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Investigation and characterization of dielectric, thermal, and chemical properties of recycled high‐density polyethylene blended with virgin polyethylene
Polymer Engineering & Science
Abstract
Dielectric performance of post‐consumer recycled HDPE blended with virgin HDPE was investigated to evaluate the possibility of using these materials for the insulation of electrical wires and cables. The presence of organic and inorganic impurities was investigated using thermal and chemical methods (TGA, DSC, and EDX). The characterization of impurities revealed different amount of inorganic impurities in recycled material that was depending on the execution of melt filtration by the recycler to prepare the recycled material. Higher values of both dielectric losses and dielectric constant were observed for post‐consumer recycled PE, with the dielectric loss of recycled material almost 17 times higher than the one of virgin PE at power frequency (60 Hz). The short‐term breakdown strength of post‐consumer recycled HDPE was observed to be slightly lower than that of virgin PE. The experimental result showed that blending the recycled stream with virgin materials was effective in order to enhance dielectric properties of recycled material. In this regards, dielectric losses decreased by almost 50% when 50% of virgin HDPE was added to the recycled material. In addition, breakdown strength was improved when virgin HDPE was added.
... In this study, we investigated the possibility of using recycled materials in the electrical cable industry for low-to high-voltage applications as a continuation of our previous study referenced in [10]. The dielectric, thermal, and chemical properties of recycled materials were characterized, along with the effect of impurities on these properties. ...
... The scale parameter of the distributions, which is commonly used as the characteristic breakdown strength for a material, indicates that virgin PE, recycled HDPE, and recycled r(PP-PE) have breakdown strengths of 84, 83, and 93 kV/mm, respectively. These values are lower than those we obtained for virgin and recycled HDPE in our previous research [10]. The difference may stem from differences in environmental conditions and the difference in the increasing voltage rate, which was 2 kV/s compared to the previous 5 kV/s. ...
... This blending approach shows promise in addressing the limitations of recycled materials. In our previous study [10], it was shown that the degree of crystallinity decreased as the proportion of recycled material increased. The same trend was observed for the melting temperature. ...
The extensive use of polyolefins, such as polyethylene (PE) and polypropylene (PP), has led to a substantial accumulation of plastic waste, raising growing concerns about environmental impact and sustainability. In this study, the dielectric, thermal, and chemical properties of recycled materials were investigated, and blending with virgin polyethylene was examined as a sustainable strategy to enhance their electrical performance and promote material reuse. Dielectric analysis demonstrated that blending recycled materials with virgin polyethylene effectively reduced dielectric losses. With the addition of only 15% virgin HDPE, the dielectric loss was significantly lowered by 40% for recycled HDPE (rHDPE) and 30% for the recycled PE-PP blend (r(PE-PP))—compared to their unblended forms. Although the original recycled materials exhibited much higher dielectric losses than virgin HDPE—24 and 28 times greater for rHDPE and r(PE-PP), respectively, at 60 Hz—the blending approach clearly improved their electrical behavior. Overall, the results highlight blending as a practical and sustainable strategy to improve the dielectric performance of recycled polyolefins, enabling their reuse in applications such as electrical cable insulation while contributing to plastic waste reduction.
... Collecting, recycling, and repurposing waste material in other production processes creates a circular economy. [12][13][14][15][16][17][18] There are two general types of waste plastic material. In the process of manufacturing polymeric products, some waste production is possible, generally known as postindustrial waste. ...
... It was reported that while the recycled materials did not meet the properties standards due to the degradation during the recycling process, there was a notable improvement in the properties once the virgin materials were blended with them. Shirzaei Sani et al. 16 used blends of post-consumer recycled and pure HDPE to evaluate their dielectric properties for their possible usage for the insulation of electrical wires and cables. It was stated that recycled HDPE displayed higher values of dielectric losses and dielectric constant, and adding virgin HDPE decreased the dielectric losses. ...
Post‐industrial low‐density and linear low‐density polyethylene blown films are mechanically recycled for reutilizing in the production of blown films for packaging applications. This process enables the production of films with lower cost and similar properties while preserving the environment and lowering the amount of waste material disposed of. The mechanical recycling process results in the production of recycled pellets. This process includes chopping, washing, drying, and reprocessing. Mixtures of these recycled materials and their virgin form with various concentrations are shaped into blown films with inherent 70 and 30 wt% loadings for low‐density polyethylene and linear low‐density polyethylene components, respectively. Fourier transform infrared spectroscopy results of the recycled material show no contamination or chemical reaction with other materials. Gel permeation chromatography is carried out on the virgin and recycled low‐density polyethylene and linear low‐density polyethylene, and the results indicate the occurrence of chain session and crosslinking during the recycling process. The decline in the thermal properties of the samples, seen from the differential scanning calorimetry results, indicates the presence of crosslinks. The effect of structural changes caused by the recycling process on the rheological properties is studied. The miscibility of the blend components is evaluated by Cole–Cole plots and then further proved by Han and Van Gurp–Palman curves. Mechanical properties display an upturn following the presence of the crosslinkes. A decline in the optical properties in the films caused by the refraction of light by the crosslink structure in the film bulk and on the surface is evident.
Highlights
LDPE and LLDPE were recycled according to the circular economy approach
Blown films containing virgin and recycled LDPE and LLDPE were produced
Chain scission and crosslinking as a result of recycling were studied
Rheological, thermal, mechanical, and optical properties were studied
... Calcium originates also from soil and dirt. SEM-EDX showed the particle contamination in recycled PE and the distribution of Ca reached 0.82 % (Shirzaei Sani et al., 2023), leading to a high value of this element up to 21276 ppm. Aluminum contamination in plastic waste stems from foils and cans which were not separated from the polyolefinic plastic waste. ...
... The peak centered at 1376 cm − 1 is attributed to symmetrical bending vibrations of C-H bonds in methyl groups, indicating the presence of PP as a contamination. Additionally, the peak centered at 1462 cm − 1 attributed to CH 2 and CH 3 bending could be ascribed to both PE and PP (Shirzaei Sani et al., 2023;Badini et al., 2023;Karaagac et al., 2021). The FTIR spectra of the PCR grades were normalized to their peak value at 1462 cm − 1 under the assumption that the number of bonds related to contaminants or newly formed bonds due to weathering or degradation was negligible compared to the quantity of unreacted C -H bonds (Mitroka et al., 2013). ...
As the severe environmental impacts of plastic pollution demand determined action, the European Union (EU) has included recycling at the core of its policies. Consequently, evolving jurisdiction now aims to achieve a recycling rate of 65% for non-PET plastic bottles by 2040. However, the widespread use of post-consumer high-density polyethylene (rPE-HD) recyclates in household chemical containers is still limited by PP contamination, poor mechanical properties, and low environmental stress cracking resistance (ESCR). Although previous studies have explored the improvement of regranulate properties through additives, few have examined whether reducing the variety of extrusion blow-moulded PE-HD packaging could offer similar benefits. Therefore, two sorted fractions of rPE-HD hollow bodies were processed into regranulates under industrial conditions, including hot washing, extrusion, and deodorisation. Subsequently, both materials underwent comprehensive characterisation regarding their composition and performance. The opaque material, which was sourced from milk bottles in the UK, exhibited greater homogeneity with minor impurities, leading to improved ductility and melt strain hardening at moderate strain rates compared to the mixed material stream, which contained approximately 2.5% PP contamination. However, both rPE-HD recyclates exhibited similar short-term creep behaviour, relatively low strain hardening moduli, and were almost devoid of inorganic particles. Considering the sum of the investigated properties, melt blending with suitable virgin material is likely one of the most effective options to maximise regranulate utilisation in hollow bodies, followed by recycling-oriented packaging design (e.g., for efficient sorting), and the employment of advanced sorting technology.
To progress towards closed-loop recycling of plastic packages it is vital to understand the origin of contaminants and to develop effective mitigation strategies. High density polyethylene (HDPE) milk bottles were sampled at
nine different locations along the recycling value chain and analysed with two gas chromatography – mass spectroscopy methods to study the presence of volatile organic compounds. The total approximated concentration of volatiles reduced over time from the production of the bottles up to the cross-docking facility for the separately collected lightweight packaging waste (from about 250 to 100 ppm), as alkanes and alkenes evaporate from the bottle. A clear maximum was observed in the number of identified of volatiles and in the total approximated concentration
in milk bottles at the sorted HDPE product. Here contaminants peaked that originate from the milk, from other packaging components (labels, caps, inlays), from other packages and from the surrounding atmosphere.
When only the milk bottles were manually separated out from this sorted product and these were mechanically recycled, flakes were obtained that contain the least amount of volatile compounds, much less than the freshly produced bottles (about 25–50 ppm). The type of volatiles present was, however, markedly different. In
the freshly produced bottles alkanes, alkenes and intentionally added anti-oxidant were found, whereas in the recycled flakes mostly contaminants were found that originated from: the milk, the other packaging components, other packages and the surrounding atmosphere. Seven different contamination pathways were discerned. The gathered knowledge facilitates the future development of food-grade recycled HDPE.
The functional properties of recycled post-consumer flexible polyethylene packaging waste have been studied using materials collected and sorted at a large-scale facility in Sweden. The studied fraction was used both as received and after simple laboratory washing in water with added sodium hydroxide at 40 °C. The materials were melt-compounded with a twin-screw extruder using two different temperature profiles and two screw configurations and injection-molded into slabs, whose thermal and mechanical properties were assessed. The results showed that the mechanical properties of injection-molded samples were not changed significantly either by the washing or by the temperature or screw configuration used in the compounding. Washing reduced the viscosity and molecular mass to a minor extent. As expected, the ash content of the compounded pellets was reduced by washing. The thermo-oxidative stability decreased with increasing compounding temperature and with washing.
Polymeric materials enjoy widespread acceptance among electrical insulation design engineers due to their multi-functional attributes (e.g., excellent dielectric properties, high strength to weight ratio, and ease of molding). However, charge accumulation at the high DC field, poor discharge resistance, low thermal conductivity, limited-service temperature range, and inadequate stiffness have proven to be severe obstructions to far-reaching utilization of these materials. To ensure the reliability of today's electrical power systems, novel dielectric materials with enhanced functionalities are essential. An idea that originated under the name of polymer nanocomposites (PNCs) is supposed to provide a viable solution to the challenges mentioned earlier. PNCs are made by mixing a small quantity of nanometer-sized fillers into a polymer matrix and dispersing them uniformly. To effectively use PNCs in electrical insulation for power apparatus, extensive research into the physical and chemical phenomena associated with these new materials is required. This article aims to provide a comprehensive review of previous research on dielectric PNCs, including synthesis, electrical and nonelectrical characterization, and attendant issues from an electrical insulation standpoint.
Polyethylene constitutes more than one-third of the world's plastic and is one of the main components in municipal waste streams. Unfortunately, varying amounts of polypropylene (PP) are usually found in recycled high-density polyethylene (rHDPE), which erodes their mechanical properties and reduces the quality of these recyclates and their possible reuse in the industry. Differential Scanning Calorimetry (DSC) is the technique commonly used to detect and determine the presence of PP in these blends, but intrinsic limitations of this method lead to inaccurate results. Thus, alternative techniques must be employed to solve these drawbacks and help to estimate more accurately the levels of the PP impurities in rHDPE. In this work, crystallization techniques, such as Temperature Rising Elution Fractionation (TREF) is used to fractionate PE and PP blends into their components to obtain quantitative information. Municipal waste samples of rHDPE contaminated with different amounts of PP have been characterized by DSC and TREF. Comparative results of both techniques show an underestimation of PP values when DSC is used as analytical technique. Results prove that TREF analysis irrespective of the crystallization rate used is valid for the identification and quantification of PP impurities in rHDPE samples, even at low PP percentages in the blend lower than 2 wt %, which could help to control the quality of rHDPE and achieve the priority of reusing and recycling adopted by the European Union for a Circular Economy of Plastics.
The current efforts in moving closer towards a circular plastics economy puts massive pressure on recycled plastics, especially recycled polyethylene (rPE) and recycled polypropylene (rPP) to enter new markets. Their market penetration remained low so far, despite PE and PP constituting the largest share of plastic wastes. However, with the current imperative of more circularity comes a new focus on performance of recyclates. Hence, a detailed understanding of composition and structure–property relationships of post-consumer recyclates has to be developed. Five recycling companies from the Austrian and German markets were asked to supply their purest high-quality rPE and rPP grades. These were characterized by differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), and Fourier-transform infrared (FTIR) spectroscopy, and micro-imaging. Technological characterization included density measurements, determination of the melt flow rate (MFR), and Charpy impact testing. All recyclates contained diverse contaminants and inclusions ranging from legacy fillers like calcium carbonate to polymeric contaminants like polyamides or polyolefin cross-contamination. The overall amount, size, and distribution of contaminants varied significantly among suppliers. Furthermore, first structure–property relationships for polyolefin recyclates that link inorganic content and polymeric purity with density and impact performance could be derived.
The presence of a polyethylene (PE) fraction in recycled polypropylene (PP) will influence the processing as well as mechanical and thermal properties of recycled polypropylene. The objective of this work has been to compare methods used to determine the fraction of PE in recycled PP, establishing calibration curves for each method. Plastics waste will be a mix of different grades – homopolymers and copolymers. It has therefore been tested how specific material grades affect the results. Characterization methods used were differential scanning calorimetry (DSC), FT-IR spectroscopy, NMR, and gel content measurement after peroxide extrusion. We have applied the derived calibration curves for two different post-consumer, recycled PP (rPP) in addition to a known 50/50 blend of PE and PP. DSC, NMR, FT-IR and gel content give quite consistent estimates of the PE content.
This study focuses on the upgrading strategies to make Fil-s (acronym for film-small), a polyolefin-based material coming from the mechanical recycling of post-consumer flexible packaging, fit for re-use in the piping sector. The effects of washing treatments (at cold and hot conditions) and the addition of an experimental compatibilizer on the chemical-physical properties of Fil-s were first assessed. The measurements of some key properties (density, melt flow index, flexural modulus, yield strength), for both Fil-s as such and the different developed Fil-s based systems, was also conducted in order to evaluate the suitability of this complex and challenging waste stream to replace virgin PE-based pipe and fitting products, in compliance to ASTM D3350 standard. The outcomes of the present work contributed to define a code, for each Fil-s system investigated, useful for identifying the level of their performance in piping applications. All the recyclates were extruded as pipes by using a pilot scale plant, but the process resulted more stable and continuous with the compatibilized Fil-s, as it was deducible from its flow properties. Moreover, the best mechanical performances were exhibited by the hot-washed Fil-s pipes, with an increase in pipe stiffness equal to 65% respect to the unwashed sample.
Polymer nanocomposites used in underground cables have been of great interest to researchers over the past 10 years. Their preparation and the dispersion of the nanoparticles through the polymer host matrix are the key factors leading to their enhanced dielectric properties. Their important dielectric properties are breakdown strength, permittivity, conductivity, dielectric loss, space charge accumulation, tracking, and erosion, and partial discharge. An overview of recent advances in polymer nanocomposites based on LDPE, HDPE, XLPE, and PVC is presented, focusing on their preparation and electrical properties.
The mechanical properties of mechanically recycled polyethylene (rPE) were studied in relation to the composition of the feedstock. This composition varied in six steps from only bottle bodies from a single type of high-density polyethylene (HDPE) to the complete composition of an industrially sorted polyethylene (PE) product, including other packaging components, other PE-based packages, sorting faults and residual waste. The rPE with the highest impact resistance was made from the single-grade bottle bodies. The addition of bodies made from other types of PE already reduced the impact resistance with 11%. All the other stepwise additions of packaging components and faultily sorted objects caused the impact resistance to decrease further. Conversely, the elongation at break grew with the stepwise addition of these packaging components and faultily sorted objects. From the used methods, the best analysis method to accurately determine the polymeric composition of the rPE was found to be near-infrared-assisted flake analysis. This method can not only be used to determine the polymeric composition, but due to the strong correlation with the impact resistance, it is also a valuable indicator for the expected mechanical properties of rPE. K E Y W O R D S mechanical properties, mechanical recycling, polyethylene bottles, polymeric composition, post-consumer plastic waste
Polypropylene (PP) and Polyethylene (PE) are widely used commodity plastics in packaging industry such as detergent bottles. To produce plastic detergent bottles, very often extrusion blown molded PE-HD as a body and injection molded PP as a screw cap are used. Separation of individual polymer type is difficult due to the similar density. Unfortunately, the melt blending of recycled post-consumer detergent bottle waste leads to deterioration of mechanical properties. Additionally, the percentage of rPP contamination in recycled PE-HD (rPE-HD) from post-consumer bottle waste can be varied depending on local waste composition and different sorting quality. This work investigates the effect of various contamination scenarios with different percentage of rPP from bottle caps in rPE-HD from bottle waste as well as their compatibilization with olefin block copolymer (OBC) on mechanical, thermal, and rheological properties. Moreover, the low temperature tensile properties of blends with OBC are also investigated in this study. The results showed that the increasing rPP contamination leads to deteriorating elongation at break and tensile impact strength. Furthermore, the addition of OBC as a compatibilizer into worse-case contamination scenario (15 wt% rPP in rPE-HD) significantly improved elongation at break and tensile impact strength. Scanning electron microscopy (SEM) confirms the improvement in adhesion between rPP and rPE-HD from recycled bottle waste with the addition of OBC as a compatibilizer. Rheological measurements reveal the interfacial interaction among rPP, rPE-HD and OBC. The low temperature tensile test demonstrated that the addition of OBC as a compatibilizer improved low temperature tensile elongation at break.
This report traces the leading scientific endeavors to enhance the dielectric strength of polymer dielectrics for energy storage and electrical insulation applications. Remarkable progress has occurred over the past 15 years through nanodielectric engineering involving inorganic nanofillers, coatings, and polymer matrices. This article highlights the challenges of dielectric polymers primarily toward capacitors and cable/wire insulation. It also summarizes several major technical approaches to enhance the dielectric strength of polymers and nanocomposites, including nanoparticle incorporation in polymers, filler‐polymer interface engineering, and film surface coating. More attention is directed to interface contributions, including rational design of core‐shell structures, use of low‐dimensional fillers and thermally conducting fillers, and inorganic surface coating of polymer films. These efforts demonstrated the enhancement in dielectric strength by 40–160% when controlling the fillers below 5 wt% in polyvinylidenedifluoride (PVDF) composites. This article also discussed the possible dielectric mechanisms and the positive role of interfaces against charge transport traps for attaining higher breakdown strength. The investigation of low‐dimensional filler/coating materials of high thermal conductivity can be key scientific subjects for future research.
Series of clay‐containing nanocomposites have been prepared and investigated using frequency‐domain dielectric spectroscopy at different temperatures. Different matrix materials have been used: neat low‐density polyethylene (LDPE) with and without compatibilizer and co‐continuous blends of LDPE with two grades of polystyrene‐b‐poly(ethylene‐co‐butylene)‐b‐polystyrene (SEBS) copolymers. Two major relaxation modes were detected in the dielectric losses of all the nanocomposites and associated with Maxwell–Wagner–Sillars interfacial polarization and dipolar relaxation, respectively. Characteristic relaxation rates, activation energies, dielectric strength, and shape parameters of these relaxation mechanismes were calculated and discussed for the LDPE/clay nanocomposites. The addition of compatibilizer was found to slightly increase the dielectric loss of the nanocomposites while slowing the dynamics due to an improved dispersion. When combined with a high loading of nanofiller (15%), the compatibilizer addition led to low‐frequency dispersion. A new relaxation process was then observed for the nanocomposites with the blend matrix. Several speculations were made as to the origin of this phenomenon, all of which were related to the SEBS phase. POLYM. ENG. SCI., 2020.
Microstructure and electrical breakdown properties of blends and nanocomposites based on low-density polyethylene (LDPE) have been discussed. A series of LDPE nanocomposites containing different amount of organomodified montmorillonite (clay) with and without compatibilizer have been prepared by means of melt compounding. Two sets of blends of LDPE with two grades of Styrene-Ethylene-Butylene-Styrene block copolymers have been prepared to form cocontinuous structure and host the nanoreinforcement. A high degree of dispersion of oriented clay was observed through X-ray diffraction, scanning, and transmission electron microscopy. This was confirmed by the solid-like behavior of storage modulus in low frequencies in rheological measurement results. An alteration in the morphology of blends was witnessed upon addition of clay where the transportation phenomenon to the copolymer phase resulted in a downsizing on the domain size of the constituents of the immiscible blends. The AC breakdown strength of nanocomposites significantly increased when clay was incorporated. The partially exfoliated and intercalated clay platelets are believed to distribute the electric stress and prolong the breakdown time by creating a tortuous path for charge carriers. However, the incorporation of clay has been shown to diminish the DC breakdown strength of nanocomposites, mostly due to the thermal instability brought by clay.
This paper proposes two methods of preparation of graphene/PEEK powders for Laser Sintering (LS) and investigates their behaviour in relation to their microstructure and their properties. Thin composite films were fabricated in an attempt to replicate the thin layer formation of the powder bed process. Both methods of composite powder preparation (wet and dry) led to enhanced mechanical performance of the composite films at 0.1 and 0.5 wt% graphene nano-platelets (GNP) concentrations. The TEM images show that the GNP act as a nucleation point in crystallisation of PEEK, being at the centre of the spherulites. The hot stage microscopy reveals a 20 s delay in the onset of GNP/PEEK nanocomposite coalescence in comparison with plain PEEK. This is a very important observation for laser sintering, as it will influence the build strategy and specific parameters (e.g. time between layers deposition, multiple exposures). The excellent electrical conductivity properties of graphene were noticeable in the nanocomposite films at concentrations above 1 wt% GNP.
Plastics have outgrown most man-made materials and have long been under environmental scrutiny. However, robust global information, particularly about their end-of-life fate, is lacking. By identifying and synthesizing dispersed data on production, use, and end-of-life management of polymer resins, synthetic fibers, and additives, we present the first global analysis of all mass-produced plastics ever manufactured. We estimate that 8300 million metric tons (Mt) as of virgin plastics have been produced to date. As of 2015, approximately 6300 Mt of plastic waste had been generated, around 9% of which had been recycled, 12% was incinerated, and 79% was accumulated in landfills or the natural environment. If current production and waste management trends continue, roughly 12,000 Mt of plastic waste will be in landfills or in the natural environment by 2050.
This paper studies the recyclability of construction and household plastic waste collected from local landfills. Samples were processed from mixed plastic waste by injection moulding. In addition, blends of pure plastics, polypropylene and polyethylene were processed as a reference set. Reference samples with known plastic ratio were used as the calibration set for quantitative analysis of plastic fractions in recycled blends. The samples were tested for the tensile properties; scanning electron microscope–energy-dispersive X-ray spectroscopy was used for elemental analysis of the blend surfaces and Fourier transform infrared (FTIR) analysis was used for the quantification of plastics contents.
In recent years, researchers have extensively investigated polymers filled with inorganic nanoparticles because these materials present improved physical properties relative to those of conventional unfilled polymers. Oxides, silica in particular, are the most commonly used inorganic particles because they possess good properties and can be fabricated at a low cost. However, oxides are hydrophilic in nature, and this leads to the presence of water at the interface between the nanoparticles and the polymer matrix. Due to the predominance of particle-matrix interfaces in nanocomposites, the presence of water at the interlayer region can be problematic. Moreover, the hydrophobic nature of most polymers, particularly for polyolefins such as polyethylene, may make it difficult to remove this interfacial water. In this paper, as-received and moistened samples of agglomerated nanosilica/polyethylene were dried using an isothermal treatment at 60℃, and the efficacy of this treatment was studied using dielectric spectroscopy. The Maxwell-Wagner-Sillars relaxation peaks were observed to shift to lower frequencies by three decades, and this was linked to a modification of the water content, due to drying, at the interfaces between silica and polyethylene and at the interfaces within the nanosilica agglomerates. The evolution of the extracted retardation time is explained by the nanosilica hydrophily and the free volume introduced by the nanoparticles.
Polyethylene/nanoclay specimens containing from 0 to 5% nanoclays were prepared from a commercially available premixed PE/nanoclay masterbatch containing 50% wt of nanoclay. The masterbatch was diluted to the desired concentration by adding PE along with various amounts of compatibilizer in order to achieve the best possible dispersion of the nanoclay platelets. The dielectric response of the compounded samples was investigated using a combination of time and frequency-domain spectroscopy in order to cover a wide frequency window. Both techniques were in good agreement when the time-domain data was transformed into frequency-domain data. Despite their low concentration, the addition of the dispersed nanoclays led to a significant alteration of the material dielectric response in the form of the appearance of various interfacial relaxation processes and an increase of charge carrier transport within the insulation material. Moreover, an onset of nonlinear charge transport process was observed at moderate fields for specimens containing a relatively low level of nanoclays. The high-field breakdown strength was shown to have been improved by the incorporation of the nanoparticles, particularly when the exfoliation was enhanced by the use of a maleic anhydride grafted polyethylene compatibilizer.
The incorporation of silica nanoparticles into polyethylene increased the breakdown strength and voltage endurance significantly compared to the incorporation of micron scale fillers. In addition, dielectric spectroscopy showed a decrease in dielectric permittivity for the nanocomposite over the base polymer, and changes in the space charge distribution and dynamics have been documented. The most significant difference between micron scale and nanoscale fillers is the tremendous increase in interfacial area in nanocomposites. Because the interfacial region (interaction zone) is likely to be pivotal in controlling properties, the bonding between the silica and polyethylene was characterized using Fourier transformed infrared (FTTR) spectroscopy, electron paramagnetic resonance (EPR), and x-ray photoelectron spectroscopy (XPS). The picture which is emerging suggests that the enhanced interfacial zone, in addition to particle-polymer bonding, plays a very important role in determining the dielectric behavior of nanocomposites.
In this work, high density polyethylene (HDPE) incorporation in virgin resin was assessed as to its electrical performance with the use of volumetric resistivity, dielectric strength, and stress tracking measurements. HDPE post-consumer packaging was collected and submitted to a basic process of plastic recovering: washing, grinding, and drying. Formulations containing 0, 25, 50, 75, and 100% of recycled material in the virgin resin were reprocessed by extrusion and injection molding with stabilization. Dielectric strength test results were analyzed by the statistical distribution of Weibull, and the maximum likelihood method. The degree of crystallinity was measured by X-ray diffraction. Atomic absorption spectroscopy was also done to identify metallic residue present in the samples. From the results analyzed, it can be concluded that the HDPE derived from post-consumer packaging can be considered in electrical insulation systems for low voltage (up to 600 V) containing as much as 75% incorporated virgin resin.
To develop new environmentally friendly and recyclable high‐voltage cable insulation materials, the effects of the particle size of zinc oxide (ZnO) on the mechanical and electrical properties of nanocomposites were investigated based on a feasibility study of polypropylene (PP) as a high‐performance cable insulation material. The small particle size of ZnO can synergistically toughen PP with a polyolefin elastomer (POE), but the large particle size of ZnO leads to lower elongation at break. Adding ZnO nanoparticles can improve the bulk resistivity of the composites and suppress space charge injection. 0.5ZnO200 has the highest direct current and alternating current breakdown field strengths, 36.6% and 14.7% higher than PP/POE, respectively. This improvement may be due to the ability of 200 nm ZnO to introduce more deep traps. However, as the nanoparticle content rises and the particle size decreases, the agglomeration becomes more frequent, leading to the overlap of inter‐nano interfaces and reducing the modification effect of the nanoparticles. This study on the effect law of nano‐ZnO with different particle sizes on the microstructure, mechanical properties, and electrical properties of PP can provide a reference for developing new recyclable high‐voltage insulated cable materials.
Polypropylene (PP), a thermoplastic material that can be recycled by melting, is viewed as a potential alternative to cross‐linked polyethylene for insulation. In this work, PP‐based composites were fabricated with surface‐modified silicon dioxide (SiO2), organized montmorillonite (OMMT), and polyolefin elastomer (POE) as fillers via a two‐step melt blending method. The dispersion states of SiO2 nanoparticles, OMMT, and POE in PP and their effects on PP crystallization were investigated. Moreover, the elongation at break, yield stress, energy storage modulus, damping loss factor, broadband dielectric spectrum, bulk resistivity, and alternating current (AC) breakdown strength of the specimens were tested. POE significantly increased the composite toughness, whereas the AC breakdown field strength and volume resistivity of POE/PP were lower. The homogeneously dispersed SiO2 and OMMT in the matrix acted as heterogeneous nucleation sites and reduced the grain size. To varying degrees, they effectively improved the dielectric properties, volume resistivity, and breakdown field strength of the composites. Hence, the composites simultaneously had excellent mechanical and dielectric properties. The volume resistivity of SiO2‐OMMT‐POE/PP with higher crystallinity was 15.4 times higher than that of POE/PP, and the breakdown field strength increased by 16.4%.
In our second installment of the infrared (IR) spectra of polymers, we finish the discussion of the spectrum of polyethylene (PE) started last time. We explore how different PE syntheses produce materials with different physical and spectroscopic properties, which introduces us to the concept of crystalline splitting and the rest of the story on CH2 rocking peaks.
Polymeric material draws a great attraction in the development of insulation for High Votage Direct Current (HVDC) applications. Insulation material is the deciding key factor to increase the operating voltage and to transmit the bulk power with minimized power loss. Premature breakdown, high withstanding temperature, and impacts of space charge accumulation are all issues faced by the insulation material. Material qualities such as dielectric, electrical, structural, and mechanical properties are directly affected by the issues. Therefore, this paper provides an overview of the dielectric properties of polymeric materials and their composites under various stress conditions. The stress includes AC, DC, superimpose and combined (AC and DC) stress under which the dielectric constant, dielectric losses, electrical strength, and space charge distribution of polymeric insulating materials such as low‐density polyethylene, high‐density polyethylene, cross‐linked polyethylene, polypropylene, and random copolymer (RCP), as well as their composites, are explored. Polypropylene and RCP outperform all other polymers in terms of breakdown strength and space charge suppression under various stress conditions. RCP is a developing material that also has the potential to be an effective thermoplastic insulation material in the future. Classification of polymeric insulation.
Plastic packaging typically consists of a mixture of polymers and contains a whole range of components, such as paper, organic residue, halogens and metals, which pose problems during recycling. Nevertheless, until today, limited detailed data is available on the full polymer composition of plastic packaging waste taking into account the separable packaging parts present in a certain waste stream, nor on their quantitative levels of (elemental) impurities. This paper therefore presents an unprecedented in-depth analysis of the polymer and elemental composition, including C, H, N, S, O, metals and halogens, of commonly generated plastic packaging waste streams in European sorting facilities. Various analytical techniques are applied, comprising of FTIR, DSC, polarized optical microscopy, ion chromatography, and ICP-OES, on more than 100 different plastic packaging products, which are all separated into their different packaging subcomponents (e.g., a bottle into the bottle itself, the cap, and the label). Our results show that certain waste streams consist of mixtures of up to 9 different polymers, and contain various elements of the periodic table, in particular metals such as Ca, Al, Na, Zn and Fe and halogens like Cl and F, occurring in concentrations between 1 and 3000 ppm. As discussed in the paper, both polymer and elemental impurities impede in many cases closed-loop recycling and require advanced pre-treatment steps, increasing the overall recycling cost.
The purpose of this paper is to provide a full characterization of post-consumer plastic film recovered from mixed municipal solid waste (MSW) treatment plants in Spain. Currently, this type of plastic waste is not recycled due to technical or economic barriers and is still sent to landfill. Different types of municipal plastic waste (MPW) from manual and automated sorting were studied: i) colour plastic film recovered by ballistic separators and then manual sorting in different seasons; ii) colour plastic film recovered by automated sorting (air suction); and iii) white plastic film from primary manual sorting process. The samples were characterized by different techniques, including the ultimate and proximate analysis, Higher Heating Value (HHV) and Lower Heating Value (LHV), metal content, Thermogravimetric Analysis (TGA) and Derivative Thermogravimetry (DTG), Fourier Transform Infrared (FT-IR) analysis and Differential Scanning Calorimetry (DSC). The results were compared to those obtained for pretreated colour and white plastic film waste and contrasted with industrial recycled film granules of polyethylene (as a reference material for packaging film). Additionally, pretreated plastic film samples were also characterized by analyzing viscosity, Pressure-Volume-Temperature (PVT) diagram, specific heat capacity and halogen and sulphur contents. Characterization data from this study will contribute to identify and develop potential recycling alternatives for a more sustainable municipal plastic waste management, which is recognized as a priority in the European Circular Economy Action Plan to use resources in a more sustainable way.
Thermoplastic elastomer nanocomposites based on respectively polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) and polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene grafted maleic anhydride (SEBS-MA) block copolymers and containing functionalized zinc oxide (ZnO) nanoparticles have been investigated as candidate materials for high voltage (HV) insulation systems. The dispersion of the organically modified ZnO nanoparticles has been successfully tuned through the MA graft and the block copolymer nanostructure. In particular, nanocomposites with signs of rheological percolation, indicating the formation of a network between individually dispersed nanoparticles and polymer chains, have been obtained at ZnO content as low as 5 wt% (0.9 vol%). This behavior resulted in an enhancement of the thermal conductivity and better control of the electrical conductivity while maintaining breakdown strength and dielectric losses in the same range of the unfilled insulating matrices. Furthermore, the resistance to surface erosion by partial discharges was significantly improved: in the presence of 5 wt% of individually dispersed ZnO nanoparticles, the eroded volume was reduced 10 times.
The effects of using a packed column as a fractionating system on thermal degradation of commonly-used polymers have been studied. The polymers investigated were virgin polyethylene (LDPE and HDPE), polypropylene (PP), and polystyrene (PS), as well as two post-consumer polymer mixtures, namely municipal plastic waste (MPW) and scrap tire. The experiments were carried out under atmospheric pressure in a 6 L semi-batch stainless steel vessel equipped with the fractionating system. The system led to total elimination of wax formation, color improvement, and reduction in the density of the resultant pyrolysis oils. The oils were analyzed according to ASTM D86, the standard test method for boiling range distribution of petroleum fractions. The obtained values were compared to the Iran standard limits established for diesel (ISIRI4903) and gasoline (ISIRI4904). Furthermore, Fourier transform infrared spectroscopy (FT-IR) was utilized to determine the chemical composition of the oils. Finally, the spectra of the generated tire and MPW-derived oils were compared with the spectra of conventional fuels, gasoline and diesel.
High density polyethylene (rHDPE) is extruded 1 to 8 times, with and without detergent, to simulate the effects of impurities on the material and on the artificial ageing process. The mechanical properties, thermal stability, rheology, Fourier transform infrared spectroscopy (FTIR), and volatile organic compound (VOC) emissions are measured. According to the results, ageing of rHDPE increases tensile strength, reduces elongation, and enhances side chain branching of the material and thus causes rheological changes. The addition of detergent reduces changes in mechanical properties and rheological behavior but accelerates thermal degradation. VOC and FTIR measurements of the samples with detergent addition show generation of harmful 1,4-dioxane. The amount of total emission, as well as emissions of important perfumes limonene and 1R-α-pinene, decreases during multiple extrusion cycles. Heating of the plastics is found to be a major factor in the VOC emission reduction. Impurities have a notable effect on the artificial ageing results.
Plastic debris in the marine environment is widely documented, but the quantity of plastic entering the ocean from waste generated on land is unknown. By linking worldwide data on solid waste, population density, and economic status, we estimated the mass of land-based plastic waste entering the ocean. We calculate that 275 million metric tons (MT) of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million MT entering the ocean. Population size and the quality of waste management systems largely determine which countries contribute the greatest mass of uncaptured waste available to become plastic marine debris. Without waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025.
Copyright © 2015, American Association for the Advancement of Science.
Treeing in low density polyethylene (LDPE) filled with alumina nanocomposite as well as unfilled LDPE samples stressed with 50 Hz ac voltage has been studied. The tree inception voltage was monitored for various samples with different nano-filler loadings and it is seen that there is an increase in tree inception voltage with filler loading in LDPE. Treeing pattern and tree growth duration for unfilled and nano-filled LDPE samples have also been studied. Different tree growth patterns as well as a slower tree growth with increase in filler loading in LDPE nanocomposites were observed. The observed slow propagation of tree growth with filler loading is attributed to the changes in the polymer crystalline morphology induced by the presence of nano-particles and the greater ability of the nanoparticles to resist discharge growth. SEM studies carried out to determine the morphology of unfilled and nano-filled LDPE showed an increase in lamellae packing in LDPE nanocomposites and this increased lamellar density leads to a reduction in the tree propagation rate. Partial discharge activities were also monitored during the electrical tree growth in both the unfilled and the nano-filled LDPE samples and were found to be significantly different. PD magnitude and the number of PD pulses per cycle were found to be lower with electrical tree growth duration in LDPE nanocomposites as compared to unfilled LDPE. The same trend was seen with increased filler loading also.
The characteristics of polypropylene/polyethylene (PP/PE) binary blends at the microscopic level have been widely studied by different researchers over the years. This communication discusses the empirical results obtained from a series of DSC and TGA tests on the selected thermal properties of PP/PE blends. Using DSC in our investigation is aimed at revealing the effects of different blending ratios of PP and PE on the melting and crystallinity behaviour of the blend systems, while the application of TGA is to study the degradation characteristics of the blends in terms of their induction time. An empirical equation is proposed and has been proved to offer a convenient means for the estimation of the overall crystallinity percent of a PP/PE system. It largely requires the knowledge of blend ratios and the densities of the pure components, and eliminates the tedious graphical integration process on determining areas under curves of thermograms. The TGA study shows that the effect of temperature on induction time of PP/PE blends follows the trend of the Arrhenius equation.
This work evaluated the incorporation of recycled high-density polyethylene (HPDE) in the virgin polymer by measuring its dielectric strength. Post-consumer containers of HDPE were collected and passed through the basic processes of plastics recovery: washing, grinding, and drying. Formulations were elaborated containing 0, 25, 50, 75, and 100% of recycled material incorporated to the virgin resin by extrusion and injection processes, stabilized with 0.2% Irganox B215. Samples of these materials were submitted to dielectric breakdown analysis by using an electrode-type sphere—plane and ramp of positive electric tension. The data were treated and analyzed by using the statistical distribution of Weibull, and the Maximum Likelihood method. The degree of crystallinity was measured by X-ray diffraction. Atomic absorption spectrophotometry was employed to identify metallic residues present in the samples. The results showed that there is a 17% decrease in the values of the dielectric strength when we compare the virgin HDPE with the 100% recycled. Therefore, formulations containing up to 50% of recycled material may be taken into consideration in the development of products in electric insulating systems.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:1730–1735, 2004
Epoxy composite is expected to become the substrate insulation of gate bipolar transistors (IGBTs) that can replace ceramics if it has high thermal conductivity. Fillers with high thermal conductivity were added to the epoxy resin, while this composite often suffers from lowering in breakdown (BD) strength. In order to reveal the above phenomena and to clarify the breakdown (BD) mechanism, we carried out experiments using several electrode structures, i.e. an MB-PWB (metal-base printed wiring board) insulation simulated structure, a rod-to-plane electrode for PD erosion resistance, and a sphere-to-sphere electrode for BD strength. As a result, it was clarified that the IGBT insulation breaks down after successive partial discharges (PDs), and the BD strength of microcomposite decreases with increasing the content of micro-fillers, while PD resistance of microcomposite is improved with increasing the content of micro-fillers. A trial was made to raise the once-lowered BD strength by adding nano-Al2O3 fillers. Above experiments were carried out for nanocomposites and nano-micro-composites. It was clarified that the nano-fillers can improve the PD resistance of composites obviously, while nano-fillers improve the BD strength of composite slightly. Such a phenomenon was found that the BD strength of composites was increased with the dispersion state of nano-fillers.
This review presents a wide-ranging broad-brush picture of dielectric relaxation in solids, making use of the existence of a `universality' of dielectric response regardless of a wide diversity of materials and structures, with dipolar as well as charge-carrier polarization. The review of the experimental evidence includes extreme examples of highly conducting materials showing strongly dispersive behaviour, low-loss materials with a `flat', frequency-independent susceptibility, dipolar loss peaks etc. The surprising conclusion is that despite the evident complexity of the relaxation processes certain very simple relations prevail and this leads to a better insight into the nature of these processes.
The ubiquitous and little-understood phenomenon of low-frequency dispersion (LFD) is described and the experimental evidence for it is summarized for a variety of dielectric and semiconducting systems. Both frequency- and time-domain behaviour are reviewed and it is pointed out that very high charge densities are being stored at low frequencies. The connection between LFD and electrochemical reactions is emphasized. The physical conditions under which LFD can be seen are discussed with particular emphasis on the distinction between interfacial and volume processes. Earlier interpretations of LFD-like phenomena in terms of Maxwell-Wagner processes and fractal geometry of contacts are briefly discussed and found to be insufficient to account for the observed facts. It is concluded that there is likely to be more than one physical or physico-chemical cause giving rise to the variety of LFD phenomena observed in nature but their common feature must be a frequency independent ratio of loss to polarization. We define an energy criterion which gives a physical basis for the interpretation of power-law responses and on this basis we propose a new electrochemical model of very general applicability giving the correct dynamic response and having the advantage of not requiring enormous electric fields to account for the very high charge storage observed. Further critical experimental studies are required to elucidate the remaining questions.
Three areas of considerable progress are identified in the area of polymeric insulation since the mid 1990s (i.e. since the inception of the Eric O. Forster Memorial Lectures): the understanding of ageing, the measurement of space charge, and the development of nanodielectrics. The paper proposes a typology to distinguish and define electrical ageing, degradation and breakdown. With reference to the principal theories of therm o-ageing, it is concluded that there is little direct evidence for ageing even though it is likely to exist, at least above a critical field. The capability to measure space charge has improved considerably and this shows considerable potential as a diagnostic tool. Space charge behaviour is extremely difficult to analyse and general predictions may be impossible in practice. It is, however, necessary to control space charge accumulation in HVDC systems. Nanodielectrics continue to offer promise and understanding is improving in this area, particularly in the development of models of interaction zones around nanoparticles.
This article discusses the theoretically deduced mechanisms for the magnitude and the trends of conduction and polarization in electrical insulation (dielectrics) with molecular and physical structure, frequency, and temperature. The discussion intends to explain the atomic, electronic, molecular, and ionic basis for these electrical properties, so that the reader can better understand why dielectrics behave the way they do. Application of these principles should also guide the reader to make estimates or rough predictions of conductivity and dielectric constant levels, and their variations, from an examination of the molecular/atomic composition of a material. Most of the discussion is more directly applicable to the condensed phases, solids and liquids. Gases, in principle, behave the same, but they have important differences because of their very much lower density and lack of restraint to molecular rotation and translation. An overriding factor in the magnitude of conduction and polarization is the number density of the participating species: electrons, ions, or dipolar molecules
The dielectric constant of polyethylene under shock compression
- E G Hauver
Hauver EG. The dielectric constant of polyethylene under
shock compression; 1970.
2021 IEEE Conference on Electrical Insulation and Dielectric Phenomena
- Shirzaei Sani
- David E Demarquette
Shirzaei Sani I, David E, Demarquette NR. 2021 IEEE Conference on Electrical Insulation and Dielectric Phenomena, 49.
2021.