Thermal Properties Of Polyethylene Research Articles

Magnetic Extraction of Weathered Tire Wear Particles and Polyethylene Microplastics.

Magnetic extraction offers a rapid and low-cost solution to microplastic (MP) separation, in which we magnetize the hydrophobic surface of MPs to separate them from complex environmental matrices using magnets. We synthesized a hydrophobic Fe-silane based nanocomposite (Fe@SiO2/MDOS) to separate MPs from freshwater. Pristine and weathered, polyethylene (PE) and tire wear particles (TWP) of different sizes were used in the study. The weathering of MPs was performed in an accelerated weathering chamber according to ISO 4892-2:2013 standards that mimic natural weathering conditions. The chemical properties and morphology of the Fe@SiO2/MDOS, PE and TWP were confirmed by Fourier transform infrared spectroscopy and Scanning electron microscopy, respectively. The thermal properties of PE and TWP were evaluated by Thermogravimetric analysis. Using 1.00 mg of Fe@SiO2/MDOS nanocomposite, 2.00 mg of pristine and weathered PE were extracted from freshwater; whereas, using the same amount of the nanocomposite, 7.92 mg of pristine TWP and 6.87 mg of weathered TWP were extracted. The retrieval of weathered TWP was 13% less than that of pristine TWP, which can be attributed to the increasing hydrophilicity of weathered TWP. The results reveal that the effectiveness of the magnetic separation technique varies among different polymer types and their sizes; the weathering of MPs also influences the magnetic separation efficiency.

Crosslinked polyethylene: A review on the crosslinking techniques, manufacturing methods, applications, and recycling

AbstractOne of the most used resins in the plastics industry is polyethylene (PE). Although PE has good impact resistance and ductility, its low maximum use temperature and mechanical strength limit some commercial development, especially for load‐bearing applications. To get better overall performances, crosslinking is performed to improve the chemical, mechanical, and thermal properties of PE. Although PE can be crosslinked by using various chemical and physical methods, this makes the resulting polymers more difficult to recycle since a three‐dimensional (3D) network is created. In this review, we first describe the different crosslinking techniques for PE to manufacture crosslinked PE (XLPE) parts. Then, as more than half of the XLPE‐based products are disposed directly after use, we present several options to reuse and recycle these products to overcome this environmental issue and find a sustainable solution. A focus is made on mechanical recycling and de‐crosslinking techniques for XLPE to generate recycled‐XLPE (r‐XLPE). Finally, a conclusion is presented on the current situation and research gaps that must be filled by future works.

Influence of peroxide cross-linking temperature and time on mechanical, physical and thermal properties of polyethylene

Abstract Polyethylene is a very common liner material for type IV pressure vessels due to its good toughness and easy processing. The property profile of the polymer can be improved by cross-linking thereby changing the nature of the polymer from thermoplastic toward more elastomeric. For this purpose, polyethylene is modified either chemically, using peroxide or silane, or physically by radiation. In the present work, a cross-linkable polyethylene grade that can be processed by rotational molding was peroxide cross-linked under variation of temperature and time. Subsequently, the material was characterized by differential scanning calorimetry, tensile tests, notched bar impact tests and permeation measurements. Two of the altogether six parameter combinations investigated did not lead to successful cross-linking resulting in very poor toughness. Stiffness, strength and permeation barrier properties, however, were much better than those of the other series due to higher crystallinity. Mechanical, physical and chemical properties changed significantly by successful cross-linking. The impact strength could be improved by a factor of more than 10. At the same time, significant losses in stiffness, strength and permeation barrier properties had to be accepted. Peroxide induced randomly distributed formation of cross-links above the melting point interfered with formation of crystalline regions upon cooling.

Effects of biochar pyrolysis temperature on thermal properties of polyethylene glycol/biochar composites as shape-stable biocomposite phase change materials.

The characteristics of biochar are of great significance to its application in the field of phase change energy storage. The objective of this research was to explore the effects of pyrolysis temperature on the characteristics of a biochar matrix and further on the heat energy storage properties of the promising green biochar-supported shape-stable biocomposite PCMs (ss-BCPCMs). Corn straw biochars (CSBCs) obtained under different pyrolysis conditions were loaded with polyethylene glycol (PEG) by an ultrasound-assisted vacuum impregnation method. The micro-morphology, specific surface area, pore structure and surface properties of biochar have been characterized and analyzed by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) method and Fourier transform infrared spectroscopy (FTIR). The thermal properties (chemical stability, latent heat storage, thermal conductivity, thermal stability, and thermal insulation) of PEG/CSBC composites have been characterized by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and laser flash analysis (LFA). The study revealed that both pore structure and surface activity of biochar are key factors affecting the energy storage performance of biochar-based ss-BCPCMs. The obtained PEG/CSBC composite showed a high latent heat storage up to 100.2 J g−1, good shape stability and leakage resistance, suggesting its high thermal storage stability that is beneficial for thermal energy storage applications. In addition, its excellent photothermal conversion efficiency (68.95%) provides application potential in photothermal energy storage.

Influence of ionic liquids on mechanical and thermal properties of polyethylene from renewable resources

Polyethylene from renewable resources produced using sugarcane as raw material was modified with phosphonium ionic liquids. Tensile properties and thermal behavior of modified biopolyethylene in air and nitrogen atmosphere were studied. The thermal degradation of ionic liquids and their influence on thermal degradation of polyethylene from renewable resources were studied by thermogravimetric analysis (TGA). In general, modification of biopolyethylene with phosphonium ionic liquids resulted in improvement of tensile properties, i.e., tensile strength and Young’s modulus. Thermal degradation of biopolyethylene modified with phosphonium ILs proceeds in one step in the range of 400–500 °C in nitrogen atmosphere. Modification of polyethylene with trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate ionic liquid resulted in increase in DTGpeaks and T10% temperatures toward higher temperature for modified polyethylene in comparison with unfilled PE sample both in air and nitrogen atmosphere.

Combined Effect of High-Temperature Shear Grinding and Gamma-Radiation on the Thermal Properties of Polyethylene

During γ-irradiation of polyethylene, its gradual amorphization accompanied by a decrease in the melting point and the heat of melting occurs. Almost complete amorphization of the polymer with crosslinking occurs at a dose of 1400 Mrad according to DSC data. In this case, the polymer retains insignificant crystallinity with a melting heat of 6.2 J/g, which is almost an order of magnitude lower than the melting heat of 118 J/g of unirradiated polyethylene. Depending on the radiation dose, there are three conditional ranges of change in DSC curve parameters: at doses up to 200, from 200 to 800, and over 800 Mrad, associated with different dose dependences of the simultaneously occurring processes of crosslinking and degradation of polymer macromolecules, as well as with radiation annealing of strained areas. High-temperature shear grinding of polyethylene, destroying the crystalline structure, leads to a decrease in the absolute value of the heats of melting and crystallization of the polymer.

DOPO-Functionalized Molybdenum Disulfide and its Impact on the Thermal Properties of Polyethylene and Poly(Lactic Acid) Composites.

The fabrication of conventional or biodegradable polymers with improved thermal and fire-resistant properties is an important task for their successful application in various branches of the industry. In this work, few-layered molybdenum disulfide was functionalized with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and introduced into polyethylene and poly(lactic acid) matrixes. The obtained polyethylene composite samples displayed improved thermal stability, significant reduction in CO emissions, improved fire-resistant properties, and over 100% increases in thermal conductivity. Poly(lactic acid) composites displayed less impressive results, but have managed to improve some values, such as CO emissions, peak heat release rate, and total heat release in comparison to pristine polymer.

Tailoring Hexagonal Gibbsite Single Crystal Nanoplatelets for Ethylene Polymerization and Nanocomposite Formation on MAO-Free Heterogeneous Bis(imino)pyridine Iron(II) Catalyst.

Ultrathin single crystal γ-Al(OH)3 (Gibbsite) nanoplatelets with average thickness <20 nm and length <800 nm, pretreated with trimethylaluminum (TMA), represent highly efficient activators and supports bis(imino)pyridine iron (II) (FeBIP) complex to produce high density polyethylene (HDPE) as well as gibbsite/HDPE nanocomposites in exceptionally high yields. Opposite to both methylaluminoxane (MAO)-activated homogeneous FeBIP catalyst and heterogenous silica-supported single site catalysts, no addition of MAO is required. At low TMA/Fe = 50 molar ratio, the superior catalyst activity (up to 6500 kg mol-1 h-1 bar-1 ) of FeBIP@TMA@Gibbsite is paralleled by controlled polyethylene particle growth without encountering reactor-fouling problems typical for homogeneous catalysts. TMA@Gibbsite is compared with other AlR3 @Gibbsite activators. The Al/Fe molar ratio governs catalyst activity as well as molar mass, molar mass distribution, and thermal properties of polyethylene. Moreover, hexagonal gibbsite nanoplatelets are uniformly dispersed in polyethylene to yield agglomerate-free polyethylene/gibbsite nanocomposites.

Preparation and thermal properties of polyethylene glycol/expanded graphite as novel form-stable phase change material for indoor energy saving

Phase change material (PCM) is a new kind of material for energy storage; its thermal properties are key factors in determining the application areas and the actual effect. The polyethylene glycol (PEG)/expanded graphite (EG) composite was prepared as a novel form-stable PCM by vacuum impregnation in this study. Nitrogen adsorption test indicated that EG belonged to materials in mesoporous scale with developed porous structure and prodigious adsorbility. The PEG/EG PCM owned excellent sealing performance and remarkable thermal storage capacity. The phase change temperatures and latent heats of the PEG/EG PCM were in range of 18.89–25.93 °C and 97.56–98.59 J·g−1 respectively. TGA and thermal performance manifested that the PEG/EG PCM presented good thermal stability and EG performed favorable conductivity and improved the thermal storage efficiency. The obtained PCMs were suitable for indoor energy saving and thermal comfort improvement.

Mechanical and thermal properties of polyethylene modified with different natural fillers

Mechanical and thermal properties of polyethylene modified with different natural fillers

Role of Cured Epoxy and Block Copolymer Addition in Mechanical and Thermal Properties of Polyethylene

Role of Cured Epoxy and Block Copolymer Addition in Mechanical and Thermal Properties of Polyethylene

Thermal properties of polyethylene glycol/carbon microsphere composite as a novel phase change material

Polyethylene glycol (PEG) as phase change materials has been extensively studied. However, it is difficult to uniformly disperse the PEG in the unmodified matrix material owing to the impregnation problem. It is therefore challenging to overcome the shortcoming of low thermal conductivity. In order to solve this problem, carbon microspheres (CMPs) prepared by the hydrothermal method is firstly proposed as the supporting matrix for preparation of PEG composite. The PEG/CMPs composite is prepared via a mutual diffusion methodology in a high-temperature environment. The test result shows the CMPs nano-material has rich oxygen-based functional groups and can be uniformly dispersed in the PEG phase. As the carbon content increases, the CMPs become gradually connected in the PEG/CMPs composite, which can result in a network with good thermal conductivity. Compared with the thermal conductivity of pure PEG, the thermal conductivity of the composite is increased by 65.07%. Owing to the existence of hydrogen bonds in the composite, the crystallinity fraction of the PEG is in the range of 102–105%. It means that the test result is higher than the theoretical value of latent heat for the composite. Finally, its cycling performance was measured. After 500 thermal cycles, the phase transition temperature of the composite remains almost constant, and the latent heat values of the melting and freezing decrease by 1.05 and 1.45%, respectively. The PEG/CMPs composite would be a promising material for thermal energy storage applications and can be used in various engineering disciplines.

Synthesis of a novel type of octyltetramethyldisiloxane-containing olefinic macromonomer and its copolymerization with ethylene

This paper reported the synthesis of a novel type of octyltetramethyldisiloxane-containing olefinic macromonomer (1-oct(7-en)yl-3-octyl-1,1,3,3-tetramethyldisiloxane or OO7), the copolymerization of OO7 with ethylene by vanadium catalyst, the evaluation of poly(ethylene-co-OO7) as additive on the flow, mechanical and thermal properties of polyethylene. The novel siloxane-containing comonomer OO7 was synthesized by a two-step hydrosilylation route, with only one oxygen atom in the molecule. The comonomer had low oxophilicity and hence could be readily copolymerized with ethylene by VCl3(THF)3 catalyst with a high activity of 14 kg/mmolV·h at the comonomer feed of 160 mmol/L. The OO7 incorporation reached to 4.9 mol%. The reactivity ratios were: rE = 41.6, rOO7 = 0.021 and rE•rOO7 = 0.87, which indicated a tendency of random copolymerization. DSC analysis revealed that the glass transition temperatures (Tg) of poly(ethylene-co-OO7) were in the range between −74.3 °C to −64.0 °C, lower than that of a LLDPE control sample of the similar composition. The melting endotherm of poly(ethylene-co-OO7) was broadened and shifted to a lower temperature range with increase of the OO7 content. Adding 10% poly(ethylene-co-OO7) as lubricant to HDPE increased 44% melt flow rate (MFR) of the blend. However, the mechanical and thermal properties of the blends were not adversely affected, compared to HDPE.

Influence of exfoliated graphite nanoplatelets on the flammability and thermal properties of polyethylene terephthalate/polypropylene nanocomposites

Nanocomposites based polyethylene terephthalate (PET)/polypropylene (PP) (70/30 wt%) blends and exfoliated graphite nanoplatelets (GNP) as reinforcing fillers were developed using melt extrusion process. The filler concentration was varied between 0 -5.98 wt percent (%) (0–7 phr). The resulting nanocomposites were characterized in terms of flame retardancy, thermal conductivity, thermal behavior, morphology and structure. Cone calorimeter analysis, limiting oxygen index (LOI) and UL94 flame rating tests revealed that addition of GNPs to PET/PP improved the flame retardancy of PET/PP/GNP nanocomposites significantly. Cone calorimeter data show a significant reduction of peak heat release rate (PHRR), mass loss rate and delayed time to ignition (TTI) due to addition of GNPs to PET/PP blend. As much as 37% reduction in PHRR and 32% increase in TTI were observed for the maximum GNP loading. Enhancements of flammability properties were attributed to the development of compact, dense, uniform char layers on the surface of nanocomposites. The effective thermal conductivity was found to vary linearly with GNP loading which was attributed to the formation of effective interconnected heat conduction bridges formed by the GNPs. It was found that the effective thermal conductivity of the nanocomposites was increased by about 80%, i.e. from 1.2 W/m.K for the unreinforced PET/PP blend to 1.9 W/m K for the 5.98 wt% (7 phr) reinforced PET/PP/GNP nanocomposites. Differential scanning calorimetry results indicated that the addition of GNPs increased crystallization temperatures but decreased degree of crystallinity of PET/PP/GNP nanocomposites. However; the melting points remained essentially unaffected. Transmission electron microscopy and field emission scanning electron microscopy showed uniform dispersion of GNPs in the matrix with the formation of interconnected GNP sheets at 3 phr. Isolated instances of exfoliation of GNPs was also observed.

Influence of diethylzinc on ethylene polymerization using iron catalyst homogeneous and supported on clay

Diethylzinc (DEZ) was introduced in ethylene polymerizations using iron based catalyst system both homogeneous and also supported on clay. The aim was to evaluate the influence of this compound on catalytic activity as well as on crystalline structure and thermal properties of polyethylene. The results showed that using the homogeneous system, the compound DEZ slightly decreased the catalytic activity while increased melting temperature of the synthesized polyethylene as observed by DSC analysis. Besides, X-ray diffraction technique showed that the crystallographic peaks of polyethylene were shifted to higher angles probably due to the dilatation of the orthorhombic unit cell by chain branching. In the polymerizations employing the iron catalyst supported on clay, the addition of DEZ also promoted an increase of the melting temperature of the polyethylene, and a slight increase in the degree of crystallinity was also observed.

Efeito da migração de composto antimicrobiano nas propriedades finais de selagem de filme poliolefínico

Films produced with blends of linear low density polyethylene and low density polyethylene (LLDPE + LDPE) containing 5 wt % of potassium sorbate (KS) were prepared by flat film extrusion. These films were characterized by differential scanning calorimetry and wavelength dispersive X-ray fluorescence. The migration profile of KS was followed by Attenuated Total Reflection-Fourier Transform Infrared and Ultraviolet spectroscopies and its effect on the sealing curve was determined. The addition of 5% of KS showed no effect in the thermal properties of polyethylene. However, the sealing properties were slightly affected by KS migration, acting as an impurity in the sealed area, which needed a higher sealing force at lower temperatures.

Evolution of Thermal Properties of Polyethylene in the Double Yield Region After Uniaxial Deformation

The double yield phenomenon was studied using specimens of linear low density polyethylene (LLDPE) uniaxially deformed up to different elongations. Extruded samples prepared at 150°C and 70 rpm were deformed at 10 mm/min. The crystallinity in the released state (after elimination of stress) was calculated using the differential scanning calorimetric technique. The crystallinity degree and melting temperature of the samples, as a function of the elongation to which they were subjected, presented a multi-step behavior. A decrement before the first yield point and an increment after this point were observed. Then, at higher elongation values, before the appearance of the second yield point, a significant decrement followed by an abrupt increment were detected. These results in the second yield region were interpreted in terms of partial melting followed by recrystallization. These experimental findings show that the partial melting-recrystallization process is one of the main mechanisms of the double yield phenomenon.

Effect of EVA copolymer on properties of different polyethylenes in silane crosslinking process

The effect of molecular structure of polyethylene (PE) [low density PE (LDPE), linear LDPE and high density PE] and silane/peroxide concentration on the grafting level and gel content in silane crosslinking process has been studied. The effect of incorporation of ethylene vinyl acetate (EVA) copolymer on the rate of crosslinking and thermal properties of PEs has been reported. The order of gel content was LDPE>linear LDPE>high density PE. With the incorporation of EVA, the rate of crosslinking increased. The degree of crystallinity did not change with crosslinking significantly. However, the shape of melting and crystallisation peaks changed, and two regions due to gel and sol parts were formed. In EVA/PE blends, two melting points were observed for both crosslinked and uncrosslinked samples. The SEM images showed the droplet matrix morphology with the EVA as the dispersed phase, especially for EVA/LDPE blend. The EVA/PE blends failed in hot set test, while the origin of PEs passed the hot set test successfully.

Preparation and thermal properties of polyethylene glycol/expanded graphite blends for energy storage

Expanded graphite is a promising heat transfer promoter due to its high conductivity, which improves the thermal conductivity of organic phase change materials. Moreover, it can also serve as supporting materials to keep the shape of the blends stable during the phase transition. After various investigation, the results showed that the maximum weight percentage of polyethylene glycol was as high as 90% in this paper without any leakage during the melting period, with the latent heat of 161.2 J g −1 and the melting point of 61.46 °C. It was found that the value of the latent heat was related to the polyethylene glycol portion, increased with the increase in polyethylene glycol content. Moreover, the measured enthalpy of the composite phase change materials was proportional to the mass ratio of the polyethylene glycol component. The melting temperatures were almost the same with different ratios of composites. The conductivity of blends was improved significantly with the high value of 1.324 W m −1 K −1 compared to the pure polyethylene glycol conductivity of 0.2985 W m −1 K −1.

Study of the Thermal Properties of Polyethylene of Different Mfi and Molecular Weight

Study of the Thermal Properties of Polyethylene of Different Mfi and Molecular Weight