Weight High Density Polyethylene Research Articles

DEVELOPMENT OF FRICTION STIR WELDING TOOL FOR HIGH-DENSITY POLY-ETHYLENE (HDPE)–CASE STUDY: FIBERGLASS COMPOSITE MATERIAL

This study aims to develop an effective Friction Stir Welding (FSW) method for composite material of High-Density Poly-Ethylene (HDPE) Pipes. The development of welding tool, there was the addition of an external heating source on the shoulder and probe/pin to overcome the problem of lack of heat resulting from friction between the tool and the material to be welded. The case study was conducted to join the short fiberglass-HDPE composite with a type of ratio of 30% by weight of short fibre and 70% by weight of HDPE, which optimizing parameters such as rotating speed, welding speed, and preheating temperature. The FSW joining process for short fiberglass-HDPE composite sheets was carried out using a Fanuc Series 21i-M CNC milling machine as the driving tool with rotational speed (ω) varied in 3 conditions, namely 600 rpm, 800 rpm and 1000 rpm, and welding speed (v) or feeding at 5 mm/minutes and 10 mm/minutes. The temperature was controlled according to the liquid point of High-Density Poly-Ethylene, which was 130oC, and raised to 150oC and 170oC. The 12 pieces of thermocouple were used along the track on the material and jig plates at the top, middle and bottom. Then, the results of joining the sheets were made in the form of specimens with sizes according to ASTM 3039. The tensile tests of the specimens were carried out at a rate of 0.01 mm/s. The results showed the highest tensile strength was an average value of 24.52 MPa at a rotational speed of 800 rpm, the feeding of 5 mm/min and the temperature of 130oC. The lowest tensile strength was an average value of 17.54 MPa at a temperature of 170°C with a speed of 600 rpm.

Utilization of Bacillus cereus strain CGK5 associated with cow feces in the degradation of commercially available high-density polyethylene (HDPE).

The accumulation and mismanagement of high-density polyethylene (HDPE) waste in the environment is a complex problem in the present scenario. Biodegradation of this thermoplastic polymer is a promising environmentally sustainable method that offers a significant opportunity to address plastic waste management with minimal negative repercussion on the environment. In this framework, HDPE-degrading bacterium strain CGK5 was isolated from the fecal matter of cow. The biodegradation efficiency of strain was assessed, including percentage reduction in HDPE weight, cell surface hydrophobicity, extracellular biosurfactant production, viability of surface adhered cells, as well as biomass in terms of protein content. Through molecular techniques, strain CGK5 was identified as Bacillus cereus. Significant weight loss of 1.83% was observed in the HDPE film treated with strain CGK5 for 90days. The FE-SEM analysis revealed the profused bacterial growth which ultimately caused the distortions in HDPE films. Furthermore, EDX study indicated a significant decrease in percentage carbon content at atomic level, whereas FTIR analysis confirmed chemical groups' transformation as well as an increment in the carbonyl index supposedly caused by bacterial biofilm biodegradation. Our findings shed light on the ability of our strain B. cereus CGK5 to colonize and use HDPE as a sole carbon source, demonstrating its applicability for future eco-friendly biodegradation processes.

Effect of Additives on the flexibility of High-Density Polyethylene Filled Cowhide Composite

Fibre-filled high-density polyethylene composite was prepared by two roll melt mixing, and pressed into standard shapes using compression moulding technique for varying fibre contents from 10% by weight up to 60w% by weight. Tests were performed on composite specimens in accordance with ASTM D638. Additives have been incorporated into the design formulation of the composite to provide flexibility and intercalate (adhesion) between the fibre and the substrate. The results obtained were compared with specimens made of 100% weight of high-density polyethylene (HDPE). Results showed that waste loads in the range of 10-40% weight for un-treated hides (UH) and plant treated cowhide (acacia nilotical) (VT), represent good mechanical, physical, thermal and morphological properties, with improved intercalation between the fibre and interface substrate due to additives. 10-40 % weight (non-degradable) HDPE can be partially replaced with rawhide and processed shredded hide (both compostable), with the highest value at 10% by weight fibre content. The breaking strength of high-density polyethylene filled untreated hide with additive (HDPE/UHA) and high-density polyethylene filled plant treated hide with additives (HDPE/VTA) stretches longer under tension by 32.7% and 3.9% respectively, more than the control at 40% content by weight. The composites are suitable for producing composite-films, useful for manufacturing bags for packaging food goods, or in shoe soles, floor tiles and any material property requiring flexibility.

Thermal and Crystallization Behaviour of Polyphenylene Sulfide in Engineering Polymer Blends with HDPE

Abstract The thermal and crystallization behaviour of polyphenylene sulfide (PPS) in its blends with high density polyethylene (HDPE) is reported. Three grades of HDPE ranging in MFI from 0.4 to 52 were used in the investigation. The effect of composition and molecular weight of HDPE on the crystallization process and morphology of PPS in the blends has been investigated by the technique of Differential Scanning Calorimetry (DSC). In the blends, PPS crystallizes in presence of molten HDPE. It is observed that the morphology of PPS in terms of crystallite size and crystallite size distribution in the blends is significantly affected by blending with HDPE. The temperature onset of melting was found to increase with increasing HDPE content and the melting peak width was found to decrease with increasing HDPE content. This indicates a larger crystallite size and a narrower crystallite size distribution of PPS in blends. The effect is more pronounced in HDPE-rich compositions. The extent of the variation in the temperature onset of melting and peak width were comparable for all the grades of HDPE. The degree of crystallinity of PPS in the blends is reduced significantly (55–70%) in HDPE-rich blends. Therefore, it is concluded that the crystallization of PPS is affected by the presence of HDPE melt. The crystallization scans of PPS in the blends, obtained in the cooling mode, did not show any evidence of accelerated nucleation. On the other hand, a marginal reduction in the temperature onset of crystallization was observed. The temperature range of crystallization of PPS in the blends was found to be less for all compositions except for 90/10 (PPS/HDPE). In summary it is concluded that blending of HDPE with PPS influences the crystal growth of PPS significantly although the effect on its homogeneous nucleation is also considerable. As a result, the morphology of PPS crystallized in blends is different from that of the homopolymer. The changes in the morphology of PPS are not sensitive to the molecular weight of HDPE probably because of the high temperature of PPS crystallization relative to the melting point of HDPE.

Resin Transfer Molding of Wood Strand Composite Panels

The purpose of this study was to develop high-performance wood strand panels for automotive application using resin transfer and compression resin transfer molding technologies. Wood strand preforms bonded with 1%, 5%, and 20% by weight low-density polyethylene and 1% by weight high-density polyethylene were impregnated with resin during the molding process and compared. The results showed that 1% low-density polyethylene is sufficient to bind wood strands into a stable preform for handling and processing. Permeability measurements using a volumetric interpretation of Darcy’s law accounted for resin flow through the thickness of the preform. When compared with previously published data on other natural fiber composites, resin transfer molded wood strand composites generally exhibited superior mechanical properties and significantly greater dimensional stability when exposed to moisture.

Theoretical and experimental assessment of UV resistance of high‐density polyethylene: Screening and optimization of hindered amine light stabilizers

AbstractHindered amine light stabilizers (HALS) are widely used chemical stabilizers for preventing polymer degradation. In this study, the effects of type of HALS and its content in high‐density polyethylene (HDPE) over the stabilization process are investigated employing density functional theory (DFT) and experimental approach. The electrophilicity index of four types of commercial HALS are compared by DFT to select the most effective one. Besides, the HDPE sample containing a phenolic antioxidant and different contents of the selected HALS are experimentally exposed to UV irradiation. The effect of HALS content on the changes in chain microstructure and molecular weight of HDPE are evaluated using gel permeation chromatography and frequency sweep rheometry. In the absence of HALS, HDPE suffers degradation and the phenolic antioxidant causes chain scission. However, by adding HALS, the chain branching and crosslinking mechanisms are predominant. The results of FTIR, DSC, and tensile analyses follow similar trends, revealing that the best stabilization performance corresponds to adding 600 ppm HALS to HDPE.

THE EFFECTS OF HIGH DENSITY POLYETHYLENE ADDITION TO LOW DENSITY POLYETHYLENE POLYMER ON MECHANICAL, IMPACT AND PHYSICAL PROPERTIES

Polyethylene materials are the most widely used polymers which we encountered everywhere in our daily life. Some of the advantages of the polyethylenes are the diversity of production types, corrosion resistance, electrical insulation and recyclability. The main production methods are compression molding, transfer molding, rotational molding, injection molding, gas-assisted injection molding, extrusion and blown film extrusion techniques. It is possible to increase the mechanical properties of low density polyethylene materials by addition of high density polyethylene materials. Both polymer has same monomers but their chemical structure and bonding properties are different. Their physical properties can change with their chemical structure and bonding properties. In this study, 25%, 50% and 75% by weight of high density polyethylene were added to low density polyethylene. Granules were pre-mixed with a mechanical mixer before production of the samples. Plastic injection molding machine was used for specimen preparation. Density, hardness, tensile test, three-point bend test, compression test, tear test and Izod impact tests were performed. Densities and hardness values of the polymer blends decrease by the increasing amount of low density polyethylene. In general, it was observed that the mechanical properties of the polymer blends increase as the high density polyethylene content increase.

Realizing self-reinforcement of polyethylene via high-speed shear processing

As one of the most representative polyolefins, polyethylene (PE) constitutes the largest consumption of thermoplastics in the world. Thus, the high-performance issue of PE, such as effective self-reinforcement, represents highly expected demand in both of academic and industrial areas. However, it induces a materials engineering challenge due to the difficulties in preparations of multiphase materials and technological complexities of processing. Here, we report a readily accessible self-reinforcement behavior of high-density polyethylene (HDPE) realized via using a commercially available technique, high-speed shear extrusion. A common grade of HDPE can be enhanced significantly for nearly 60%, depending on the rotation speed. The chromatography indicates that the molecular weight of HDPE is nearly constant after experiencing high-shearing effect. While a quasi-solid-like character is detected in the HDPE melt, which could be attributed to the increment of entanglement causing by severe mixing during extrusion. Subsequently, the enhanced entanglement enables the appearances of high orientation structure and specific crystalline morphology, which are responsible for the mechanical reinforcement observed. Our present study offers a promising avenue to access the manufacture of structural parts using polyolefin resins.

Melt die-swell behavior of polyoxymethylene blended with ethylene-vinyl acetate copolymer and high-density polyethylene

The influence of extrusion conditions (temperature ranging from 170 to 220 °C, loads varying from 1.2 to 12.5 kg) and high-density polyethylene (HDPE) content on swelling behavior of polyoxymethylene (POM)/ethylene-vinyl acetate copolymer (EVA)/HDPE blend melts was examined. It was found the melt die-swell ratio of the blends decreased approximately linearly with rise in temperature, while it increased as a quadratic function with increasing shear rate or shear stress. The melt die-swell ratio increased with increasing HDPE weight fraction under constant test temperature, and the effect of temperature on the sensitivity of the melt die-swell ratio to the HDPE weight fraction was insignificant, while the effect of load on the melt die-swell ratio was significant. The correlation between the melt die-swell ratio of the blends and the HDPE weight fraction followed a quadratic relation. The melt extrudate swell behavior mechanisms of the blends during the die extrusion flow are discussed.

The coupling relation between chain architectures and secondary flow field determined by an unusual dependence of shish-kebabs on molecular weight of high-density polyethylene

Selecting high molecular weight has become a quite popular approach for effective tuning of more shish-kebabs in semi-crystalline polymers. However, here, an unusual dependence of shish-kebabs on molecular weight of high-density polyethylene (HDPE) is found under the injection molding with a secondary flow. Characterization with electron microscope and X-ray scattering of the crystal structures reveals that the richest shish-kebabs develop in the HDPE with medium high molecular weight (HMW) chains rather than in the HDPE with more HMW chains. Both macroscopic scales (fluid behaviors related to the intensity of flow) and molecular scales (rheological properties related to orientation and relaxation) need to be overall considered and a physical model has been proposed to explain how the coupling between the chain architectures and the secondary flow field contributes to the unusual phenomenon. The factors, such as molecular parameters, interfaces between dispersed phase, and matrix as well as the properties of filler, profoundly influence both the two scales, which can be employed to tune the morphology related to physical properties. These significant results provide a simple but effective morphology control technique under a secondary flow field.

Flexural and impact properties of POM/EVA/HDPE blends and POM/EVA/HDPE/nano-CaCO3 composites

The Polyformaldehyde (POM)/ethylene–vinyl acetate copolymer (EVA)/high-density polyethylene (HDPE) blends and POM/EVA/HDPE composites filled with nanometer calcium carbonate (nano-CaCO3) were prepared using a twin-screw extruder. The effects of the HDPE weight fraction on the flexural and impact properties of the blends and composites were investigated at room temperature. The results showed the flexural modulus and strength of the blends and composites decreased slightly with increasing the HDPE weight fraction. The values of the flexural modulus of the composites were higher than those of the blends, while the values of the impact fracture strength of the blends were higher than those of the composites under the same HDPE weight fraction. This indicated that the impact fracture toughness of the POM could be improved with the HDPE, while the flexural stiffness of the POM blends could be enhanced with the nano-CaCO3 to some extent.

Tensile properties of polyformaldehyde blends and nanocomposites

Abstract The effects of the compositions and tensile rates on the tensile properties of the polyformaldehyde (POM)/ethylene-vinyl acetate copolymer (EVA)/high-density polyethylene (HDPE) blends and POM/EVA/HDPE composites filled with nanometer calcium carbonate were investigated by means of a tensile test machine at room temperature. The results showed that the Young’s modulus, tensile yield strength, and tensile elongation at break of the blends and the composites decreased nonlinearly with increase in the HDPE weight fraction; it should be attributed to the low stiffness and strength of the HDPE resin; the difference in the Young’s modulus and tensile yield strength between the blends and the composites was insignificant under the same experimental conditions. Both the Young’s modulus and tensile yield strength of the blends and the composites increased nonlinearly with increase in the tensile rate in the case of low tensile rate level. Moreover, the predictions of the Young’s modulus and tensile strength were roughly close to the measured data from the blends.

Melt extrudate swell behavior of POM/EVA/HDPE/nano-CaCO3 composites

Abstract Polyformaldehyde (POM)/ethylene-vinyl acetate copolymer (EVA)/high-density polyethylene (HDPE) composites filled with nanometer calcium carbonate (nano-CaCO3) were prepared using a twin-screw extruder. The effects of load and temperature on the melt extrudate swell behavior of the composites were investigated, by using a melt flow rate instrument under experimental conditions, with temperatures ranging from 170°C to 220°C and loads varying from 1.2 kg to 12.5 kg. The results showed that the melt die-swell ratio (B) of the composites decreased linearly with a rise of temperature as the load was fixed, while it increased nonlinearly with increase in the melt volume flow rate (MVR) and load, when the test temperature was constant; they also showed that B is a quadratic function of shear rate or shear stress. The value of B increased nonlinearly with an increase of the HDPE weight fraction (ϕ) as the temperature was constant, and the temperature sensitivity of B to ϕ was insignificant, while the effect of load was significant. The correlation between B and ϕ obeyed a quadratic equation.

Morphology and Stress Whitening of Heterophasic Poly(propylene) Copolymer/High Density Polyethylene Blends

AbstractSummary: Effect of high density polyethylene (HDPE) addition on the morphology of heterophasic poly(propylene) copolymer (HPC) was investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Stress whitening developed upon dart impact was evaluated using Gardner‐type impact tester. In the TEM study of HPC/HDPE blends, a core‐shell morphology was observed of HDPE encapsulated by ethylene‐propylene rubber (EPR). At low HDPE weight fractions (95/5 and 90/10 HPC/HDPE), the size of dispersed phase increased compared to pure HPC. However, further increase in HDPE leads to a decrease in domain size. The impact strength reached a maximum at 90/10 HPC/HDPE blend, and then decreased with further increase in HDPE content. The stress whitening of HPC was decreased with addition of HDPE. This decrease is attributed to the difference in the shrinkage between HPC and HPC/HDPE blends. The pressure‐volume‐temperature relationship supports that an additional volume contraction of HDPE can reduce the stress whitening of HPC.

Analysis of the Biotribological Behavior for the Stainless Steel/Polyethylene Contact Using a Knee Prosthesis Simulator

In this work, a friction and wear simulator was used to reproduce the Anterior-Posterior (AP) sliding and the Flexion-Extension (FE) rotation generated in the knee joint during human gait cycle. We chose to simplify the contact geometry between the Total Knee Arthroplasty (TKA) femoral component and tibial insert. A 304L stainless steel cylinder which replaces the femoral component was loaded onto a flat High Density Polyethylene (HDPE) block which replaces the tibial insert. The tribological behavior of the considered contact was analyzed by tracking the number of cycles, the friction coefficient, the roughness of the wear track on HDPE, the HDPE weight loss and the damage mechanisms. The friction coefficient shows a gradual increase with the number of cycles for both AP and FE kinematics. The evolution of friction coefficient with the number of cycles is not affected by the value of the imposed normal load in the case of AP sliding. For the FE rotation, decreased friction coefficient is obtained when the imposed normal load increases. For both considered AP and FE kinematics, the roughness of the wear track on the HDPE is not affected by the imposed normal load. It shows a progressive decrease when the number of cycles increases. The wear of HDPE obeys the Archard law and the wear coefficient increases with the normal force. For a given value of normal load, the obtained wear coefficient for the AP sliding is larger than that obtained for FE rotation. A predominant adhesive wear mechanism was identified for both AP and FE kinematics. Under the same normal load, damage development in terms of plastic deformation, micro-cracking and debonding is more pronounced for the AP sliding if compared with the FE rotation. For a given kinematics, the damage severity increases with the normal load. This finding is in good agreement with the predicted values of the wear coefficient according to the Archard law.

Adhesive wear and frictional characteristics of UHMWPE and HDPE sliding against different counterfaces under dry contact condition

The current work evaluates the wear and frictional performance of ultrahigh molecular weight polyethylene (UHMWPE) and high density polyethylene (HDPE) sliding against different metal counterfaces, stainless steel(SS), mild steel (MS) and aluminium (Al), under dry contact condition. The experiments were conducted using pin on disc machine at different sliding distances (0–40·32 km), 15 N applied load and 2·8 m s–1 sliding velocity. Interface temperatures and frictional forces were measured simultaneously during the sliding, while specific wear rates were determined for every 1·68 km sliding distance. Based on the optical microscopy of the worn surface and wear track, frictional and wear results were analysed and discussed. The experimental results showed that the type of counterface material significantly influences both frictional and wear performances of the selected polymers. This was mainly due to the film transfer characteristics. Higher temperature and friction coefficient for UHMWPE and HDPE were evident when sliding took place against Al counterface. Sliding the polymers against stainless steel showed low friction coefficients compared to other counterfaces.

Toughening of recycled polystyrene used for TV backset

AbstractThe recycled polystyrene (rPS) was toughened with ethylene‐octylene copolymer thermoplastic elastomer (POE) and high‐density polyethylene (HDPE) with various melt flow index (MFI), compatibilized by styrene‐butadiene‐styrene copolymer (SBS) to enhance the toughness of rPS for use as TV backset. The rPS/POE binary blends exhibited an increased impact strength with 5–10 wt % POE content followed by a decrease with the POE content up to 20 wt %, which could be due to poor compatibility between POE and rPS. For rPS/POE/SBS ternary blends with 20 wt % of POE content, the impact strength increased dramatically and a sharp brittle‐ductile transition was observed as the SBS content was around 3–5 wt %. Rheological study indicated a possible formation of network structure by adding of SBS, which could be a new mechanism for rPS toughening. In rPS/POE/HDPE/SBS (70/20/5/5) quaternary blends, a fibril‐like structure was observed as the molecular weight of HDPE was higher (with lower MFI). The presence of HDPE fibers in the blends could not enhance the network structure, but could stop the crack propagation during fracture process, resulting in a further increase of the toughness. The prepared quaternary blend showed an impact strength of 9.3 kJ/m2 and a tensile strength of 25 MPa, which can be well used for TV backset to substitute HIPS because this system is economical and environmental friendly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Unexpected molecular weight dependence of shish-kebab structure in the oriented linear low density polyethylene/high density polyethylene blends

In this study, highly oriented shish-kebab structure was achieved via imposing oscillatory shear on the melts of linear low density polyethylene (LLDPE)/high density polyethylene (HDPE) blends during the packing stage of injection molding. To investigate the effect of molecular weight of HDPE on the formation of shish-kebab structure, two kinds HDPE with large melt flow index (low molecular weight) and small melt flow index (high molecular weight) were added into LLDPE matrix. The structural characteristics of LLDPE/HDPE blends were systematically elucidated through two-dimensional wide-angle x-ray scattering, scanning electron microscopy, and differential scanning calorimetry. Interestingly, an unexpected molecular weight dependence of shish-kebab structure of the prepared samples was found that the addition of HDPE with low molecular weight resulted in an higher degree of orientation, better regularity of lamellar arrangement, thicker lamellar size, and higher crystal melting temperature than that adding HDPE with high molecular weight. Correspondingly, the blend containing low molecular weight HDPE had better tensile strength. A possible mechanism was suggested to elucidate the role of HDPE molecular weight on the formation of shish-kebab structure in the oriented blends, considering the change of chain mobility and entanglement density with change of molecular weight.

Viscoelasticity and viscoplasticity of semicrystalline polymers: Structure–property relations for high-density polyethylene

Observations are reported on two commercial grades of high-density polyethylene (HDPE) in uniaxial tensile tests, relaxation tests, creep tests and cyclic tests with a strain-controlled deformation program. Constitutive equations are derived for the viscoelastic and viscoplastic responses of semicrystalline polymers at three-dimensional deformation with small strains. A polymer is modeled as a two-phase continuum consisting of a crystalline skeleton and an amorphous phase treated as a transient network of chains. Its viscoelastic response is associated with thermally activated rearrangement of strands in the temporary network. The viscoplastic behavior reflects fine and coarse slip of lamellar stacks and sliding of junctions between chains in the network. Adjustable parameters in the stress–strain relations are found by fitting the experimental data. The study focuses on the effect of molecular weight of HDPE on its mechanical properties.

Studies on HDPE functionalized by ultraviolet irradiation and interfacial interaction of HDPE/STC blend

Compared with ultraviolet irradiation in air, high density polyethylene (HDPE) could be very quickly functionalized by ultraviolet irradiation in ozone atmosphere, introducing oxygen-containing groups such as C=O and C-O onto the molecular chains of HDPE. After ultraviolet irradiation in ozone atmosphere, the molecular weight of HDPE decreased, its distribution became wider, the melt index (MI) increased, and the water contact angle decreased. After irradiating for a short time in ozone atmosphere, the interfacial interaction between the irradiated HDPE and sericite-tridymite-cristobalite (STC) particles is improved. The yield and notched impact strength of the HDPE/STC (60/40) blend with 10 min-irradiated HDPE are increased from 25.5 MPa and 61 J/m for the nonirradiated HDPE/STC (60/40) blend to 30.2 MPa and 360 J/m for the irradiated blend, respectively.