Oxidation Of Low Density Polyethylene Research Articles

Electrochemical Oxidation and Functionalization of Low‐Density Polyethylene

AbstractPlastic waste is a serious environmental issue, and polyethylene (PE) is a significant component. The chemically inert nature of PE makes its recycling/upcycling process challenging. Thus, a novel method was demonstrated that enables the selective electrochemical functionalization and deconstruction of low‐density polyethylene (LDPE) by using low‐cost transition metal electrocatalysts at room temperature (23±2 °C) and low cell voltage (±1 V). Three different electrode and electrolyte combinations were studied for the oxidation of LDPE: copper metal/copper (II) ions, nickel metal/nickel (II) ions, and stainless steel/iron (II) and (III) ions. The copper and nickel electrode/electrolyte pairs showed a promising capability for oxidation and chain‐scission of LDPE. In contrast, the stainless‐steel and iron electrode/electrolyte pair showed no activity towards LDPE oxidation or depolymerization. The electrolysis of LDPE offers a new vista for the depolymerization and upcycling of plastics, further understanding of the process is needed.

Analysis and microbial degradation of Low-Density Polyethylene (LDPE) in Winogradsky column

Plastic pollution is threatening the world and the life in it. Cost-effective and eco-friendly treatment is the need of the hour. Treating plastics using chemical methods adds up chemicals into the environment with toxic byproducts. The physical method, a slow and expensive process, is not the better alternative. The process should rely on the environmental sources producing eco-friendly byproducts. The byproducts such as biofuel could be utilized for a sustainable environment, but the conversion of plastics into biofuel is expensive. Hence, biodegradation is the better, sustainable, and cost-effective process for plastic/any other pollutant removal. The study focuses on the construction of Winogradsky column using dumpsite soil. The column amended with Low-Density Polyethylene (LDPE) serves as a carbon source for native microbes. The utilization of microbes in every niche for the degradation enhances the degradation of LDPE. The Otteri soil resulted in 35.4 ± 0.3%, while Kodungaiyur and agriculture soil show 29.7 ± 0.6% and 19.8 ± 0.8%. The AFM analysis shows the disruption of smooth LDPE surface by forming ridges and grooves, which further confirms the occurrence of degradation. The FTIR analysis shows the incorporation of OH, CO, and other CO–O–CO in the CH backbone of LDPE. The oxidation of LDPE will aid in cleavage and result in the process of weathering. The tensile strength decreased after LDPE treatment (23.88 MPa - control, 22.50 MPa – Kodungaiyur, and 14.92 MPa – Otteri). Thus, utilizing the native microbes present in every niche enhances the degradation of pollutants.

Plastic ingestion by the Wels catfish (Silurus glanis L.): detailed chemical analysis and degradation state evaluation.

Plastic ingestion by various organisms within different trophic levels, including humans, is becoming a serious problem worldwide. Plastic waste samples are often found concentrated in an organism's digestive tract and can be degraded and further translocate to the surrounding tissue or circulatory systems and accumulate in food chains. In the present work, we report a detailed chemical analysis and degradation state evaluation of a relatively large piece of plastic waste found in the gastrointestinal tract of a Wels catfish (Silurus glanis L.) caught in the Bodrog River (Danube River basin), eastern Slovakia. Chemical analysis by surface-sensitive X-ray photoelectron spectroscopy (XPS) was performed to identify the surface composition of the digested plastic piece. Micro-Fourier transform infrared (μFTIR) spectroscopy showed that the plastic waste was oxidized low-density polyethylene (LDPE), with some nylon fibers adhered on the surface. Glyceraldehyde adhered onto LDPE was also detected, which might come from the carbohydrate metabolism of that fish. A morphology study by digital optical microscopy indicated solid inorganic particles attached to the surface of LDPE. A degradation study by differential scanning calorimetry (DSC) showed considerable oxidation of LDPE, leading to fragmentation and disintegration of the plastic waste material.

Evaluating weathering of food packaging polyethylene-nano-clay composites: Release of nanoparticles and their impacts

Nano-fillers are increasingly incorporated into polymeric materials to improve the mechanical, barrier or other matrix properties of nanocomposites used for consumer and industrial applications. However, over the life cycle, these nanocomposites could degrade due to exposure to environmental conditions, resulting in the release of embedded nanomaterials from the polymer matrix into the environment. This paper presents a rigorous study on the degradation and the release of nanomaterials from food packaging composites. Films of nano-clay-loaded low-density polyethylene (LDPE) composite for food packaging applications were prepared with the spherilene technology and exposed to accelerated weathering of ultraviolet (UV) irradiation or low concentration of ozone at 40°C. The changes in the structural, surface morphology, chemical and physical properties of the films during accelerated weathering were investigated. Qualitative and quantitative changes in properties of pristine and aged materials and the release of nano-clay proceeded slowly until 130h irradiation and then accelerated afterward resulting complete degradation. Although nano-clay increased the stability of LDPE and improved thermal and barrier properties, they accelerated the UV oxidation of LDPE. With increasing exposure to UV, the surface roughness, chemiluminescence index, and carbonyl index of the samples increased while decreasing the intensity of the wide-angle X-ray diffraction pattern. Nano-clay particles with sizes ranging from 2 to 8nm were released from UV and ozone weathered composite. The concentrations of released nanoparticles increased with an increase in aging time. Various toxicity tests, including reactive oxygen species generation and cell activity/viability were also performed on the released nano-clay and clay polymer. The released nano-clays basically did not show toxicity. Our combined results demonstrated the degradation properties of nano-clay particle-embedded LDPE composites toxicity of released nano-clay particles to A594 adenocarcinomic human alveolar basal epithelial cells was observed, which will help with future risk based-formulations of exposure.

Anionic surfactant induced oxidation of low density polyethylene followed by its microbial bio-degradation

Hydrocarbon solubilization ability of surfactants was utilised for the deterioration of polyethylene during its thermal oxidation. Carbonyl index of polyethylene treated with Sodium dodecyl sulphate (SDS) at 60 °C for 1 month was found to be higher than thermally oxidised polyethylene as observed in FTIR study. Moreover, higher oxidation of polyethylene was witnessed after treatment of control polyethylene with 1%–10% of sodium dodecyl benzene sulphonate, sodium stearate, sodium octyl sulphate and sodium dodecyl sulphate at 60 °C for 1 month. Oxidation level of polyethylene treated by surfactant was higher as the availability of soluble oxygen and chain scission increased due to the attachment of surfactant to the polyethylene surface. Weight loss of 7.006 ± 0.05%, 1.76 ± 0.05% and 0.83 ± 0.05% were maximum which was achieved after bacterial treatment of oxidised polyethylene with 6%, 8% and 10% SDS, with L. fusiformis using peptone for 1 month, respectively. Along with weight loss after bacterial incubation, a decrease in the amount of carbonyls and an increase in the amount of unsaturated hydrocarbon were observed for the conversion of carbonyls into unsaturated hydrocarbon through biotic Norrish-type mechanisms. The biodegradation through β-oxidation mechanisms, by which oxidised polyethylene molecule was utilised to produce necessary energy for bacteria, was confirmed by a decrease in intrinsic viscosity and a decrease in the viscosity average molecular weight (Mv) of bacterially treated polyethylene. Nevertheless, an increase in the amount of carbonyls was observed after 1 month of bacterial incubation of polyethylene treated with SDBS and thermally oxidised polyethylene which was due to oxidation by oxidative enzymes released by Lysinibacillus fusiformis.

Oxidation of low density polyethylene by a laccase-mediator system

Oxidation of low density polyethylene by a laccase-mediator system

Studying Thermally Induced Chemical and Physical Transformations in Common Synthetic Polymers: A Laboratory Project

A simple project is described for introducing students to some experimental procedures commonly used to measure the effects of thermal treatment on synthetic polymers. The thermally induced changes that occur in the commodity polymers low-density polyethylene (LDPE), poly(ethylene terephthalate) (PET), and poly(vinyl chloride) (PVC) are examined as a function of the time of thermal treatment in an air-circulating oven. In particular, simple procedures are described for determining (i) the polymer hydroperoxide (POOH) content and carbonyl index (CI) of LDPE, (ii) the extent of whitening of PET, and (iii) the extent of discoloration or "yellowing" of PVC, all of which change during thermal treatment. The POOH content of LDPE is determined using a ferrometric method and the CI of this polymer is measured by both Fourier transform infrared spectroscopy and a staining technique involving 2,4-dinitrophenylhydrazine. The thermal oxidation of LDPE and the kinetics of formation of its POOH and carbonyl species are discussed with reference to the accepted mechanism for the autooxidation of polyolefins. The whitening of PET and the yellowing of PVC during thermal treatment are explained by means of a crystallization process and a "zip" dehydrochlorination reaction, respectively.

Oxidation of LDPE and LDPE grafted with itaconic acid, in contact with water

The accumulation of carboxyl groups in low-density polyethylene (LDPE) and LDPE grafted with itaconic acid on the macromolecules kept in hot water, aqueous electrolytic solutions, ethyl and isobutyl alcohols have been investigated. Simultaneously, a photo-initiated oxidation by UV-radiation has also been studied. It was revealed that functionalization of the polyethylene accelerated its thermal and photo-oxidation processes in water. The depth which the oxidation front of macromolecules reached in aqueous media was larger than that in air. Alkalisation of the aqueous solutions led to a faster oxidation of functionalised polyethylene, but in acidic media the oxidation behaviour did not in fact change as compared with that in an inert environment. When oxidation was photo-initiated in an aqueous medium the light caused a decisive influence on the acceleration of the process. The results obtained show that such oxidation was accelerated owing to hydroperoxide decomposition initiated by water.

The antioxidizing effect of sterically hindered amines in thermal oxidation of low density polyethylene

The antioxidizing effects of sterically hindered amines during thermal oxidation of low density polyethylene (LDPE) at 100° were studied and compared with those of antioxidants of the phenolic type, by measurements of melt flow index, ultimate elongation and carbonyl index as functions of ageing time. For some of the sterically hindered amines (Spinuvex A 36, Chimassorb 944, Tinuvin 622), the antioxidizing effects were also studied by processing in a Brabender Plastograph at 150°. The effects were related to the oxidability of the amines. A mechanism was proposed to account for the action of sterically hindered amines in thermal oxidative stabilization of LDPE.

Oxidation of low density polyethylene (LDPE) by purple hydrocarbon

Oxidation of low density polyethylene (LDPE) by purple hydrocarbon

Influence of hindered piperidines on the thermal oxidation of low density polyethylene

The effect of two commercial hindered piperidines, Tinuvin 770 and Hostavin N20, on the thermal oxidation of low density polyethylene (LDPE) in the melt is examined using Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), ultraviolet (uv) spectrometry and Melt Flow measurements. The results show that the hindered amines offer no thermo-stabilization and behave as pro-oxidants. In comparison, two phenolic antioxidants, Topanol (BHT) and Hostanox 03 (butyric acid 3,3-bis(3-tert-butyl-4-hydroxyphenyl) ethylene ester), show antioxidant behaviour, as expected, whereas dilauryl thiodipropionate (Hostanox SE 1) behaves as a pro-oxidant. The thermal degradation of LDPE films in air is also influenced by these additives. The implications of the results are discussed on the basis of antioxidant and nitroxyl radical effectively competing with oxygen for the macroalkyl radicals during melt processing. This competition is inefficient in the melt but not in the solid film.

ESCA studies of the photo-oxidation and the γ-radiation-induced oxidation of low density polyethylene

ESCA has been used to monitor the changes in the surface chemistry of low density polyethylene during exposure to uv light (γ > 300 nm) and γ-radiation. In photo-oxidation, oxygen uptake is reflected by CO, and OCO functional group formation and the rate of reaction is shown to decrease gradually in the top 150 Å of the exposed surface. By the use of sandwich layers, the extent of oxygen uptake in the front surface is found to be double that at a depth of 20 μm. γ-irradiation shows similar trends to photo-oxidation although the extent of oxidative functionalisation is less.

Matériaux composites à base de graves et de liants polymères II: Ozonisation du polyéthylène et dosage des hydropéroxydes et des péroxydes derivés

The study of the oxidation of low density polyethylene is carried out under fluidized conditions in air and ozone. Special attention is paid to the formation of peroxides and hydroperoxides. Their production is optimized according to various parameters (temperature, time, quantity of ozone, flow of the gaseous current) using an experimental design method. Peroxides and hydroperoxides are titrated by a colorimetric method using diphenylpicrylhydrazyl as reagent. A correlation between i.r. carbonyl ratio and the yield of peroxides has been established.

Mechanism of ketone formation in the thermooxidation and radiolytic oxidation of low density polyethylene

During the initial stage of the thermooxidation of unstabilized LDPE at 95°C the rate of initiation has been found to be first order in hydroperoxide concentration whereas the initiation of radiation-induced oxidation at 25°C was independent of the hydroperoxide concentration. In both cases, the ketone accumulation is much more important than that of hydroperoxide. According to a kinetic analysis of thermooxidation, this result can be attributed to a chain reaction in which secondary peroxy radicals abstract tertiary hydrogen atoms from secondary hydroperoxides to form hydroperoxy alkyl radicals R 1Ċ(OOH)R 2 which decompose by β-scission to give ketones and hydroxyl radicals. The overall result of these reactions is the production of ketones and water in equal amounts and the regeneration of hydroperoxide. Kinetic analysis of the radiation-induced oxidation leads to the conclusion that hydroperoxy radicals HO . 2 also participate in the attack on the tertiary hydrogen of the secondary hydroperoxides.

The kinetics and mechanism of radiation induced oxidation of polyethylene, complicated by the diffusion of oxygen

The mechanism of oxidation of low density polyethylene (LDPE) at room temperature, and the effect of oxygen diffusion on the process, have been studied. Ionizing radiation was used to initiate oxidation. The use of a model of a semi-infinite medium enabled the kinetics of oxidation of PE films to be studied directly from IR spectro-photometric measurements. An equation was obtained, which relates the optical density of the oxidation products to the kinetic and diffusional parameters of the reaction. Analysis of this equation has enabled the kinetically controlled and diffusion controlled regions of oxidation to be distinguished. The oxidation rate constant and its dependence on the rate of initiation were determined. The possibility of degenerate branching of the oxidation reaction chain is examined. It is shown that in the mechanism of oxidation of LDPE irradiated with a dosage of 5 Mrad, no stage of degenerate chain branching occurs.

Study of thermal oxidation of polyolefins. VI. Change of molecular weight distribution in the thermal oxidation of polyethylene and polypropylene

AbstractIn the thermal oxidation of low density polyethylene (PE) in the melt phase and isotactic polypropylene (PP) in the solid phase, the changes in molecular weight distribution (MWD), weight average molecular weights (Mω), and average number of chain scissions have been studied by gel permeation chromatography (GPC).It has been established that in the case of PP degradation, there is an increase in molecular weight during the induction period both at 80 and 760 torr with simultaneous scission of the macromolecules. In contrast, a similar tendency can be observed in the degradation of PE only at very low (20 torr) pressures, i.e., the degree of molecular weight increases proportional to the length of induction period.For both polymers at the temperature of investigations, considerable molecular weight decrease can be detected both at reduced and atmospheric pressures at the onset of measurable oxygen absorption.In the maximum rate oxidation of PE and PP, the increase of temperature, oxygen pressure, and degradation time each causes a shift of the MWD curves towards lower molecular weights.The average number of chain scissions against the amount of absorbed oxygen was also studied. It has been found that the average number of chain scissions per 1 mole absorbed oxygen is considerably higher for PE than for PP.Molecular weight studies performed in the kinetic range of thermal oxidation show that under given conditions, Intermolecular combination reactions and chain scissions may occur simultaneously.

Study of the thermal oxidation of polyolefins. IV. Formation, characterization, and decomposition of polyethylene hydroperoxide

AbstractA study was made on the structure and decomposition rate of polyethylene hydroperoxide obtained by the initiated oxidation of low density polyethylene. It was established that the decomposition is not a simple unimolecular process. The rate was found to be dependent on the amount of carbonyl groups formed during the synthesis.