post-process stability of the modified surface. Those tests were performed extensively, up to 160 hours (contact angle) and 240 hours (atomic force microscopy).

Predicting the double-yield phenomenon in low-density polyethylene film using three-network viscoplastic model

Several Semi-Crystalline Polymers (SCPs) exhibit a Double-Yield (DY) phenomenon in the stress vs. strain response when subjected to uniaxial tensile load. There are only few constitutive models that can predict the DY phenomena at different temperatures and strain rates. These models were developed considering no deformation of crystalline phase, when the amorphous phase gets deformed, whereas in reality all the phases deform concurrently. In this investigation, a Three-Network (TN) viscoplastic model was employed to capture the DY phenomenon in the Low-Density Polyethylene (LDPE) films by considering simultaneous deformations in the amorphous and crystalline (lamellar) phases. The TN model comprised of three parallel networks, A, B, and C, with A and B consisting of non-linear springs and dashpots in series with each other and C containing a non-linear spring solely. While network A of the TN model influences the inter-lamellar shear resistance and the first yield point in the engineering stress vs. strain curve, networks B and C operate together to predict the second yield point. Furthermore, network B regulates the resistance to intra-lamellar shear fragmentation and orientation of lamellar phases. Network C accounts for both the rubbery effect of the amorphous phase and the resistance to fibril deformation along the loading direction at higher strains. To retrieve the TN model parameters, uniaxial tensile tests were conducted on the LDPE films at two different strain rates and temperatures ranging from ambient temperature (25 °C) to 110 °C. The engineering stress vs. strain graphs exhibited the DY phenomenon for all temperatures considered. Stress vs. strain curves were calibrated using the TN model in MCalibration software at certain temperatures (25 °C, 50 °C, 70 °C, and 90 °C) and loading rates (∼10−3/s and 10−2/s). The calibration results corroborated the experimental findings, particularly in terms of capturing the DY phenomenon. Also, simulations using calibrated TN model parameters satisfactorily predicted experimental stress-strain plots at remaining temperatures (40 °C, 60 °C, 80 °C, and 110 °C), demonstrating its versatility in predicting stress and strain characteristics. For the wide range of temperature (25 °C–110 °C) and strain rates considered, an overall difference of ∼5% is observed between the experimental and predicted stress vs. strain data.

Insights into the mechanism of plastics’ fragmentation under abrasive mechanical forces: An implication for agricultural soil health

AbstractThe application of agricultural plastic products such as mulch, greenhouse covers, and silage films is increasing due to their economic benefits in providing an early and better‐quality harvest. However, mechanical abrasion of these plastic materials by soil particles could result in generation of microplastic (MP) pollutants that could harm soil organisms and impact food safety. This study aims to better understand the physicochemical mechanisms resulting in the fragmentation of low‐density polyethylene (LDPE). Herein, we used pellets and films to study the impacts of abrasive wear forces on their surface morphology variations and fragmentation behavior. An innovative laboratory approach was developed to abrade the plastic surface under controlled normal loadings and abrasion durations. The investigation of the plastics’ surface morphology variations due to the abrasion process revealed microcutting as the dominant process at low normal force (4 N). However, a combination of microploughing and microcutting occurred for new LDPE films by increasing the normal force to 8 N. Despite the significant surface morphology variations of the new LDPE film due to the abrasion process; the water contact angle did not alter. Furthermore, the fragmentation behavior of photodegraded LDPE pellets and films was compared to the new plastics. The extent of MPs (3 µm < dp < 162 µm) generation due to fragmentation was studied using fluorescence microscopy imaging. The localized stress and strains at the contact sites of plastic and sand particles resulted in abrasion of the plastic surface. According to the results, the normal loadings and duration of abrasion played a significant role in the degree of fragmentation of plastics. Increasing the normal loading applied during the abrasion process from 2 to 8 N linearly increased the number of generated plastic fragments by more than five times for pellets and more than three times for film. Photodegradation significantly enhanced the extent of MPs fragmentation. Moreover, the limitations of this study and the implications for agricultural soil health were discussed.

Cladosporium cladosporioides (strain Clc/1): a candidate for low-density polyethylene degradation

BackgroundPlastic is one of the most widely used materials worldwide in various fields, including packaging and agriculture. Its large quantities require proper disposal and for this reason more and more attention is paid to the issue of degrading plastic. Thanks to the production of non-specific enzymes, fungi are able to attack complex and recalcitrant xenobiotics such as plastics. In recent years, several spectroscopic methods were used to study the plastic degradation ability of different fungal species. Among these, Fourier transform infrared (FT-IR) and FT-Raman spectroscopy techniques are the most used. Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful technique which uses metal nanoparticles (NPs) to enhance the Raman signal of molecules adsorbed on the NPs surface. In this work, the isolation of different fungi from field-collected plastic debris and the ability of these isolates to growth and colonizing the low-density polyethylene (LDPE) were explored by using scanning electron microscope (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and SERS spectroscopies.ResultsForty-seven fungal isolates belonging to 10 genera were obtained; among them only 11 were able to grow and colonize the LDPE film. However, after 90 days trial, only one isolate of Cladosporium cladosporioides (Clc/1) was able to carry out the initial degradation of the LDPE film. In particular, based on SEM observations, small cavities and depressed areas of circular shape were visible in the treated samples. Additionally, ATR-FTIR, normal Raman and SERS analyses supported the structural changes observed via SEM. Notably, ATR-FTIR and normal Raman spectra showed a significant decrease in the relative intensity of the methylene group bands. Similarly, the SERS spectra of LDPE after the fungal attack, confirmed the decrease of methylene groups bands and the appearance of other bands referring to LDPE polyphenolic admixtures.ConclusionsThese results suggest that Cladosporium cladosporioides Clc/1 is able to carry out an initial degradation of LDPE. Moreover, combining ATR-FTIR, Raman and SERS spectroscopies with SEM observations, the early stages of LDPE degradation can be explored without any sample pretreatment.Graphical

Multivariate analysis of enriched landfill soil consortia provide insight on the community structural perturbation and functioning during low-density polyethylene degradation

Plastic-enriched sites like landfills have immense potential for discovery of microbial consortia that can efficiently degrade plastics. In this study, we used a combination of culture enrichment, high-throughput PacBio sequencing of 16 S rRNA and the ITS gene, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) to examine the compositional and diversity perturbations of bacterial and fungal consortia from landfill soils and their impact on low-density polyethylene (LDPE) film biodegradation over a 90-day period. Results showed that enrichment cultures effectively utilized LDPE as a carbon source for cellular growth, resulting in significant weight reduction (22.4% and 55.6%) in the films. SEM analysis revealed marked changes in the micrometric surface characteristics (cracks, fissures, and erosion) and biofilm formation in LDPE films. FTIR analyses suggested structural and functional group modification related to C-H (2831–2943 cm⁻¹), and CH₂ (1400 cm⁻¹) stretching, CO and CC (680–950 cm⁻¹) scission, and CO incorporation (3320–3500 cm⁻¹) into the carbon backbone, indicative of LDPE polymer biodegradation. Enrichment cultures had lower diversity and richness of microbial taxa compared to soil samples, with LDPE as a carbon source having a direct influence on the structure and functioning of the microbial consortia. A total of 26 bacterial and 12 fungal OTU exhibiting high relative abundance and significant associations (IndVal > 0.7, q < 0.05) were identified in the enrichment culture. Bacterial taxa such as unclassified Parvibaculum FJ375498, Achromobacter xylosoxidans, unclassified Chitinophagaceae PAC002331, unclassified Paludisphaera and unclassified Comamonas JX898122, and six fungal species (Galactomyces candidus, Trichosporon chiropterorum, Aspergillus fumigatus, Penicillium chalabudae, Talaromyces thailandensis, and Penicillium citreosulfuratum) were identified as the putative LDPE degraders in the enrichment microbial consortium cultures. PICRUSt2 metagenomic functional profiling of taxonomic bacterial taxa abundances in both landfill soil and enrichment microbial consortia also revealed differential enrichment of energy production, stress tolerance, surface attachment and motility pathways, and xenobiotic degrading enzymes important for biofilm formation and hydrolytic/oxidative LDPE biodegradation. The findings shed light on the composition and structural changes in landfill soil microbial consortia during enrichment with LDPE as a carbon source and suggest novel LDPE-degrading bacterial and fungal taxa that could be explored for management of polyethylene pollution.

Antimicrobial plastic films against SARS‐COV‐2 and pathogenic bacteria

AbstractPolymeric films are used in numerous applications in the biomedical area. The incorporation of antimicrobial agents into these materials can prevent their surface from acting as a source of contamination of viruses and bacteria. In the present work, cinnamon and eucalyptus essential oils were incorporated into low‐density polyethylene (LDPE) by melt extrusion, as confirmed by Fourier transform infrared spectroscopy. For the success of incorporation, talc was used as an oil carrier and fixer. Despite high processing temperatures used (up to 175°C), the oleophilic character of talc was able to minimize oil losses, as proven by thermogravimetry. Good thermal and mechanical properties evaluated by differential scanning calorimetry and tensile tests were confirmed. In addition, antimicrobial tests confirmed film activity against virus SARS‐CoV‐2 and bacteria Staphylococcus aureus and Escherichia coli. LDPE films incorporated with both oils showed significant antiviral properties against SARS‐CoV‐2, with viral titers reduction between 95.89% and 100%. Cinnamon oil showed more efficient antibacterial properties than eucalyptus oil, with relative bacterial growths of films next to zero (0.37% for E. coli and 2.07% for S. aureus). To the best of our knowledge, no previous work has developed plastic films incorporated with essential oils with confirmed antiviral properties against SARS‐CoV‐2.

Micromechanical modeling of the visco-hyperelastic–viscoplastic​ behavior and fracture of aged semicrystalline polymers

This work presents a micromechanical-based visco-hyperelastic–viscoplastic constitutive model for low-density polyethylene (LDPE) films subjected to accelerated ultraviolet (UV) aging. The model captures the evolution of the mechanical and fracture properties of the material. Our proposed framework assumes that the semicrystalline polymer’s macromechanical behavior is the sum of the intermolecular and macromolecular network contributions. The intermolecular part of the model follows a nonlinear composite mixture rule, combining the contribution of the crystalline and amorphous phases, each represented rheologically by a linear elastic spring in series with a nonlinear viscous dashpot. The rheological representation of the macromolecular network consists of a series of two Langevin springs capturing deformation-induced conformation change and interatomic bond deformation between Kuhn segments, as well as a viscous dashpot for chain relaxation. We have developed a novel framework that reformulates the eight chain model to include the energy densities associated with both conformation change and interatomic bond deformation, providing a more accurate description of macromolecular network mechanical and fracture behavior. The aging of semicrystalline polymers results from two competing mechanisms: oxidation-induced strengthening resulting from chemicrystallization and crosslinking, and oxidation-induced softening resulting from chain scissions and chemicavitation. Our proposed model accurately captures the effect of UV aging on the mechanical behavior of the semicrystalline material. Additionally, we introduce the novel concept of a ”healthy network” to predict the evolution of the strain to fracture. The model accurately predicts the evolution of the mechanical behavior and elongation at break over a wide range of UV irradiation doses.

Biodegradation of low density polyethylene (LDPE) by Paenibacillus Sp. and Serratia Sp. isolated from marine soil sample

Low Density Polyethylene (LDPE) is recalcitrant and poses serious threats to our environment. The present study explored the LDPE biodegradation potential of aerobic bacteria enriched from offshore of RK beach Visakhapatnam. These isolates were specifically enriched in MSAM medium which contains LDPE as the source of carbon and energy for the growth. Six strains were isolated; among these S-6 & S-2 are the most potent strains which were attributed to the degrading ability. The phenotypic fingerprint such as Gen III biolog was used to identify the LDPE degrading S-6 as Paenibacillus sp. and S-2 as Serratia sp. respectively. Gen III Microlog, a phenotypic microarray; have been used for analysis of relative capabilities for substrate utilization of S-6 and S- 2 strains. The contact time of 72 h, temperature of 37 °C, pH of 7.1, inoculum volume 4% v/v, and weight of LDPE films 0.030 g were found to be optimal conditions for biodegradation of LDPE. Efficiency of these microbes (Paenibacillus sp. and Serratia sp) in degradation of LDPE was studied by percent weight reduction during a time period of 35 days. The Paenibacillus sps. proved to be most efficient with a weight loss of 22.46% compared to Serratia sps. with a weight loss of 9.5%. These bacterial species are capable of utilising LDPE as the sole carbon and energy source.

Linear low density polyethylene film process capability analysis

This study aimed to identify and present applications of the process capability indices in a process of a company in Vale do Paraíba. To reach this objective, applied research of exploratory and quantitative nature was carried out. After the adjustment, it was possible to observe the uniform distribution of data centered on the nominal value, without exceeding the lower and upper limits, which produced an adjusted process within specifications. As a contribution of this research, we point out the use of this statistical tool in problem solving and as a tool for decision making.

Characterization of low-density polyethylene (LDPE) films degraded using bacteria strains isolated from oil-contaminated soil

ABSTRACT This study assessed the low-density polyethylene (LDPE) film degradation potential of microorganisms isolated from oil-contaminated soil and also analyzed the morphological and chemical composition of LDPE films after the biodegradation period. The bacteria strains isolated from oil-contaminated soil were standardized and used to degrade the pretreated LDPE films in mineral salt media. Thereafter, they were incubated for 78 days at 37°C in an incubator shaker, and the degraded LDPE films were analyzed quantitatively and qualitatively (using scanning electron microscope (SEM) images and energy dispersal x-ray (EDX)). Isolates A32 and BTT4 amongst other bacteria isolates showed the highest LDPE film degradation activity, with a weight reduction of 71.80% and 89.72% respectively, and were identified using the 16S rRNA sequencing technique. The EDX results showed that LDPE film incubated with A32 has the highest reduction in carbon and nitrogen (23.8% and 44.9% respectively) when compared with the Control. However, LDPE film incubated with BTT4 had an increase in calcium and chlorine (139% and 40% respectively), when compared with the control. Similarly, the SEM images showed the appearance of pinholes, cracks and particles on the surfaces of LDPE films incubated with A32 and BTT4 contrary to the controls. A32 and BTT4 were identified as Proteus mirabilis (Accession number: MN124173.1) and Proteus mirabilis (Accession number: KY027145.1) respectively. Proteus mirabilis showed viable plastic biodegradation potentials and may be useful in the management of plastic waste, leading to a reduction in global plastic waste and a clean environment.

Recalibrating polyparameter linear free energy relationships and reanalyzing mechanisms for partition of nonionic organic compounds to low-density polyethylene passive sampler

Equilibrium passive sampling techniques based on the low-density polyethylene (LDPE) film are increasingly used for determining the concentration of contaminants in water and air. Reliable models capable of predicting LDPE–water and LDPE–air partition coefficients (KiLDPEw and KiLDPEa) would be very useful. In previous studies, polyparameter linear free energy relationships (PP-LFERs) based on Abraham's solute descriptors were calibrated for LDPE–water and LDPE–air systems. Unfortunately, a portion of unreliable partition coefficients and solute descriptors were included in the calibration sets of these previous studies, leading to unexpected system parameters and predictive performance in the regression results. In this study, more reliable PP-LFERs were recalibrated for LDPE–water and LDPE–air systems (20‒25 °C) using carefully collected reliable partition coefficients and solute descriptors of various polar and nonpolar compounds (over one hundred and with low redundancy) from the literature, as well as the robust regression method. The PP-LFERs performed well with root-mean-square errors of 0.15–0.25 log units and successfully predicted KiLDPEw and KiLDPEa values spanning over 10 orders of magnitude for compounds with reliable descriptors. The partitioning mechanisms of compounds to LDPE were also reanalyzed and compared in detail with n-alkanes (C6–C16). Generally, LDPE is more prone to form dispersion interactions with solutes than n-alkanes, while it is more difficult to form cavities in LDPE. In addition, the crystallinity of LDPE is not the sole reason for the distinct constant terms presenting in PP-LFERs for LDPE–water and n-hexadecane–water systems.

Force-Based Characterization of the Wetting Properties of LDPE Surfaces Treated with CF4 and H2 Plasmas.

Low-density polyethylene (LDPE) films are widely used in packaging, insulation and many other commodity applications due to their excellent mechanical and chemical properties. However, the water-wetting and water-repellant properties of these films are insufficient for certain applications. In this study, bare LDPE and textured LDPE (T-LDPE) films were subjected to low-pressure plasmas, such as carbon tetrafluoride (CF4) and hydrogen (H2), to see the effect of plasma treatment on the wetting properties of LDPE films. In addition, the surface of the LDPE film was textured to improve the hydrophobicity through the lotus effect. The LDPE and T-LDPE films had contact angle (θ) values of 98.6° ± 0.6 and 143.6° ± 1.0, respectively. After CF4 plasma treatments, the θ values of the surfaces increased for both surfaces, albeit within the standard deviation for the T-LDPE film. On the other hand, the contact angle values after H2 plasma treatment decreased for both surfaces. The surface energy measurements supported the changes in the contact angle values: exposure to H2 plasma decreased the contact angle, while exposure to CF4 plasma increased the contact angle. Kinetic friction force measurements of water drops on LDPE and T-LDPE films showed a decrease in friction after the CF4 plasma treatment, consistent with the contact angle and surface energy measurements. Notably, the kinetic friction force measurements proved to be more sensitive compared to the contact angle measurements in differentiating the wetting properties of the T-LDPE versus 3× CF4-plasma-treated LDPE films. Based on Atomic Force Microscopy (AFM) images of the flat LDPE samples, the 3× CF4 plasma treatment did not significantly change the surface morphology or roughness. However, in the case of the T-LDPE samples, Scanning Electron Microscopy (SEM) images showed noticeable morphological changes, which were more significant at sharp edges of the surface structures.