High-density Polyethylene Samples Research Articles

Influence of interface voltage on charge build-up under high voltage

Abstract The interface voltage appearing when two materials are brought into contact was measured with a high sensitive pressure-wave-propagation measurement setup in various low density and high density polyethylene samples coated either with aluminum or gold electrodes. The samples were then tested under high voltage (40 kV/mm) for 24 h to assess the correlation between interface voltage and charge injection at 22 °C. Aluminum electrodes induce a positive interface voltage toward the insulator favoring electron injection at the cathode while gold electrodes induce a negative interface voltage toward the insulator favoring hole injection at the anode. After the injections due to interface voltage, charges diffuse more easily in low density polyethylene that triggers a subsequent injection due to heterocharges buildup.

Multimodal Non-Destructive In Situ Observation of Crystallinity Changes in High-Density Polyethylene Samples with Relation to Optical Parameters during Tensile Deformation

Abstract: Many non-destructive optical testing methods are currently used for material research, providing various information about material parameters. At RECENDT, a multimodal experimental setup has been designed that combines terahertz (THz) spectroscopy, optical coherence tomography (OCT), infrared (IR), and Raman spectroscopy with a tensile test stage. This setup aims to gather material information such as crystallinity and optical parameters of high-density polyethylene (HDPE) during a tensile test. The setup compares common IR and Raman spectroscopy and the less common optical methods THz and OCT. Complementarity is achieved through different frequency ranges and measurement approaches, resulting in different measured optical material parameters and depths. During tensile testing, HDPE samples with varying crystallinity were analysed, and the determined optical parameters such as refractive index, birefringence, scattering coefficient of decay, and penetration depth can be correlated with the change in crystallinity. These findings demonstrate that the optical methods and their outcomes can be interconnected. With further optimization of the experimental setup, it would be possible to observe the alignment of fibres in fibre composite panels and the stress distribution of polymers effectively. This opens interesting possibilities for polymer characterization in the future, including quality control during moulding processes and material testing.

Development and Validation of an ICP‐OES Method to Determine Extractable and Leachable Metals in HDPE (Plastic) Pharmaceutical Packaging Material

ABSTRACTThe safety and effectiveness of pharmaceutical medicines depend heavily on extractables and leachables. Patients may be adversely affected by contaminants that enter drug products through packing materials. As a result, regulatory organizations like the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) have set standards and regulations for evaluating and managing extractables and leachables. Characterizing the packing materials, carrying out extraction experiments and checking the extracted solutions for contaminants are all parts of this research. As part of the process for approving new drugs, regulatory agencies make use of these data. In present work, an inductively coupled plasma optical emission spectroscopy (ICP‐OES) method is developed and validated for quantifying trace elements from a high‐density polyethylene (HDPE) packaging material. The approach delineated in accordance with United States Pharmacopoeia (USP) <661.1> and <661.2> for the comprehensive analysis of 16 metallic elements including aluminium, arsenic, cadmium, chromium, cobalt, lead, mercury, nickel, titanium, vanadium, zinc, zirconium, barium, manganese, calcium and tin is applicable for evaluating the efficacy of packaging materials. The method detection limits (MDLs) complied as per USP 39‐NF 34 <661.1> along with relative standard deviations (RSDs) obtained were ranging from 0.3% to 3.1% and recoveries of all elements spiked at two different trace levels in HDPE samples were within 97%–110%, providing sensitive, accurate and reproducible methodology.

Improving Environmental Stress Cracking Resistance of High-Density Polyethylene Grades by Comonomer Addition and Nanocomposite Approach.

The aim of this paper is to determine the effect of polymer density, correlated to the comonomer content, and nanosilica addition on the mechanical and Environmental Stress Cracking Resistance (ESCR) characteristics of high-density polyethylene (HDPE). In this regard, five HDPE samples with similar Melt Flow Index (MFI) and molar mass but various densities were acquired from a petrochemical plant. Two polymerization reactors work in series and differ only in the amount of 1-buene comonomer fed to the second reactor. To ascertain the microstructure of the studied samples, GPC and SSA (successive self-nucleation and annealing) analyses were accomplished. All samples resulted having similar characteristics but slightly various SCB/1000 C=7.26-9.74 (SCB=Short Chain Branching). Consequently, meanwhile studied HDPEs reveal similar notched impact and stress at yield values, the tensile modulus, stress-at-break, and elongation-at-break tend to demonstrate different results with the SCB content. More significantly, ESCR characteristic varied considerably with SCB/1000 C extent, so that higher amount of SCB acknowledged advanced ESCR. Notably, blending HDPE sample containing higher amount of SCB/1000 C, with 3 wt.% of chemically modified nanosilica enhanced ESCR characteristic by 40 %. DFT (Density Functional Theory) calculations unveiled the role of the comonomer, quantitatively by binding energies and qualitatively by Non Covalent Interaction (NCI) plots.

Optimization Course of Titanium Nitride Nanofiller Loading in High-Density Polyethylene: Interpretation of Reinforcement Effects and Performance in Material Extrusion 3D Printing.

In this study, titanium nitride (TiN) was selected as an additive to a high-density polyethylene (HDPE) matrix material, and four different nanocomposites were created with TiN loadings of 2.0-8.0 wt. % and a 2 wt. % increase step between them. The mixtures were made, followed by the fabrication of the respective filaments (through a thermomechanical extrusion process) and 3D-printed specimens (using the material extrusion (MEX) technique). The manufactured specimens were subjected to mechanical, thermal, rheological, structural, and morphological testing. Their results were compared with those obtained after conducting the same assessments on unfilled HDPE samples, which were used as the control samples. The mechanical response of the samples improved when correlated with that of the unfilled HDPE. The tensile strength improved by 24.3%, and the flexural strength improved by 26.5% (composite with 6.0 wt. % TiN content). The dimensional deviation and porosity of the samples were assessed with micro-computed tomography and indicated great results for porosity improvement, achieved with 6.0 wt. % TiN content in the composite. TiN has proven to be an effective filler for HDPE polymers, enabling the manufacture of parts with improved mechanical properties and quality.

Combined effect of montmorillonite Cloisite 30B and graphene nanoplatelets on high‐density polyethylene matrix under high strain rate dynamic compression

AbstractLaminated polymer composites are widely used in ballistic barriers where polyethylene can be applied. The mechanical properties of polymers can be improved with the addition of nanofillers. Therefore, this work evaluates the effect of the combination of montmorillonite Cloisite 30B (OMt) and graphene (Gr) on the dynamics compression properties obtained from a split‐Hopkinson pressure bar (SHPB) test for nanostructured maleinized high‐density polyethylene (HDPE). The nanofillers are incorporated into the polymeric matrix in its molten state, and their dispersion is evaluated through x‐ray diffraction and transmission electron microscopy analyses. Thermal analysis, including differential scanning calorimetry and thermogravimetric analysis are performed. Additionally, the viscoelastic behavior of the materials is studied from the results of storage and loss modulus obtained by dynamic‐mechanical analysis. Under the SHPB test conditions, it is possible to evaluate the material stress–strain curve, identifying its yield point, compressive strength, and deformations to calculate the elastic stiffness and toughness of the material. The nanocomposite with 3% OMt and 0.75% Gr (wt.%) shows the highest average compressive strength and toughness values. Furthermore, this sample shows similar Tpeak temperature, improved crystallinity index, storage, and loss modulus, with similar glass transition temperature compared to the HDPE sample.

Fabrication, Structural Characterization, and Photon Attenuation Efficiency Investigation of Polymer-Based Composites.

Experiments have assessed various polymer composites for radiation shielding in diverse applications. These composites are lighter and non-toxic when compared to lead (Pb), making them particularly effective in diagnostic imaging for shielding against low-energy photons. This study demonstrates the fabrication of four composites by combining a base material, specifically a high-density polyethylene (HDPE) polymer, with 10% and 20% silicon (Si) and silicon carbide (SiC), respectively. Additionally, 5% molybdenum (Mo) was incorporated into the composites as a heavy metal element. The composites obtained were fabricated into 20 disks with a uniform thickness of 2 mm each. Discs were exposed to radiation from a low-energy X-ray source (32.5-64.5 keV). The chemical and physical properties of composites were assessed. The shielding ability of samples was evaluated by determining the linear and mass attenuation coefficients (μ and μm), radiation protection efficiency (RPE), half-value layer (HVL), and mean free path (MFP). According to our findings, supplementing HDPE with additives improved the attenuation of beams. The μm values showed that composite X-ray shielding characteristics were enhanced with filler concentration for both Si and SiC. Polymer composites with micro-molecule fillers shelter X-rays better than polymers, especially at low energy. The HVL and MFB values of the filler are lower than those of the pure HDPE sample, indicating that less thickness is needed to shield at the appropriate energy. HC-20 blocked 92% of the incident beam at 32.5 keV. This study found that increasing the composite sample thickness or polymer filler percentage could shield against low-energy radiation.

Reinforced HDPE with optimized biochar content for material extrusion additive manufacturing: morphological, rheological, electrical, and thermomechanical insights

The development of efficient and sustainable composites remains a primary objective of both research and industry. In this study, the use of biochar, an eco-friendly reinforcing material, in additive manufacturing (AM) is investigated. A high-density Polyethylene (HDPE) thermoplastic was used as the matrix, and the material extrusion (MEX) technique was applied for composite production. Biochar was produced from olive tree prunings via conventional pyrolysis at 500 °C. Composite samples were created using biochar loadings in the range of 2.0–10.0 wt. %. The 3D-printed samples were mechanically tested in accordance with international standards. Thermogravimetric analysis (TGA) and Raman spectroscopy were used to evaluate the thermal and structural properties of the composites. Scanning electron microscopy was used to examine the fractographic and morphological characteristics of the materials. The electrical/dielectric properties of HDPE/biochar composites were studied over a broad frequency range (10–2 Hz–4 MHz) at room temperature. Overall, a laborious effort with 12 different tests was implemented to fully characterize the developed composites and investigate the correlations between the different qualities. This investigation demonstrated that biochar in the MEX process can be a satisfactory reinforcement agent. Notably, compared to the control samples of pure HDPE, biochar increased the tensile strength by over 20% and flexural strength by 35.9% when added at a loading of 4.0 wt. %. The impact strength and microhardness were also significantly improved. Furthermore, the Direct current (DC) conductivity of insulating HDPE increased by five orders of magnitude at 8.0 wt. % of biochar content, suggesting a percolation threshold. These results highlight the potential of C-based composites for the use in additive manufacturing to further exploit their applicability by providing parts with improved mechanical performance and eco-friendly profiles.Graphical

Gamma-ray shielding effectiveness, thermal, and dielectric properties of filler-reinforced high-density polyethylene/boron carbide composites

The present research prepared samples of pure high-density polyethylene (HDPE)/boron carbide reinforced with iron dioxide, aluminum dioxide, iron, and aluminum. The effectiveness of the prepared samples as a shielding material against gamma-rays and their thermal and dielectric properties have been evaluated. The shielding characteristics of the prepared composites were investigated theoretically using the Phy-X/PSD program and experimentally for gamma-rays emitted from 131Cs and 60Co radioactive isotopes. The shielding evaluation included the mass attenuation coefficient (μ/ρ), half value layer (HVL), mean free path (MFP), atomic and electronic cross-sections (σa&σe), effective atomic number and electron density (Zeff &Neff), and exposure build-up factor (EBF). The EBF peaks of samples containing Fe and Fe2O3 are 103 times lower than pure HDPE. The results indicate that samples C2 and C3 have a higher ability to protect against gamma radiation than that of the other investigated samples. X-ray diffractometer (XRD) spectrum shows that adding B4C, Fe, Fe2O3, Al, and Al2O3 to HDPE caused an increase in its full width at half maximum (FWHM) value and a decrease in its average crystallite diameters (D) at its primary characteristic scattering angle of 21.49°. Adding multiple types of fillers to HDPE results in a minor shift in the melting temperature of the hosting matrix as proved from differential scanning calorimetry (DSC) data. The composite of HDPE/B4C/Al2O3 60/10/30 demonstrated the most significant values of dielectric parameters in comparison with the other composites, in good accord with the XRD results. The ac conductivity relied on the dopant type in the hosting matrix; the highest value was observed for HDPE/B4C/Al2O3 composite.

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.

Tribological performance analysis of sustainable basalt micro-filler loaded bio-based polypropylene and high density polyethylene composites

The current research work involves the fabrication and tribological properties analysis of constant basalt filler reinforced (30 wt %) bio-based polypropylene (PP) and high density polyethylene (HDPE) thermoplastic composites. Compression molding technique is used after an internal mixing process in order to produce composite samples. The physical and hardness properties have been evaluated for both neat polymers and composite samples. In order to study the coefficient of friction (COF) and specific wear rate (SWR) of PP and HDPE composite samples, the Taguchi and Analysis of Variance (ANOVA) methodologies were applied. For PP samples, the optimum parameters in response to COF are found to be 0 wt% basalt (rank 3), 9 N load (rank 1), 200 r/min speed (rank 4), and 100 m distance (rank 2); for the SWR output, the optimum parameters are 30 wt% basalt (rank 1), 6 N load (rank 4), 100 r/min speed (rank 2), and 200 m distance (rank 3). For HDPE samples, the optimum parameters in response to COF are 0 wt% basalt (rank 1), 6 N load (rank 3), 100 r/min speed (rank 4), and 100 m distance (rank 2); for the SWR output, the optimum parameters are 30 wt% basalt (rank 1), 6 N load (rank 3), 100 r/min speed (rank 4), and 150 m distance (rank 2). Consistently, it has been shown that incorporating basalt fillers to PP and HDPE composites has more dramatically decreased SWR than COF. The depth of wear constantly rises according to increasing load, irrespective of the processing variables, as shown in 2D depth profiles. It is discovered that the confirmation tests carried out for the optimum parameters are within statistically acceptable bounds. The depth profile plots revealed that the worn track edges are found with polymer bumps because of deep grooves and softened polymer debris, which commonly observed more with HDPE samples due to low softening temperature. Moreover, the worn surfaces of the composites have plowed lines and cracks that are brought about by the micro-cutting and micro-plowing activity of the erosive asperities counterface. In addition to surface characteristics, the transfer films created during sliding also significantly influenced the mode of sample wear.

Odour characterisation of high-density polyethylene recycled with sepiolite by sensory evaluation

In recent years, the production and consumption of plastics has increased. This growth in production has resulted in an increasing amount of plastic waste, which is a global problem. Among plastics, high density polyethylene (HDPE) is one of the most widely used polymers in the packaging industry, so its waste is used in the recycling process. One of the main disadvantages of accepting recycled HDPE in production processes is its odour, which makes it impossible to use in production lines. The aim of this work is to reduce and/or eliminate the odours present in the HDPE samples selected for recycling through the use of sepiolites. FTIR analysis of the HDPE samples sent for recycling showed the presence of small amounts of polypropylene (PP), (PET), flexible polyurethane, dirt and adhesives, which could be the cause of the bad odour. Washing the sample showed a decrease in odour, probably due to the removal of dirt and other products that can lead to the degradation of the plastics responsible for the odour. The characterisation of the mixture of sepiolites and HDPE aims to analyse the mechanical and thermal stability of the sample. Not only can pre-washing lead to odour reduction, but also extrusion and injection processes at elevated temperatures can lead to the removal of volatile or semi-volatile compounds. Sensory analysis showed a reduction in odour in HDPE samples with sepiolites, particularly with 15% Pensil sepiolite, to the detriment of mechanical stability. At lower concentrations of sepiolite, the results are good from a sensory, mechanical and thermal point of view, which could mean an industrial application in the manufacture of benches, flower pots, etc.

The evidences for the existence of evanescent wave-induced scattering in the transmission SAXS of high-density polyethylene

In an earlier study of ours (Li et al., IUCrJ,2019 6, 968–983), we conjectured that small-angle X-ray scattering (SAXS) in semicrystalline polymers might be from evanescence wave-induced scattering (Ievi) rather than claimed by classical scattering theory, the incident X-ray-induced scattering (Iin). In this study, we systematically compared Ievi and Iin under the influence of various factors, i.e., linear crystallinity, the number of lamellar crystals (N), the characteristic penetration depth of evanescent wave (dp*) and long period distribution, identifying the method to distinguish SAXS in semicrystalline polymers is from Iin or Ievi. Applying this method to SAXS of a high-density polyethylene (HDPE) sample, it was found that even excluding the influence of instrumental broadening and lamellar thickness/long period dispersity, the SAXS peak in HDPE is still greater than theoretically maximum peak width induced by Iin, indicating the SAXS in HDPE is not induced by incident X-ray directly. Excluding the interference of long period dispersity, it was found that dp* was around 5.9 nm, clearly demonstrating the existence of evanescent wave. Besides, results indicated that the lateral size determined with new theory is accurate, which in turn demonstrated that our assumption that Ievi is from a lamellar stack parallel to incident X-ray is reasonable. Taking all evidences together, it can be concluded safely that SAXS in HDPE is induced by evanescent wave.

Study of radiation attenuation properties of HDPE/ZnO at energies between 47.5 and 266 keV

Seven different composites of high-density polyethylene (HDPE) were fabricated as potential flexible, lightweight and non-toxic radiation shields based on zinc oxide (ZnO) concentrations of 0%, 2%, 4%, 6%, 8%, 10% and 12%. The linear and mass attenuation coefficient (μ, μm), radiation protection efficiency (RPE) and mean free path (MFP) of the proposed HDPE-based composites were estimated. The shielding parameters, including μ, μm, RPE and MFP, of the seven samples were determined utilising eight X-ray standard radiation qualities (N-60 to N-300) at voltages of 60, 80, 100, 120, 150, 200, 250 and 300 kVp for effective energies of 47.5, 67.6, 83.3, 100, 126, 166, 218 and 266 keV, respectively. The μ results of the seven HDPE composite materials were between 0.1188 cm−1 and 0.4788 cm−1. The 12% HDPE/ZnO sample has the highest attenuation across all incident X-ray beam energies among the selected composites. The result revealed that the measured μm results align with the theoretical XCOM results for all samples, with an average error of 3.39%. Additionally, a composite containing 12% ZnO had a minimum MFP value and the highest percentage of RPE obtained from a 12% HDPE/ZnO sample with about 38.05%, compared with 17.09% of pure HDPE sample at 47.5 keV energy. This work concludes that adding ZnO to the HDPE polymer increases its shielding effectiveness for X-rays at these low energies, commonly used in radiation research and hospitals' radiology departments. In addition, increasing either the thickness or the ZnO concentration in the samples could enhance its practical usage as a radiation shield.

Crystallinity and Oscillatory Shear Rheology of Polyethylene Blends.

Crystallinity and rheological behavior are significant for processing semi-crystalline polymers with fine mechanical properties. There is always an economical need to create a less expensive new material with better properties. Non-isothermal crystallization and oscillatory shear rheology of different branch-type polyethylene-polyethylene blends were investigated. Samples of high-density and low-density polyethylene (HDPE/LDPE) (20/80, 40/60, 60/40 and 80/20 weight ratios) and two types of high-density and linear low-density polyethylene (HDPE/LLDPE) (40/60 and 60/40 weight ratios) were prepared via extrusion. The materials were tested by differential scanning calorimetry (DSC) at several cooling rates (5, 10, 20, 30 and 40°/min) and by oscillation rheometry (ARES G2) at low angular frequency range to prove their miscibility or immiscibility. It was found that the one-peak melting endotherm of the 80-20% HDPE-LDPE blend could indicate miscibility in the solid phase, while the other HDPE-LDPE blends with two-peak curves are partially or not miscible. In contrast, all the HDPE-LLDPE blends indicate co-crystallization, but the 40-60% HDPE-LLDPE butylene blend is probably immiscible. It was revealed that complex viscosity decreases with angular frequency: linearly for HD-LD blends and not linearly for HD-LLDPE blends. The complex viscosity shows linear behavior with composition for HD-LLDPE blends, while there is a positive-negative deviation for HD-LD blends. In the liquid phase, according to rheological measurements, the HDPE-LDPE blends are not or partially miscible, while the HDPE-LLDPE blends are probably miscible.

Thermal degradation of virgin and waste plastics: Estimation of kinetic and thermodynamic parameters using model‐free iso‐conversional methods

AbstractKinetic triplets—apparent activation energy (Ea), pre‐exponential factor (A), and the reaction model—were estimated for the thermal degradation of three primary virgin and waste plastics, as well as mixed plastics waste. Model‐free iso‐conversional FWO, KAS, Starink, Kissinger and Vyzovkin and Friedman methods were employed for the kinetic analysis. The apparent activation energy was determined by the integral methods as 206.5‐209.1 kJ mol−1 and 195.6‐198.8 kJ mol−1 for the virgin and waste high‐density polyethylene (HDPE), 211.6‐214.1 kJ mol−1 and 183.1‐186.6 kJ mol−1 for the virgin and waste polypropylene (PP), 144.0‐163.1 kJ mol−1 and 159.7‐167.1 kJ mol−1 for the virgin and waste polystyrene (PS), and 173.6‐178.9 kJ mol−1 for the mixed plastics waste respectively. Ea was found to follow the trend HDPE > PP > PS with higher values for HDPE and PP virgin samples than that for their waste and marginally smaller for the virgin PS than its waste. Degradation of all plastic samples followed Avrami‐Erofeev equation with n varying between 1.0 and 1.8. The effect of conversion on Ea suggested the degradation of both virgin and waste HDPE to consist of multiple parallel reactions while that of others to be more complex. FTIR analysis of the evolved gases was used to explain the possible reaction mechanism. A small difference between the enthalpy change and the apparent activation energy (6‐7 kJ mol−1) for all plastic samples indicated favourable pyrolysis reactions. The estimated kinetic parameters and thermodynamic properties showed the stability of different plastics as HDPE > PP > PS.

Study of a Conical Plasma Jet with a Cloth-Covered Nozzle for Polymer Treatment.

Although atmospheric pressure plasma jets (APPJs) have been widely employed for materials modification, they have some drawbacks, such as the small treatment area (couple of cm2). To overcome this limitation, a funnel-like APPJ with a wide exit has been proposed. In this work, a gas-permeable cotton cloth covered the nozzle of the device to improve the gas flow dynamics and increase its range of operation. The funnel jet was flushed with Ar, and the plasma was ignited in a wide range of gas flow rates and the gap distances between the exit nozzle and the sample holder. The device characterization included electric measurements and optical emission spectroscopy (OES). To evaluate the size of the treatment and the degree of surface modification, large samples of high-density polyethylene (PE) were exposed to plasma for 5 min. Afterward, the samples were analyzed via water contact angle WCA measurements, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). It was found that surface modification occurs simultaneously on the top and bottom faces of the samples. However, the treatment incorporated different functional groups on each side.

Thermal expansion of high‐density polyethylene in hot plate welding applications

AbstractThis research studies high‐density polyethylene (HDPE) behavior that is not easily identifiable in a production setting, but is, nevertheless, necessary for consideration when specifying equipment performance for hot plate welding (HPW) applications. Thermal expansion in polymers can depend on several factors, such as the specific type of polymer, its degree of cross‐linking, and the temperature range over which the expansion occurs. This physical behavior can affect the process by prolonging the cycle time if the equipment is not sized correctly for the application. This research uses HDPE samples with different surface areas and varying process parameters (force and temperature) to collect data on the sample size change. Experimental results are compared with a recommended industrial guideline of 0.2 to 0.5 MPa of pressure for the Matching stage (stage for surface conformation). Obtained findings indicate that this industrial guideline is very temperature dependent. Data collected in the experiment were used to develop a mathematical model for thermal expansion under different parameters. This study also presents a visual interpretation of HDPE behavior on the effect of temperature if the pressure is increased or decreased.

High density polyethylene and butanol-gasoline blends: A material compatibility study

We are now well on the path of transitioning away from the fossil fuel resources on cutting down their consumption as much as possible. The fuels chosen for this study include ethanol-butanol (EB) -gasoline, acetone-butanol-ethanol (ABE) -gasoline and methanol-butanol (MB) -gasoline blends. High density polyethylene (HDPE) is a polymer that is extensively used in several auto parts and fuelling infrastructure materials. Incompatibility between these blends and fueling infrastructure system should be studied comprehensively for the adoption of these alternative fuels to be faster and hassle free. This study intends to gauge the changes in HDPE because of its immersion in the gasoline-alcohol blends mentioned for a period of 4, 30 & 90 days. The changes were ascertained by studying the mass, tensile strength, elongation, and hardness of the samples before and after immersion into blends. Sophisticated techniques were used to characterize the morphological and chemical changes of the polymer. The results showed that there was an increase in the mass of the HDPE samples as a result of the absorption of the blends by the polymeric samples. A decrease in tensile strength and hardness values were recorded for the samples whereas the elongation values were found to increase. Studies revealed that there was neither fuel degradation nor any oxidative degradation of the polymeric sample. The results indicated an increase in the mass and elongation of the HDPE as a result of the absorption of the fuel leads to lesser stable polymeric matrix and decrease in the percentage crystallinity. Hence this investigation led us to the conclusion that all the fuels blends studied are highly compatible with HDPE, even in instances where a change in the mechanical properties is seen, it is similar to that seen in gasoline.

Polyethylene Incorporating Diels-Alder Comonomers: A "Trojan Horse" Strategy for Chemically Recyclable Polyolefins.

Polyolefins with periodic unsaturation in the backbone chain are sought after for synthesizing chemically recyclable polymers or telechelic polyolefin macromonomers. Here we introduce a bottom-up synthesis of unsaturated high-density polyethylene (HDPE) via copolymerization of ethylene with dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-3,5-dicarboxylate followed by post-polymerization retro-Diels-Alder to unveil hidden double bonds in the polymer backbone. The incorporation of this "Trojan Horse" comonomer was varied and a series of unsaturated HDPE polymers with block lengths of 1.2, 1.9, and 3.5 kDa between double bonds was synthesized. Cross metathesis of unsaturated HDPE samples with 2-hydroxyethyl acrylate yielded telechelic ester terminated PE macromonomers suitable for the preparation of ester-linked PE. These materials were depolymerized and repolymerized, making them suitable candidates for chemical recycling. The ester-linked PE displayed thermal and mechanical properties comparable to commercial HDPE.