High-density Polyethylene Research Articles

Assessment of Performance and Deactivation Resistance of Catalysts in the Pyrolysis of Polyethylene and Post‐Consumer Polyolefin Waste

AbstractIn the present work, the catalyst performances of USY and REY zeolites and MgO, ZnO, and MgxAlOy oxides are investigated in the pyrolysis of virgin high‐density polyethylene (HDPE) and of post‐consumer polyolefin waste. The influence of operation parameters and catalyst deactivation resistance over four reaction cycles are evaluated. The results indicate that basic oxides do not show relevant cracking activity, so that the only identified effect for these catalysts is the production of liquid products with higher contents of paraffins when compared to thermal pyrolysis. Among the evaluated oxides, MgxAlOy is the most active and resistant to deactivation. The zeolites promote cracking and secondary reactions of isomerization, cyclization, and aromatization. Particularly, USY promotes the production of higher‐quality oils and shows higher deactivation resistance, when compared to REY. Additionally, a significant loss of catalyst activity is identified in reactions conducted with post‐consumer polyolefin wastes. However, increase in rates of coke formation and the presence of contaminants (such as halogens and metals) are not detected in the catalysts after the reactions.

High-Density Polyethylene Custom Focusing Lenses for High-Resolution Transient Terahertz Biomedical Imaging Sensors.

Transient terahertz time-domain spectroscopy (THz-TDS) imaging has emerged as a novel non-ionizing and noninvasive biomedical imaging modality, designed for the detection and characterization of a variety of tissue malignancies due to their high signal-to-noise ratio and submillimeter resolution. We report our design of a pair of aspheric focusing lenses using a commercially available lens-design software that resulted in about 200 × 200-μm2 focal spot size corresponding to the 1-THz frequency. The lenses are made of high-density polyethylene (HDPE) obtained using a lathe fabrication and are integrated into a THz-TDS system that includes low-temperature GaAs photoconductive antennae as both a THz emitter and detector. The system is used to generate high-resolution, two-dimensional (2D) images of formalin-fixed, paraffin-embedded murine pancreas tissue blocks. The performance of these focusing lenses is compared to the older system based on a pair of short-focal-length, hemispherical polytetrafluoroethylene (TeflonTM) lenses and is characterized using THz-domain measurements, resulting in 2D maps of the tissue refractive index and absorption coefficient as imaging markers. For a quantitative evaluation of the lens effect on the image resolution, we formulated a lateral resolution parameter, R2080, defined as the distance required for a 20-80% transition of the imaging marker from the bare paraffin region to the tissue region in the same image frame. The R2080 parameter clearly demonstrates the advantage of the HDPE lenses over TeflonTM lenses. The lens-design approach presented here can be successfully implemented in other THz-TDS setups with known THz emitter and detector specifications.

Comparison of Antioxidants to Increase the Oxidation Stability of Pyrolysis Oils of Three Plastics Using Iodine Value

Pyrolysis is an excellent method for recovering mixed and contaminated plastics that are no longer recyclable. Special attention must be paid to the stability of the fuel to avoid the formation of undesirable products. This can be achieved by additives such as antioxidants. In this study, high-density polyethylene, polypropylene, and polystyrene plastic waste are slowly pyrolyzed to a maximum of 470 degrees Celsius. A gasoline fraction (0–190 °C) and a diesel fraction (190–320 °C) are then obtained from these. Three antioxidants are added to these fractions: pyrocatechol, phenol, and freshly produced algal pyrolysis oil; the latter is described in the literature as containing particularly high levels of antioxidants. The oxidation stability of these mixtures and the change in the iodine number over time are measured using a newer method than the commonly used method of Wijs. Phenol improves the oxidation stability best, followed successively by algae pyrolysis oil and pyrocatechol. The oxidation stability of the gasoline fraction of the polypropylene pyrolysis oil with phenol is 49% higher than that of the same fraction without antioxidants.

The Effect of Processing Conditions on the Microstructure of Homopolymer High-Density Polyethylene Blends: A Multivariate Approach.

In this work, a multivariate approach was utilized for gaining some insights into the processing-structure-properties relationships in polyethylene-based blends. In particular, two high-density polyethylenes (HDPEs) with different molecular weights were melt-compounded using a twin-screw extruder, and the effects of the screw speed, processing temperature and composition on the microstructure of the blends were evaluated based on a Design of Experiment-multilinear regression (DoE-MLR) approach. The results of the thermal characterization, interpreted trough the MLR (multilinear regression) response surfaces, demonstrated that the composition of the blends and the screw rotation speed are the two most important parameters in determining the crystallinity of the materials. Furthermore, the rheological data were examined using a Principal Component Analysis (PCA) multivariate approach, highlighting also in this case the most prominent effect of the weight ratio of the two base polymers and the screw rotation speed.

Optimisation of Process Parameters to Maximise the Oil Yield from Pyrolysis of Mixed Waste Plastics

The study sought to optimise process parameters of thermal pyrolysis of mixed waste plastic (MWP) to maximise pyrolytic oil yield. High-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS) were used as feedstocks for pyrolysis. Response surface methodology (RSM) and Box–Behnken design (BBD) were used to optimise the pyrolysis process. The optimisation was carried out by varying three independent variables, namely, reaction temperature (460–540 °C), residence time (30–150 min), and size of MWP feedstock (5–45 mm), to increase the liquid oil yield. A BBD matrix was used to generate the design of the experiments, and 15 experiments were conducted. The highest liquid oil yield of 75.14 wt% was obtained by optimising the operating parameters, which were a reaction temperature of 535.96 °C, a reaction time of 150 min, and a feedstock particle size of 23.99 mm. A model was developed to determine the relationships among the independent variables, and analysis of variance (ANOVA) was used to investigate their impact on maximising oil yield. ANOVA results showed that the temperature and residence time had the maximum impact on oil yield, followed by feedstock size. Physicochemical analysis of the properties of the plastic pyrolytic oil (PPO) revealed that the crude PPO obtained from the MWP had higher water (0.125 wt%) and sulfur content (5.12 mg/kg) and lower flash point (<20 °C) and cetane index (32), which makes it unsuitable for use as an automobile fuel. However, these issues can be resolved by upgrading the PPO using different posttreatment techniques, such as distillation and hydrotreatment.

Temperature and salt concentration behavior of a compact rectangular salinity gradient solar pond

Design of economical and effective solar ponds which are useful thermal energy storage devices, remains a huge challenge. The present work aims at investigating the thermal performance of low cost mini salt gradient solar pond. The portable pond was fabricated as a rectangular configuration having a volume of 0.5m3. Polystyrene and high density polyethylene sheets were employed for insulating the walls. The top of the pond was covered with a slender glass so that the dust accumulation could be prevented without affecting the absorption of solar radiation. Sodium chloride salt was used as the medium and the three salt gradient regions namely lower convective, non-convective, and upper convective regions were established through injection filling technique. The temperature and salt gradient data were observed experimentally for a period of 20 days at Coimbatore, India. The pond could absorb significant amount of available radiation (around 65%) and the maximum temperature of the pond was observed to be 49oC. Frequent washing of the water surface is necessary to maintain stable salt gradient. Nevertheless, portable pond fabricated with low cost materials exhibited good potential of storing solar energy for solar thermal applications.

Uranium accumulation in environmentally relevant microplastics and agricultural soil at acidic and circumneutral pH

The co-occurrence of microplastics (MPs) with potentially toxic metals in the environment stresses the need to address their physicochemical interactions and the potential ecological and human health implications. Here, we investigated the reaction of aqueous U with agricultural soil and high-density polyethylene (HDPE) through the integration of batch experiments, microscopy, and spectroscopy. The aqueous initial concentration of U (100 μM) decreased between 98.6 and 99.2 % at pH 5 and between 86.2 and 98.9 % at pH 7.5 following the first half hour of reaction with 10 g of soil. In similar experimental conditions but with added HDPE, aqueous U decreased between 98.6 and 99.7 % at pH 5 and between 76.1 and 95.2 % at pH 7.5, suggesting that HDPE modified the accumulation of U in soil as a function of pH. Uranium-bearing precipitates on the cracked surface of HDPE were identified by SEM/EDS after two weeks of agitation in water at both pH 5 and 7.5. Accumulation of U on the near-surface region of reacted HDPE was confirmed by XPS. Our findings suggest that the precipitation of U was facilitated by the weathering of the surface of HDPE. These results provide insights about surface-mediated reactions of aqueous metals with MPs, contributing relevant information about the mobility of metals and MPs at co-contaminated agricultural sites.

Effect of geomembrane liner on landfill stability under long-term loading: interfacial shear test and numerical simulation.

Clay liners have been widely used in landfill engineering. However, large-scale clay excavation causes secondary environmental damage. This study investigates the feasibility of replacing clay liners with high-density polyethylene (HDPE) geomembranes with different specifications and parameters. Laboratory interface shear tests between municipal solid waste (MSW) samples of different ages and geomembranes were conducted to study the influence of landfill age on interface shear strength. Finite element method was adopted to compare the long-term stability of landfills with HDPE geomembrane versus clay as intermediate liner. The interfacial shear test results show that the cohesion of MSW increases in a short term and then decreases with landfill age. The internal friction angle exhibits an increasing trend with advancing age, however, the rate of its increment declines withage.The rough accuracy of the film surface can increase the interfacial shear strength between MSW. The simulation results show that, unlike clay-lined landfills, the sliding surface of geomembrane-lined landfills is discontinuous at the lining interface, which can delay the penetration of slip surfaces and block the formation of slip zone in the landfill. In addition, the maximum displacement of landfills with geomembrane is 10% lower than that with clay, and the absolute displacement of slope toe decreases with the increase of roughness at the interface of geomembrane. Compared with clay-lined landfills, the overall stability safety factor increased by 18.5-30%. This study provides references for landfill design and on-site stability evaluation, contributing to enhanced long-term stability.

Detection of plastic, cellulosic micro-fragments and microfibers in Laternula elliptica from King George Island (Maritime Antarctica)

It is generally acknowledged that microplastic pollutants are prevalent in ocean waters and sediments across a range of tropical, temperate, subpolar, and polar regions. The waters surrounding King George Island are significantly impacted by human activities, particularly those related to scientific stations, fishing, and tourism. Organisms, such as Laternula elliptica, can be used as environmental monitors due to the likelihood that they will bioaccumulate pollutants. The goal of this study was to quantify and identify plastic and cellulosic micro-fragments and microfibers present in the soft body of clams (n = 21), collected from Fildes Bay near sewage and wastewater discharges. Plastic and cellulose microfragments and microfibers were counted, and their compositions were determined using FT-IR. All 21 individuals sampled contained fragments and fibers, with a total of 900 items detected (42.86 ± 25.36 mean ± SD items per individual), or 1.82 items g.wet mass−1. 58 % of items were cellulose and 22 % plastic. Considering the plastic polymer compositions, 28.57 % were polyethylene terephthalate (PET), 21.43 % acrylic, 14.29 % high-density polyethylene (HDPE), 14.29 % Polypropylene (PP), 7.14 % ultra-high drawn polyethylene filament (UHMWPE), 7.14 % polyester and 7.14 % Polyethylene. The quantities and prevalence of MP in L. elliptica were higher than those found in other Antarctic marine species, and even in bivalves from populated regions of the world. Our work assessed the pollution status of L. elliptica near an effluent of wastewater plants and found that 95 % of individuals displayed MP and 100 % microfibers that could impact their population.

Effect of reaction media on hydrogenolysis of polyethylene plastic waste: Polymer-surface interactions in small alkane/polymer blends

The polymer reaction media and its properties can be altered by recycling a fraction of liquid products or adding alkane solvents. Less clear is whether this strategy affects hydrogenolysis. Herein, we investigated the effect of short-chain alkanes Cn consisting of n carbons (n=8, 16, and 32) on the upcycling of high-density polyethylene (HDPE) plastic waste to lubricant-range products over Ru/TiO2 catalysts by multiscale simulations and experiments. First, we trained a force field for polymer/surface interactions on a Ru22 nanoparticle (NP) supported on TiO2. Using replica exchange molecular dynamics simulations, we studied the effect of small hydrocarbons on the adsorption of a surrogate polymer, C142, on the catalyst. We found segregation of long chains (C142) at the catalyst surface due to the enthalpy gained by adsorbing more C-C bonds of the long chains, compensating for entropic losses upon adsorption. Short-chain molecules decrease the adsorbed carbons of long chains on the Ru NP due to blocking Ru active sites. Compared to the bulk chains, competitive adsorption results in a broader, heavy-tailed distribution of end-to-end distance of adsorbed chains. Our experiments demonstrated that catalyst activity declines significantly beyond simple dilution due to changes in polymer adsorption, and tuning the reaction media by creating suitable blends impacts hydrogenolysis. Density distributions for a 50:50%wt mixture of PP and PE show that PE chains are segregated at the surface, so they are prone to C-C bond breaking much faster than PP chains. H/D exchange experiments show preferential deuteration of PE, while CH3 groups of PP remain undeuterated. This may be explained by the preferential sorption of PE over PP, leading to specific distribution in the polymer blend.

Hydrocracking of a HDPE/VGO Blend: Influence of Catalyst-to-Feed Ratio on Fuel Yield and Composition

The effects that the catalyst-to-feed ratio have on the yields of products and composition of the naphtha and light cycle oil (LCO) fractions in the hydrocracking of a blend composed of high-density polyethylene (HDPE) and vacuum gasoil (VGO) using a PtPd/HY catalyst were assessed. The hydrocracking runs were carried out in a batch reactor fixing the following operation conditions: 420 °C, 80 bar, 120 min and an HDPE-to-VGO ratio of 0.2 gHDPE gVGO−1, varying the catalyst-to-feed mass ratio within the 0.05–0.1 gcatalyst gfeed−1 range. The obtained results exposed that a catalyst-to-feed mass ratio of 0.075 gcatalyst gfeed−1 provided the best results, since the conversion of the heavy cycle oil (HCO) fraction and of the HDPE offered quite high values (73.1 and 63.9%, respectively) without causing an excessive overcracking in the form of gas products (the yield of gases was of 25%). Moreover, an interesting yield of naphtha (37.0 wt%) with an RON within the commercial standards (92.5) was obtained. With regard to coke formation, not-so-developed structures were formed for a catalyst-to-feed mass ratio of 0.075 gcatalyst gfeed−1, easing their combustion and presumably extending the lifespan of the catalyst.

Effects of process conditions and nano-fillers on the cell structure and mechanical properties of co-injection molded polypropylene-polyethylene composites

Compared with traditional injection foaming, co-injection foaming serves as a method to prepare products with high-quality surfaces and enhanced mechanical properties, demonstrating excellent technical advantages and economic benefits. The effects of high-density polyethylene (HDPE) content, foaming agent content, melting temperature of core material, and nano-organic montmorillonite (OMMT) content on the cell structure, mechanical properties, and crystallization behavior of isotactic polypropylene (iPP)/HDPE composite foam prepared by co-injection foaming were systematically studied. At a foaming agent content of 2 wt.%, HDPE content of 30 wt.%, OMMT content of 3 wt.%, and the melting temperature of core material of 190 °C, the composite foam exhibited a cell size measuring 85 μm, a cell density of 2.5 × 105 cells/cm3, a tensile strength of 25.8 MPa, and an impact strength of 12.5 kJ/m2. The addition of HDPE reduced the crystallinity of iPP matrix, while enhancing the solubility of carbon dioxide within the matrix. The non-miscible interface between HDPE and iPP helped reduce the energy barrier for cell nucleation. Furthermore, the introduction of OMMT as a nucleating agent in iPP/HDPE composite material dramatically decreased the energy barrier for cell nucleation. These synergistic effects result in foam with the smaller cell size and the higher cell density, exhibiting excellent comprehensive mechanical properties. This work provides a feasible method for preparing composite foam with excellent comprehensive performance.

Compatibility study of high density polyethylene grade 80 gas pipe with synthetic polyglycol-based brake oil

High Density Polyethylene (HDPE) is one attractive technical option for the transportation and distribution of natural gas and hydrocarbons given the advantages in long-term mechanical strength, lifespan, maintenance costs and resistance to chemical aging. This study investigates the compatibility of extruded pipe material from copolymerized HDPE-80 with DOT 3 brake fluid. Machined standard specimens from inner (IL) and outer (OL) pipe layers are aged in commercial synthetic polyglycol-based oil for 7 days at laboratory conditions. The percent mass changes are +2.2% and +1.9% respectively for IL and OL pipe surfaces. These results are in the same range of published sorption data for other oils and fuels. Stress-strain parameters (E, σ y, σ CD, σ f, ε y, Δ ε CD, ε f) and fracture work are established and thoroughly discussed for both pipe sides. For IL, the reduction of E, σ y and ε f are respectively 28.0%, 13.9% and 22.7%, while for OL they are 22.6%, 7.7% and 25.1%. Globally, it is concluded that strength properties degradation in DOT 3 oil is more important for IL compared to OL. There is an important loss of ductility for both pipe sides. Ageing caused IL crystallinity ( Xc) to increase while OL showed inverse results probably because of frozen anti-oxidants in the outer surface layers following water quenching during extrusion. Before and after ageing, the as-received OL is found to be more resilient to oxidation than corresponding IL, as higher OIT parameters are also shown in the case of crude oil compatibility investigations. DOT 3 brake oil seem to accelerate the degradation of HDPE-80 thermal stability with a higher intensity for IL.

Rheological and Thermal Characterization of Glycerol Monostearate (GMS) as Compatibilizer on Polyethylene-Palm Stearin Composite

Addition of high percentage of palm stearin (PS) into a blend with high density polyethylene (HDPE) may result in the blend instability and poor flowability of the composite during injection moulding process. The undesirable effect of the PS addition arises from lack of interaction between the PS and HDPE matrix. To improve the interaction between the two components, a compatibilizer was added to the blend. The objective of this work is to study the effect of glycerol monostearate (GMS) compatibilizer concentration (1-5 wt%) on the HDPE-PS composite with PS content of 40 wt.%. The thermal properties of the HDPE-PS composite were characterized using torque analysis, differential scanning calorimetry (DSC) analysis and rheology analysis. It was found that melting temperature of the HDPE-PS composite decreases with GMS concentration. The presence of GMS in the HDPE-PS composite had improved composite flowability indicate suitability of the GMS as compatibilizer for the HDPE-PS composite.

Effects of chemical treatment and gamma-ray irradiation on the structure-properties of sunn hemp and okra hessian cloth reinforced high-density polyethylene composites: A comparative study

Okra hessian cloth and Sunn hemp hessian cloth were prepared and treated with 5, 10, and 15 wt% alkali solutions for 1 h. The optimized concentration of alkali is 10 wt%. The untreated and treated hessian cloths reinforced high-density polyethylene (HDPE) composites were then prepared using the compression molding method. Alkali-treated, and 55 wt% fiber contents reinforced composites showed improved mechanical properties among 40, 45, 50, 55, 60, and 65 wt% fiber contents composites. 55 wt% fiber contents reinforced composites were then irradiated under gamma-ray at doses 2.5–7.5 kGy at the rate of 6 kGy/h. According to the X-ray diffraction analysis results, only alkali-treated Okra reinforced, and Sunn hemp-reinforced HDPE composites had higher crystallinity values than untreated and irradiated composites. Surface micrographs showed that the Okra-HDPE and Sunn hemp-HDPE had better matrix and fiber attachment. Cross-linking between the two varieties of fibers and matrix was seen using Fourier-transform infrared (FTIR) spectroscopy. Both irradiated composites exhibited greater hydrophobicity in their water intake characteristics compared to untreated and alkali-treated composites. The tensile strength ( TS) value of Sunn hemp composite for 5 kGy gamma-ray irradiation dose is 68 MPa, which is 14% and 42% higher than that of treated and untreated composites, respectively. For comparison, the TS value for 5 kGy dose irradiated Okra composite is 66 MPa, which is 17% and 44% higher than that of treated and untreated composites, respectively. Young’s modulus ( Y) values of irradiated Okra composite and irradiated Sunn hemp composite showed higher values than that of other composites. Both irradiated composites have better thermal and structural characteristics than untreated and alkali-treated composites.

Entropy Barrier Mitigation and Harnessing Localized Upcycled Graphene Nanoplatelets in Polypropylene/High-Density Polyethylene Nanoblends

In pursuit of a sustainable future, the focus on thermoplastic compounding emerges as a transformative avenue. Strategically blending and compounding thermoplastics unlock the potential for eco-friendly materials, addressing pressing environmental concerns. Polymer blending is a widely utilized technique that offers significant advantages in terms of cost-effectiveness and the development of materials with diverse properties. However, achieving compatibility between polymers remains a challenge due to their non-negligible entropy, particularly in the case of immiscible polymers like Polypropylene (PP) and High-Density Polyethylene (HDPE). The success of such systems heavily depends on optimizing factors such as additive selection, mixing methodology, composition, and processing conditions. Despite the extensive industrial usage of polymers like PP and HDPE, there is still limited understanding regarding the impact of blending these polymers, especially when graphene is introduced. This study addresses these challenges by overcoming the entropy barrier between PP and HDPE using a high shear rate thermo-kinetic mixer and employing upcycled graphene nanoplatelets (GNP) as a type of low-cost graphene material through interface engineering. The GNP content in the blends ranged from 0 to 1 wt%, and through meticulous selection of the polymer weight fraction and the use of minimal GNP content, GNP was strategically localized at the blend interface. This resulted in remarkable mechanical performance achieved through the optimized manufacturing technique. Incorporating 0.1 wt% GNP resulted in a significant 38% increase in tensile modulus, while flexural modulus and flexural strength saw respective increments of 39% and 22% compared to neat PP. Further enhancements were observed with higher GNP contents. This study illuminates the transformative potential of thermoplastic compounding as a key driver toward a sustainable future.Graphical

Flexible, chemically bonded bismuth/tungsten‐based polyvinyl alcohol‐polyvinyl pyrrolidone composite for gamma and neutron shielding application

AbstractIn this paper, the gamma and neutron shielding behavior of chemically bonded high atomic number (Z), tungsten trioxide‐polyvinyl alcohol‐polyvinylpyrrolidone (PW), and bismuth oxide‐polyvinyl alcohol‐polyvinylpyrrolidone (PB) composites were reported at varying thickness. The PW and PB composites were prepared through the dissolution technique rather than the commonly used dispersion technique. The gamma and neutron attenuation characteristics of the composites were studied using 22Na (0.511 and 1.274 MeV energy) and 252Cf (0–10 MeV energy) sources, respectively. The half value layer of PW and PB composite was found to be 61.22 ± 0.914 mm and 48.29 ± 1.52 mm and the linear attenuation coefficient was found to be 0.115 and 0.144 cm−1 at 0.511 MeV, respectively. Further, the experimental gamma‐ray attenuation results were validated theoretically using Phy‐X software and found to be well in agreement with the experimental data. Both the composites also showed similar neutron shielding behavior when compared to the commercially used high‐density polyethylene (HDPE). The developed composites possess good mechanical properties as they did not show any cracks or wrinkles after undergoing 5400 bending cycles during the flex test, showing their high durability of flexibility. Thus, these composites are found to be suitable for shielding both, the gamma‐rays and neutrons.

Gamma-ray shielding effectiveness, thermal, and dielectric properties of filler-reinforced high-density polyethylene/boron carbide composites

The present research prepared samples of pure high-density polyethylene (HDPE)/boron carbide reinforced with iron dioxide, aluminum dioxide, iron, and aluminum. The effectiveness of the prepared samples as a shielding material against gamma-rays and their thermal and dielectric properties have been evaluated. The shielding characteristics of the prepared composites were investigated theoretically using the Phy-X/PSD program and experimentally for gamma-rays emitted from 131Cs and 60Co radioactive isotopes. The shielding evaluation included the mass attenuation coefficient (μ/ρ), half value layer (HVL), mean free path (MFP), atomic and electronic cross-sections (σa&σe), effective atomic number and electron density (Zeff &Neff), and exposure build-up factor (EBF). The EBF peaks of samples containing Fe and Fe2O3 are 103 times lower than pure HDPE. The results indicate that samples C2 and C3 have a higher ability to protect against gamma radiation than that of the other investigated samples. X-ray diffractometer (XRD) spectrum shows that adding B4C, Fe, Fe2O3, Al, and Al2O3 to HDPE caused an increase in its full width at half maximum (FWHM) value and a decrease in its average crystallite diameters (D) at its primary characteristic scattering angle of 21.49°. Adding multiple types of fillers to HDPE results in a minor shift in the melting temperature of the hosting matrix as proved from differential scanning calorimetry (DSC) data. The composite of HDPE/B4C/Al2O3 60/10/30 demonstrated the most significant values of dielectric parameters in comparison with the other composites, in good accord with the XRD results. The ac conductivity relied on the dopant type in the hosting matrix; the highest value was observed for HDPE/B4C/Al2O3 composite.

Justification of usability of the heat accumulator of phase transition in vehicles’ engines pre-start warming-up procedure

BACKGROUND: The trend of activity increase in exploration of transpolar areas has been observed for recent years. Negative temperatures, the key feature of the North, have a negative impact on state of piston engines of on-ground transport. In engine’s cylinders, the process of transition of liquid fuel in gaseous state goes before the mixture ignition. Negative temperatures affect the phase transition process and impede the working body homogenization. Therefore, engine pre-start warming-up procedure goes before successful engine start. Existing typical methods of pre-start warming-up demand fuel consumption and, generally, significant staff resources. Achievements of modern science offer new technologies for solving the issues of warming-up procedures based on accumulating, storage and deployment of heat energy produces by an engine during its operation. AIM: Justification of usability of the heat accumulator of phase transition in pre-start warming-up procedure for vehicles’ engines operating in conditions of negative temperatures of cold climate. METHODS: Numerical values of heat accumulator charging period depending on temperature of heat-accumulating material at various initial temperatures of coolant as well as values of the discharging period depending on temperature of heat-accumulating material at various coolant rates were defined experimentally. High-density polyethylene was used as a heat-accumulating material. RESULTS: As a result of the described experiment, curves of heat accumulator charging period depending on heat-accumulating material temperature at various initial temperatures of coolant and curves of heat accumulator discharging period depending on coolant temperature at various coolant rates were built. CONCLUSIONS: It is found that the heat accumulator of phase transition with high-density polyethylene as a heat-accumulating material can be used for improving the reliability of vehicles’ piston engine start in conditions of negative temperatures of cold climate.

Zinc Oxide Filler Effect on Dissipation Factor of High-Density Polyethylene

Polymer Nano-composites (PNC) are efficient materials that consist of polymer matrix and nanoparticles to create a new generation with excellent properties. In this paper a PNC filler-based Zinc oxide (ZnO) is used for enhancing the dissipation factor (DF) or Tan δ of the obtained polymer compared to the individual polymer material and improving the electrical properties of high-density polyethylene (HDPE). The electrical properties of HDPE are investigated under different concentrations of zinc oxide including (0, 10, 20, 30, and 40 wt.%) as well as under different conditions including the variations of temperature (25-150 Celsius) and frequencies (0.1 kHz to 1 MHz). The simulation results reveal that inclusion Zinc oxide as filler can improve the electrical properties of HDPE. In addition to that the minimum value of dissipation factor and the best electrical properties can be obtained at concentration 10 % loading compared to the other concentration levels. Curve fitting solutions were performed to determine the best fit for the experimental results. African Vultures Optimization Algorithm (AVOA) was used to determine the optimal value of zinc oxide filler percentage to obtain the best optimal value of dissipation factor.