Mechanical Properties Of Polyethylene Research Articles

Effect of Using Alkoxy - Silane (ethoxy silane) Coupling Agent to Enhance the Mechanical Properties of Bio-Composites

This research work investigated the effect of alkoxy silane (ethoxy silane) on the mechanical properties of polyethylene/ dried powdered pine apple peels composite. The pine apple peels was washed in distilled water, sun dried for about eight hours and later oven dried at a temperature of 60oC for about three hours. The dried pine apple peels was pulverized and sieved using a mechanical sieve arranged in descending order of fineness. The alkoxy-silane (ethoxy-silane) coupling agent (2%) was first hydrolyzed in ethanol to deliver the alkoxy functional silane to the interior of the pineapple peels and ion-free water at room temperature for 6 hours. This was followed by addition of the dried powdered pineapple peels into the hydrolyzed coupling agent solution in a reactor at a temperature of about 80 ◦C for 20 minutes. The formed product was oven dried at 110 ◦C for 3 hours and pulverized using a locally made grinding machine and sieved using a set of sieves arranged in descending order of fineness in accordance with BS1377:1990 standard as was reported by Rajan et al., (2007) to obtain pineapple peels coated with the coupling agent (150mμ). The recycled polyethylene waste was washed using distilled water, sun-dried and shredded in a shredding machine. The pineapple peels powder coated with alkoxy silane and the shredded recycled polyethylene waste were blended using a two-roll rheo-mixer at 50°C and a rotor speed of 60 rpm. The percentage of the powdered pineapple peels coated with coupling agent in the recycled polyethylene matrix was varied from 10% to 40% to produce four different compositions. A hydraulic pressing machine was used to compress the produced composites for about ten minutes applying a pressure of about 25 tons at 130°C. The produced composite samples were allowed to cool to room temperature under sustained pressure before being removed from the hydraulic press for various mechanical tests. The impact tests were performed according to ASTM D256 standard using Impact testing machine model EXT94064/6705CE, 300 J. Flexural test was performed using Universal Testing Machine model TUE-C-100, according to ASTM D790. The hardness tests were performed according to ASTM D785 standard using Rockwell Scale K hardness testing machine. The results showed that maximum flexural strength of 10.8MPa and 384Hv were recorded at 40wt.% reinforcement. The developed composite can be used applications where moderate strength will be required.

The effect of boron carbide doping content on the mechanical properties of polyethylene

ABSTRACT This paper presents Martin Buber‘s unpublished manuscript ‘Fragen und Antworten. Die jüdische Besiedlung Palästinas’ in the original German with English translation and contextualizes it within the main stations of Buber‘s Zionist thinking: cultural Zionism, religious Zionism, and Zionism of realization. It problematizes Buber‘s reflection on Jewish settlements in Palestine with reference to the significance of Zionism for humanity as well as the possibility of reconciliation between Jews and Arabs in the Middle East. It also addresses the problem of Jewish terror, framing it in correlation with the restrictions on Jewish migration to Palestine and the catastrophe of the Shoah.

Location-controlled crazing in polyethylene using focused electron beams and tensile strain

Abstract This study explores the use of focused electron beam (FEB) dot irradiation and tensile stress to control crazing formation in polymers at the microscale. Polyethylene (PE) containing carbon was subjected to FEB dot irradiation at 5–20 kV of accelerating voltage, followed by nominal strains of 0–70 %. The results revealed that FEB irradiation affects the structure and mechanical properties of PE. The Raman spectroscopy showed a glassy polymer of amorphous structure with the intensity changed after irradiation, which led to craze formation at the location of the electron beam dot irradiation after the tensile deformation. Rhombus-shaped crazes were observed at the locations of the electron beam irradiation in the dot area, which were evenly distributed and sized. Our findings provide insights into the control of crazing location in polymers and provide a promising approach to controlling the different shapes and sizes of crazing in polymers for future applications.

Influence of Functionalization on the Crystallinity and Basic Thermodynamic Properties of Polyethylene

Polymer functionalization, the grafting of functional groups onto polymer chains with strong intermolecular interactions, is a promising approach currently being explored to improve the recyclability and field use properties of commercially important polymeric materials. The mechanical properties of polyethylene (PE) are closely tied to the degree of crystallinity, which is expected to be influenced by polymer functionalization. We perform atomistic molecular dynamics (MD) simulations to study the effect of the functional groups on the change of the degree of crystallinity, as well as thermodynamical and local mechanical properties of a linear PE melt. In particular, we consider ester and amide groups as model polar functional groups. In both of these functionalized PE materials, we observe the densification and suppression of crystallization for functionalized PEs in the melt. Our simulation findings inform on the potential use of functionalization of PE as an approach to improve the recyclability of petroleum-based polymer materials.

Simultaneous enhancement in processability and mechanical properties of polyethylenes via tuning the molecular weight distribution from unimodal to bimodal shape

Semicrystalline polymers with bimodal molecular weight distribution (MWD) have captured broad interest in academia and industry. Current efforts to understand the effect of bimodal MWD shape compared with unimodal shape are mixed with factors such as molecular weight, chain branching or phase separation. The collective effect is difficult to decouple in order to elucidate the independent contribution of MWD shape on the properties of polymers. In this work, a chain transfer polymerization method has been utilized to prepare well-defined linear unimodal and bimodal polyethylenes (PEs), to serve as a model system for the study of the impact of the MWD shape on the crystallization, rheology and mechanical properties of semicrystalline polymers. It has been demonstrated that PEs with bimodal shape display simultaneously enhanced crystallinity, processability, Young's modulus and tensile strength while ductility is unaffected. Compared to unimodal PEs with comparable molecular weights, bimodal PEs show about 40% lower processing viscosity, while exhibiting up to 30% greater tensile strength. This represents the first systematic comparative investigation of MWD shape-property relationship at the same molecular weight over a wide molecular weight range. This work indicates that semicrystalline polymers with bimodal MWD shape have the merit to overcome the trade-off between processing and performance without altering average molecular weight, chain structure or chemical composition.

Structures of the co‐branching reactive products of isotactic polypropylene with high‐density polyethylene and the effect on the in situ compatibilization of mixed recycled materials

AbstractThe recycling of petroleum‐based polymers such as polypropylene (PP) and polyethylene (PE) is an effective means of reducing environmental pollution. However, the incompatible PP and PE blended waste is difficult to separate accurately, which reduces the quality of the recycled material. In this paper, the trifunctional acrylate monomer (trimethylolpropane triacrylate), peroxide (2,5‐dimethyl‐92,5‐di[tert‐butylperoxy] hexane) and free radical activity modifier (zinc dimethyldithiocarbamate) were applied to in situ generate the copolymer of isotactic polypropylene and high‐density polyethylene (iPP‐co‐HDPE) with a long‐chain co‐branched structure via a melt blending method. The co‐crystallization of the branched copolymer chain segments with the chemical identical homopolymers vastly improved the compatibility of iPP and HDPE components. This in situ co‐branching compatibility strategy resulted in a significant improvement in the mechanical properties of PE and PP mixed wastes. The temperature gradient extraction method was used to separate the co‐branching modified iPP/HDPE blends. The results confirm that the separated iPP‐co‐HDPE components have a highly co‐branched structure. The significant improvement in compatibility resulted in a large increase in elongation at break and impact strength of the iPP/HDPE blends, which provides an economic and effective method for the recycling of mixed PE and PP wastes.

Atomic insights into synergistic effect of pillared graphene by carbon nanotube on the mechanical properties of polymer nanocomposites

Molecular dynamics simulations have been performed to explore the underlying synergistic mechanism of pillared graphene or non-covalent connected graphene and carbon nanotubes (CNTs) on the mechanical properties of polyethylene (PE) nanocomposites. By constructing the pillared graphene model and CNTs/graphene model, the effect of the structure, arrangement and dispersion of hybrid fillers on the tensile mechanical properties of PE nanocomposites was studied. The results show that the pillared graphene/PE nanocomposites exhibit higher Young’s modulus, tensile strength and elongation at break than non-covalent connected CNTs/graphene/PE nanocomposites. The pull-out simulations show that pillared graphene by CNTs has both large interfacial load and long displacement due to the mixed modes of shear separation and normal separation. Additionally, pillared graphene can not only inhibit agglomeration but also form a compact effective thickness (stiff layer), consistent with the adsorption behavior and improved interfacial energy between pillared graphene and PE matrix.

Effect of high shear rate on the mechanical properties of polyethylene, poly(ethylene terephthalate), polystyrene and polypropylene waste blend

The effect of high shear rate on the mechanical properties of polyethylene (PE), poly(ethylene terephthalate) (PET), polystyrene (PS) and polypropylene (PP) waste blend was investigated. The process was carried out at a temperature of 120°C using a counter-rotating twin-screw extruder. A constant screw speed of 250 rpm and a constant weight ratio of the PE/ PET/PS/PP components of 1:1:1:1 were used. The preliminary research showed that the high shear rate had no effect on the impact strength. However, the significant improvement in the flexural properties was observed as compared to those obtained at a lower screw speed of 80--120 rpm.

Effects of environmental temperature on the mechanical properties of polyethylene fiber‐engineered cementitious composites

AbstractEngineered cementitious composites (ECC) incorporated with synthetic fibers possess extraordinary tensile capacity; however, temperature sensitivity of synthetic fiber arouses concern about the reliability of ECC working at extremely environmental temperature. This article is aimed to study the influence of environmental temperatures, from −20 to 90°C, on the mechanical properties of polyethylene (PE) fiber reinforced ECC (PE‐ECC). Experiments were conducted from four different angles, that is, compressive, and tensile properties of composites, fiber bridging behavior of composites, fracture toughness of cementitious matrix, and tensile property of PE fiber bundle. It is demonstrated that temperatures have significant impacts on the tensile and compressive strength of PE‐ECC. Furthermore, the test results indicated that the tensile strength of PE fiber, fracture toughness of matrix and fiber bridging strength all decreased, while the elongation of fiber and crack opening displacement are increased with temperature increasing from −20 to 90°C. On this basis, a pseudo‐strain‐hardening index is utilized to explain the mechanism underlying the temperature‐dependent behaviors of PE‐ECC.

Organic solvents effect on the physical and mechanical properties of polyethylene

High-density polyethylene (PE) swelling in organic solvents, orthodichlorobenzene and orthoxylene, was investigated. The PE specimen swelling kinetics was described with the first-order equation. For the first time, the PE specimen swelling rate constant was shown to decrease with increasing thickness of the specimens. The equilibrium PE specimen swelling was evaluated. It was found that equilibrium swelling independent of specimens’ thickness. PE specimen storage in organic solvents was shown to change its mechanical characteristics (tensile strength, Young’s modulus, and elongation at break) due to polymer plasticization. We showed that an increase in flexibility and elongation at break becomes noticeable after relatively short-term immersion of the PE specimens into these organic solvents. However, the tensile strength of swollen specimens remains enough high. The interaction between polymer chains and solvent molecules was not detected. The results obtained are important for design and operation of PE coatings and PE products, such as pipes, tanks, and other accessories subjected to contacts with oil products.

Preparation, thermal, and mechanical properties of polyethylene glycol/expoxy resin composites as form‐stable phase change materials

AbstractA series of polyethylene glycol (PEG)/epoxy (EP) resin composites with various mass loadings of PEG (50%–80%), in which PEG acted as phase change materials (PCMs) and EP served as the supporting matrix to afford structural strength and avoided the leakage of melt PEG, was made via casting mold technique. The effect of PEG mass content on the form‐stability, thermal property, morphology, and mechanical property of the composite phase change materials (CPCMs) were characterized by Fourier transformation infrared spectroscope (FTIR), differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), and atomic force microscopy (AFM), respectively. The results displayed that the EP was compatible well with the PEG, and the CPCMs showed excellent form‐stability, good thermal reliability and stability even with 80 wt% PEG loading and under high temperature. In addition, the average adhesion force of the PEG/EP CPCMs increased as the PEG mass loading increased. In summary, the as‐prepared form‐stable PEG/EP CPCMs had promising potential for practical latent heat thermal energy storage (LHTES) applications.

Gas permeability and mechanical properties of polyethylene films subjected to ultraviolet irradiation

ABSTRACT The effect of ultraviolet (UV) irradiation on gas permeability and mechanical properties of low-density polyethylene (LDPE) films was investigated in the temperature range from 20°C to 60°C. It was shown that UV exposure of the films resulted in their artificial aging, which is manifested as a decrease in gas permeability and as a variation in structure and mechanical properties of the LDPE films. A correlation between gas permeability and mechanical characteristics of the LDPE films subjected to the action of temperature and UV irradiation was found. The novelty of the performed investigations is due to the fact that the gas permeability of polymers exposed to the combined effects of UV radiation and temperature has not been studied so far.

Compressive Properties and Constitutive Model of Semicrystalline Polyethylene.

The mechanical properties of polyethylene (PE) materials are greatly influenced by their molecular structures, environmental temperature, and strain rate. In this study, static and dynamic compression tests were performed on two semicrystalline PE materials—ultrahigh molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE). The stress–strain curves of HDPE and UHMWPE under uniaxial compression at temperatures of −40–120 °C and strain rates of 0.001–5500 s−1 were obtained. The research findings suggest that both the UHMWPE and HDPE showed significant strain rate-strengthening effect and temperature-softening effect. In particular, HDPE exhibited better compression resistance and high-temperature resistance. The relationships between the yield stress and temperature and between the yield stress and strain rate for both materials were fitted, and the Cowper–Symonds constitutive model was built while considering the temperature effect. The parameters of the constitutive model were obtained and input into LS-DYNA software to simulate the dynamic compression process of HDPE. The simulation result was consistent with the test result, validating the accuracy of the constitutive parameters.

Electrospun polyamide/graphene oxide nanofibers as fillers for polyethylene: Preparation and characterization

AbstractThe morphology, crystallinity, and mechanical properties of polyethylene (PE) composites containing 0, 3.5, 7, 10.5, and 14 wt% polyamide 6 (PA6) and graphene oxide (GO)/PA6 electrospun mats were investigated. The differential scanning calorimetry (DSC) and wide angle X‐ray diffraction analysis results showed the formation ofɣcrystals in PA6 nanofibers where it increased with the addition of GO nanoplates. The crystallinity of PA6 mats was smaller than that of PA6 granule, but increased with the addition of GO. GO nanoplates at 2.5 wt% introduced a second higher melting peak 237°C for PA6 nanofiber. The DSC results showed that the crystallinity behavior of PE was affected by the presence of the nanofibers and GO nanoplates due to their nucleation effect. The mats enhanced the elastic modulus and yield strength of PE by 121 and 33%, respectively. Although ductility was dropped, the yield phenomenon of PE was preserved with the addition of the nanofibers. The nanofiber bridging mechanism was observed in the composites after failure in tensile test. The PE/PA6 nanocomposites can be used in PE applications with improved mechanical/barrier/conductivity properties such as tanks, containers, pipes, ropes, packaging, greenhouse films, and so on specially for those, which color change, or antistatic properties are important.

Synergistic Flame Retardant Effect of Organic Boron Flame Retardant and Aluminum Hydroxide on Polyethylene

This study aimed to develop an organic/inorganic synergistic flame retardant on polyethylene (PE). Hexakis-(4-boronic acid-phenoxy)-cyclophosphazene (CP-6B) was used as organic flame retardant to improve the flame retardant efficiency of aluminum hydroxide (ATH) on PE. The limiting oxygen index (LOI) value of PE/20 %ATH/20 %CP-6B reached 27.0 %, and vertical burning (UL 94) V-0 rating was attained. The peak heat release rate (pk-HRR) of PE/20 %ATH/20 %CP-6B was 33.7 % and 75.5 % of pure PE and PE/40 %ATH, respectively. The flame retardant mechanism of PE composites was also investigated using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), muffle furnace, Fourier transform infrared (FTIR), and Pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). The results showed that ATH/CP-6B was an efficient flame retardant, which was effective in the gas phase and condensed phase simultaneously. CP-6B improved the flame retardant efficiency of PE/ATH and reduced the effect of ATH on the mechanical properties of PE.

Antibacterial and Antifungal Properties of Composite Polyethylene Materials Reinforced with Neem and Turmeric.

With the increased scientific interest in green technologies, many researches have been focused on the production of polymeric composites containing naturally occurring reinforcing particles. Apart from increasing mechanical properties, these additions can have a wide range of interesting effects, such as increasing the resistance to bacterial and fungal colonization. In this work, different amounts of two different natural products, namely neem and turmeric, were added to polyethylene to act as a natural antibacterial and antifungal product for food packaging applications. Microscopic and spectroscopic characterization showed that fractions of up to 5% of these products could be dispersed into low-molecular weight polyethylene, while higher amounts could not be properly dispersed and resulted in an inhomogeneous, fragile composite. In vitro testing conducted with Escherichia coli, Staphylococcus aureus, and Candida albicans showed a reduced proliferation of pathogens when compared to the polyethylene references. In particular, turmeric resulted in being more effective against E. coli when compared to neem, while they had similar performances against S. aureus. Against C. albicans, only neem was able to show a good antifungal behavior, at high concentrations. Tensile testing showed that the addition of reinforcing particles reduced the mechanical properties of polyethylene, and in the case of turmeric, it was further reduced by UV irradiation.

Morphology and Mechanical Properties of Polyethylene Terephthalate/Ethylene Propylene Diene Monomer (PET/EPDM) in the Presence of Nanoclay

This research deals with the mechanical properties, microstructure, and interrelations of triple nanocomposite based on PET/EPDM/Nanoclay. These properties were examined in different percentages of PET/EPDM blend with compatibilizer (Styrene-Ethylene/Butylene-Styrene)-G-(Maleic anhydrate) (SEBS-g-MAH). Results showed that the addition of 15% SEBS-g-MAH improved the toughness and impact strength of this nanocomposite. SEM micrographs indicated the most stable fuzzy microstructure in a 50/50 mixture of scattered phases of EPDM/SEBS-g-MAH. The effects of percentages of 1, 3, 5, 7 nanoclay Cloisite 30B (C30B) on the improvement of the properties were evaluated. With the addition of nano clay, the toughness and impact strength was reduced. Thermal destruction of nanoclay in processing temperature led to the decreasing dispersion of clay plates in the matrix and a reduction in the distances of nano clay plates in the composite compared to pure nano clay. XRD and TEM analysis was used to demonstrate the results. By adding 1% of nanoclay to the optimal sample, maximum stiffness, and Impact strength, among other nanocomposites, was achieved.

Effect of hornbeam sawdust size on the mechanical properties of polyethylene composites

Composite materials obtained with natural and sustainable fibers can be used successfully in many areas on their own. In recent years, high-strength fibers such as hemp, sisal, linen, jute, wood sawdust and bamboo are more preferred in composite materials. In this study, the effect of the hornbeam sawdust size on the mechanical properties of polyethylene was investigated. For this purpose, different sizes of hornbeam sawdust were added to polyethylene. Hornbeam sawdust was added to the polyethylene matrix in four different weight ratios (5, 10, 15 and 20%) by way of the extrusion method. Test samples were prepared out of those mixtures by injection-molding. Tensile, Izod impact and hardness tests were performed on the samples. The elastic modulus increased with increasing hornbeam sawdust content. However, elongation at break and Izod impact strength values decreased. Modulus of elasticity, tensile strength, elongation at break and Izod impact strength values decreased with increasing hornbeam sawdust size. The morphology of composite samples was examined by scanning electron microscopy. The results show that the hornbeam sawdust can be used as a filler in polymer-based composites.

Effect of calcium carbonate on the mechanical properties of polyethylene terephthalate/polypropylene blends with styrene-ethylene/butylene-styrene

The effect of CaCO3 on the mechanical properties of polyethylene terephthalate/polypropylene (PET/PP) blends with styrene-ethylene/butylene-styrene (SEBS) as a compatibilizer was investigated. Samples with different compositions of PET/PP/CaCO3 blend were prepared by injection molding method with CaCO3 content of 0, 2, 4, 6, 8 and 10 wt%. The ratio of PET/PP was fixed at 90/10, while compatibilizer SEBS had a fixed ratio of 5%. The samples were formed according to the ASTM D638, ASTM D790, and ISO 868 standards. The results show that adding 2% of CaCO3 helps to improve the mechanical properties of the plastic sample. Specifically, tensile strength and the flexural strength increase as CaCO3 increases from 0 to 2%. With 2% of CaCO3, the tensile strength and the flexural strength gain the highest value of 34.79 MPa, and 60.59 MPa, respectively. However, if the sample content is more than 4% CaCO3, both the tensile strength and the flexural strength will experience a decline as the percentage of CaCO3 rises. The SEM microstructure indicates that CaCO3 particles are well dispersed on the PET substrate. Additionally, the number of particles increases when enhancing the CaCO3 content in the blends.

Effect of film fabricating conditions and its implications on mechanical properties of high-density polyethylene film

The use of plastics, especially High-Density Polyethylene (HDPE) film has increased rapidly in recent years due to its low cost, lightweight and excellent mechanical properties which is depended on the extrusion condition in the owner’s film fabrication machine. The blown film process is the common process used to make a thermoplastic film in large volumes. However, many research performed long ago in the mechanical properties of polyethylene only concerned on the effect of conventional processing parameters such as temperature and pressure in blown film machines and neglected the significant effect of critical extrusion conditions. We did the study to know the effect of critical extrusion conditions such as output rate, blow-up ratio (BUR) and neck-point height (NPH) which was intended to get the optimum film fabrication conditions in a blown film extrusion machine. Each parameter was performed in five different conditions by increasing one parameter and controlling the other. The resin first melted, conveyed, and delivered before finally blown to form the film. The mechanical properties observed were impact resistance, tensile strength, elongation, tear strength, and young modulus. The result indicates that increasing the output rate, BUR and NPH imparted in the film’s orientation balance, bubble shape, relaxation, and crystallization effects will lead to the increase of impact resistance, decrease of tear strength, and balance of film direction properties. The excessive and low amount of output rate, BUR and NPH are not desirable as it decreases the mechanical properties from HDPE film whether in mechanical direction or transverse direction. Hence, the optimum operating condition depends on which mechanical properties that needed to be achieved by film fabricators.