Degradation Of Low-density Polyethylene Research Articles

Investigations on the effect of kaolin catalyst on the yield of various products obtained from pyrolysis of low-density polyethylene (LDPE) wastes and reaction kinetics.

The pyrolysis characteristics of low-density polyethylene (LDPE) wastes were investigated in a batch pyrolyzer in the temperature range of 550-650°C for a varying heating rate (5, 10, 15, 20, and 25°C/min) alone and using kaolin catalyst (10, 15, and 20% w/w). The yield distribution of various products under varying operating conditions was investigated, and the corresponding favourable conditions for maximum yield of pyrolytic oil (PO) were identified. The possible effect of the catalyst on pyrolysis kinetics was explored by extracting activation energies from the TGA experiments. The various model-free iso-conversion methods estimated the activation energy of 162-166kJ/mol during thermal degradation of LDPE, while it shifted to a lower range (138-145kJ/mol) on catalytic treatment. The catalytic pyrolysis with a 20% (by mass) catalyst in a batch pyrolyzer provided the maximum PO yield with the least solid residue at 600°C using a heating rate of 20°C/min, while the temperature of 600°C with 10% catalyst showed the least liquid product with more solid residue. The presence of a catalyst improved the oil quality with transparency and lower viscosity due to lighter hydrocarbons and higher aromatic content. The FTIR analysis detected various organic groups-alkanes, alkenes, cyclic, and aromatics in the oil. GC tests of gaseous products confirmed the gases like hydrogen, propane, butane, and propylene. The present study aims to provide technical know-how for the effective utilization of LDPE wastes towards clean energy sources and create a plastic-free green environment.

Advances in plastic mycoremediation: Focus on the isoenzymes of the lignin degradation complex

This study investigates P. ostreatus and A. bisporus biodegradation capacity of low density polyethylene (LDPE) oxidised to simulate environmental weathering. Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were used to analyse the degradation of LDPE treated with fungal cultures. Molecular implications of LDPE degradation by P. ostreatus and A. bisporus were evaluated by Reverse transcription followed by quantitative PCR (qRT-PCR) of lac, mnp and lip genes expression. After 90 days of incubation, FT-IR analysis showed, for both fungal treatments, an increasing in the intensity of peaks related to the asymmetric C-C-O stretching (1160 to 1000 cm−1) and the -OH stretching (3700 to 3200 cm−1) due to the formation of alcohols and carboxylic acid, indicating depolymerisation of LDPE. This was confirmed by the SEM analysis, where a widespread alteration of the surface morphology was observed for treated LDPE fragments. Results revealed that the exposure of P. ostreatus to oxidised LDPE treatment led to a significant increase in the expression of the lac6, lac7, lac9, lac10 and mnp2 genes, while A. bisporus showed an over-expression in lac2 and lac12 genes. The obtained results offer new perspectives for a biotechnological use of P. ostreatus and A. bisporus for plastic bioremediation.

Ultraviolet Shielding Performance of Coconut Coir as a Filler in Low-Density Polyethylene (LDPE) Plastic Mulch

Plastic mulch is a layer of material applied to the soil surface to maintain moisture retention in the soil by preventing evaporation, reduce weed growth by blocking sunlight from reaching underlying weeds, and optimize fertilizer use by minimizing nutrient loss to the environment. However, the degradation of low-density polyethylene (LDPE), a thermoplastic commonly used for mulching, into microplastics due to exposure to UV radiation. This research explored the potential of coconut coir, a natural fiber with a high lignin content ranging from 30 to 46%, as a UV protective agent. The objective was to develop biodegradable plastic-based mulch composites that have better resistance to UV exposure by incorporating coir as a filler material in LDPE-based composites. Different ratios of coconut fiber were used (10%, 20%, 30%, and 40%), and Maleic anhydride grafted polyethylene (PE-g-MAH) was used as a binder at 2% of total weight mixed with LDPE in a rheomixer (80 rpm, 120°C for 10 min). The resulting plastic mulch bio-composites were evaluated for thermal, mechanical, UV resistance, and biodegradability properties. The results showed that the higher addition of coconut coir resulted in a decrease in the thermal and mechanical characteristics of the composite. However, the addition of higher coconut coir in the composite at 40% can provide an increase in the composite's resistance to ultraviolet light exposure, and the properties are easily degraded by the environment (biodegradable).

Visible-light driven photodegradation of low-density polyethylene (LDPE) using BiOCl–ZrO2 nanocomposite: A sustainable strategy for mitigating plastic pollution

This study aims to reduce plastic pollution by decomposing low-density polyethylene (LDPE) through an environmentally friendly approach using a novel BiOCl–ZrO2 nanocomposite under visible-light irradiation at room temperature. Visible-light irradiation is a form of clean energy, so we explored the feasibility and prospective solution for plastic waste mitigation by utilizing visible-light to attain sustainable development goal 7 (SDG 7). To fabricate photodegradable LDPE, it was blended with BiOCl nanoparticles (NPs) and its nanocomposite (BiOCl–ZrO2) separately via a facile solution casting method. The fabricated samples were assessed for the degradation of LDPE before and after 24 days of visible-light irradiation at room temperature. The prepared nanocomposites were thoroughly characterized by different analytical techniques, including XRD, FT–IR, XPS, FE–SEM, TGA, BET and UV–Vis DRS. The successful photodegradation of low-density polyethylene (LDPE) using a BiOCl–ZrO2 nanocomposite is supported by the presence of a higher carbonyl index, as evidenced by FT–IR analysis. The field-emission scanning electron microscopy (FE–SEM) analysis unveiled numerous perforations and prominent coarse morphological attributes, suggesting significant decomposition and disintegration of the LDPE film across the active surface sites of BiOCl–ZrO2. The weight reduction of LDPE@BiOCl–ZrO2 (600 ˚C) (10 wt%) composite film reached 48.67% under visible-light irradiation for 24 days at room temperature. The degradation rate exhibited significant sensitivity to variations in the concentration of the BiOCl–ZrO2 nanocomposite within the LDPE film. Investigation of the photodegradation mechanism suggested the formation of a type–II heterojunction–based photocatalytic system. The relatively low bandgap energy of ZrO2 (3.1 eV), facilitates the rapid migration of conduction band electrons to the conduction band of BiOCl. This migration process is facilitated by the favourable energy level alignment between the conduction bands of ZrO2 and BiOCl, enabling efficient electron transfer between the two materials. The large band gap of BiOCl (3.56 eV) permits the movement of valence band holes to the ZrO2 valance band. The spontaneous circulation of charge carriers within the heterostructure crystal maintains the charge separation and defers the recombination rate for an extended period. The photodegraded LDPE fragments are biodegradable and help to reduce plastic pollution. The environmental friendliness of the BiOCl–ZrO2 nanocomposite-assisted plastic waste remediation process was investigated using carbon footprint measurement. A tentative estimation suggested that the remediation process of 100 Kg of plastic waste may contribute to around 0.133 tons of carbon footprint.

Evaluation of Fenton, Photo-Fenton and Fenton-like Processes in Degradation of PE, PP, and PVC Microplastics

The global problem of microplastics in the environment is “inspiring” scientists to find environmentally friendly and economically viable methods to remove these pollutants from the environment. Advanced oxidation processes are among the most promising methods. In this work, the potential of Fenton, photo-Fenton, and Fenton-like processes for the degradation of microplastics from low-density polyethylene (LDPE), polypropylene (PP), and poly(vinyl chloride) (PVC) in water suspensions was investigated. The influence of three parameters on the efficiency of the degradation process was tested: the pH of the medium (3–7), the mass of added iron (10–50 times less than the mass of microplastics), and the mass of added H2O2 (5–25 times more than the mass of added iron). The effectiveness of the treatment was monitored by FTIR-ATR spectroscopy. After 60-min treatments, the PP microparticles were found to be insensitive. In the Fenton treatment of PVC and the photo-Fenton treatment of LDPE and PVC, changes in the FTIR spectra related to the degradation of the microplastics were observed. In these three cases, the treatment parameters were optimized. It was found that a low pH (3) and a high iron mass (optimal values were 1/12 and 1/10 of the mass of the microplastics for LDPE and PVC, respectively) favored all three. The degradation of LDPE by the photo-Fenton treatment was favored by high H2O2 concentrations (25 times higher than the mass of iron), while these concentrations were significantly lower for PVC (11 and 15 times for the Fenton and photo-Fenton treatment, respectively), suggesting that scavenging activity occurs.

Effect of thermal-oxidative and mechanical degradation of recycled LDPE on foaming

In this study, we investigated the effect of recycling process on the molecular structure, viscoelasticity and foaming behavior of low density polyethylene (LDPE). A series of LDPE samples with different recycling process was prepared by multiple extrusion using a twin-screw extruder. The molecular weight distribution (MWD) was characterized by gel permeation chromatography (GPC). Wider MWD indicated the generation of higher molecular weight products. Small-amplitude oscillation rheology showed reduced loss factors, indicating that the chain entanglement was more difficult to relax. Moreover, nonlinear viscoelasticity was investigated using elongational rheology and molecular stress function (MSF) model. The results showed a steeper strain hardening exhibited in recycled LDPE. The correlated parameter β in the MSF model indicated that the recycling did not significantly change the branches regularity in LDPE, while the increasing [Formula: see text], the other correlated parameter, indicated that the chain entanglement was enhanced, which was corresponded to the improvement of high molecular weight component. The foaming results revealed that the recycled LDPE had finer cellular structure and higher nucleation density. Moreover, despite adding PP and active CaCO3 to simulate the impurities, the foamability loss of these mixed samples was well restricted and still valuable. Recycled LDPE is instead better than its corresponding virgin one in foaming performance, exhibiting the application potential for further developments.

Screening of Fungal Isolates for Biodegradation Potentials of Low-Density Polyethylene from Selected Dumpsites

Polyethylene is the most commonly used synthetic plastic and poorly degraded in natural environments. This study was designed to evaluate biodegradation potentials of low-density polyethylene by fugal isolates from Station Market, Kaduna State, Nigeria. Soil samples were collected at a depth of 20cm using a sterilized hand towel and taken to microbiology laboratory, Kaduna State University. Fungi were isolated and each colony was repeatedly sub-cultured on freshly prepared SDA to obtain pure isolates. Pure separated single colonies were maintained on sterile slants at 4˚C for further investigation. Low-density polyethylene (LDPE) sheets were cut into bits and immersed in xylene and boiled for 15 minutes to dissolve and crushed. The LDPE powder was added to a mineral salt medium (MSM) containing salts in 1liter of distilled water after which the fungal isolates were introduced. Scanning electron microscopy and Fourier- Transform Infrared Spectroscopy (FTIR) analysis were used to determine the changes in the polymer bond of LDPE sheet after the biodegradation. The findings shows that Aspergillus niger, Aspergillus flavus, Brown rot and White rot fungi showed 21.1%, 16.1%, 17.6%, and 18.3% reductions in the polyethylene discs after incubation respective. Therefore, the study concludes that fungal species play a significant role in the degradation of LDPE and can be used in future studies for the degradation of complex plastic materials. Finally, the study recommends that Aspergillus niger and Aspergillus falvus be considered as potential candidates to degrade LDPE.

Ozone-based in-situ reactive extrusion for rapid functionalisation and degradation of low density polyethylene

Improving the hydrophilicity of low density polyethylene (LDPE) expends its use in blends. LDPE melt was rapidly functionalised and degraded by ozone in twin-screw extruder by varying extrusion times from one to seven and temperatures from 160 °C to 240 °C. Abundant oxygen-containing groups, such as carbonyl group (CO) at 1718 cm−1, hydroxyl group (-OH) at 3400 cm−1 and aldehyde group (-CHO) at 1740 cm−1, were generated into ozone treated PE, resulting in improved hydrophilicity. At 200 °C, ozone treated PE exhibited a high melt flow index (21.5 g/10 min) and low complex viscosity modulus due to molecular degradation. Nevertheless, cross-linking occurred at a higher temperature of 240 °C. A higher crystal peak temperature of ozone treated PE at 200 °C was attributed to the introduction of oxygen atoms. The poor thermal stability of ozone treated PE was evidenced by a lower initial decomposition temperature. The oxidation induction time of ozone treated PE at 200 °C declined from 32 min for one extrusion to 12 min for seven extrusions demonstrating a vulnerability of ageing. Increasing the extrusion times gradually enhanced the tensile modulus of the ozone treated PE at 200 °C, while raising the treatment temperature had no effect on the tensile properties. Rapid functionalisation and degradation of LDPE were successfully achieved using ozone in reactive extrusion, thus broadening the applications of ozone treated PE in composites.

Degradation of low-density polyethylene by the bacterium Rhodococcus sp. C-2 isolated from seawater

Low-density polyethylene (LDPE), which accounts for 20% of the global plastic production, is discharged in great quantities into the ocean, threatening marine life and ecosystems. Marine microorganisms have previously been reported to degrade LDPE plastics; however, the exploration of strains and enzymes that degrade LDPE is still limited. Here, an LDPE-degrading bacterium was isolated from seawater of the Changjiang Estuary, China and identified as Rhodococcus sp. C-2, the relative abundance of which was dramatically enhanced during PE-degrading microbial enrichment. The strain C-2 exhibited the degradation of LDPE films, leading to their morphological deterioration, reduced hydrophobicity and tensile strength, weight loss, as well as the formation of oxygen-containing functional groups in short-chain products. Sixteen bacterial enzymes potentially involved in LDPE degradation were screened using genomic, transcriptomic, and degradation product analyses. Thereinto, the glutathione peroxidase GPx with exposed active sites catalyzed the LDPE depolymerization with the cooperation of its dissociated superoxide anion radicals. Furthermore, an LDPE degradation model involving multiple enzymes was proposed. The present study identifies a novel PE-degrading enzyme (PEase) for polyethylene bioremediation and promotes the understanding of LDPE degradation.

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.

Wood decay fungi show enhanced biodeterioration of low-density polyethylene in the absence of wood in culture media.

The involvement of microorganisms in low-density polyethylene (LDPE) degradation is widely studied across the globe. Even though soil, landfills, and garbage dumps are reported to be promising niches for such organisms, recently the involvement of wood decay fungi in polyethylene degradation is highlighted. In light of this, 50 fungal samples isolated from decaying hardwoods were assessed for their wood degradation ability and for their depolymerization enzymatic activities. For the LDPE deterioration assay, 22 fungal isolates having wood decay ability and de-polymerization enzymatic activities were selected. Fungal cultures with LDPE sheets (2 cm x 10 cm x 37.5 μm) were incubated in the presence and in the absence of wood as the carbon source (C) for 45 days. Degradation was measured by weight loss, changes in tensile properties, reduction in contact angle, changes of functional groups in Fourier-transform infrared spectroscopy, Scanning electron microscopic imaging, and CO2 evolution by strum test. Among the isolates incubated in the absence of wood, Phlebiopsis flavidoalba out-performed the other fungal species showing the highest percentage of weight reduction (23.68 ± 0.34%), and the lowest contact angle (64.28° ± 5.01). Biodegradation of LDPE by P. flavidoalba was further supported by 46.79 ± 0.67% of the mass loss, and 3.07 ± 0.13% of CO2 emission (mg/L) in the strum test. The most striking feature of the experiment was that all the isolates showed elevated degradation of LDPE in the absence of wood than that in the presence of wood. It is clear that in the absence of a preferred C source, wood decay fungi thrive to utilize any available C source (LDPE in this case) showing the metabolic adaptability of fungi to survive under stressful conditions. A potential mechanism for LDPE degradation is also proposed.

Degradation of LDPE Using the Winogradsky Column Containing Otteri Dumpsite Soil: Prediction of Mechanism and Metabolites Determination

Background of the Research: Plastic pollution has taken over the world. Toxicity of the plastics and other pollutants is enhanced due to the formation of microplastics and nano-plastics that attract Persistent Organic Pollutants (POPs). The need for the treatment of plastic waste in the current scenario led to the rise of various treatment processes. Biodegradation, an eco-friendly approach to eliminate plastics urged to discover plastic-utilizing bacteria and plastic-eating worms. Bacterial degradation of plastics has been extensively studied utilizing the entire microbial community. Hence, the current research focuses on the biodegradation of Low-Density polyethylene (LDPE) using Winogradsky Column constructed using dump yard soil. LDPE degradation was determined using FTIR and GC-MS analysis, which is used to analyze the degradation mechanism of LDPE. Methods: Sample Collection and Column Construction: The soil samples collected from the Chennai dump yard were used to construct Winogradsky columns. The column with LDPE and enrichment sources is used to study LDPE degradation. Analysis of LDPE Degradation: The LDPE sheet after incubation was washed with surfactant and ethanol. The dried sheet was analyzed for weight loss and the metabolites were identified using GC-MS analysis. The GC-MS chromatogram was used to determine the pattern of degradation by the microbial community in the dump yard soil. Results: The mass spectral analysis of GC peaks has been carried out using the electron ionization method, and ions were detected using positive ions scanning mode. The GC peaks appeared at 22.532 and 23.117 min in the control LDPE sheet, which was found to be nonadecane and octacosane, whereas, in the treated LDPE sheet, the GC peaks appeared at 22.467 and 23.062 min. The fragmentation pattern indicates the loss of m/z 14, which confirms the loss of methylene (-CH2-) fragments in alkyl chains. The difference in retention time could be correlated with the increase of CH2 in the alkyl chain length and molecular weight. Higher molecular weight alkanes, such as C16, C18, and C20 above appeared at higher retention times. The presence of longer alkyl chains indicates the LDPE polymer chains. The treated LDPE sample has been analyzed, and the fragmentation pattern indicates the presence of aliphatic chains of C16 or C18. Conclusion: The current study provides an efficient method to utilize the microbial community as a whole to degrade LDPE. The degradation mechanism of LDPE was determined using GC-MS analysis. The high molecular weight polymeric chain was degraded to small chains, and the formation of alcohol indicates the occurrence of terminal oxidation. Hence, this confirms the degradation of LDPE by the microbiome present in the dump yard soil.

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

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.

Biocomposite materials based on polyethylene and amphiphilic polymer-iron metal complex

Objectives. To obtain and study the properties including degradability of polymer composite materials (PCM) based on low-density polyethylene (LDPE) obtained by introducing an environmentally friendly additive comprising an oxo-decomposing additive (ODA) based on an amphiphilic polymer-iron metal complex, which accelerates the process of polymer degradation.Methods. PCMs based on LDPE and ODA were produced by processing in laboratory extruders in the form of strands, granules, and films. Thermodynamic properties were determined by differential scanning calorimetry in the temperature range 20-130 °C. In order to assess the performance characteristics (physical and mechanical properties) of the PCM, tensile strength and elongation at break were determined. The biodegradability of PCM was evaluated by Sturm's method, with the biodegradation index being determined by the amount of CO2 gas released as a result of microorganism activity, as well as composting by placing the PCMs for six months in biohumus. Changes in physical and mechanical properties and water absorption of the films during storage were evaluated. The photochemical degradability of the PCM was determined by exposing it to ultraviolet radiation for 100 h (equivalent to approximately one year of exposure of the films under natural conditions). The appearance of the composite samples following removal from the biohumus was determined using an optical microscope with ×50 magnification in transmitted and reflected light.Results. Following biodegradation by composting, the physical and mechanical properties of PCMs decrease by an average of 40.6%. This is related to the structural changes that occur in composites during storage in biohumus, i.e., the formation of a looser structure due to the development of large clusters of microorganisms that affect the formation of microcracks. It leads to the stage of fragmentation of the polyethylene matrix and indicates the progress of biological degradation of composites. In this case, the water absorption of the composite samples was 63% after 96 h of exposure. The biodegradability index determined by the Sturm method after 28 days of bubbling had changed by 82%, indicating an intensive biodegradation process. Exposure to ultraviolet radiation for 96 h resulted in the complete destruction of the PCMs, which turned into small “flakes.” This method is the most effective for the degradation of LDPE- and ODA-based PCMs.Conclusions. According to the results of the study of ODA-containing PCMs based on an amphiphilic polymer-iron metal complex, the tested filler-modifier can be recommended for the production of PCMs offering an accelerated degradation period.

A pyrolysis model for the thermal decomposition of low-density polyethylene blended with ammonium polyphosphate and pentaerythritol

In this work, a semi-empirical pyrolysis model is developed to predict the thermal decomposition behavior of an intumescent fire retardant (IFR) system consisting of ammonium polyphosphate/pentaerythritol (APP/PER) with the ratio 3:1 (wt/wt) in a low-density polyethylene (LDPE) matrix. This work is based on a previously developed semi-global reaction mechanism for the degradation of LDPE and APP/PER, which consists of two consecutive first-order reactions for the LDPE and five first and second-order reactions for the APP/PER combination. The apparent properties that define heat transport inside the pyrolyzing solid are determined via inverse modeling of cone calorimeter experiments for the pure LDPE and then for the complete IFR system. This is achieved by using the Shuffled Complex Evolution optimization algorithm. The flame heat flux in the cone calorimeter experiments is also evaluated by targeting the heat release rate (HRR) data in the optimization process of one of the cone radiative heat setups. The optimized parameters and flame heat feedback are in line with the literature and the robustness of the model is assessed by a comparison with the experimental data for a wide range of cone heat fluxes. Ignition times and peaks of HRR and total HRs are within the engineering accuracy whatever the flux conditions for both pure LDPE and the IFR system.

Simulations mapping the influence of oxygen, extruder residence time, and mechanical shear on low-density polyethylene structure during recycling

We present a computational study of the development of structural properties for recycled low-density polyethylene (LDPE). First, we apply the population balance method together with the method of moments to study the mutual influences of scission and crosslinking reactions. Then, we study the combined effects of extruder residence time and oxygen concentration as the initiator of thermo-mechanical degradation in the recycling process of LDPE in a twin-screw extruder. Further, we extend the models to study the influence of mechanical scission. We explore various case study scenarios to incorporate the effect of extruder residence time and mechanical shear. It is concluded that the competition between random scission and crosslinking, as well as the presence of oxygen, play important roles in the degradation of LDPE during recycling. Random scission is a key factor in terms of altering molecular weight distribution (MWD) during a recycling extrusion process. The various explored scenarios with mechanical scission demonstrate the sensitivity of molecular structure to the combination of competing mechanisms during recycling.

Degradation of low density polyethylene by Bacillus species

Since its invention, polyethylene (PE) has brought many conveniences to human production and life. In recent years, however, environmental pollution and threats to human health caused by insufficient PE recycling have attracted widespread attention. Biodegradation is a potential solution for preventing PE pollution. In this study, Bacillus subtilis and Bacillus licheniformis, which are widespread in the environment, were examined for their PE degradation abilities. Biodegradation of low-density polyethylene (LDPE) was assessed by weight loss, Fourier transform infrared spectroscopy (FTIR), and high performance liquid chromatography (HPLC) analyses. Weight losses of 3.49% and 2.83% were observed for samples exposed to strains B. subtilis ATCC6051 and B. licheniformis ATCC14580 for 30 days. Optical microscopy revealed obvious structural changes, such as cracks, pits, and roughness, on the surfaces of the microorganism-exposed LDPE sheets. Oxidation of the LDPE sheet surfaces was also demonstrated by the FTIR-based observation of carbon-unsaturated, –OH, –NO, –C=C, and –C–O bonds. These results support the notion that B. subtilis ATCC6051 and B. licheniformis ATCC14580 can degrade PE and could potentially be used as PE-biodegrading microorganisms. Further research is needed to examine potential relevant degradation mechanisms, such as those involving key enzymes.

Efficient and controllable synthesis of zeolite Beta nanospheres and hollow-boxes using a temperature-sensitive bifunctional additive

Zeolite Beta nanospheres and hollow-boxes are successfully obtained through a simple one-pot hydrothermal crystallization route, using tetraethylammonium hydroxide (TEAOH) as the structure-directing agent (SDA) assisted with a temperature-sensitive bifunctional additive N-methyl-2-pyrrolidone (NMP). The influences of crystallization temperature, Si/Al ratio, and TEAOH content on the synthesis and physicochemical properties of zeolite Beta as well as the formation of hollow structure are investigated in detail. It reveals that the role of NMP changes from “crystallization promoter” (CP) to “hollow-directing agent” (HDA). And the acceleration effect of NMP decreases upon the crystallization temperature (120–160 °C) due to the decomposition of TEAOH. Meanwhile, high synthesis temperature (≥180 °C), high Si/Al ratio (≥30), and low TEAOH content (TEAOH/SiO2 ≤ 0.2) may lead to the formation of undesired zeolites ZSM-5 and/or ZSM-12. The obtained Beta nanosphere and hollow-box catalysts exhibit excellent catalytic activity in the degradation of low-density polyethylene (LDPE) due to their high external surface area and acid density.

Microbial degradation of low density polyethylene by Exiguobacterium sp. strain LM-IK2 isolated from plastic dumped soil.

Low-Density Polyethylene (LDPE) is one of the significant environmental pollutants as it is resistant to natural degradation. In this study, we reported the LDPE-degrading bacterial straini.e., Exiguobacterium sp. strain LM-IK2 isolated from plastic dumped soil which shows potential degradation capability. The percent weight loss of LDPE was calculated as -5.70 ± 0.7 after 90days of incubation in a carbon-free MSM medium. The Field Emission Scanning Electron Microscopy (FE-SEM) analysis shows that LDPE films show slight surface disruption after treatment with bacteria. The Fourier Transform Infrared Spectroscopy (FTIR) revealed the chemical changes in LDPE films e.g., formation and reduction of typical carbonyl peaks after incubation with bacteria. The X-Ray Diffraction (XRD) analysis displayed an increase in percent crystallinity, with a slight change in total carbon content. Genetic analysis showed the presence of Laccase (167bp) and Alkane Hydroxylase (330bp) genes that are responsible for LDPE degradation.Thus, Exiguobacterium sp. strain LM-IK2 has the potential to degrade LDPE and could be further explored to improve its efficiency in the bioremediation of LDPE.