Neat High Density Polyethylene Research Articles

Flammability and thermal stability of thermoplastic-based composites filled with natural carbon

This investigation characterized flammability and thermal stability for a novel sustainable composite engineered for use in building applications. Flammability and thermal stability of coal plastic composites composed of coal (40–60 wt.%) and high-density polyethylene were compared to commercial wood–plastic composites. Pyrolysis thermogravimetric analysis results indicated that coal plastic composites possessed a single-step decomposition and higher char residue, while wood–plastic composites had two-step decomposition, with the first peak occurring at much lower temperatures. Thermogravimetric analyses in air suggest coal plastic composites, compared to wood–plastic composites and neat high-density polyethylene, were more thermally stable. Flash ignition temperatures for coal plastic composites were higher than high-density polyethylene and wood–plastic composites, while self-ignition temperatures were in the same range as wood–plastic composites. Rate of burning data indicated coal plastic composites were slower burning than wood–plastic composites, with increasing coal content slowing burning rate by 19.9%–27.6%. Cone calorimeter testing showed 27% and 59% reduction in total heat release and total smoke release as coal content increased while coal plastic composite with 60 wt.% coal possessed lower overall flammability in comparison with predominant commercially available wood–plastic composite products. Coal improved composite overall thermal stability and flammability by acting as char former and foaming agent.

Valorization Strategy for Leather Waste as Filler for High-Density Polyethylene Composites: Analysis of the Thermal Stability, Insulation Properties and Chromium Leaching.

Leather waste (BF) and high-density polyethylene (HDPE) were compounded in a lab scale internal mixer and processed by means of injection molding. In this study, leather waste and HDPE composites were characterized by instrumental techniques such as differential scanning calorimetry (DSC), thermo-gravimetric Analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Physical integrity of composites against chemical exposure and chromium-leaching properties of the composites were also investigated. This study shows that the incorporation of 30% leather waste fiber into HDPE composites decreases the thermal conductivity of the composite samples by 17% in comparison to that of neat HDPE samples. Composites showed no thermal degradation during processing cycle. Strong interfacial bonding between leather waste and polymer results in comparable low-leachate levels to maximum allowed concentration for nonhazardous waste, and good chemical resistance properties. The BF/HDPE composites could be a promising low-cost alternative in industrial application areas of HDPE, where high-mechanical strength and low-thermal conductivity is required.

Recycled LDPE/PETG blends and HDPE/PETG blends: mechanical, thermal, and rheological properties

The recycled low density polyethylene (LDPE), recycled high density polyethylene (HDPE) and recycled polyethylene terephthalate G copolyester (PETG) as post-processed plastic wastes from extrusion blow molding process were modified with blending process to improve the properties of those plastic wastes and decrease the amount of plastic wastes in the plastic processing plants. The recycled PETG was blended with recycled LDPE and recycled HDPE in various concentration from 0 wt% to 100 wt% in increments of 10 wt% as referred to LDPE/PETG blends and HDPE/PETG blends respectively prepared by co-twin screw extruder. The addition of PETG in the blending of LDPE and HDPE improved the mechanical properties and MFI of those polymer blends but decreased thermal stability, storage modulus, loss modulus and complex viscosity as compared to those of neat LDPE and neat HDPE. LDPE/PETG blends illustrated better impact properties and flexibility than those of HDPE/PETG blends.

Effect of Filler Particle Size on the Recyclability of Fly Ash Filled HDPE Composites.

Fly ash polymer composites are innovative high-performance materials that reduce the environmental worries and disposal complications of heavy industry produced fly ash. This study developed and characterized such composites of high-density polyethylene (HDPE) matrices and found that the use of small (50–90 µm) particles of fly ash could give rise to the tensile modulus (~95%) and tensile strength (~7%) of their reinforced composites when compared to neat HDPE materials. While these results themselves convey a strong message of how fly ash can be effectively utilized, this was not the key aim of the current study. The study was extended to examine the effect of fly ash particle size on the recyclability of relevant HDPE composites. The extrusion-based multiple recycling of composites gave slightly lower mechanical properties, primarily due to filler/matrix delamination when large fly ash particles were used. Compared to freshly made fly ash-filled HDPE composites, although using small (50–90 µm) fly ash particles reduced the tensile modulus and tensile strength of recycled composites, the values were still far above those from neat HDPE materials. This novel insight directs the effective utilization of fly ash and provides long-term sustainable and economical solutions for their practical applicability.

Influence of the amphiphilic molecule on high-density polyethylene crystallization

The influence of organic additives on crystallization of polyolefins has not been paid enough attention due to the low dosage, but it may have a significant impact on the properties of polyolefins. In the paper, the organic amphiphilic molecules were introduced into high-density polyethylene (HDPE) through melt blending, and compared with neat HDPE. It is mainly discussed for the following aspects including analysis of crystal structure and morphology using wide-angle X-ray diffraction (WAXD) and polarized optical microscopy (POM), respectively; analysis of crystallinity, crystal rate, crystal growth and crystallization enthalpy, using the differential scanning calorimetry (DSC). The research indicates that the organic amphiphilic molecules may act as an internal lubricant. On the one hand, HDPE molecular chains are easy to fall off from crystal lattices, resulting in lagging crystallization peak, simultaneously reducing the interaction between HDPE molecules should induce the lower activation energy (ΔEm) to increase the crystallinity of HDPE. On the other hand, the amphiphilic molecules should be exclude from HDPE crystal to the amorphous area due to poor compatibility; thus, the HDPE/amphiphilic molecules blends, similar to neat HDPE, conduct homogeneous nucleation, and the growth of monocrystal performs the tendency of the zero-dimension to the two-dimension with increase in temperature of isothermal crystallization and decreasing cooling rate of non-isothermal crystallization. It is hoped that through these studies, people will pay more attention to the impact of organic additives on the performance of HDPE.

The effect of nanoclay on the nonlinear viscoelastic behavior of high‐density polyethylene

AbstractThe study's main motivation is to determine the creep behavior of high‐density polyethylene (HDPE)‐based nanocomposites in unexpected situations where short‐term constant loading may occur. On this basis, the short‐term creep behavior of 1 wt.%, 3 wt.%, and 5 wt.% nanoclay reinforced HDPE nanocomposites were investigated at room temperature (23 ± 1°C) and strain rate of 1E‐4 1/s under 8, 12, and 16 MPa stress levels. As the nanoclay reinforcement ratio by weight increased, the creep resistance and modulus of neat HDPE increased at 8 MPa stress level, but they decreased at 12 and 16 MPa stress levels. The absorbed energy that corresponds to the area under the stress–strain curve increase as the stress level increase from 8 to 16 MPa. However, absorbed energy decreases as nanoclay reinforcement increases for 8 MPa. The curves produced from the four‐element Burger's model and Findley's power law models were compared with the creep curves obtained from the experiments. The four‐element Burger model was found to fit the creep curves better than Findley's power‐law model. Also, some regression curves were given for interpolations to give intermediate values of the maximum creep strain values at different stress levels. The presented models can be used to evaluate creep strain, considering the usage fields of parts or semi‐products produced from nanoclay/HDPE nanocomposites.

Influences of dispersion media for chemically modified cellulose nanofibers on rheological and mechanical properties of cellulose nanofiber reinforced high-density polyethylene

Cellulose nanofibers (CNFs) have exceptional mechanical and thermal properties, but the use of these materials to reinforce polyolefins is challenging. In the present study, ethanol, acetone, isopropyl alcohol (IPA) and water were used as dispersion media for alkenyl succinic anhydride-modified CNFs (ACNFs). Masterbatches were prepared from these ACNFs wetted in the various liquids and then melt-compounded with high-density polyethylene (HDPE) using a twin-screw extruder, followed by injection-molding. The morphologies of the resulting HDPE/ACNF composites were characterized using optical and electron microscopy, and the rheological and mechanical properties of these composites were also evaluated. The results showed that the storage and loss moduli as well as the tensile moduli and strength of the composites produced using the organic liquids were higher than those of the composite made using water, owing to the better dispersion of ACNFs in the HDPE matrix in the former. This improved dispersion would be expected to increase the contact area between the ACNFs and the matrix and to enhance the orientation of the HDPE molecules. IPA was found to give the highest tensile modulus and strength among the organic liquids used in this study. The tensile modulus and strength of the composite containing ACNFs produced from IPA were, respectively, four times and two times higher than those of the neat HDPE. IPA is a relatively non-toxic, inexpensive compound, and so could be readily adopted for industrial scale processing.

Thermo‐oxidative aging of high‐density polyethylene reinforced with multiwalled carbon nanotubes

AbstractThe purpose of this study was to investigate the influence of aging on the properties of high‐density polyethylene (HDPE) reinforced with multi‐wall carbon nanotubes (MWCNTs). Nanocomposites were prepared with nanotubes at 0, 1, 3, and 5 wt%. The long‐term durability of the prepared materials was evaluated by thermo‐oxidative aging test. Test bodies were aged at 110°C for up to 10 weeks. The nanocomposites were characterized by differential scanning calometry, thermogravimetric analysis (TGA), 13C‐NMR, elongation at break, and transmission electron microscopy. The aging mainly occurred on the surface of the samples and the neat HDPE showed a strong yellowing after the aging. A strong reduction in elongation at break was seen. For neat HDPE, the elongation at break was reduced from roughly 1400–25%. When HDPE was reinforced with the nanotubes, the reduction was less dramatic.

Synergic Enhancement of High-density Polyethylene through Ultrahigh Molecular Weight Polyethylene and Multi-flow Vibration Injection Molding: A Facile Fabrication with Potential Industrial Prospects

General-purpose plastics with high strength and toughness have been in great demand for structural engineering applications. To achieve the reinforcement and broaden the application scope of high-density polyethylene (HDPE), multi-flow vibration injection molding (MFVIM) and ultrahigh molecular weight polyethylene (UHMWPE) are synergistically employed in this work. Herein, the MFVIM has better shear layer control ability and higher fabrication advantage for complex parts than other analogous novel injection molding technologies reported. The reinforcing effect of various filling times and UHMWPE contents as well as the corresponding microstructure evolution are investigated. When 5 wt% UHMWPE is added, MFVIM process with six flow times thickens the shear layer to the whole thickness. The tensile strength and modulus increase to 2.14 and 1.39 times, respectively, compared to neat HDPE on the premise of remaining 70% impact strength. Structural characterizations indicate that the enhancement is attributed to the improvement of shish-kebab content and lamellae compactness, as well as related to the corresponding size distributions of undissolved UHMWPE particles. This novel injection molding technology with great industrial prospects provides a facile and effective strategy to broaden the engineering applications of HDPE materials. Besides, excessive UHMWPE may impair the synergistic enhancement effect, which is also reasonably explained.

Mechanical, dynamic and tribological characterization of HDPE/peanut shell composites

Polymer composites reinforced with natural fibres are more appealing than conventional materials due to their accessibility, renewability, low weight and price, low density, and biodegradability. There are a wide variety of different natural fibres, such as nutshells, flax, and palm, which can be applied as reinforcements or fillers, showing potential as replacements for inorganic fibres. Plastics are often somewhat economical when producing complex shapes, and the possibility of obtaining composite materials with reduced demoulding times, as no chemical reaction is required, makes them very interesting from an industrial point of view. Moreover, polymers are increasingly used for tribologically stressed components, whereby plastic components replace metallic bearings, gear wheels, or sliding elements. In this regard, this work's objective was to produce composites of high-density polyethylene (HDPE) with different proportions (2, 4, 6, 8. and 10 wt%) of peanut shell (PS) filler and evaluate the influence on the dynamic mechanical and tribological properties of the addition of different amounts of filler. The strain (%) increases with fibre contents of 2 and 4 wt%, but at higher fibre contents, a considerable reduction, approximately 4 times for a fibre content of 6 wt% and an even more substantial reduction for fibre contents of 8 wt% and 10 wt%, could be observed. From the Dynamic Mechanical Analysis (DMA) tests, it could be observed that E' is practically constant for composites for all fibre contents between −20 °C and ~50 °C at 1.5 Hz and 10 Hz, which is ~6 times higher than that of neat HDPE under the same conditions. The tribological assays were carried out by the reciprocating sliding wear test with loads of 10, 20, and 30 N. Although the wear rate (k) and wear volume (V) increased with increasing applied load, these values were similar for fibres with different wt% contents. Thus, the addition of fibre does not modify the tribological properties of HDPE. By Raman spectrum analysis, similar intensities and positions of the bands of the HDPE vibrational mode before and after wear tests could be observed.

Application Properties Analysis as a Dielectric Capacitor of End-Of-Life Tire-Reinforced HDPE.

The purpose of the present research is to obtain waste of polymeric composite as an insulator capacitive application. Rubber materials, once they end their useful life, may be difficult to reuse or recycle. At present, research only uses one tire recycling method, which involves grinding and separating steel and fibers from vulcanized rubber, and then using the rubber particles for industrial capacitors. The methodology for this research is to compare the permittivity (ε′ and ε″) between high-density polyethylene (HDPE) and the polymer matrix compound, consisting of an HDPE polymeric matrix blended with end-of-life tire particles (ground tire rubber (GTR)), to analyze the feasibility of using such tires as electrically insulating materials (dielectrics). The incorporation of carbon black in the GTR compounds modifies conductivity; GTRs carry a significant amount of carbon black, and therefore some electrical properties may change significantly compared to highly insulating polymer substrates. The performed experimental study is based on a dynamic electric analysis (DEA) test developed in the frequency range of 10−2 Hz to 3 MHz and at different temperatures (from 35 to 70 °C) of different samples type: HDPE neat and HDPE compounds with 10%, 20% and 40% of GTR loads. A sample’s electrical behavior is checked for its dependence on frequency and temperature, focused on the permittivity property; this is a key property for capacitive insulators and is key for examining the possible applications in this field, for HDPE + GTR blends. Results for the permittivity behavior and the loss factor show different electrical behavior. For a neat HDPE sample, no dependence with frequency nor temperature is shown. However, with the addition of 10%, 20%, and 40% amount of GTR the HDPE compounds show different behaviors: for low frequencies, interfacial polarization relaxation is seen, due to the Maxwell–Wagner–Sillars (MWS) effect, performed in heterogeneous materials. In order to analyze thermal and morphological properties the differential scanning calorimetry (DSC) test and scanning electron microscopy (SEM) have been used. Results obtained show that adding waste tire particles in an HDPE matrix allows HDPE + 40% GTR blends to act as a dielectric in capacitors, increasing the capacitor dielectric efficiency in the low frequencies due to the MWS effect, which increases the dielectric constant.

Effect of waste fillers addition on properties of high-density polyethylene composites: mechanical properties, burning rate, and water absorption

Generally, fillers are added in thermoplastic polymers to enhance their mechanical properties, reduces cost, and improve appearance of the composites. In this paper, high-density polyethylene (HDPE) was compounded with different waste fillers such as silica, kaolin, calcium carbonate, and fly ash with an aim to compare the composite performance and effects of different filler loading. Tensile test, impact test, burning test, and water absorption were used to characterize the HDPE composites. Results show that addition of fillers in HDPE improved the tensile modulus, reduced 14% of the burning rate, and increased water absorption over time, compared to unfilled HDPE. However, tensile strength, impact strength, and elongation at break reduced by 30–50%, 50%, and 98% compared to the neat HDPE, respectively. Addition of calcium carbonate in HDPE shows the best fire retardant, the highest tensile strength, and the longest elongation at break as compared to composites with silica, fly ash, and kaolin.

Influence of processing methods on the mechanical and barrier properties of HDPE-GNP nanocomposites

In order to improve the barrier properties of Graphene nanoPlatelets (GnP)–High-Density PolyEthylene (HDPE) composites made by melt mixing, extra processing steps were investigated (solution mixing prior to melt mixing, cryomilling of the HDPE pellets into a fine powder, coating of the GnP with low molecular weight wax or with a thermoplastic elastomer, and microlayer co-extrusion). The associated mechanical properties were characterized by a flexural test and a notched Izod impact test. The barrier properties were evaluated by the permeation to oxygen. Each method resulted in a different state of dispersion and alignment of the graphene nanoplatelets, leading to a specific evolution of the barrier and mechanical properties. Microlayer co-extrusion led to a better relative improvement of the barrier properties versus neat HDPE. Solution mixing did result in an improvement of the barrier properties only if the composite was not further processed by melt mixing and extrusion. Starting with a fine HDPE powder did improve the barrier properties but affected the flexural properties. Lastly, a coating of the GnP with a thermoplastic elastomer enhanced the resistance to impact and barrier properties, but a coating with wax did not show any improvement.

Passive daytime radiative cooling inorganic-polymeric composite artificial lawn for the alternative to the natural lawn

The natural lawn needs complex maintenance (e.g., fertilizer dressing, manicuring, soil disinfection and disinsection), so the artificial lawn is increasingly desired and applied in the sports arena. However, the most artificial lawns are made of the organic materials, which could accumulate the thermal energy under direct sunlight. The accumulated thermal energy also leads to increasing the temperature of the artificial lawn and its surroundings, which eventually impact the athletic experience. Moreover, an efficient, eco-friendly, and economical technique that can provide the cooling for the artificial lawns without extensive energy input is lacking. Herein, a novel inorganic-polymeric composite for preparing passive daytime radiative cooling artificial lawn using chromium oxide (Cr2O3) particle-embedded high-density polyethylene (HDPE) is demonstrated. By reflecting 50% NIR irradiance and radiating heat through the atmosphere’s long-wave infrared transmission window (LWIR, εLWIR = 0.86), this composite-covered device displayed a temperature of 30.7 °C, much lower than those of HDPE-covered device (43.4 °C) under solar simulator (intensity~0.34 W/cm2). Similarly, this composite exhibits a better cooling effect than the neat HDPE under direct sunlight. Moreover, for further improving the cooling property of the composite, the titanium dioxide (TiO2) was utilized to enhance the reflectance of the HDPE/Cr2O3 composite without affecting the visual effect and thermal emissivity, where the total reflectance increases by 5%. Meanwhile, the outdoor thermal measurement showed that the cooling effect of the HDPE/Cr2O3/TiO2 composite artificial lawn is on a par with that of the natural lawn.

The effect of secondary nanofiller on mechanical properties and formulation optimization of HDPE/nanoclay/nanoCaCO3 hybrid nanocomposites using response surface methodology

AbstractMechanical properties were evaluated in high‐density polyethylene (HDPE) containing plate‐like nanoclay (NC) and particulate nano calcium carbonate (nCaCO3). A two‐step melt mixing method was utilized to prepare nanocomposites withNC/nCaCO3 hybrid content varying from 7 to 15 wt%. Optimization of the morphological, rheological and mechanical characteristics was carried out via Response Surface Methodology by considering nanofiller loadings and compatibilizer (PE‐g‐MA) content as independent variables. The findings revealed that a nanocomposite composed of 9 wt% PE‐g‐MA, 3.5 wt%NC, and 10 wt%nCaCO3 was optimal. This composition exhibited 50% enhancement in Young's modulus and 8% improvement in yield strength over neat HDPE. Despite the reduced impact strength in all of the prepared nanocomposites, the incorporation ofnCaCO3 prevented a sudden decrease in the toughness caused by the nanoclay. Further, the fracture behavior observed by scanning electron microscopy (SEM) images suggested that nCaCO3 activated new toughening mechanisms.

Influence of poly(butylene succinate) and calcium carbonate nanoparticles on the biodegradability of high density-polyethylene nanocomposites

The biodegradation is becoming one of the most imperative properties of plastic products nowadays to promote the sustainable development and the conservation of the environment. In this framework, the main objectives of this study are to prepare an environmental friendly high density polyethylene (HDPE) nanocomposite and investigate the effect of the incorporation of nanoparticles of calcium carbonate (NPCC) and poly butylene succinate (PBS) on the prepared nanocomposites. The nanocomposites of HDPE/PBS/NPCC samples were prepared by the addition of PBS and NPCC at (1, 2 and 4 wt%) to HDPE matrix using the injection molding technique. Morphological, mechanical, thermal, physical and biodegradation analysis were conducted on the nanocomposite samples. The mechanical properties of the samples were improved (the elongation at break by 35%, and the impact strength by 26%) compared to the neat HDPE. Moreover, the thermal and physical properties were enhanced by reinforcement NPCC to the nanocomposites. The biodegradation occurrence in the HDPE nanocomposite samples was proved by the Scanning Electron Microscope (SEM) observations and the weight loss percentage (0.265 wt% after 8 weeks).

Melt rheology and extrudate swell properties of talc filled polyethylene compounds

An experimental study of high-density polyethylene (HDPE) composites filled with talc (0–15 wt.%) was carried out to investigate the rheological properties. The apparent melt viscosity, melt density, and die-swell ratio (B) of the composites were measured at constant shear stress and constant shear rate by using a melt flow indexer and capillary rheometer. The experimental conditions were set to a temperature range from 190 to 220 °C for both apparatuses whereas a load range from 5 to 12.16 kg was selected for melt flow indexer and shear rate range from 1 to 10000 s−1 for capillary rheometer. The initial study showed that the talc particulates did not influence the melt viscosity compared with the neat HDPE but decreased the elasticity of the polymer system. The HDPE/talc systems obeyed power-law model in shear stress–shear rate variations and were shear thinning, meanwhile, the die-swell increased with an increased wall shear rate and shear stress. The melt density of the composites increased linearly with an increase of the filler weight fraction and decreased with the increase of the testing temperature. The talc-HDPE composites showed compressible in the molten state.

Reprocessing of High-Density Polyethylene Reinforced with Carbon Nanotubes

High-density polyethylene (HDPE) was compounded with 3 wt% carbon nanotubes (CNTs). In order to simulate mechanical recycling, both the nanocomposite and neat HDPE were repeatedly extruded and subsequently analysed by tensile tests, Charpy impact strength, differential scanning calorimetry (DSC), oxidation induction time (OIT), Gel Performance Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR) and TEM After 10 cycles of extrusion, thermal, mechanical, and rheological tests did not reveal any significant degradation. In order to better study the effect of the CNTs, a large number of cycles were simulated by processing the materials for up to 200 min. After 200 min of processing, the neat HDPE was significantly degraded whereas the nanocomposite was almost unaffected.

Influence of talc fillers on bimodal polyethylene composites for ground heat exchangers

AbstractIn this study, a commercial grade of talc is used as filler in a bimodal high‐density polyethylene (HDPE) used for the pressure pipe application. The composites are characterized by thermogravimetric analysis (TGA), differential scanning calorimetry, dynamic mechanical thermal analysis, and tensile testing. The results illustrate that the presence of talc has a considerable effect on the material properties and the pipe life‐length. It is presented that the thermal stability measured by TGA is enhanced, while the oxidation induction time decreases in cooperation of the talc. The nucleation behavior of talc particles during crystallization has no obvious effect on melting temperature; however, an increase in crystallization temperature is evidenced. Storage modulus as recorded from the dynamic mechanical analysis is also increased in all composites, furthermore, the temperature of the α relaxation is shifted toward higher temperature and finally the strain hardening modulus for the HDPE/talc composites is assessed and compared to the neat HDPE as a measure of environmental stress crack resistance.

Fabricating a partial wetting structure for improving the toughness of intumescent flame‐retardant HDPE

ABSTRACTA multistep processing method was developed to fabricate a partial wetting morphology for improving toughness of flame retardant polymer. In the first step, high‐density polyethylene (HDPE) and nylon 6 (PA6) were melt‐extruded with intumescent flame retardant (IFR) for fabricating HDPE/PA6/IFR blends with a core–shell structure (core: IFR, shell: PA6). At the second step, maleic anhydride‐grafted‐linear low‐density polyethylene (LLDPE‐g‐MAH) was melted with HDPE/PA6/IFR at processing temperatures slightly below the melting temperature of PA6 to produce a partial wetting morphology in which LLDPE‐g‐MAH phase with the sphere was dispersed at the HDPE/PA6 interface. The effect of the LLDPE‐g‐MAH content on the impact strength was investigated, and high toughness was exhibited in the blend with 2 wt % LLDPE‐g‐MAH. Its elongation at break and notched impact strength were 43 and 270% higher, respectively, than that of neat HDPE. The unique interface failure mode was responsible for the high impact strength. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48735.