High-density Polyethylene Powder Research Articles

Cold spray deposition of high density polyethylene composite powders

In this paper, we investigate the use of the cold spray additive manufacturing technique to deposit micron-sized composite particles of high-density polyethylene (HDPE) compounded with either micron or nanometer sized particles of silicon dioxide (SiO2) or copper (Cu). In this study, the mass fraction of the SiO2 and copper particles added into the final composite powders was varied between 0.5 % and 9.1 % and the deposition efficiency of each composite powder was measured. Deposition of the composite powders onto an HDPE substrate was successful even at the highest particle loadings tested. In each case, an optimal mass fraction of silicon dioxide or copper particles was observed with a maximum value of deposition efficiency larger than that of the pure HDPE. For the silicon dioxide composite powders, the deposition efficiency nearly doubled compared to the pure HDPE powders. The improvement of deposition efficiency at moderate particle loadings is likely due to the increase in the impact kinetic energy of the particles resulting from the increase in the density of the composite powders. While the decrease in deposition efficiency at high particle loadings is likely the result of the increased coverage of the silicon dioxide and copper particles on the surface of the HDPE powders limiting the interaction between the HDPE of the composite powder with the HDPE substrate. SEM images show that it is possible to create a smooth, dense, and uniform thin-film polymer composite coating using cold spray.

Influence of trimodal polymerization on melt rheology, thermal, and mechanical properties of HDPE resin

AbstractTrimodal polymerization of polyethylene has become a research interest in recent years due to its excellent potential for altering material properties and overcoming the limitations of the bimodal process. Here, we have comprehensively investigated the effects of manipulating polymerization parameters, such as split value (SV), hydrogen‐to‐ethylene ratio (H2/C2), and stage switching, on the rheological, thermal, and mechanical properties of synthesized trimodal high‐density polyethylene (HDPE). The synthesized samples were obtained through three consecutive stages in a slurry lab‐scale reactor. The results of molten state analysis demonstrate that recipe modification, particularly SV and H2/C2 balancing in the second and third stages, had a dramatic effect on the rheological properties including dynamic moduli, G′‐G″ crossover, and the shear‐thinning behavior. Concurrently, improvements in physio‐mechanical properties, such as sagging behavior and slow crack growth resistance (SCG), were observed compared to the bimodal resin. The thermal characterization indicates that the polymerization adjustments made did not notably impact the thermal properties of HDPE samples (e.g., Tm), throughout the all‐recipe manipulation. However, minor fluctuations in crystallinity and crystallization kinetics were observed which was presumably attributed to the molecular weight of the final resin. Overall, in our trimodal polymerization recipe, the HDPE powder is within the specified range of particle size distribution, which ensures excellent bulk density and flowability.Highlights Influence of polymerization parameters such as split value, H2/C2, and stage switching in properties of trimodal HDPE. HDPE resin received from split value and H2/C2 balancing have superior SCG and sagging resistance. All HDPE samples synthesized by different recipes have similar thermal properties.

Characterisation of High‐Density Polyethylene (DiaPow HDPE HX R) Powder for Use in Additive Manufacturing

High‐density polyethylene (HDPE) is largely processed using conventional manufacturing techniques. However, there is a need to investigate its processability when fabricated using additive manufacturing (AM) in an effort to use this polymer for high‐end applications, such as the fabrication of human implants. In this regard, the current study investigated the intrinsic and extrinsic properties of HDPE powders (DiaPow HDPE HX R) from Diamond Plastics GmbH, to determine its feasibility of use in powder bed fusion (PBF). Powder characterisation was undertaken using a scanning electron microscope (SEM), melt flow index (MFI) testing, tapped density testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier‐transform infrared (FTIR) spectroscopy, and hot‐stage microscopy. The analysis revealed that this high‐density polyethylene powder is suitable for processing using PBF based on the particle size distribution (PSD) (65–92 μm), flowability (Hausner ratio = 1.22 ± 0.02), melting point range (125.7–135.2 degrees Celsius), enthalpy of melting (170.51 J/g), and thermal stability (the materials starts to degrade at 350.0 degrees Celsius and completely degrades at 500.0 degrees Celsius). It also showed good coalescence behaviour. However, the narrow sintering window (7.9 degrees Celsius) of the material indicates possible challenges of shrinkage and curling during printing. The material was also found to have poor absorptive properties of infrared radiation at 10.6 μm, which might make sintering using CO2 lasers challenging.

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.

Processing and characterization of HDPE and MDPE processed by rotational moulding

Rotational moulding otherwise called as roto moulding is a process used to produce hollow plastic products with nearly stress free objects with the help of a bi axial rotational moulding machine which rotates the mould in two axes with minimum speed of rotation. Plastic granules pulverized into fine powders are used to produce hollow parts such as water tanks, fuel tanks, kayak boats, refrigerated panel etc. The present work investigates the mouldability of High Density Poly Ethylene (HDPE) and Medium Density Poly Ethylene (MDPE) powders by rotational moulding process. A lab model roto moulding machine has been fabricated. There are two rotating frames – an inner and an outer frame – both rotating about two mutually perpendicular axes. The driving torque is given by a motor. The machine was designed to accommodate a rectangular shape stainless steel mould. Both MDPE and HDPE were processed at three different internal air temperature and the mechanical properties were estimated as per ASTM standards. Both tensile and impact strength were observed to be improved by the increase in internal air temperature. Hardness values observed shows no significant effect on internal air temperature. The MDPE products showed higher impact strength while HDPE products showed higher tensile strength. The morphology of the MDPE and HDPE powders and the microstructure of the products were studied under optical microscope.

Effect of carbon black masterbatch and polymer process aids based on fluoroelastomer and hyper branch polymers on melt fracture of bimodal polyethylene

This research has been conducted with the view of the effect of various polymeric processing aids (PPA) on the stick-slip phenomenon in polyethylene compounds. In the extrusion process of thermoplastic polymers, such as polyethylene, for proper and efficient products like wire coatings, pipes, bottles, and films, it is desirable that the final products, gain a smooth surfaces and be polished. In the industry, it is also necessary that the rate of extrusion process is as high as possible, dislike the pressure of this process is as low as possible, so that it can be used for the most part from process machines and thus reduce process costs so much as practical. In this study, MBM and MBR masterbatches (containing 35-40% carbon black) were added to high density polyethylene powder (PE100) and the effect of these masterbatches on the reduction of viscoelastic phenomenon was confirmed. In the next step, three types of PPA with commercial names of Viton, Fx and Daikin with concentrations of 50, 100 and 150 ppm were added to the PE100MBR and PE100MBM compounds to reduce the melt fracture of the samples. The capillary rheometry test determined the quantity changes in the stick-slip phenomenon. The microscopy test also showed qualitatively the changes that occurred in the extrudates. The torque meter test also determined the effect of the PPA on the ampere and the energy consumed by the extruder. Finally, samples were produced with these features due to the importance of reducing energy in the process as well as improving the quality of the extrudates. Depending on the structure of the fluoroelastomer and hyper branch polymers, it has been found that adding these kind of materials has improved processability, and finally the appearance of the product is smoother and polished.

Correction to: Optimization of Cold Spray Deposition of High-Density Polyethylene Powders

We regret that the original article contained an incorrect initial for the first listed author. The name should have been published to read: Trenton P. Bush.

Optimization of Cold Spray Deposition of High-Density Polyethylene Powders

When a solid, ductile particle impacts a substrate at sufficient velocity, the resulting heat, pressure and plastic deformation can produce bonding between the particle and the substrate. The use of a cool supersonic gas flow to accelerate these solid particles is known as cold spray deposition. The cold spray process has been commercialized for some metallic materials, but further research is required to unlock the exciting potential material properties possible with polymeric particles. In this work, a combined computational and experimental study was employed to study the cold spray deposition of high-density polyethylene powders over a wide range of particle temperatures and impact velocities. Cold spray deposition of polyethylene powders was demonstrated across a range broad range of substrate materials including several different polymer substrates with different moduli, glass and aluminum. A material-dependent window of successful deposition was determined for each substrate as a function of particle temperature and impact velocity. Additionally, a study of deposition efficiency revealed the optimal process parameters for high-density polyethylene powder deposition which yielded a deposition efficiency close to 10% and provided insights into the physical mechanics responsible for bonding while highlighting paths toward future process improvements.

Physical and Mechanical Properties of Wood Plastic Composites from Teak Wood Sawdust and High Density Polyethylene (HDPE)

Sawdust is a waste from furnitureindustry which is mostly left in the garbage or burn for landfill in hugequantities every year. Efforts to find utilization of this material haveresulted mostly in low value. However, sawdust waste can be considered as analternative to fabricate fiber reinforced polymer composites for furniturefunction. This study was undertaken to determine the physical and mechanicalproperties of wood plastic composites, which were made under laboratoryconditions by hot pressing of high-density polyethylene (HDPE) with teakwoodsawdust as filler. Seven levels of mixed flour, 10, 20, 30, 40, 50, 60 and 70%,based on the composition by weight was added to the HDPE powder with palm oilas coupling agent. A flat pressing technology, the simplest method for capableof large dimension wood plastic panel production, was used to manufacturetesting specimens in dimensions 5.8 x 7.3 cm2. Investigation of themechanical property of the composites material, according to the Americansociety for testing and materials (ASTM) method, was done by impact strengthtester. The measurement results were found that impact strength was decreased uponthe increasing of the sawdust up to 30 % mixing then gradually increased. However,by increasing mixed flour content, water resistance of the panels wasnegatively influenced. The best appearance of composites material in comparisonwith the natural woods was ~30% sawdust powder mixing. The woodplastic panels were utilized for construction of a Thai spirithouse as an outdoor decoration.

Influence of Particle Size on Optical Constants From Pellets Measured With Terahertz Pulsed Spectroscopy

Particle size is shown to influence both the overall value and the measurement precision of the refractive index and absorption coefficient of a sample diluted with high density polyethylene (HDPE) powder and compressed in a pellet. However, excessive grinding of a sample before it is mixed with HDPE powder can result in the formation of large particle clusters. These aggregates can induce internal scattering of the terahertz pulse within the pellet as well as lead to different mechanical properties of the pellet, which may change the distribution of air pores. These phenomena result in extracted optical constants with low accuracy and precision. The present work introduces a simple experimental procedure to improve the precision and accuracy of optical constants from spectroscopic pellets. This procedure consists of moderately grinding the sample powder in fine HDPE powder with a pestle and mortar. The standard deviation of the refractive index of Prussian blue has been observed to reduce from 0.14 to 0.02 following this procedure.

Preparation and properties of wood plastic composite reinforced by ultralong cellulose nanofibers

Wood plastic composites (WPCs) were reinforced by ultralong cellulose nanofibers (CNF), which were extracted from poplar flour. To solve the aggregate problem of CNF in nonpolar high density polyethylene (HDPE), a new method, which was corresponding to preblending the mixture of wood flour and HDPE powder in the CNF suspension with continuously stirring at 80°C for 2 h was used before the extrusion process. The capillary rheological tests showed CNF could increase the apparent viscosity of WPCs obviously. From the SEM images, abundant CNF were distributed on the fracture surface of WPCs uniformly and compactly like “spider web.” Compared with WPC without CNF, the bending strength, bending modulus, and impact strength of WPCs with 20 wt% CNF increased by 93.01, 153.64, and 116.55%, respectively. The thermal expansion coefficient of WPCs with 20 wt% CNF decreased by 61.30%. The storage modulus of WPCs was greatly improved with the addition of CNF. POLYM. COMPOS., 37:1206–1215, 2016. © 2014 Society of Plastics Engineers

Polymer Powder Treatment in Atmospheric Pressure Plasma Circulating Fluidized Bed Reactor

The surface activation of high-density polyethylene powder using a remote plasma process at atmospheric pressure is investigated. The developed circulating fluidized bed plasma reactor enables to carry fine-grained powder particles repetitively through the afterglow of 64 dielectric barrier discharges of argon with O2 and CO2 admixtures. The evolution of particle size distribution during conveying in the reactor is monitored by laser diffraction and reveals that only a small particle fraction is lost during the process. The contact angle of activated powder samples steadily decreases with increasing treatment time. The surface activation is most effective for O2 admixtures of 0.25 vol% and CO2 admixtures of above approximately 1 vol%, respectively.

Phase change materials based on high-density polyethylene filled with microencapsulated paraffin wax

A modified in situ polymerization microencapsulation procedure for the preparation of microcapsules with paraffin wax cores (43wt.%) and melamine–formaldehyde resin shells having a uniform size distribution and a spherical shape with average diameters of approximately 15μm was developed. The high-density polyethylene/microcapsule blends were prepared via two routes. In the first case, the dry high-density polyethylene powder covered by microcapsules was simply hot pressed, whereas, in the second case, the dry high density polyethylene/capsule powder was first blended in the molten state to obtain better homogeneity before hot pressing. It was observed that both systems behave qualitatively the same with comparable mechanical properties and thermal behavior.The thermal stability of high-density polyethylene/microcapsule blends characterized by thermogravimetry is significantly lower than that of neat high-density polyethylene. The selected characteristic temperatures of degradation decreased by more than 200°C compared with the related temperatures for neat high-density polyethylene.An analysis based on Differential Scanning Calorimetry revealed separated melting and crystallization behavior of wax within the capsules and high density polyethylene in the blends. The enthalpies of melting and crystallization are proportional to the amount of individual components in the material. The capsules have a strong plasticizing effect on the high density polyethylene, resulting in a significant decrease in the melting and crystallization temperatures. The plasticizing effect was also confirmed by measurements of the tensile mechanical properties and rheological behavior.

고밀도 폴리에틸렌 분진의 열분해성과 착화에너지

Abstract - The aim of this work is to provide new experimental data on t he pyrolysis character-istics and the minimum ignition energy (MIE) by using the same high-density polyethylene (HDPE) powder in domestic HDPE dust explosion accident. To eval uate the explosion sensitivity of HDPE, thermo-gravimetric analysis (TGA), differential scanning calorimeter (DSC) and MIE ap-paratus (MIKE-3, Kuhner) was conducted. The measurements showed the volume median diameter of 61.6 μm but the particle number density of 98 % in the range 0.4~4 μm. The ignition temper-ature from the results of TGA and DSC in HDPE dust layers was observed in the range of 380~490 ℃. MIE was measured under 1 mJ in the HDPE dust concentration of 1200~1800 g/m 3 , it was found that the ratio of particle number density in the range 0.4~4 μm was very high (98%). Key words : high-density polyethylene powder, dust explosion, pyrolysis, minimum ignition en-ergy 1) † Corresponding author:hanpaule@kosha.or.kr Copyright ⓒ 2014 by The Korean Institute of Gas

Physical and mechanical properties of flat pressed HDPE composite filled with a mixture of bagasse/rice husk

Rice husk and bagasse are two by-product from agriculture and the sugar cane industry that have been produced in huge quantities every year. Flat pressing technology can be considered an alternativeto produce large dimension wood plastic panels. This study was undertaken to determine the physical and mechanical properties of wood plastic composites, which were made under laboratory conditions by hot pressing using high-density polyethylene (HDPE) and some agriculture wastes (bagasse/rice husk) as filler. Four levels of mixed flour, 30, 40, 50, and 60 %, based on the composition by weight, we remixed with the HDPE powder without using coupling agent. A conventional flat-press was used to manufacture testing specimens in dimension 35 × 35 × 1 cm at 1 gr/cm3 density. The modulus of elasticity of the panels increased with the increase in lignocellulosic fiber content. Modulus of rapture for all panels increased as the HDPE content increased. Formulations with increasing mixed flour were found to have a higher swelling thickness and water absorption after 2 and 24 h. As expected, by the increasing mixed flour content, water resistance of the panels was negatively influenced.

The effect of melt flow index, melt flow rate, and particle size on the thermal degradation of commercial high density polyethylene powder

The powder of EX5 grade of high density polyethylene—without any additives—manufactured by Amirkabir petrochemical company was separated by shaker equipment. The separated powder of average diameter ~25, ~62.5, ~87.5, ~112.5, ~137.5, ~175 and the particles >200 μm was tested by a thermogravimetric (TG) analysis instrument in nitrogen atmosphere and heating rates of 10, 20, and 30 °C min−1. In addition, the separated powders were analyzed by a melt flow index (MFI) instrument, and the viscosity average molecular mass (Mv) of the powders was tested by a viscometer. Kinetic evaluations were performed by Friedman and Kissinger analysis methods and apparent activation energy for the overall degradation of the powders was determined. The effects of molecular mass, MFI, MFR, and particle size on the degradation TG curve, derivative thermogravimetry curve breadth, and activation energy of thermal degradation were considered. The results showed that the Mv of EX5 pipe grade produced by two serial reactors is increased by increasing of the particle size and, MFI is decreased with a little deviation by particle size increasing. The particle size has no obvious effect on the melt flow rate (MFR), and MFR as function of molecular mass distribution does not change very much. The results showed that the powder with bigger particles and higher molecular mass moderately increases the activation energy and shifts the degradation curve to the higher temperatures.

The influence of pore formers on the microstructure of plasma-sprayed NiO–YSZ anodes

Four types of pore formers: high-density polyethylene (HDPE), polyether-ether-ketone (PEEK), mesocarbon-microbead (MCMB) carbon powder, and baking flour, are processed and characterized, then incorporated with NiO–YSZ nano-agglomerate powder to produce plasma sprayed SOFC anode coatings. Scanning electron microscopy (SEM) of the coating microstructure, gas permeability measurements, and porosity determinations by image analysis are used to evaluate the effectiveness of each potential pore former powder. Under the spray conditions studied, the flour and MCMB pore former powders are effective as plasma sprayed pore formers, increasing the permeability of the coatings by factors of four and two, respectively, compared to a similarly sprayed NiO–YSZ coating without pore formers. The HDPE powder is unable to survive the plasma spray process and does not contribute to the final coating porosity. The PEEK pore former, though ineffective with the current powder characteristics and spray parameters, exhibits the highest relative deposition efficiency and the most favorable thermal characteristics.

Structure and adhesion properties of acrylic acid grafted high‐density polyethylene powders synthesized by a novel photografting method

AbstractA novel photografting, nonvapor, and nonliquid phase living graft polymerization was developed to functionalize high‐density polyethylene (HDPE) powder. The structure and adhesion properties of HDPE powder grafted with acrylic acid (AA) were studied by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), water contact angle, peel strength, and graft degree measurements. The result shows that HDPE powder can be grafted with AA via the method with a short reaction time and a high monomer conversion. The graft degree increases with the reaction time. Then, the hydrophilicity of the grafted HDPE powder increases also. The peel strength of HPDE/steel joint improved significantly when acrylic acid grafted HPDE powder was used as hot melt adhesive in place of ungrafted HDPE powder. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Processing and physical properties of native grass‐reinforced biocomposites

AbstractBig blue stem grass fiber‐reinforced high density polyethylene powder biocomposites were fabricated using two separate processing schemes: (1) by compounding biofiber with the thermoplastic powder in an extruder and subsequently injection molding the extrusion pellets and (2) by combining biofiber and the powder thermoplastic powder using a modified sheet molding compounding (SMC) line and subsequently compression molding the sheet material. The physical properties including storage modulus, heat deflection temperature (HDT), notched Izod impact strength, and morphology were evaluated with dynamic mechanical analysis, Izod impact strength measurement, and microscopy observation. It was found that compression‐molded specimens achieved similar modulus values to injection molded specimens for grass‐reinforced high density polyethylene (HDPE) composites. The stiffness of the compression‐molded specimens is related to the consolidation state of the samples, which depends on compression molding conditions such as temperature, pressure, and mold type. Compression‐molded specimens exhibited a higher HDT and notched Izod impact strength compared to injection‐molded samples. Grass fiber‐reinforced cellulose acetate butyrate (CAB) biocomposites made with SMC processing had similar physical properties with grass fiber‐reinforced HDPE composites, which indicates that natural fiber‐reinforced CAB biocomposites have the potential to replace polyolefin‐based composites for automotive applications. POLYM. ENG. SCI. 47:969–976, 2007. © 2007 Society of Plastics Engineers.

Evaluation of the Internal Particle Morphology in Catalytic Gas-Phase Olefin Polymerization Reactors

An unsteady-state diffusion model is developed to calculate the transport of penetrant molecules in semicrystalline nonporous polyolefin films and porous powders in terms of the internal particle morphology (i.e., pore size distribution and crystallinity) of the polymer. To calculate the diffusion coefficient of penetrant molecules in a semicrystalline nonporous polymer matrix, the free volume theory is employed. Moreover, to calculate the diffusion coefficient of penetrant species in a porous polymer matrix, a dual diffusion model, accounting for the molecular diffusion of penetrant in the pores and the amorphous polymer phase, is developed. A novel experimental setup, comprising a gravimetric magnetic suspension microbalance connected in series with an optical view cell, is employed to carry out dynamic sorption/swelling experiments of ethylene and propylene in both nonporous films and porous high-density polyethylene (HDPE) powders. Experimental sorption measurements, along with the developed unsteady-state diffusion model, are then employed to calculate the diffusion coefficient of R-olefins in porous and nonporous semicrystalline HDPE as well as the overall porosity of HDPE powders. Finally, to reconstruct the pore size distribution in a porous polyolefin particle in terms of the estimated overall particle porosity and the size distribution of the microparticles, a diffusionlimited aggregation (DLA) model is developed. It is shown that the morphological characteristics of porous polyolefin particles (i.e., porosity and pore size distribution) can be described using the proposed DLA model in terms of the size distribution of the microparticles and the extent of microparticles fusion.