High Density Polyethylene Resins Research Articles

Elevating Recycling Standards: Global Requirements for Plastic Traceability and Quality Testing

Globally, we produced 489 million tonnes of plastic in 2023 and we recycled only 8.17%. This study navigates the landscape of recycling practices, highlighting the imperative to reevaluate and upgrade industry-standard protocols. The central focus of this study is on integrating more robust traceability criteria and advanced quality testing methodologies to improve recycled plastics with intrinsic value, particularly in anticipation of future market applications. The investigation examines the prevailing industry standard traceability and quality framework. It then assesses the applicability of those standards using technical datasheets for recycled high-density polyethylene resin grades. This study proposes a paradigm shift toward a more sophisticated analytical approach. This comprehensive framework aims to transcend traditional quality and traceability evaluation. This paper employs a mixed methodological approach, including a thematic analysis of relevant industry standard regulations and an in-depth literature review, to address the need for an operational framework for recycling quality. This study highlights that recycling quality depends on technical attributes determining functionality and application suitability. While some properties are measured, the conventional framework does not address the degradation level of recycled plastic. This study concludes with broader considerations, emphasising the need for a traceability model to disclose material history and composition. This study advocates an industry-wide upgrade in recycling standards, prioritising traceability and quality testing. The proposed enhancements in testing grids and the improved understanding of recycling quality collectively contribute to a holistic framework, unlocking the intrinsic value of recycled plastics for future market applications.

Microstructural design characteristics of high-density polyethylene for thick-walled pressure pipe applications

Advancements in process technology and structure-property relationship-based design of high-density polyethylene has led to development of high-performance bimodal polyethylene grades suitable for large diameter thick-walled pressure pipe applications. These high-density bimodal products have enhanced design life, high pressure rating and sag resistance for fabrication of large diameter thick-walled pipe. Achieving optimal balance of these performance properties require controlled microstructural characteristics. The design characteristics are intricately influenced by catalyst type and process technology employed in resin manufacturing. In this study, we systematically establish correlations between microstructural characteristics of seven commercially available bimodal PE resins, produced using dual slurry or gas phase reactors, and their most relevant performance properties. We conducted comprehensive microstructural characterization of all samples using GPC-IR (high-temperature gel permeation chromatography coupled with an infrared composition detector), 13C NMR (nuclear magnetic resonance), TREF (temperature rising elution fractionation) and DSC (differential scanning calorimetry) techniques. Additionally, we measured mechanical, thermal, and rheological properties, focusing on crystallization kinetics, density, slow crack growth resistance (PENT and strain hardening modulus SHM) and low-frequency shear rheology of these products. Comparisons were made between key properties of interest, including slow crack growth resistance and low-frequency rheology (relevant for sag resistance), and microstructural characteristics. Theoretical and empirical correlations based on phenomenological models were employed for this analysis. The detailed study contributes to determining the critical levels of short and long chain branching, as well as molecular weight distribution characteristics essential to produce bimodal PE-4710 certifiable high-density polyethylene resins with low sag resistance. These design principles may serve as a foundation for the efficient design of reactor recipes and post-reactor modification processes, contributing to the evolution of pressure pipe polyethylene resin development and paving the way for design of next-generation pressure pipe grades.

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.

Manufacture and experimental evaluation of a hydrokinetic turbine for remote communities in Colombia

The manufacture and experimental evaluation of a hydrokinetic turbine of 1 kW are presented. A water velocity of 1.5 m/s, with a power coefficient of 0.4382, a tip speed ratio of 6.325, an angle of attack and pitch angle of 5 and 0 degrees, respectively, a blade length of 0.79 m, a drive train efficiency of 70% and a S822 hydrofoil profile were used for the design. The blades were designed and manufactured by Computer Aided Design (CAD) and Computer Aided Manufacturing techniques (CAM) with a solid cross-section in order to provide the required strength. They were made of Prolon MS (Castnylon + Molybdenum). The platform that supports the turbine was a modular floating raft simple to install, flexible, and durable made of high density polyethylene resin. The supporting structure of the turbine generator was made of stainless steel. The turbine was constructed of high quality and durable materials. To determine the efficiency of the designed turbine, the electrical power and kinetic energy of the river were measured. The experimental assays of the turbine were performed in the Sinú River located in Córdoba (Colombia), obtaining an overall equipment efficiency of 0.5359.

Recycled carpet-reinforced composites from post-consumer polypropylene carpet and recycled HDPE resin

Carpets significantly contribute to landfills, forming 3.5 % of the U.S. landfill waste, with less than 10 % being recycled. This study uses intact carpets to create functional composites as a potential solution to this problem. This research introduces a feasible method for manufacturing recycled composites through compression molding of post-consumer polypropylene (PP) carpet and recycled high-density polyethylene (HDPE) resin. Optimal molding temperature and composition ranges were identified using a comprehensive three-level full factorial design of experiments (3D-DOE), resulting in impressive flexural strength (>40 MPa) and flexural modulus (>2000 MPa). Reproducibility tests of 10 specimens yielded 41.8 ± 2.0 MPa flexural strength and 2200 ± 150 MPa flexural modulus. These composites, containing up to 70 % potentially-landfilled carpet and 30 % recycled resin, surpassed the performance for the strength of commercialized thermoplastics, making them suitable for structural applications. The findings present a promising approach to address carpet landfilling while reducing reliance on additives.

Predicting High-Density Polyethylene Melt Rheology Using a Multimode Tube Model Derived Using Non-Equilibrium Thermodynamics.

Based on the Generalized bracket, or Beris-Edwards, formalism of non-equilibrium thermodynamics, we recently proposed a new differential constitutive model for the rheological study of entangled polymer melts and solutions. It amended the shortcomings of a previous model that was too strict regarding the values of the convective constraint release parameter for the model not to violate the second law of thermodynamics, and it has been shown capable of predicting a transient stress undershoot (following the overshoot) at high shear rates. In this study, we wish to further examine this model's capability to predict the rheological response of industrial polymer systems by extending it to its multiple-mode version. The comparison with industrial rheological data (High-Density Polyethylene resins), which was based on comparison with experimental data available in (a) Small Amplitude Oscillatory shear, (b) start-up shear, and (c) start-up uniaxial elongation, was noted to be good.

Life Cycle Assessment of Plastic Resin: A Case Study of the Petrochemical Industry in Thailand for the Production of HDPE Resin

Life cycle sustainability is an important tool for assessing product performance based on the three pillars of environment, economy and society. This study examined the life cycle impact, cost and social implications of high-density polyethylene (HDPE) resin. Environmental assessment revealed nonrenewable energy as the greatest impact followed by carcinogens, respiratory inorganics and global warming while economically, the operational cost of HDPE resin production was significantly highest. The social impact assessment following the United Nation Environmental Programme (UNEP)/ Society of Environmental Toxicology and Chemistry (SETAC) guidelines demonstrated optimal performance for all indicators except for gender ratio and disabled employee criteria which were lower human rights indicators than other companies. The subcategory of occupational health and safety should be specified in future aspects, such as rate of disease from company operation. Energy efficiency and material acquisition should be improved to reduce the environmental impact and positively redress declining costs, leading to decrease in disease rate among workers in the local community. Results suggested that improving environmental impact would increase economic performance through optimal energy efficiency, while the social life cycle assessment indicator should mainly focus on health and safety in the event of disease arising from business operations.

Experimental study on the effect of molecular weight and chemical composition distribution on the mechanical response of high‐density polyethylene

AbstractThis article aims to appraise the effect of microstructure comprising molecular weight distribution and chemical composition distribution on the mechanical properties of high‐density polyethylene (HDPE). HDPE resins were synthesized using several titanium–magnesium‐supported Ziegler–Natta catalysts in the industrial gas phase reactor under the same polymerization condition. Gel permeation chromatography and crystallization elution fractionation (CEF) were conducted on the resins to characterize the molecular weight and comonomer distribution. Crystallization, thermal and rheological behavior were evaluated following differential scanning calorimetry, polarization light microscopy, and rheometric mechanical spectrometry. The resins with higher soluble fraction in trichlorobenzene below 80°C (highly branched low molecular weight chains) exhibited longer crystallization time based on the crystallization kinetic obtained from the Avrami model. Rheological determination of the molecular weight between entanglements (Me) and the average lamella thickness based on the Gibbs–Thomson equation revealed that the entanglement density and impact strength decreased, and the average lamella thickness increased with an increase in the ratio of CEF eluted fraction below 80°C to the crystallizable fraction in the range of 80–90°C.

Composites Based on Iroko Wood Flour Stabilized Using High Density Polyethylene Resin Recovered: 1. Mechanical Properties

Nowadays, waste management has become one of the major priorities for the protection of ecosystems. Among these wastes, those of plastic origin require particular importance. As an alternative solution to this problem, this waste is reused for other purposes such as the development of new materials. The work presented proposes, on the one hand, to develop a composite based on Iroko wood flour stabilized by high density polyethylene resin (Hdpe) and, on the other hand, to measure its mechanical characteristics. To do this, resin mass contents varying from 10 to 60% were mixed with the flour to obtain composites according to a well-defined method. The variation of these mechanical properties has been studied as a function of the proportions of the binder. The measurements carried out related to the behavior in compression, in flexion and in traction. It appears that the mechanical strengths increase for high levels of binder. In addition, for each resin content, the composite has an increasingly resistant behavior in compression than in traction and in flexion. For example, for 60% of Hdpe, the strengths are equal to 23.95 MPa in compression, 18.22 MPa in tension and 13,17 MPa in flexion. However, from 50%, the material adopts an increasingly stable behavior. In addition, it becomes more ductile and deformable as the binder content increases. The use of the proposed method is an alternative for the management of the waste.

Integrity and cost evaluation of natural fibers/HDPE composite tailored for piping applications

This paper focused on the establishment of performance level and cost of plantain fibers reinforced High Density Polyethylene (HDPE) matrixes as gas pipeline material using pressure containment of the new materials as performance criterion. The cost of modified plantain fibers, the cost of plantain fibers reinforced HDPE (PFRHDPE) and the cost of PFRHDPE master batch (HDPE resin + plantain fiber particles + stabilizer, plasticizer) for pipes extrusion production and pipelines fittings injection productions were established. The burst pressure evaluated for available standard outside diameter ratio (SDR) using the ultimate tensile strength of PFRHDE is very much greater than the standard SDR design pressures even when the temperature derating factors were applied. The Maximum Allowable Operating Pressure (MAOP) of PFRHDPE and induced stresses of pressurized pipes established indicated that the new material is suitable for pipeline design for natural gas and liquid petroleum (LPG) lines. The PFRHDPE developed has better specific properties than the conventional steel and HDPE pipe material in terms of yield strength, elastic modulus and density of the new material. But in terms of cost, steel and HDPE has approximate desirability for selection with PFRHDPE. The energy required to manufacture and process steel products is about 480 MJ/m2, while that of plastics is about 320 MJ/m2. The study further established that PFRHDPE can be applied in the design of oil and gas gathering, transportation and distribution lines.

Effect of Temperature on Pyrolysis Oil Using High-Density Polyethylene and Polyethylene Terephthalate Sources From Mobile Pyrolysis Plant

This research aims to study the effect of temperature, collecting time, and condensers on properties of pyrolysis oil. The research was done be analyzing viscosity, density, proportion of pyrolysis products and performance of each condenser towers for the pyrolysis of high-density polyethylene (HDPE) and polyethylene terephthalate (PET) in the mobile pyrolysis plant. Results showed that the main product of HDPE resin was liquid, and the main product of PET resin was solid. Since the pyrolysis of PET results in mostly solid which blocked up the pipe, the analysis of pyrolysis oil would be from the use of HDPE as a raw material. The pyrolysis of HDPE resin in the amount of 100 kg at 400, 425, and 450°C produced the amount of oil 22.5, 27, and 40.5 L, respectively. The study found that 450°C was the temperature that gives the highest amount of pyrolysis oil in the experiment. The viscosity was in the range of 3.287–4.850 cSt. The density was in the range of 0.668–0.740 kg/L. The viscosity and density were increased according to three factors: high pyrolysis temperature, number of condensers and longer sampling time. From the distillation at temperatures below 65, 65–170, 170–250, and above 250°C, all refined products in each temperature range had the carbon number according to their boiling points. The distillation of pyrolysis oil in this experiment provided high amount of kerosene, followed by gasoline and diesel.

Effect of the melt flow index of an HDPE matrix on the properties of composites with wood particles

Composites of wood waste and high-density polyethylene (HDPE) resins and different melt flow index (MFIs) was development in this work. Therefore, it was possible to assess their effect on the mechanical, thermal, and morphologic properties of these composites. The formulations were prepared using a twin-screw extruder, and the MFI, tensile strength, flexural strength, and impact strength of the composites were analyzed. Additionally, the thermal properties were evaluated by differential scanning calorimetry (DSC). Finally, structural analyses using optical microscopy (OM) and scanning electron microscopy (SEM) were performed to assess the particles’ dispersion, distribution, and adhesion to the polymer matrix. The results indicated that composites from HDPE resins with a lower MFI yielded a better dispersion of the wood waste. During processing was observed, reduce the MFI and better dispersion of the polymer matrix, which positively influenced some of the mechanical properties analyzed in the study.

Influence of the chemical structure of para‐bridged group on the antioxidant behavior of hindered phenol antioxidants in HDPE resin

AbstractA hindered phenol antioxidant with rigid para‐bridged group (antioxidant AP) was synthesized to study the effect of the chemical structure on the antioxidant properties of hindered phenol antioxidants in high density polyethylene (HDPE). Antioxidant behavior of series of hindered phenol antioxidants with different para‐bridged groups in HDPE resin was also investigated by the thermal oxidation experiment, the mobility test, and the long‐term accelerated thermal aging test. The results showed that the rigidity of para‐bridged group and the molecule size have the important influences on the antioxidant performance of hindered phenol antioxidants in the HDPE resin, and the antioxidant abilities of antioxidant AP and Irganox 1,330 with the aryl para‐bridged group was superior to Irganox 1,098 and 1.0G dendritic antioxidant with the alkyl para‐bridged group at the same testing conditions. Compared with the hindered phenol antioxidants with alkyl para‐bridged group, the hindered phenol antioxidants with aryl para‐bridged group have better thermal oxygen stability and less mobility in the HDPE resin. Irganox 1,010 with ester groups is prone to hydrolysis to increase the mobility rate in hot water and the migration resistance of hindered phenol antioxidants in n‐hexane. Moreover, the high content of phenolic OH group and the aryl para‐bridged group are favorable for improving the antioxidant performance of hindered phenol antioxidants.

Life‐Cycle Assessment of Recycling Postconsumer High‐Density Polyethylene and Polyethylene Terephthalate

This study aims to quantify the overall environmental performances of mechanical recycling of the postconsumer high‐density polyethylene (HDPE) and polyethylene terephthalate (PET) in Jordan. The life‐cycle assessment (LCA) methodology is used to assess the potential environmental impacts of recycling postconsumer PET and HDPE. It quantifies the total energy requirements, energy sources, atmospheric pollutants, waterborne pollutants, and solid waste resulting from the production of recycled PET and HDPE resin from the postconsumer plastic. System expansion and cut‐off recycling allocation methods are applied. The analysis has been carried out according to the LCA standard, series UNI EN ISO 14040‐14044:2006. A standard unit of output (functional unit) is defined as “one ton of PET flake” and “one ton of HDPE pellet.” The results of the production of virgin resin are compared with the “cut‐off” and “system expansion” recycling results. Depending on the allocation methods applied, a nonrenewable energy saving of 40–85% and greenhouse gas emission saving of 25–75% can be achieved. Based on two allocation methods, PET and HDPE recycling offers important environmental benefits over single‐use virgin PET and HDPE. LCA offers a powerful tool for assisting companies and policy‐makers in the waste plastic industry. Furthermore, the “system expansion” recycling method is not easy to apply because it requires detailed data outside of the life cycle of the investigated product.

EFFECT OF CaCO3 FILLER ON THE DEGRADATION OF HIGH DENSITY POLYETHYLENE (HDPE) FILM CONTAINING PROOXIDANTS

The aim of this work is investigation of effect of CaCO3 filler on the degradation of high density polyethylene (HDPE) films containing stearate salts as prooxidant additves. The films with thickness of 30 µm were prepared by adding 0.3 % (w/w) prooxidant additives mixture (manganese (II) stearate/feric stearate/cobalt (II) stearate ratio of 18:4:1) and CaCO3 filler from 5 to 20 % (w/w) in HDPE resins using twin screw extruder. The films were carried out accelerated weathering treatment according to ASTM G154 standard (340 nm UV lamp, 8 hours UV, 4 hours condensation at 50 0C) for maximum duration of 96 hours. The mechanical properties, FTIR analysis, Differential Scanning Calorimetry (DSC), Thermo gravimetric analysis (TGA) and Scanning Electron Microscope (SEM) were used to assess the changes in the structure and surface morphology of films during accelerated weathering. The results showed that the degradation rate of HDPE films decreased by adding CaCO3 filler and versused with CaCO3 filler content. FTIR traces revealed that CaCO3 filler didn’t affect to the mechanism of polyethylene degradation. After 96 hours of aceelerated weathering treatment, the elongation at break of the HDPE film with 5 % CaCO3 almost unchanged while this value of the HDPE films with 10 and 20 % CaCO3 decreased significantly (96 % and 100 %, respectively).

Effect of short chain branches distribution on fracture behavior of polyethylene pipe resins

In this paper, a series of unimodal and bimodal high density polyethylene (HDPE) pipe resins with the similar molecular weight distribution and low short chain branches (SCB) contents were investigated to discover the relationship between short chain branches distribution (SCBD) and fracture behaviors. Three characterization methods, namely temperature rising elution fractionation (TREF), high temperature gel permeation chromatography (HT-GPC) and self-annealing fraction (SSA), have been effectively combined to qualitatively analyze investigate the SCBD of HDPE pipe resins. The results showed the preference of incorporation of SCB into long chains caused the enhancement of yielding stress and strain hardening (SH) modulus, and thus the extension of rupture time. On one hand, this kind of SCB distribution is conductive to induce the nucleation of long chains and form more void volume in the neighborhood of long chains indicating faster migration speed of polymer chains. On the other hand, short chains with less SCBs are easy to rapidly occupy nearby sites on the crystal growth front of long chains to co-crystallize. Whereas, these HDPE resins with the more SCBs incorporated into short chains spent much longer time occupying the growth front, so that parts of these types of short chains form very thinner lamella differentiated from the main crystallizing region. During the initiation and propagation of craze, these parts were firstly broken and their resistance to slow crack growth was based on the incorporating degree of SCBs into short chains. Therefore, besides molecular weight distribution, SCBD is another main cause for long-term properties of HDPE pipe resins.

Quantification of Greenhouse Gas Emissions from Production of Young Buddings of Rubber in Malaysia

A study on quantification of greenhouse gas emissions was carried out with the objectives to quantify greenhouse gas emissions and identify the main greenhouse gas sources resulting from production of two whorl young buddings in polybags. The study was based on the Intergovernmental Panel on Climate Change 2007, fourth assessment report on global warming potential for a 100 year time horizon involving 32 rubber nurseries in Malaysia. The production and usage of N fertiliser as well as production of both high density polyethylene resin E and diesel are the four main processes which contribute to the release of greenhouse gas emissions resulting from the production of one two whorl young budding in a polybag. The greenhouse gas emissions from these four main processes and production of two whorl young buddings in polybags will potentially be reduced with a shortened growth period coupled with increase in bud-grafted success rate of individual grafters.

Transient Swell of a High Density Polyethylene Using Adjustable Gap Slit Die

Abstract A novel slit die with an adjustable gap is designed to perform transient swell measurements while changing the die gap dynamically. A generalized control model is developed to predict time-dependent swell using characteristic relaxation time and corresponding steady state swell as model parameters. Further, a series of slit dies are designed and used to measure steady state thickness swell of a high-molecular-weight blow-molding grade high density polyethylene resin under various operating and geometrical conditions. A generalized expression for steady state thickness swell is obtained by applying multi-variable nonlinear regression on thus obtained steady state thickness swell data, and is used in the empirical control model to predict transient extrudate swell.

COMPARISON OF MANGANESE LAURATE, MANGANESE PALMITATE AND MANGANESE STEARATE ON ACCELERATING DEGRADATION OF HDPE DURING NATURAL WEATHERING

High density polyethylene (HDPE) degradation has been studied. In this study, HDPE was incorporated with manganese laurate, manganese palmitate and manganese stearate as pro-oxidant additives. Preparation of samples were conducted by adding the HDPE resin with pro-oxidant additives in the range of 0-1.0 wt %. A twin screw extruder was employed prior to the injection molding technique. Samples were subjected to natural weathering for the maximum duration of 24 weeks. Assessments on the change of the properties of samples after natural weathering treatment were conducted by FTIR analysis, tensile testing and average molecular weight analysis. In term of their capabilities to accelerate degradation of HDPE, manganese stearate exhibited more influence than manganese laurate and manganese palmitate. The carbonyl group’s peak arises as a result of oxidation during the treatment as revealed by FTIR traces. Samples with pro-oxidant additives shows a loss of their strain at break. The amount of pro-oxidant additives increases the degradation of samples.

DC electrorheological response of polyethylene/organically modified layered silicate nanocomposites

The present work reports the electrorheological (ER) response of high-density polyethylene (HDPE)/organically modified silicate layers nanocomposites based on four commercially available HDPE matrices. Two single-site catalyzed bimodal resins, one single-site catalyzed unimodal resin and one Ziegler–Natta catalyzed unimodal resin are studied. It is revealed that the distinct separation of the two modes of the bimodal HDPE resins significantly enhances the ER response. It is proposed that the slower structural relaxation modes introduced by higher molecular weight species in the bimodal HDPE matrices enhance the ER response of the nanocomposites. This is ascribed to the longer induction time for leaking current density, which is an indicator of mobility and release of immobilized cationic surfactants at the silicate layers surface induced by field exposure. It is found that the screening effect of prematurely released cationic surfactants leads to a weaker ER response in nanocomposites whose matrices have faster relaxation modes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017