High-density Polyethylene Surface Research Articles

Large-area fabrication and applications of patterned surface with anisotropic superhydrophobicity

Recently, anisotropic superhydrophobic surfaces have aroused much attention due to their promising applications. However, large-area fabrication of low-cost superhydrophobic surfaces with obvious anisotropicity is still a huge challenge. In this work, a home-made melt hot-pressing method was proposed to facilely fabricate aligned micro-patterns on high-density polyethylene surface. Such surface displays anisotropic superhydrophobic characteristic with a static water contact angle of 152°and 145° respectively in parallel and perpendicular direction. Moreover, it has low surface adhesion and decent mechanical stability, showing promising applications for hydraulic triboelectric generator with self-cleaning ability, milk residue reduction and drag reduction. Considering the facile fabrication process and inexpensive thermoplastic polymer used, this study not only provides the possibility of large-area and low-cost preparation of orderly patterned surfaces with anisotropic superhydrophobicity, but also opens a new pathway toward wide application of anisotropic superhydrophobic surface.

Thermal Stability and Flame Resistance of the Coextruded Wood-Plastic Composites Containing Talc-Filled Plastic Shells

Talc is a popular filler for the fabrication of plastic composites. The presence of talc helps improve mechanical, thermal, and flame resistance properties of the composite. In this work, we report the influence of a talc-filled plastic shell layer on thermal stability and fire flammability of the core-shell structured wood high-density polyethylene (HDPE) composites manufactured through coextrusion. The result showed that morphological analysis of the char layer after combustion confirmed the formation of a continuous surface char layer with talc addition in the composites, helping block fire penetration and enhance overall fire resistance of the composites. The shell thickness averaged at 1.0±0.2 mm, which represents a fair thick shell over a 10 mm thick WPC core layer. The surface of regular wood-filled HDPE showed large cracks, allowing more rapid fire penetration and reducing its fire resistance. At 800°C, average residual weight for all composite was 21.5±13.8%, most of which was attributed to the inorganic nonvolatile talc components. With the increase of talc level, THR values of coextruded WPC decreased from 302.47 MJ/m2 (5 wt% of talc) to 262.96 kW/m2 (50 wt% of talc). When talc content in the shell layer was less than 25 wt%, the flame resistance properties were slightly enhanced compared with the composites containing unmodified HDPE shells. When talc content in the shell exceeded 25 wt%, the composite’s total heat release and its rate substantially decreased.

Facile Fabrication of Biomimetic Water Pinning Microstructures on Polyethylene Surfaces with Robust Superhydrophobic Wetting State

Applying hot-embossing technology, a simple and cost-effective method for the fabrication of microstructured High Density Polyethylene (HDPE) surfaces with a robust superhydrophobic wetting state is proposed. Micro-meshes and micro-grooves in the flexible template are filled by the PE melt in the hot embossing process. Subsequently, a two-stage microstructure on the PE film surface is formed. This PE film exhibits a contact angle of 151.8° ± 2° and roll-off angle of > 90° when a 5 µL water droplet is dropped on its surface. Water pinning ability on the surface is figured out and roll-off angles are as a quadratic function of specified water droplet volume. Specifically, a 356 µN water pinng force appears on the HDPE film due to the solid-vapor composite interface on its surface. Meanwhile, self-cleaning and immersion tests reveal that the HDPE surface with micro-pillars exhibit robust Cassie impregnating wetting state against external pressure. The proposed method for facial fabrication of microstructured surfaces is an appropriate candidate for the development of droplet manipulation and functional biomimetic polymer surfaces.

Robust Hybrid Hydrophilic Coating on a High-Density Polyethylene Surface with Enhanced Mechanical Property.

Acoustic aeration on a sonochemical surface could have a major impact on sensitivity because of the serious reflection/scattering of sound waves. Recently, we found that the trapped air in the crevices can be reduced by covering the surface with a hydrophilic coating, thus preventing the bubble formation upon ultrasound agitation. Here, we developed an epoxy-based hybrid polymer coating that shows greatly enhanced mechanical adhesion on a high-density polyethylene (HDPE) surface. The strong bonding of C-O-C and the benzene ring as the backbone ensures excellent mechanical strength, and the hydrophilic polar groups of -OH/-NH2 on dopamine display bubble suppression. The existing -OH groups in the cross-linked matrix, which is constructed by adding the monomer PEGMA and cross-linker PEGDA, form a strong chemical bond with the HDPE surface via dehydration, which largely enhanced the adhesion force. The coated HDPE surface maintained a low contact angle of less than 45°, which is the critical angle for avoiding bubbles, after a long period period of abrasion cycling of 160 times under 9.8 kPa pressure. The coated HDPE surface displayed excellent bubble removal performance under ultrasound agitation from room temperature to 60 °C. The strengthened mechanical adhesion of the epoxy-based hydrophilic coating displays extensive applications on a variety of surfaces for acoustic bubble removal.

Surface patterning of high density polyethylene by oblique argon ion irradiation

Oblique ion beam induced spontaneous patterning opens up a simple and inexpensive route to fabricate useful nanoscale textured materials that have important implications in biosensors, optoelectronic devices, templates for liquid crystal orientation, etc. In this regard, the evolution of patterns over high density polyethylene surfaces induced by 100 keV Ar+ irradiation at off normal incidences of 30°, 40°, and 50° with a fluence of 5 × 1016 Ar+ cm−2 has been investigated. Structural modifications have been analyzed using high resolution X-ray diffraction. An increase in crystallite size and a decrease in parameters such as dislocation density (δ), microstrain (ϵ), and distortion (g) have been observed after oblique Ar+ irradiation with an increase in the angle of incidence from 30° to 40°. Atomic force microscopy analysis revealed that the wavelength of ripplelike patterns decreases from 3.19 μm to 2.51 μm, while its amplitude increases from 77.4 nm to 101 nm with an increase in the angle of incidence from 30° to 40°. Similarly, with an increase of oblique incidence to 40°, the root mean square (Rq) and average surface roughness (Rav) have been found to increase. These results are accredited to the curvature dependent sputtering and smoothing processes at oblique incidences. The possible correlation between ion beam sputtering induced patterning and the structural modification in the matrix has been established and discussed.

Improving the adhesion of glass/polypropylene (glass-PP) and high-density polyethylene (HDPE) surfaces by open air plasma treatment

The objective of this study was to investigate the bonding between glass reinforced polypropylene (glass-PP) and high-density polyethylene (HDPE) surfaces. As glass-PP and HDPE surfaces possess low surface energy inherently, atmospheric plasma treatment enhances the adhesion characteristics between the surfaces by increasing their surface energies. Both the materials were subjected to atmospheric/air plasma by varying parameters such as plasma intensity and number of treatments. Optimal plasma treatment conditions were determined based on the bond strength of the materials. Various characterization techniques such as FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), DSC (differential scanning calorimetry) and surface energy determination via wettability inks, were employed to understand the surface modification following plasma treatment. Furthermore, the effect of plasma treatment on glass-PP surface versus a neat polypropylene (neat PP) surface was characterized to understand and establish a baseline. Improvement in bond strength of glass-PP-HDPE panels was observed, GΙc (Mode 1 interlaminar fracture toughness) value of glass-PP- HDPE panels increased from 0.1 N/mm to 5.5 N/mm (after plasma treatment) whereas, the GΙc value of neat PP- HDPE panels increased from 0.4 N/mm to 2.8 N/mm (after plasma treatment). Enhancement in the surface energy of glass-PP and HDPE surfaces was observed, surface energy of glass-PP increased from 28 mN/m to 58 mN/m and the surface energy of HDPE surface increased from 28 mN/m to 72 mN/m.

Synergetic effect of cross-linking and interfacial interaction in carbon fiber reinforced thermoplastic to enhance its tensile strength by electron-beam irradiation

A carbon fiber reinforced thermoplastic (CFRTP) was irradiated with a high energy electron-beam. As a result, the tensile strength of high-density polyethylene (HDPE)-based CFRTPs was significantly improved by gradually increasing the electron-beam dose. It was confirmed that the adhesion between CF and HDPE was improved and the surface properties of CF and HDPE were readily modified by electron-beam. It was verified from spectroscopic analysis that various oxygen-containing functional groups were formed on the surface of CF and HDPE by irradiation and we believe that strong attractive interactions took place among these functional groups at the interface of CFs and HDPE. Finally, it was conclusive that electron-beam irradiation provided two main effects on CFRTPs. One was cross-linking of thermoplastic resin for efficient load transfer from resin to CF and the other was formation of surface functional group and attractive interaction of these functional groups at the interface of fiber and matrix. These two effects showed synergetic contribution to enhance the mechanical properties of CFRTP.

On investigation of rheological, mechanical and morphological characteristics of waste polymer-based feedstock filament for 3D printing applications

In this study, a novel route for the preparation of feedstock filaments for fused deposition modelling from recycled high-density polyethylene (HDPE) and low-density polyethylene (LDPE) waste polymers has been explored. For improving the properties of HDPE/LDPE-recycled polymers, Fe powder has been reinforced through single-screw extrusion. It has been observed that Fe powder (from 0 wt% to 25 wt%) in the LDPE and HDPE matrices has shown increasing trend in melt flow index. Furthermore, Fe powder reinforcement resulted in 36.66% improvement in hardness of reinforced HDPE polymer and 64% in LDPE. Mechanical properties (peak elongation, peak strength, break strength and shore D hardness (SDH)) have been improved significantly with the addition of 6 wt% and 10 wt% reinforcement of Fe powder in the matrix of LDPE and HDPE, respectively. The results of study suggest that morphological properties, such as SDH and percentage porosity, have direct relation with mechanical properties as it has been found that the sample with better mechanical properties was also having high hardness and low porosity. Scanning electron microscopy and energy-dispersive X-ray spectroscopy have been performed on 3D printed functional parts and it has been observed that highly dense texture of HDPE and low surface roughness resulted in better mechanical properties.

Acoustic Bubble Suppression by Constructing a Hydrophilic Coating on HDPE Surface.

Ultrasonic bubbles on the solid surface of various sonochemical devices largely affect signal resolution due to the serious reflection/scattering of sound waves. The Laplace pressure of the cavitation bubble can be tuned by constructing an ultrathin hydrophilic layer, which leads to the solvation or pinching off of the bubbles from the surface. In this article, we successfully coated a polydopamine polymer layer on the high-density polyethylene (HDPE) surface. The formed hydrophilic layer with a contact angle of less than 45° almost completely eliminates the bubbles in both water and 32.5 vol % diesel exhaust fluid solutions upon sonication, which results in the operation of the piezoelectric sensor over 500 h, while the sensor with pure HDPE only ran for less than 2 h. Further, the coated sensors showed high stability under the temperatures of 60-80 °C. An improved mechanical property was confirmed via abrasion test, enabling long-term stability in harsh environments, including acidic urine and ultrasonic agitation. The acoustic bubble suppression via the hydrophilic polymer coating on HDPE surface displays broad applications, particularly with acoustic sensors, sonobuoys, and nondestructive surface detection in sonochemistry.

Tissue response to porous high density polyethylene as a three-dimensional scaffold for bone tissue engineering: An experimental study

High density polyethylene (HDPE) is a synthetic biomaterial used as a three-dimensional scaffold for bone defect reconstruction. Reports differ with regard to its biological response, particularly its osteoconductive capacity. The aim of the present work was to histologically and histomorphometrically evaluate tissue response to porous HDPE. An in vivo study was conducted in rat tibia to evaluate osteogenic capacity, angiogenesis, inflammatory response, and the presence of multinucleated giant cells 14 and 60 days post-biomaterial implantation. Histological examination 14 days post-implantation showed fibrovascular tissue inside pores and on the surface of porous HDPE, acute inflammatory response, scant multinucleated giant cells (MNGCs), and lamellar bone in contact with the biomaterial. An increase in the proportion of lamellar bone tissue, no inflammatory response, and a decrease in the number of MNGCs were observed at 60 days. The histomorphometric study showed a significant time-dependent increase both in the area of bone tissue formed in contact with the porous HDPE (14d: 24.450 ± 11.623 µm2 vs. 60d: 77.104 ± 26.217 µm2, p < 0.05) and in the percentage of bone tissue in contact with the porous HDPE (osseointegration). A significant decrease in the number of MNGCs was also observed at 60 days post-implantation. Porous HDPE showed adequate osteoconductive properties, and only caused an initial inflammatory response. Although this biomaterial has traditionally been used juxtaosseoulsy, its adequate osteoconductive properties broaden the scope of its application to include intraosseous placement.

EFFECT OF ADDING BORON CARBIDE (B4C) TO POLYMER FOR PRODUCING SURFACE COMPOSITE BY FRICTION STIR PROCESSING

Friction stir processing (FSP) is a new solid state technique, it is employed for theimprovement of the mechanical properties of a material and the production of surface layercomposites instead of conventional processing technologies. This research aims to study theability of applying Friction Stir Processing (FSP) to modify the surface of high densitypolyethylene (HDPE) reinforcing by B4C with a particle size of 0.4?m, Groove in themiddle of HDPE surface made to fill by B4C. Varity in the groove depth (0.6, 1.2 and1.8)mm used according to B4C ratio on HDPE substrate particles. Friction stir process wascarried out, using tool with cylindrical shape of pin and shoe tool to produce surface layercomposite. The effect of processing parameters including rotational and transverse speeds onthe mechanical properties of composite layer was studied. Wear test results show apronounced improvement in wear resistance of HDPE surface through reinforcementadditions of B4C at a ratio (5%, 10% and 15% ), where wear rate improved by (60%, 71%and 63%) respectively, as compared with as received HDPE, the surface compositeHDPE/B4C have good wear resistance. Hardness test results indicate that the hardness ofcomposite layer reinforced with (5%,10% and 15%) particles improved by( 26%, 35% and28% )respectively as compared with received HDPE. OM revealed that high tool rotationalspeed resulted in homogeneous distribution of B4C particles and vice versa.

Migration and performance of erucamide slip additive in high‐density polyethylene bottle caps

ABSTRACTDiffusion of erucamide and their morphology on surface characteristics of high‐density polyethylene (HDPE) screw caps depend on storage conditions. Erucamide performance relies on its amount, distribution, and consistency on the surface of HDPE. Specific application and removal torques can be achieved by controlling the amount of erucamide on the surface. The surface amount and the torque increased to an optimum level at 38 and 50 °C within 120 hours of incubation, while they remained unchanged for lower temperatures. Erucamide diffused to the surface and formed flat plate‐like crystal structures at similar time and temperature. These flat‐plates can slide over each other and provide the slip required to decrease the torque. An increase in contact angle demonstrated that hydrophobic hydrocarbon‐chains of amide slip additives were oriented toward the air interface. An optimum surface amount of erucamide for proper sealing torque could be produced at a different combination of storage time and temperature. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46822.

Surface Spectroscopic Signatures of Mechanical Deformation in High-Density Polyethylene (HDPE).

High-density polyethylene (HDPE) has been extensively studied, both as a model for semi-crystalline polymers and because of its own industrial utility. During cold drawing, crystalline regions of HDPE are known to break up and align with the direction of tensile load. Structural changes due to deformation should also manifest at the surface of the polymer, but until now, a detailed molecular understanding of how the surface responds to mechanical deformation has been lacking. This work establishes a precedent for using vibrational sum-frequency generation (VSFG) spectroscopy to investigate changes in the molecular-level structure of the surface of HDPE after cold drawing. X-ray diffraction (XRD) was used to confirm that the observed surface behavior corresponds to the expected bulk response. Before tensile loading, the VSFG spectra indicate that there is significant variability in the surface structure and tilt of the methylene groups away from the surface normal. After deformation, the VSFG spectroscopic signatures are notably different. These changes suggest that hydrocarbon chains at the surface of visibly necked HDPE are aligned with the direction of loading, while the associated methylene groups are oriented with the local C2v symmetry axis roughly parallel to the surface normal. Small amounts of unaltered material are also found at the surface of necked HDPE, with the relative amount of unaltered material decreasing as the amount of deformation increases. Aspects of the nonresonant SFG response in the transition zone between necked and undeformed polymer provide additional insight into the deformation process and may provide the first indication of mechanical deformation. Nonlinear surface spectroscopy can thus be used as a noninvasive and nondestructive tool to probe the stress history of a HPDE sample in situations where X-ray techniques are not available or not applicable. Vibrational sum-frequency generation thus has great potential as a platform for material state awareness (MSA) and should be considered as part of a broader suite of tools for such applications.

A directional entrapment modification on the polyethylene surface by the amphiphilic modifier of stearyl-alcohol poly(ethylene oxide) ether

A novel entrapment modification method involving directional implantation of the amphiphilic modifier of stearyl-alcohol poly(ethylene oxide) ether (AEO) into the high-density polyethylene (HDPE) surface is proposed. This modification technique allows the AEO modifier to be able to spontaneously attain and subsequently penetrate into the swollen HDPE surface with its hydrophobic stearyl segment, while its hydrophilic poly(ethylene oxide) (PEO) segment spontaneously points to water. The AEO modifier with a HLB number below 8.7 was proved appropriate for the directional entrapment, Nevertheless, AEOs with larger HLB numbers were also effective modifiers in the presence of salt additives. In addition, a larger and hydrophobic micelle, induced respectively by the AEO concentration above 1.3 × 10−2 mol/L and the entrapping temperature above the cloud point of AEO, could lead to a sharp contact angle decline of the modified surface. Finally, a hydrophilic HDPE surface with the modifier coverage of 38.9% was reached by the directional entrapment method, which is far larger than that of 19.2% by the traditional entrapment method.

Biodegradation of thermally treated high-density polyethylene (HDPE) by Klebsiella pneumoniae CH001.

Biodegradation of plastics, which are the potential source of environmental pollution, has received a great deal of attention in the recent years. We aim to screen, identify, and characterize a bacterial strain capable of degrading high-density polyethylene (HDPE). In the present study, we studied HDPE biodegradation using a laboratory isolate, which was identified as Klebsiella pneumoniae CH001 (Accession No MF399051). The HDPE film was characterized by Universal Tensile Machine (UTM), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Atomic Force Microscope (AFM) before and after microbial incubation. We observed that this strain was capable of adhering strongly on HDPE surface and form a thick biofilm, when incubated in nutrient broth at 30°C on 120rpm for 60days. UTM analysis showed a significant decrease in weight (18.4%) and reduction in tensile strength (60%) of HDPE film. Furthermore, SEM analysis showed the cracks on the HDPE surface, whereas AFM results showed an increase in surface roughness after bacterial incubation. Overall, these results indicate that K. pneumoniae CH001 can be used as potential candidate for HDPE degradation in eco-friendly and sustainable manner in the environment.

Application of advanced sampling and analysis methods to predict the structure of adsorbed protein on a material surface.

The use of standard molecular dynamics simulation methods to predict the interactions of a protein with a material surface have the inherent limitations of lacking the ability to determine the most likely conformations and orientations of the adsorbed protein on the surface and to determine the level of convergence attained by the simulation. In addition, standard mixing rules are typically applied to combine the nonbonded force field parameters of the solution and solid phases the system to represent interfacial behavior without validation. As a means to circumvent these problems, the authors demonstrate the application of an efficient advanced sampling method (TIGER2A) for the simulation of the adsorption of hen egg-white lysozyme on a crystalline (110) high-density polyethylene surface plane. Simulations are conducted to generate a Boltzmann-weighted ensemble of sampled states using force field parameters that were validated to represent interfacial behavior for this system. The resulting ensembles of sampled states were then analyzed using an in-house-developed cluster analysis method to predict the most probable orientations and conformations of the protein on the surface based on the amount of sampling performed, from which free energy differences between the adsorbed states were able to be calculated. In addition, by conducting two independent sets of TIGER2A simulations combined with cluster analyses, the authors demonstrate a method to estimate the degree of convergence achieved for a given amount of sampling. The results from these simulations demonstrate that these methods enable the most probable orientations and conformations of an adsorbed protein to be predicted and that the use of our validated interfacial force field parameter set provides closer agreement to available experimental results compared to using standard CHARMM force field parameterization to represent molecular behavior at the interface.

Characterization and Lifetime Estimation of High Density Polyethylene Containing a Prodegradant Agent

High density polyethylene (HDPE) samples, containing different concentrations of prodegradant additive d2w®, were prepared. The properties of the samples were evaluated through differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), rheometry, and scanning electron microscopy (SEM). The work contributes to decreasing the products made of non-biodegradable polymeric materials derived from fossil sources which are have become a problem due to their increasingly inappropriate disposal and long degradation time in the environment. The obtained results indicated that there was no degradation of the samples due to processing. No significant changes in melting temperature, crystallinity, viscoelastic behavior, molecular weight and chemical composition were observed. Images from SEM analysis showed particles on HDPE surface, attributed to prodegradant additive d2w®. Oxidation Onset Temperature (OOT) results showed that the additive d2w® accelerated the degradation of HDPE. The activation energy (Ea) was determined by Ozawa-Wall-Flynn method. The obtained values were used for lifetime estimation of the samples. At 25°C, HDPE with d2w® showed a lifetime 50% higher than that of HDPE without this additive. This fact is attributed to the presence of stabilizers in masterbatch d2w® and the absence of oxygen in thermogravimetric analysis.

Improved Bond Strength of Cyanoacrylate Adhesives Through Nanostructured Chromium Adhesion Layers.

The performance of many consumer products suffers due to weak and inconsistent bonds formed to low surface energy polymer materials, such as polyolefin-based high-density polyethylene (HDPE), with adhesives, such as cyanoacrylate. In this letter, we present an industrially relevant means of increasing bond shear strength and consistency through vacuum metallization of chromium thin films and nanorods, using HDPE as a prototype material and cyanoacrylate as a prototype adhesive. For the as received HDPE surfaces, unmodified bond shear strength is shown to be only 0.20 MPa with a standard deviation of 14 %. When Cr metallization layers are added onto the HDPE at thicknesses of 50 nm or less, nanorod-structured coatings outperform continuous films and have a maximum bond shear strength of 0.96 MPa with a standard deviation of 7 %. When the metallization layer is greater than 50 nm thick, continuous films demonstrate greater performance than nanorod coatings and have a maximum shear strength of 1.03 MPa with a standard deviation of 6 %. Further, when the combination of surface roughening with P400 grit sandpaper and metallization is used, 100-nm-thick nanorod coatings show a tenfold increase in shear strength over the baseline, reaching a maximum of 2.03 MPa with a standard deviation of only 3 %. The substantial increase in shear strength through metallization, and the combination of roughening with metallization, may have wide-reaching implications in consumer products which utilize low surface energy plastics.

Bacterial repopulation of drinking water pipe walls after chlorination

The short-term kinetics of bacterial repopulation were evaluated after chlorination of high-density polyethylene (HDPE) colonized with drinking water biofilms and compared with bare HDPE surfaces. The effect of chlorination was partial as a residual biofilm persisted and was time-limited as repopulation occurred immediately after water resupply. The total number of bacteria reached the same levels on both the bare and chlorinated biofilm-fouled HDPE after a seven-day exposure to drinking water. Due to the presence of a residual biofilm, the hydrophobicity of chlorinated biofilm-fouled surface exhibited much lower adhesion forces (2.1 nN) compared to bare surfaces (8.9 nN). This could explain the rapid repopulation after chlorination, with a twofold faster bacterial accumulation rate on the bare HDPE surface. γ-Proteobacteria dominated the early stages of repopulation of both surfaces and a shift in the dominance occurred over the colonization time. Such observations define a timescale for cleaning frequency in industrial environments and guidelines for a rinsing procedure using drinking water.

The effect of CH4/H2 ratio on the surface properties of HDPE treated by CHx ion beam bombardment

The surface of high density polyethylene (HDPE) substrate was bombarded by the CH[Formula: see text] group ion beam, which was generated by the mixture of CH4/H2. Varying the CH4/H2 ratio, HDPE surfaces with different chemical bond structures and properties were obtained. Raman and XPS results show that [Formula: see text] and [Formula: see text] bond structures are formed at HDPE surface bombarded by CH[Formula: see text] group ions. The [Formula: see text] bond fraction at bombarded HDPE surface depends on the H2 ratio in CH4/H2 mixture, because the H ion/atom/molecule can improve the growth of [Formula: see text] bond structure. For HDPE surface bombarded by CH4/H2 = 50/50, [Formula: see text] bond fraction reaches the maximum of 30.5%, the surface roughness decreases to 17.04 nm, and the static contact angle of polar H2O molecule increased to 140.2[Formula: see text].