High-density Polyethylene Chains Research Articles

Electron‐Irradiated Montmorillonite/Polyethylene Composite Separator for High‐Performance Lithium‐Ion Battery

ABSTRACTSeparators play a significant role in the safety and performance of lithium‐ion batteries. In this study, composite separators were fabricated using montmorillonite (MMT) as a filler in a high‐density polyethylene (HDPE) matrix, followed by electron irradiation to enhance the safety and performance of separator. Electron irradiation induces chemical bonds by crosslinking between HDPE chains, also between the MMT and HDPE. MMT features a two‐dimensional layered structure with a high surface area, providing abundant crosslinking sites. MMT is treated with a silane coupling agent, which induces layer exfoliation. The exfoliation increases the surface area of MMT, thereby providing more crosslinking sites. Additionally, the surface modification of MMT enhances its affinity with HDPE, leading to better dispersion of MMT within the HDPE matrix. Simultaneously, electron irradiation in an air atmosphere generates polar functional groups, improving the electrolyte affinity of the separator. Consequently, the safety of the MMT composite separator was significantly enhanced, exhibiting a high puncture strength of 0.52 N μm−1 and a thermal shrinkage rate of 21.4% at 135°C for 30 min. Li//LCO cells using the composite separator demonstrated superb cycle stability with a discharge retention of 98.7% and a coulombic efficiency of 99.6% after 200 cycles at 0.5 C, and exhibited rate capability maintaining 74.5% of the capacity at 20 C compared to 0.5 C.

Morphological analysis of mechanically recycled blends of high density polyethylene and polypropylene with strong difference in melt flow index

Polyolefin (PO) blends are difficult to separate due to density and chemical structure similarities. The associated waste treatment in the context of mechanical recycling is therefore complicated by the establishment of multi-phase morphologies that are not yet fully understood. In the present work, a high density polyethylene (HDPE) with a very high melt flow index (MFI) and a polypropylene (PP) with a very low MFI are deliberately mingled to better understand the full spectrum of morphological variations for PO blending. The linkage with the control over injection mold-based mechanical properties such as tensile strength, elasticity modulus, elongation at break, and impact strength is made. This is done supported by the connecting of experimental analyses at different scales, including (i) the molecular scale via size exclusion chromatography and Fourier transform infrared spectroscopy (FTIR), and (ii) the meso-scale via scanning electron and polarized light microscopy as well as differential scanning calorimetry, including a differentiation between the bulk and surface region. Emphasis is both on blends processed once and re-processed either once, twice or three times. For the single processing, it is demonstrated that in most cases a droplet morphology is obtained, with smaller droplets in case HDPE is the minor component and with a dominance of HDPE at the surface even for 60% PP, due to a better HDPE flowability. It is further shown that the scission of PP chains and crosslinking of HDPE chains respectively facilitates and inhibits crystallization, at least if meso-scale -mixing as more evident during re-processing is not taking over. It is also highlighted that the properties of PP can be enhanced by adding up to 10 wt% HDPE, acting as a filler, and that the (ideally) reprocessed blends remain suitable for application.

Polyethylene terephthalate conversion into liquid fuel by its co-pyrolysis with low- and high-density polyethylene employing scrape aluminium as catalyst

ABSTRACT The co-pyrolysis of polyethylene terephthalate (PET) with low-density polyethylene (LDPE) and high-density polyethylene (HDPE) was carried out in a batch steel pyrolyzer in order to convert the PET into pyrolysis oil as its pyrolysis alone resulted in wax and gases. The study also aimed to increase the aromatic content of pyrolysis oil by the interaction of degradation fragments of linear chains of LDPE and HDPE with the benzene ring of PET during the pyrolysis. The reaction conditions were optimized for a higher yield of pyrolysis oil which were found to be 500 °C pyrolysis temperature with a heating rate of 0.5 °Cs−1, 1 h reaction time and 20 g of the initial mass of polymer mixture having 20% PET, 40% LDPE and 40% HDPE. Waste aluminium particles were applied as an economical catalyst in the process. The thermal co-pyrolysis yielded 8% pyrolysis oil, 32.3 wax, 39.7 wt% gases and 20% coke while the catalytic co-pyrolysis produced 30.2% pyrolysis oil, 4.2% wax, 53.6 wt% gases and 12% coke. The fractional distillation of catalytic oil resulted in 46% gasoline range oil, 31% kerosene range oil and 23% diesel range oil. These fractions resembled the standard fuels in terms of their fuel properties as well as FT-IR spectra. The GC-MS analysis revealed that the catalytic co-pyrolysis favoured the formation of relatively short-chain hydrocarbons with olefins and isoparaffins as major components while the thermal co-pyrolysis formed long-chain paraffins. The naphthenes and aromatics were also found in higher amounts in the catalytic oil compared with the thermal oil.

Effects of residual wax content on the thermal, rheological, and mechanical properties of high‐density polyethylene

AbstractThe influence of residual wax content on the thermal, rheological, and mechanical behavior of two high‐density polyethylene (HDPE) samples from different lots of the same supplier was characterized. HDPE with a low wax content presented a higher melting temperature and a wider melting endotherm. A decrease in the degree of crystallinity and thermal stability of HDPE with a higher wax content was observed. Thermograms obtained by DSC indicated a small additional exothermic transition associated with the exclusion of residual wax. A higher wax content in HDPE produces a decrease in its viscosity due to a lubricating effect, which allows the sliding of HDPE chains of high molecular weight. In contrast, HDPE with lower wax content achieves greater elongational viscosity and melt strength. The mechanical testing results show that HDPE with higher wax content presented lower Young's modulus, tensile strength, elongation at break, and Izod impact strength than HDPE with lower wax content. The results obtained show that a relatively slight difference in wax content significantly affects HDPE properties.

Morphology, phase diagram, and properties of high‐density polyethylene/thermally treated waste polyethylene wax blends

AbstractWaste polyethylene wax is thermally treated using a rotary evaporator to reduce unwanted components. Fourier transform infrared proves the absence of undesirable material. Wax is extruded with high‐density polyethylene (HDPE) at various loadings to study its morphology and final properties. Scanning electron microscopy and differential scanning calorimeter were employed to obtain the phase diagram showing the immiscibility of blends containing more than 20 wt% of wax. Due to the low melting temperature of the wax and its plasticating effect on HDPE, a decrease in melting temperature, enthalpy of fusion, and crystallinity with increasing wax content of the blend is observed. The phase diagram displays four possible phases depending on temperature and wax loading. Improved processability of HDPE/wax blends is demonstrated using complex viscosity curves. Han plots prove the miscibility of wax and HDPE in the melt state even at high concentrations of wax. HDPE/wax compounds have lower crystallinity, and wax particles, acting as weak spots, lower the elastic modulus, yield stress, and stress and strain at break as wax content increases. An increase in yield strain is observed due to the more effortless extension of HDPE chains at higher wax content. In 10 wt% of wax is accepted as the upper limit for wax incorporation into the HDPE matrix.

High-density polyethylene/asphaltene composites: Thermal, mechanical and morphological properties

In this work, a series of high-density polyethylene (HDPE)/asphaltene composites were fabricated via the melt blending method. The composites were characterized, and the degradability, thermal, and mechanical stabilities of the products were analyzed. TGA results showed that HDPE/asphaltene composites had better thermal properties, e.g. higher degradation temperatures than asphaltene-free pristine HDPE. The high intermolecular interactions between the asphaltene and HDPE resulted in the degradation mechanism break, delaying the decomposition of composites and increasing their thermal stabilities. The results of DSC analysis indicated that the presence of asphaltene induces higher crystallinity and melting temperature in the composite matrix. According to the XRD results, the crystalline size was increased by increasing the asphaltene loading level due to the nucleating effect of asphaltene and the proper interactions developed between the asphaltene particles and HDPE chains. The proper dispersion of asphaltene in the composite matrix was confirmed by SEM images. The obtained results from the hardness analysis indicated higher mechanical stability for the composites, proportional to the content of the incorporated asphaltene to the composite. The results showed that asphaltene can be considered as an appropriate choice to improve the HDPE properties.

Role of percent grafting and chain length of fully fluorinated pendant units in the grafted acrylic compound on crucial characteristic properties of high density polyethylene

This comprehensive study paves way to investigate the effects of not only the extent of grafting but also the chain length of the perfluorinated pendant tail presenting in the three different fluoroalkyl acrylate monomers on the significant characteristic properties; namely the thermal behavior, crystal structure quality, mechanical performance and morphological structure of high density polyethylene (HDPE). The individual graft copolymerizations of the monomer onto HDPE were conducted at the content level from 5 % to 30 % via bulk-melt polymerization. The characterizations of copolymers were performed with differential scanning calorimeter (DSC), powder X-ray diffractometer, universal testing machine and scanning electron microscope (SEM) techniques. As for the results deduced from DSC analysis, both the melting temperatures of HDPE and degree of crystallinity were found to increase systematically with the enhancement in the percent grafting level up to 10 % beyond which the parameters were noted to decrease drastically and reach towards globally minimum values. According to the XRD results, as the percentage of grafting enhanced, the remarkable expansions were observed in unit cell parameters of HDPE crystallized in the orthorhombic symmetry. Moreover, the presence of relatively higher amount of -CF2 groups in the perfluorinated pendant tail caused the formation of three-dimensional lateral repulsions due to its helix structure. Furthermore, there seemed to remarkably improve in the mechanical performance features in case of percent grafting level of 70.6 % where the tensile strength, Modulus and impact strength parameters were measured to be about 42.51 MPa, 539.90 MPa and 41.11 kj/m2, respectively. These reinforcements were found to be explained by the improvement in the regulation, orientations, alignments of HDPE chains. Furthermore, the formation of thick, bulky and long-fibrils were observed at high percent grafting.

Effects of strain rate and temperature on the mechanical behavior of high‐density polyethylene

ABSTRACTThe objective of this work is to initiate the discussion about multiphysics relationships between the molten and solid states of high‐density polyethylene (HDPE). The extrusion and the injection processes are employed to prepare samples, and the experimental procedures, using differential scanning calorimetry, dynamic thermomechanical analysis (DMTA), thermal gravimetric analysis, and rheological measurements, are defined to choose the optimal variables. After different characterizations, the extrusion and injection temperatures of 220 and 230 °C have been chosen. To investigate the viscoelastic behavior of HDPE, the DMTA is used. To perform the high strain rate tensile tests, tensile machine was equipped with a specific furnace. Two temperatures, −20 and 20 °C, with strain rates varying from 0.001 to 100 seconds−1 were used to compare the flow characteristics. Results showed that by increasing the strain rate the molecular mobility of the HDPE chains is decreased. In addition, to the tests at −20 °C, the increase of Young's modulus can be properly observed, under high strain rates. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48778.

Observations of a novel strengthening mechanism in HDPE nanocomposites

Previous strengthening mechanisms described in literature for high density polyethylene (HDPE) carbon nanotubes composites are typical of those observed in fibre reinforced polymeric micro composites. Here, we present a new molecular level strengthening mechanism based on HDPE carbon nanotubes composite, which has not been reported before to the best of authors’ knowledge. The HDPE nanocomposite was produced by melt intercalation technique via twin-screw extrusion. Thereafter, the samples were subjected to mechanical tensile tests and scanning electron microscope (SEM) examination. Carbon nanotubes (CNTs) were found to be disentangled from the polymer molecules after yielding and prior to breaking. SEM and optical microscopic observations revealed visible black agglomerate bands at 45° appeared after yielding and prior to the breaking of the ductile HDPE. It was observed that CNTs were pushed out from the intricate mechanical interlocking with the thermoplastic polymeric chains of HDPE during strain hardening.

Composite Contains Large Content of In Situ Microfibril, Prepared Directly by Injection Molding: Morphology and Property

AbstractDuring vibration injection molding (VIM), the in situ microfibril composite (MFC) based on high‐density polyethylene (HDPE)/polystyrene (PS) is molded. A large content of uniform microfibrils with an average diameter about 0.55 µm can be found from the surface to the center region. This phenomenon shows a big difference from the skin‐core structure of CIM samples as a result of shear flow. Apart from the PS phase going through a big deformation, the molecular chains of HDPE are also stretched along the flow direction. And finally, some super crystalline, like shish‐kebab, hybrid shish‐kebab structures exist in the strong shear region. Both the microfibril and super crystalline structure make a contribution to the mechanical improvement of the composite according to the mechanical testing results. This work can simplify the traditional MFC process, achieve the goal of direct fibrillation and provide a new idea of utilizing the properties of immiscible polymer systems.

The massive formation of hybrid shish‐kebab structures in HDPE/PA6 microfibril blend subjected to melt second flow

ABSTRACTDuring the melt second flow process, the synergetic effect of intense shear and polyamide 6 (PA6) microfibrils finally results in the massive formation of highly oriented crystalline structures in the entire thickness of high‐density polyethylene (HDPE)/PA6 microfibril blend. Interestingly, not only does the small microfibril induce HDPE crystallization to form typical hybrid shish–kebab structure, but the large microfibril (about 2 μm in diameter) also induces the formation of local hybrid shish–kebab structure. For the small PA6 microfibril, the oriented HDPE chains caused by the intense shear are absorbed on the whole surface of the microfibril and then a complete polymer underlayer is formed. Subsequently, the crystal nuclei appear on the underlayer, and then the other oriented HDPE chains overgrow from the nuclei in the form of folded chains and grow perpendicular to the microfibril. Finally, the typical hybrid shish–kebab structure is formed. While for the large PA6 microfibril, a few HDPE chains can be still absorbed on the microfibril surface due to the high surface energy of PA6. However, the driving force is insufficient to absorb largely oriented HDPE chains to form complete hybrid shish but only local adsorption layer, so the local hybrid structure is formed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45274.

Fotodegradasi High Density Polyethylene Yang Mengandung Aditif Okso-Biodegradasi

High Density Polyethylene (HDPE) is a type of plastic that widely used for packaging because it has good mechanical properties. HDPE is naturally non-biodegradable, and the consequence it will increase plastic waste that will damage the environment. To increase their biodegradability, it is necessary to add an oxo-biodegradation additive in the form of a stearate metal compound. This oxo-biodegradation additive is a chromophore that can absorb UV light. Polyethylene oxo-biodegradation films are prepared by mixing HDPE and cobalt stearate to homogeneous on various compositions. To know the effect of adding cobalt stearate into HDPE has done by photodegradation process. The polyethylene oxo-biodegradation film was given irradiation using UV light in the wavelength range 280-300 nm at room temperature for 10 days. After irradiation, in the ATR spectrum shows an absorption peak at 1712 cm-1 wavenumber indicatied the presence of a carbonyl group with a stronger intensity. The higher concentration of cobalt stearate added in HDPE, increases the peak intensity of carbonyl group. This is due to the increasing number of chromophores from cobalt stearate that can absorb UV light, the faster the breakdown of HDPE chains into small fragments so that HDPE is rapidly degraded in nature.

Fabrication of multilayer graphene oxide-reinforced high density polyethylene nanocomposites with enhanced thermal and mechanical properties via thermokinetic mixing

High density polyethylene (HDPE) was compounded with thermally exfoliated graphene oxide (TEGO) by thermokinetic mixing in a short time. High shear rates during the compounding process provided high exfoliation and proper dispersion of graphene layers in the polymer matrix. Different TEGO/polymer ratios were used to get efficient melt mixing. Structural analysis by spectroscopic techniques confirmed the exfoliation of TEGO sheets and the coverage of their surfaces by HDPE chains. Furthermore, homogeneous dispersion of graphene sheets in the matrix led to the enhancement in the mechanical and thermal properties of HPDE-based nanocomposites. Especially stress concentration sites were significantly reduced by preventing the agglomeration and restacking of graphene sheets in the matrix. Therefore, the tensile modulus and strength of HDPE nanocomposite increased about 36.5% and 45.7%, respectively, with the incorporation of 2 wt% TEGO. Microscopy analysis showed the separation of graphene layers in the cross-sectional area of composite specimens. TEGO-reinforced HDPE nanocomposites showed high thermal stability compared to the neat sample.

Investigation on the synergistic effect of γ-aminopropyltriethoxysilane and polyethylene-grafted glycidylmethacrylate on the properties of high-density polyethylene/poplar wood flour composites and their synergistic mechanism

Wood–plastic composites were prepared from poplar wood flour and high-density polyethylene (HDPE) by melt blending and injection molding techniques, using polyethylene-grafted glycidylmethacrylate (HDPE- g-GMA) as compatibilizer and γ-aminopropyltriethoxysilane as coupling agent. The scanning electron microscopy results showed that a stronger interfacial adhesion was formed between the wood flour and HDPE matrices during the combined use of γ-aminopropyltriethoxysilane and HDPE- g-GMA, while the X-ray photoelectron spectroscopy results showed that more HDPE chains are linked to the surface of poplar wood flour through the formation of chemical bonding in the presence of γ-aminopropyltriethoxysilane and HDPE- g-GMA. So, HDPE- g-GMA and γ-aminopropyltriethoxysilane showed a synergistic effect on the improvement of compatibility between the poplar wood flour and HDPE matrices and better mechanical properties of wood–plastic composites could be obtained. Furthermore, the thermogravimetric analysis results also indicated the synergistic effects to some extent. The synergistic mechanism of γ-aminopropyltriethoxysilane and HDPE- g-GMA was proposed on the basis of investigation results.

Preparation and properties of Barium titanate (BaTiO3) reinforced high density polyethylene (HDPE) composites for electronic application

In this study, 3-Aminopropyltriethoxysilane (KH550) with polar amino groups is applied to modify the surface of Barium titanate (BaTiO3) particles. When volume fraction of BaTiO3 further increases to 50 vol%, the dielectric constant and loss of HDPE control increase from 2.5 and 0.02 to 18.5 and 0.10 at 10 MHz, respectively, with the volume resistivity of HDPE control decreasing from 3.6 × 1013 Ω m to 3.5 × 1011 Ω m. The increased amount of modified BaTiO3 can increase the flexural strength and modulus HDPE composites from 8 and 90 MPa to 14 and 780 MPa, respectively. However, the increase of modified BaTiO3 can restrict mobility of HDPE chains and decrease the crystallinity of HDPE composites.

Machine direction orientation of high density polyethylene (HDPE): Barrier and optical properties

In this study, blown films were produced from three different high density polyethylene (HDPE) resins. Further, these blown films were oriented along the machine direction using either traditional machine direction orientation (MDO) or compression roll drawing (CRD MDO) technology. The stretched/oriented films were compared for their water vapor transport and optical properties as a function of the extent of orientation (i.e., draw ratio, DR). In addition to that, these properties were directly compared between the oriented and unoriented (blown) films of the same thickness. The present study revealed that the water vapor transmission rate (WVTR) as a function of draw ratio (DR) went through a maxima. Detailed morphological characterization showed that initially, at low DR, stretching resulted in lamellar organization (along the MD). Consequently, the tortuosity in the diffusion path decreased and the overall WVTR increased. However, beyond a critical DR, lamellar crystals transformed to microfibrillar crystals. During this process the amorphous content of the HDPE chains decreased and geometric redistribution of the amorphous phase occurred along with some orientation. As a combination of all these effects, the WVTR was found to decrease beyond the critical DR. Unlike transport properties, optical properties monotonically improved as a function of DR. Further, for both, the barrier and optical properties, the absolute values were found to be a strong function of the resin physical properties. Finally, compression roll drawing technology (CRD MDO) utilizes a patented process that simultaneously applies a stretching and compressive force to orient polymer chains homogeneously without any tiger striping (uneven deformation). Consequently, CRD MDO stretched samples showed a lower surface roughness compared to their traditional MDO stretched counterpart. Therefore, for the same resin and DR, CRD MDO stretched samples displayed markedly better barrier properties and optics, especially lower total haze and higher gloss.

Dynamic mechanical properties of high density polyethylene and teak wood flour composites

The dynamic mechanical properties of high density polyethylene (HDPE) and teak wood flour (TWF) composites at varying volume fraction (Φf) of TWF from 0.00 to 0.32 have been studied. In HDPE/TWF composites, storage modulus (E′) decreased at Φf = 0.05, then increases with Φf; however, values were lower than HDPE up to Φf = 0.16, due to a pseudolubricating effect of filler. Loss modulus (E″) values were higher than HDPE in β and α relaxation regions while in γ relaxation region values were marginally equal to HDPE. Tan δ value decreases with Φf which may be due to enhanced amorphization and decreased crystallinity of HDPE. In presence of maleic anhydride grafted HDPE (HDPE-g-MAH), E′ values were lower than HDPE/TWF composites. In HDPE/TWF/HDPE-g-MAH, E″ were slightly higher than HDPE/TWF due to slippage of HDPE chains facilitated by the extent of degradation of coupling agent. Tan δ were higher for both systems than the rule of mixture.

Magnetic high density polyethylene nanocomposites reinforced with in-situ synthesized Fe@FeO core-shell nanoparticles

Magnetic high density polyethylene (HDPE) polymer nanocomposites (PNCs) with different loadings of iron@iron oxide core-shell nanoparticles (NPs) were fabricated by in-situ thermal decomposition of organometallic iron precursors in the HDPE-xylene solution. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) measurement indicated that the HDPE chains were physically adsorbed onto the surface of NPs instead of forming chemical bonding during the formation of these PNCs. Transmission electron microscopy (TEM) micrographs revealed that the iron core NPs surrounded with iron oxide shell were formed in the HDPE hosting matrix with good dispersion, an inter-network structure was formed when the particle loading reached 10.0 wt%. Mössbauer spectrum analysis showed that the oxidization content of the iron NPs decreased with increasing the particle loading. The X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) characterization demonstrated that the crystalline structure of HDPE matrix was not influenced by the incorporation of the NPs; however, fusion heat and crystalline fraction of the HDPE matrix decreased with the introduction of these NPs. The melt rheological behaviors were significantly changed as indicated by different complex viscosities, storage moduli and loss moduli between pristine HDPE and its PNCs. Magnetic property investigation revealed a soft ferromagnetic behavior for these HDPE PNCs at room temperature and the coercivity was decreased with increasing the particle loading. Thermal gravimetric analysis (TGA) demonstrated that the thermal stability of these HDPE PNCs was enhanced in the presence of the NPs. Dielectric properties of the HDPE PNCs were also investigated and discussed in detail.

Isothermal and nonisothermal crystallization of HDPE composites containing multilayer carton scraps as filler

AbstractThe influence of multilayer carton scraps (MC) on crystallization kinetics of high‐density polyethylene (HDPE) is detailed in this contribution. HDPE/MC composites were prepared by melt mixing, and a maleated linear low density polyethylene (MAPE) was added as compatibilizer. The crystallization kinetics of HDPE/MC/MAPE was analyzed as function of composition both in isothermal and nonisothermal conditions. The multilayer carton scraps appear to promote the onset of crystallization of HDPE, acting as efficient nucleating agent. The presence of MAPE as compatibilizer slightly reduces the nucleating efficiency of MC: the compatibilizer induces a delay in the onset of crystallization, caused by the need to exclude the bulky pendant groups of maleated linear low‐density polyethylene from the crystals, as HDPE and MAPE chains cocrystallize. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Compatibilization Effects of PE-g-MA on Mechanical, Thermal and Swelling Properties of High Density Polyethylene/Natural Rubber/Thermoplastic Tapioca Starch Blends

Effect of polyethylene grafted maleic anhydride (PE-g-MA) on mechanical, thermal and swelling characteristic of high density polyethylene (HDPE)/natural rubber (NR)/thermoplastic tapioca starch (TPS) blends were studied. The measurements from differential scanning calorimetric (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), proved the effectiveness of PE-g-MA as compatibilizer in improving the miscibility between HDPE/NR – TPS blends. A decrement in crystallinity index was found after adding PE-g-MA. It is due to restriction in mobility of the HDPE chains. In the presence of PE-g-MA, the blends have better thermal stability. On top of that, the storage modulus which is reflected to the blend stiffness also increased as indicated the improvement in HDPE/NR – TPS interaction.