Low-density Polyethylene In Presence Research Articles

The impact of arbuscular mycorrhizal fungi and endophytic bacteria on peanuts under the combined pollution of cadmium and microplastics

It remains unclear how symbiotic microbes impact the growth of peanuts when they are exposed to the pollutants cadmium (Cd) and microplastics (MPs) simultaneously. This study aimed to investigate the effects of endophytic bacteria Bacillus velezens SC60 and arbuscular mycorrhizal fungus Rhizophagus irregularis on peanut growth and rhizosphere microbial communities in the presence of Cd at 40 (Cd40) or 80 (Cd80) mg kg−1 combined without MP or the presence of low-density polyethylene (LDPE) and poly butyleneadipate-co-terephthalate (PBAT). This study assessed soil indicators, plant parameters, and Cd accumulation indicators. Results showed that the application of R. irregularis and B. velezens significantly enhanced soil organic carbon and increased Cd content under the conditions of Cd80 and MPs co-pollution. R. irregularis and B. velezens treatment increased peanut absorption and the enrichment coefficient for Cd, with predominate concentrations localized in the peanut roots, especially under combined pollution by Cd and MPs. Under treatments with Cd40 and Cd80 combined with PBAT pollution, soil microbes Proteobacteria exhibited a higher relative abundance, while Actinobacteria showed a higher relative abundance under treatments with Cd40 and Cd80 combined with LDPE pollution. In conclusion, under the combined pollution conditions of MPs and Cd, the co-treatment of R. irregularis and B. velezens effectively immobilized Cd in peanut roots, impeding its translocation to the shoot.

Blending of Low-Density Polyethylene and Poly(Butylene Succinate) (LDPE/PBS) with Polyethylene-Graft-Maleic Anhydride (PE-g-MA) as a Compatibilizer on the Phase Morphology, Mechanical and Thermal Properties.

It is of significant concern that the buildup of non-biodegradable plastic waste in the environment may result in long-term issues with the environment, the economy and waste management. In this study, low-density polyethylene (LDPE) was compounded with different contents of poly(butylene succinate) (PBS) at 10-50 wt.%, to evaluate the potential of replacing commercial plastics with a biodegradable renewable polymer, PBS for packaging applications. The morphological, mechanical and thermal properties of the LDPE/PBS blends were examined in relation to the effect of polyethylene-graft-maleic anhydride (PE-g-MA) as a compatibilizer. LDPE/PBS/PE-g-MA blends were fabricated via the melt blending method using an internal mixer and then were compression molded into test samples. The presence of LDPE, PBS and PE-g-MA individually in the matrix for each blend presented physical interaction between the constituents, as shown by Fourier-transform infrared spectroscopy (FTIR). The morphology of LDPE/PBS/PE-g-MA blends showed improved compatibility and homogeneity between the LDPE matrix and PBS phase. Compatibilized LDPE/PBS blends showed an improvement in the tensile strength, with 5 phr of compatibilizer providing the optimal content. The thermal stability of LDPE/PBS blends decreased with higher PBS content and the thermal stability of compatibilized blends was higher in contrast to the uncompatibilized blends. Therefore, our research demonstrated that the partial substitution of LDPE with a biodegradable PBS and the incorporation of the PE-g-MA compatibilizer could develop an innovative blend with improved structural, mechanical and thermal properties.

Soil as a source of polyethylene degrading microorganisms

The presence of low-density polyethylene (LDPE) degrading microorganisms was found in the soils of the Republic of Moldova. Under standard soil conditions the LDPE biodegradation was relatively slow, implying the possibility of long-term negative environmental impacts from soil pollution by LDPE. It was observed that the biodegradation rates could be substantially improved by adding glucose into the soil (0,5%). LDPE biodegradation rates depended on the soil type and on the presence or absence of increased environmental stress for the soil microbial biomass. The highest biodegradation rate was observed in the case of a virgin forest soil sampled from the Orhei region: on day 41 after adding glucose into the soil with introduced LDPE the soil microbial biomass was 6.1% higher than in the control without LDPE, while the extent of LDPE degradation reached 2.3%.

Comparison of the Biodegradation of Polypropylene (PP) and Low Density Polyethylene (LDPE) by Pseudomonas aeruginosa and Staphylococcus aureus at Different pH Ranges under Mesophilic Condition

The present study aims to assess the temporal variations of some biotic and abiotic biodegradation parameters of 2 polymers (LDPE and PP) by the bacteria P. aeruginosa and S. aureus at acidic, neutral, and alkaline pH under mesophilic conditions. LDPE and PP fragments were immersed in the mineral solutions free of carbon sources containing P. aeruginosa or S. aureus cells. The initial pH values ​​(pHi) of solutions were 5, 7 and 9. Incubation was carried out at 28°C for 10, 20, 30, 40, 50 and 60 days. Results showed that during incubations, the pH of the solutions varies over time. In most cases, the electrical conductivity and cell abundances increased. The weights of the polymers decreased. The cell abundance apparent increasing rates (CAAIR), the electrical conductivity apparent increasing rates (ECAIR), and the polymer weight apparent decreasing rates (PWADR) were estimated. The highest PWADR in the presence of LDPE was 0.4 mg/10days with P. aeruginosaat pHi 5 and 7, and 0.6 mg/10days with S. aureus under pHi 7. For PP, it was constant (0.7 mg/10days) under all pHi with S. aureus, but decreased in the presence of P. aeruginosa with increasing in pHi solutions. The ECAIR with LDPE decreased with increasing pHi with both bacterial species.The highest ECAIR of PP was recorded under pHi 5 with S. aureus and under pHi 7 with P. aeruginosa.The highest CAAIR with LDPE was 185.18 CFU/10days for P. aeruginosa at pHi 5 and 116.79 CFU/10days for S. aureus at pHi 7. With PP, it was 297.61 CFU/10days for P. aeruginosa at pHi 5 and 67.64 CFU/10days for S. aureusat pHi 7. The biodegradation parameters values recorded with of P. aeruginosa differed significantly (P<0.05) from those recorded with S. aureus under each pHi.

A mechanistic understanding of polyethylene biodegradation by the marine bacterium Alcanivorax

Polyethylene (PE) is one of the most recalcitrant carbon-based synthetic materials produced and, currently, the most ubiquitous plastic pollutant found in nature. Over time, combined abiotic and biotic processes are thought to eventually breakdown PE. Despite limited evidence of biological PE degradation and speculation that hydrocarbon-degrading bacteria found within the plastisphere is an indication of biodegradation, there is no clear mechanistic understanding of the process. Here, using high-throughput proteomics, we investigated the molecular processes that take place in the hydrocarbon-degrading marine bacterium Alcanivorax sp. 24 when grown in the presence of low density PE (LDPE). As well as efficiently utilising and assimilating the leachate of weathered LDPE, the bacterium was able to reduce the molecular weight distribution (Mw from 122 to 83 kg/mol) and overall mass of pristine LDPE films (0.9 % after 34 days of incubation). Most interestingly, Alcanivorax acquired the isotopic signature of the pristine plastic and induced an extensive array of metabolic pathways for aliphatic compound degradation. Presumably, the primary biodegradation of LDPE by Alcanivorax sp. 24 is possible via the production of extracellular reactive oxygen species as observed both by the material’s surface oxidation and the measurement of superoxide in the culture with LDPE. Our findings confirm that hydrocarbon-biodegrading bacteria within the plastisphere may in fact have a role in degrading PE.

Biodegradation Capacity and Activity Enzymatic of Bacillus subtilis against Low-Density Polyethylene

Aims: The objective of this work was to determine the degradation capacity of low-density polyethylene by the bacterium Bacillus subtilis and analyze the production of extracellular laccase activity.
 Methodology: The experiments was realized in 50 mL of culture medium, added with a fragment of known dry weight (1 cm2 colorless polyethylene bag squares), and were incubated at 28°C, pH 6.5, for 6 months under static conditions, determining the growth of the bacterium by dry weight (68, 75, and 91 mg), the production of extracellular protein (271, 234, and 326.1 mg/mL), and the degradation of the substrate by dry biodegraded (8.57%, 5.88%, and 11.76%).
 Results: The production of extracellular laccase enzyme was analyzed in presence of polyethylene, finding an enzymatic activity of laccase of 2.06, 1.49, and 2,03 U/mL, while in the control without substrate, no enzymatic activity was observed, which suggests that this enzyme may participate in the degradation of polyethylene. In addition, some characteristics of the extracellular enzymatic activities were analyzed, such as stability at 4oC and 28oC, optimal pH and temperature, the effect of protein and substrate concentration.
 Conclusion: The extracellular protein production and dry weight of the bacterium are higher in the presence of low-density polyethylene. The laccase activity is very stable at 4oC and 28oC, the most effective pH and temperature, were 4.5 and 28oC, and present an incubation time of 5 minutes, and this data suggest that this enzymatic activitiy may participate in the degradation of low density polyethylene.

Microplastics in zooplankton in the eastern Arabian Sea: The threats they pose to fish and corals favoured by coastal currents

The baseline study of Microplastics (MPs) in zooplankton (copepods, chaetognaths, decapods, and fish larvae) from six different zones along India's west coast (off Kanyakumari/Cape Comorin, Kochi, Mangalore, Goa, Mumbai, and Okha) in the Eastern Arabian Sea (EAS) is presented here with their vast ecosystem impacts. This investigation revealed that zooplankton in all six zones accumulated MPs pellets (52.14%), fibres (28.40%), films (10.51%), and fragments (8.95%). The highest average retention of MPs (MPs/individual) was found in fish larvae (av. 0.57 ± 0.18) while copepods had the lowest (av. 0.03 ± 0.01). The presence of low-density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate was confirmed by Raman Spectra of MPs. The MPs in zooplankton found in this study (av. 22 ± 7 pieces/m3) were nearly 2-fold greater than those found in some of the world's most densely populated areas. It is shown that the strong southerly coastal currents could advect the MPs contaminated water mass too far away, having the potential to affect the fish and corals.

Evaluating melt foamability of LLDPE/LDPE blends with high LLDPE content by bubble coalescence mechanism

Bubble coalescence mechanism was introduced to evaluate the melt foamability of polymer blends. Linear low-density polyethylene (LLDPE), with excellent mechanical properties but poor foamability, was blended with small amounts of low-density polyethylene (LDPE), which was expected to impart the desired foaming-related properties to LLDPE. The presence of LDPE in LLDPE matrix provided only a small improvement in linear viscoelasticity under small deformations, but a significantly large improvement in nonlinear behavior under large deformations. A critical coalescence radius curve was simulated using a pressure-balanced bubble growth model to evaluate bubble coalescence and foamability of the blends, taking into account the linear and non-linear behaviors. It was found that the steep stress growth caused by LDPE addition can dramatically increase the pressure of large bubbles and then effectively inhibit the coalescence of adjacent bubbles, thus improving the foamability of LLDPE/LDPE blends. The theoretical predictions derived from the bubble coalescence mechanism were also confirmed by experiments.

Recycling of Polypropylene/Polyethylene Blends: Effect of Chain Structure on the Crystallization Behaviors.

The combination of high-density polyethylene (HDPE), low-density polyethylene (LDPE) and polypropylene (PP) is frequently found in polymer waste streams. Because of their similar density, they cannot be easily separated from each other in the recycling stream. Blending of PP/ polyethylenes (PEs) in different ratios possibly eliminate the sorting process used in the regular recycling process. PP has fascinating properties such as excellent processability and chemical resistance. However, insufficient flexibility limits its use for specific applications. Blending of PP with relative flexible PEs might improve its flexibility. This is a unique approach for recycling or upcycling, which aims to maintain or improve the properties of recycled materials. The effects of the branched-chain structures of PEs on the crystallization behavior and the related mechanical properties of such blends were investigated. The overall kinetics of crystallization of PP was significantly influenced by the presence of PEs with different branched-chain structures. The presence of LDPE was found to decrease the overall crystallization rate while the addition of HDPE accelerated the crystallization process of the blends. No negative effect on the mechanical performance and the related crystallinity was observed within the studied parameter range.

Anti-wetting polyvinylidene fluoride membrane incorporated with hydrophobic polyethylene-functionalized-silica to improve CO2 removal in membrane gas absorption

Membrane gas absorption (MGA), an attractive technology for carbon dioxide (CO2) separation was used in conjunction with polyvinylidene fluoride (PVDF) membranes. In order to improve the membrane’s CO2 absorption flux and gas selectivity, silica nanoparticles functionalized with low-density polyethylene (LDPE) were incorporated into PVDF matrix to produce an anti-wetting protection layer to overcome membrane wetting; a critical issue in regards to the MGA process. FESEM micrograph and EDX line-scan profile clearly show that f-silica were dispersed evenly in the composite membrane due to the better interactions with PVDF polymer chains in the presence of LDPE. LEPw, a measure of membrane wettability, was improved from 4.75 bar (pristine PVDF membrane) up to 13.55 bar for silica/PVDF composite membrane. More importantly, embedding silica nanoparticles into PVDF matrix improved both the CO2 absorption flux from 0.66 × 10−4 mol/m2 s to 2.32 × 10−4 mol/m2 s (3.5 times higher) and selectivity from 3.48 up to 29.4 (8.5 times higher) in comparison to the pristine PVDF membrane. In short, the results indicated that f-silica was effective in producing anti-wetting protection in PVDF membrane to improve CO2 removal in membrane gas absorption.

Effect of nanoclay on mechanical and thermal properties of triblock SBS (styrene–butadiene–styrene) and its binary blend nanocomposites: comparison between polyethylene and polystyrene

ABSTRACTIn this study, the effect of organo-modified nanoclay (OMMT) on the mechanical and thermal properties of SBS and its blend with low-density polyethylene (LDPE) and polystyrene was investigated. The effect of nanoclay content in the presence of LDPE or PS on the final properties of SBS was studied by tensile tester, dynamic mechanical thermal analysis (DMTA), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Addition of nanoclay affected the mechanical and rheological properties. From X-ray and DMTA results, it was found that due to more affinity between the nanoparticles and the SBS/PE blend, the 2 theta characteristic peak of nanoclay shifted to lower angles. SEM studies showed better dispersion and lower inter-particle distance of nanoparticles in SBS/PE composites in comparison with SBS/PS and SBS composites, confirming the XRD and DMTA results. It can be concluded that nanoclay acts as a compatibilizer in the SBS/LLDPE blend. TGA studies showed higher stability of SBS/PS composites compared to SBS and SBS/PE ones.

Effect of blending on fuel gas composition of pyrolysed plastic wastes

An investigation into the effects of blending on the gaseous product distribution of plastic wastes was successfully carried out. Waste Low Density Polyethylene (LDPE) and waste High Density Polyethylene (HDPE) samples were subjected to thermal pyrolysis in an electric tubular furnace. A study was also carried out to investigateFirst, the effect of heating rate on the volume of the gaseous products was studied. Previous research by other authors showed appreciable gas production occurred at a minimum heating rate of 20oC/min as such hHeating rate valuess of 22oC/min, 26oC/min and 32oC/min were adoptedused . It showed thatwith results showinged that a higher heating rates favoured the production of non-condensable gases in HDPE but caused a persistent decrease in LDPE. The investigation into the effects of blending was then carried out at a temperature range of 480oC – 600oC and heating rate of 22oC/min using blends of 0%, 20%, 40%, 50%, 60%, 80% and 100% LDPE in HDPE. The gaseous product was analysed by gas chromatography and results obtained showed a similarity in hydrocarbon product distribution for both LDPE and HDPE gas products. 100% LDPE showed a composition of 21.84%, 47.39%, 20.78%, 8.40%, and 1.59%; and 100% HDPE showed a composition of 18.88%, 46.91%, 22.89%, 9.59%, and 1.73% for C1, C2, C3, C4, and C5+hydrocarbon molecules respectively. The presence of LDPE in blends of LDPE-HDPE favoured the production of C1 up to 99 mol. %.

Wheat gluten/LDPE based thermoplastic vulcanizates containing LDPE-g-MA as compatibilizer

Traditionally, thermosetting wheat gluten based rubbers are produced from a glycerol plasticized gluten rubber precursor which spontaneously crosslinks during high temperature molding. We prepared thermoplastic elastomers by extruding the gluten rubber precursor at high temperature in presence of low density polyethylene (LDPE) to which maleic anhydride grafted LDPE (LDPE-g-MA) was added. At a proper LDPE/LDPE-g-MA ratio the desired phase-separated thermoplastic vulcanisate (TPV) morphology was obtained which consisted of finely dispersed gluten rubber particles, covalently anchored to the thermoplastic matrix. The TPVs with rubber contents up to 70wt% can be injection molded multiple times without loss of performance. Interestingly, the water absorption of the TPVs is much lower than that of classical gluten rubber materials while the rubber elastic recovery is maintained. The behavior in tensile testing was rationalized in terms of the TPV-typical heterogeneous, plastic deformation mechanism. The low strains at break were related to the presence of contaminants.

Gamma irradiated LDPE in presence of oxygen. Part I. Non-isothermal crystallization

Non isothermal crystallization of low density polyethylene (LDPE) samples irradiated under three different atmospheres was analyzed. The used doses were between 33 and 222kGy and the atmospheres content 0, 21 and 100% of oxygen. At a given radiation dose, the amount of produced gel is higher when the oxygen content present in the radiation process is lower.The temperature and the enthalpy of crystallization of the modified polymer decreased almost linearly with the radiation dose. Different classic models were used to predict the development of the relative degree of crystallinity (in the range 0.01–0.3 crystallinity fraction) as a function of temperature and several parameters were analyzed. The values of half-time of crystallization (t1/2) and the parameter Zc, from Avrami's method which characterize the kinetics of non-isothermal crystallization, showed that the crystallization rate, at the same cooling rate, decreased with increasing radiation dose and, at the same dose, with the decrease in the oxygen content. The activation energy for crystallization increased with the radiation dose and with the reduction of the oxygen content, indicating that the increment in molecular crosslinking restricts the crystallization process.

Friction and Wear Behavior of POM Composites Filled with LDPE and Wood Fibers

Polyoxymethylene (POM) composites filled with low-density polyethylene (LDPE) and wood fibers were prepared by injection-molding. Friction and wear tests were carried out in a reciprocating sliding tribotester. Results showed that 5wt.%LDPE acted effectively as the internal lubricant for POM. Further addition of the wood fiber increased the wear rate of the POM/LDPE composites but had little effect on the coefficient of coefficient in the presence of LDPE. SEM observations showed that the main wear mechanism for unfilled POM was adhesive wear, while in the case of POM composites abrasion and fatigue seemed to govern the wear process. It was suggested that, the POM/LDPE/Wood fiber composite, which is low-cost and environmentally friendly, has the potential for tribological applications.

Influences of contents and molecular weights of LDPE on DOP plasticization of PVC

Influences of contents and molecular weights of low-density polyethylene (LDPE) on dioctyl phthalate (DOP) plasticization in the poly(vinyl chloride) (PVC) plastisol (PVC/DOP/AO = 100/30/6.5) were investigated using DMA and DSC. The plasticization effects of DOP on the PVC plastisol were found to decrease with increasing LDPE content. A negligible plasticization effect of DOP on the PVC plastisol was found when the LDPE content was equal to or higher than 75 parts per 100 parts by weight of LDPE and PVC together. Based on thermal fractionation experiments, a favorable interaction between LDPE and DOP was developed during melt blending of LDPE and the PVC plastisol. The present interaction enabled the incorporation of DOP into LDPE and decreased the plasticization effects of DOP on the PVC plastisol. A further decrease in the plasticization effects of DOP on the PVC plastisol by the presence of LDPE was found with increasing LDPE molecular weights. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2548–2555, 2002

Oxidation of d‐Limonene in Presence of Low Density Polyethylene

ABSTRACTHeadspace oxygen contents of sodium citrate‐water buffers containing d‐limonene with and without low density polyethylene (LDPE) were measured on a weekly basis for 10 wk. d‐Limonene was readily sorbed into LDPE. Results indicated first order kinetics for limonene oxidation. GC/MS analyses determined production of limonene oxidation end‐products, including d‐carvone, carveol, limonene oxide, perrilaldehyde and linalool, as well as α‐terpineol, a hydrolysis product. Headspace oxygen contents of the d‐limonene/buffer (control) samples were lower thau that of the d‐limonene/buffer/LDPE samples, suggesting a higher oxidation rate in the control than in LDPE. Oxidation rate constants and half‐lives were 5.9 × 10‐3 log(%O2) wk‐1, t1/2= 116 wk for control and 1.2 × 10‐3 log(%O2) wk‐1, t1/2= 580 wk for LDPE samples, respectively.

DSC study of thermal decomposition of peroxide and azo derivative mixtures in the presence of LDPE

The thermal decompositions of azodicarbamide (AZDICA), 2,2′-azobisisobutyronitrile (AIBN), benzoyl peroxide (Bz2O2), dicumyl peroxide (DICUP) andα, α′-bis(t.-butylperoxy)-m/p-diisopropylbenzene (PEROXIMON F) in binary and ternary mixtures containing low density polyethylene (LDPE) have been studied by means of DSC alone. Binary mixtures including 2% by weight of Bz2O2 or DICUP develop a decomposition heat of 64.2 and 59.1 J/g mixture, respectively. These values are higher than those measured for the decomposition of the pure peroxides. In all the ternary mixtures studied, containing LDPE, a peroxide and an azoderivative, the absolute enthalpic values attributed to the peroxide are lower than those obtained from the LDPE-peroxide mixtures. The enthalpy changes observed have been interpreted on the basis of interactions of the peroxide radicals with the polymer support and with the azo derivative.