Extrusion Of Polyethylene Research Articles

Extrusion and Injection Molding of Polyethylene Loaded with Recycled Textiles: Mechanical Performance and Thermal Conductivity

The aim of this project was to assess the thermal conductivity of polyethylene (PE) filled with carbon black (CB), specifically for geothermal pipes. The project explored the potential modification of PE’s thermal conductivity by incorporating recycled textile fibers. Different types of shredded recycled fibers were tested, including two types of polyamide fibers with varying contaminations and one type of polyester fiber. Following several preparation steps, various composite materials were manufactured and compared to bulk PE using various testing methods: Differential Scanning Calorimetry analysis (DSC), mechanical testing (flexural and tensile), and laser flash analysis (LFA). The results revealed alterations in the mechanical properties of the composite materials in comparison to PE filled with CB. The LFA tests demonstrated the effectiveness in reducing polymer thermal diffusivity at higher temperatures, particularly when the material was loaded with recycled polyester fillers.

Anti-Microbial, Thermal, Mechanical, and Gas Barrier Properties of Linear Low-Density Polyethylene Extrusion Blow-Molded Bottles.

Microbial contamination can occur on the surfaces of blow-molded bottles, necessitating the development and application of effective anti-microbial treatments to mitigate the hazards associated with microbial growth. In this study, new methods of incorporating anti-microbial particles into linear low-density polyethylene (LLDPE) extrusion blow-molded bottles were developed. The anti-microbial particles were thermally embossed on the external surface of the bottle through two particle deposition approaches (spray and powder) over the mold cavity. The produced bottles were studied for their thermal, mechanical, gas barrier, and anti-microbial properties. Both deposition approaches indicated a significant enhancement in anti-microbial activity, as well as barrier properties, while maintaining thermal and mechanical performance. Considering both the effect of anti-microbial agents and variations in tensile bar weight and thickness, the statistical analysis of the mechanical properties showed that applying the anti-microbial agents had no significant influence on the tensile properties of the blow-molded bottles. The external fixation of the particles over the surface of the bottles would result in optimum anti-microbial activity, making it a cost-effective solution compared to conventional compounding processing.

CO2 measurement in aquaria using a plastic film colourimetric indicator

The preparation of a colourimetric, plastic film indicator is described, based on the extrusion of low-density polyethylene, LDPE, mixed in with a small amount (5 wt%) of a CO2 sensitive pigment, which is blue and yellow in the absence and presence of CO2, respectively. The pigment comprises a mixture of a pH-indicator dye, Xylenol Blue, XB, with a base, tetrabutyl ammonium hydroxide, coated onto nanoparticles of silica. The extruded XB-LDPE film exhibits a reversible sensitivity towards dissolved CO2, units: %CO2, and a striking colour change over the key operating range, 1–2 %CO2, that needs to be maintained to keep both the fish and any plant-life healthy in an aquarium at 25 °C. The CO2 sensitivity of the XB-LDPE indicator is independent of the pH and ionic strength of the water under test and so can be used to measure %CO2 in sea- and fresh-water aquaria. Digital photography coupled with digital colourimetric analysis, DCA, is used to quantify the response of the XB-LDPE indicator in aquarium sea- and freshwater, and a user-friendly macro is provided to make this process simple to effect. The XB-LDPE indicator offers an attractive, faster, more stable, and much more informative alternative to the popular current, qualitative, drop-checker method for measuring %CO2. The possible use of the XB-LDPE indicator to measure %CO2 in natural waters is discussed.

Permeation of vegetable oils and slippery properties of extrusion coated paperboard

AbstractDue to the ability of oils to penetrate into the structure of polymers, it is possible to create slippery surfaces with low water droplet sliding angles based on polymer coatings. Polylactic acid, polybutylene succinate and low‐density polyethylene extrusion coatings were used as such surfaces in this study. The process of penetration of vegetable oils into the polymers was studied with the subsequent investigation of slippery behaviour of such system. Cottonseed oil and castor oil showed promising properties as lubricants. For oil infused polymer surfaces the water droplet sliding angles were significantly lower than for the untreated extrusion coating. The penetration of the permeant into the upper layers of the coating was confirmed by alteration of the static water contact angle, sliding angle and also by the cross section images. LDPE extrusion coating infused with castor oil showed the lowest water sliding angle − 8°. Biopolymers, being a main focus in this study, exhibited also promising results, PLA reached sliding angle of 14° with both olive and castor oil. Dependence of polymer permeability on various factors is rather complex and the wide range of oils used in this work helps to interpret the barrier performance of the studied materials. Degree of bond saturation, viscosity and polarity were found to influence mostly on the oil permeation through the studied polymers.

A Novel Accelerated Aging Test for Floats in a Floating Photovoltaic System

Countries around the globe have recently been actively developing a new type of solar power system known as the floating photovoltaic (FPV) system. The FPV system is advantageous in terms of efficiency and is economic; however, the environmental conditions on the surface of water are harsher than on the ground, and regulations or standards of the long-term durability of the float are insufficient. As a result, this study aims to investigate the durability of the float through three types of accelerated aging tests, including the damp heat test, the ozone-aging test, and the ultraviolet (UV) aging test. After the 7-day damp heat test (80 °C/95% RH), the results revealed that four groups of high-density polyethylene (HDPE) extrusion specimens neither produced more oxygen-containing functional groups, according to Fourier-transform infrared (FTIR) spectrum analysis, nor became more easily broken by the tensile test. Furthermore, more oxygen-containing functional groups were produced after the 7-day ozone-aging test (80 °C/95% RH/500 ppm) than the 17-day UV-aging test (60 °C/0% RH/60 kW·h·m−2). On the contrary, UV aging would make HDPE specimens harder and more brittle than ozone aging. To conclude, both ozone- and UV-aging tests can evaluate the durability of the float quickly and efficiently.

Finite Element Model of Equal Channel Angular Extrusion of Ultra High Molecular Weight Polyethylene

Abstract Ultra-high molecular weight polyethylene (UHMWPE) used in biomedical applications, e.g., as a bearing surface in total joint arthroplasty, has to possess superior tribological properties, high mechanical strength, and toughness. Recently, equal channel angular extrusion (ECAE) was proposed as a processing method to introduce large shear strains to achieve higher molecular entanglement and superior mechanical properties of this material. Finite element analysis (FEA) can be utilized to evaluate the influence of important manufacturing parameters such as the extrusion rate, temperature, geometry of the die, back pressure, and friction effects. In this paper, we present efficient FEA models of ECAE for UHMWPE. Our studies demonstrate that the choice of the constitutive model is extremely important for the accuracy of numerical modeling predictions. Three considered material models (J2-Plasticity, Bergstrom-Boyce, and the three-network model) predict different extrusion loads, deformed shapes, and accumulated shear strain distributions. The work has also shown that the friction coefficient significantly influences the punch force and that the two-dimensional (2D) plane strain assumption can become inaccurate in the presence of friction between the billet and the extrusion channel. Additionally, a sharp corner in the die can lead to the formation of the so-called “dead zone” due to a portion of the material lodging into the corner and separating from the billet. Our study shows that the presence of this material in the corner substantially affects the extrusion force and the resulting distribution of accumulated shear strain within the billet.

The in-line detection method of sharkskin melt flow instability during polyethylene extrusion based on pressure analysis

Abstract This paper is concerned with the issues of occurrence and detection of melt flow instabilities forming during polyethylene extrusion. A novel method of in-line detection and evaluation of sharkskin melt flow instability occurring during the extrusion of linear low density polyethylene (LLDPE) was developed. The application of the dynamic pressure analysis procedure with three different signal processing methods allows to obtain both quantitative and qualitative information about the phenomena which caused the distortion of the surface of the extrudate during the technological process. Investigations were carried out with two commercial LLDPE grades with different molecular weight distributions. In-line evaluation of the efficiency of the novel measuring system was preceded by off-line rheological experiments which allowed to obtain broad information about the influence of the macromolecular structure of selected polyethylenes on their properties in the molten state and their potential ability to create sharkskin instability. The preliminary multi-criteria assessment of the structure-rheological properties relationship allowed the verification of the sensitivity of the novel measuring system and the definition of proposals for the selection of appropriate signal processing methods for the different types of melt fracture instabilities formed on the extrudate surface.

Capillary extrusion of polypropylene/high-density polyethylene immiscible blends as studied by rheo-particle image velocimetry

The capillary extrusion of polypropylene (PP) and high-density polyethylene (HDPE) immiscible blends was studied in this work by rheo-particle image velocimetry (Rheo-PIV). The PP/HDPE blends were prepared by single screw extrusion and extruded through a transparent capillary die at a temperature of 200 °C and concentrations of 80/20, 60/40, 40/60 and 20/80 wt%, respectively. PIV measurements described accurately the flow behavior of PP/HDPE blends and revealed continuous velocity profiles in the die, without macroscopic phase separation, for all the blends in the resolution range of the PIV technique. The flow behavior of all the blends was shear-thinning (power-law) type and their viscosities laid in between the values corresponding to the neat polymers and increased in an exponential way along with the concentration of the highest viscosity component in the blend (HDPE). Also, it was found that the extruded blends acquired a stratified morphology and that HDPE mitigates extrudate distortions in PP, meanwhile PP eliminates slip and flow instabilities in HDPE by migrating to the region of highest shear stresses in the die. Migration of PP to the capillary wall was corroborated by Raman spectroscopy measurements on the periphery of solid extrudates. Finally, via calculations of the density of the molten blends under flow using the velocity profiles in the die, we show that the homopolymers are compatible in the molten state and follow a simple inverse relation for their density, and an exponential one for their viscosity.

High-Speed Extrustion of Polyethylene in the Acceleration of Projectiles in Ballistic Launchers

Acceleration of projectiles in ballistic launchers by means of high-speed extrusion of polyethylene through a tapered adapter is experimentally and theoretically studied. Quasi-one-dimensional gas-dynamic model of a polydisperse mixture of gas and powder particles and a viscoplastic model of a deformable piston are used. The results of numerical simulation of the process under study and the results of a series of shots from a powder ballistic launcher are given. The influence of the geometry of a tapered section and input velocity of the deformable piston on the output velocity of a projectile is experimentally investigated.

Using mixed goal programming to optimize performance of extrusion process for multiple responses of irrigation pipes

The performance of the polyethylene extrusion process used in the plastic industry was optimized using mixed goal programming. Four responses, the roll weight, production cycle time, distance between emitters, and thickness, are crucial. After a combination of initial factor settings was determined, individual and moving range control charts were established for each response. Two-phase optimization was implemented using L18 and L9 arrays for conducting experiments. A two-phase fuzzy goal programming model was formulated and employed to determine the combination of optimal factor settings, which was used to perform experiments. The results showed a significant reduction in the average production time from 13.0 to 11.316 min. Moreover, the average respective relative percentages of variability reduction for the roll weight, production cycle time, distance between emitters, and thickness were 48.547%, 49.048%, 47.174%, and 63.704%, respectively, and the corresponding estimated process capability indices for the combination of initial (optimal) factor settings were 0.202 (1.440), 0.330 (0.914), and 0.460 (1.456). Such improvement results in significant reduction in quality costs.

Roles of Slip Agent in Blown Film Extrusion of Linear Low Density Polyethylene

Roles of Slip Agent in Blown Film Extrusion of Linear Low Density Polyethylene

Effect of Co-monomer Styrene on Reactive Compatibilization of PE/Wood-flour Composites

Compatibilization between polyethylene(PE) and wood-flour was achieved by means of direct reactive extrusion of PE, wood-flour, maleic anhydride(MAH), co-monomer styrene(St) and dicumyl peroxide. Mechanical properties and heat distortion temperature(HDT) of the PE/wood-flour composites were tested, and impact cracking surfaces of the composites were observed via scanning electron microscope. Effect of St on reactive compatibilization of the composites was evaluated. Experimental results indicated that the anchoring strength of interface in the composites was obviously strengthened after St was added. Mechanical properties and HDT of the composites raised with increase of use level of St on the initial stage, and then gradually descended. When use level of St ran up to 1.5%, mechanical properties and HDT of the composites were best. At this moment, the mole ratio of St and MAH was approximately 1:1.

Effects on Oxygen‐barrier Properties of Pretreating Paperboard with a Starch–Poly(Vinyl Alcohol) Blend before Polyethylene Extrusion

Polyethylene (PE) extrusion coating was performed on paperboard pre‐coated with water‐borne barrier coatings based on starch–poly(vinyl) (PVOH)–plasticizer blends in order to investigate that how the addition of a plasticizer to the pre‐coating affects the oxygen‐barrier properties of the board after PE extrusion coating. The plasticizers used were glycerol, polyethylene glycol (PEG) and citric acid (CA). Photomicrographs showed that the barrier coating layers were rather smooth, but defects were observed in the starch–PVOH layers when a plasticizer was added. Starch–PVOH layers had oxygen‐barrier properties similar to those of pure PVOH without plasticizers. When a sufficient number of layers (four layers) were applied to cover defects, the starch–PVOH layers containing CA showed oxygen transmission rate (OTR) values similar to those of starch–PVOH layers without plasticizer. The adhesion of PE to pre‐coated paperboard decreased when a plasticizer was added to the pre‐coating recipes. PE extrusion coating resulted in a reduction in the OTR in the case of pre‐coating formulations containing plasticizers. A lower OTR after polyethylene extrusion was observed with PEG as plasticizer than with CA as plasticizer. This could be explained by the increase in brittleness due to cross‐linking under the high temperature load during the extrusion process. Dynamic mechanical analysis of the films showed a substantial increase in storage modulus between 100°C and 200°C for CA‐containing starch–PVOH films. The contact angle of diiodomethane on the pre‐coating layer decreased when a plasticizer was added to the coating recipe indicating an increase in wetting of the PE melt. Addition of PEG to the pre‐coating led to a greater wetting than the addition of CA, and this may have sealed some defects in the pre‐coating leading to lower OTR values.

A study of “worms” melt fracture in polyethylene extrusion blow molding process using capillary rheometry

During the polyethylene (PE) blow molding process of large size drums, string-like defects, which are referred to here as worm melt fracture, can sometimes be observed on the extrudate surface. Such string-like defects, in various shapes and sizes, are also observed in the capillary extrusion at high shear rates after the slip-stick transition. The PE resin with broader molecular weight distribution (MWD) exhibits a greater degree of worm melt fracture while narrow MWD PE resin, which has higher slip velocity and a uniform slip layer, shows a lesser degree of worm melt fracture. It is hypothesized that the worm melt fracture is related to the die build-up. Based on the mechanism of the fast die build-up, it is proposed that the cohesive slip layer, which is a failure within the polymer melts at an internal surface, could emerge out from the die as these string-like materials attached on the extrudates. The broader MWD resin, which has more small polymer chains and a lower plateau modulus, is postulated to have a weaker polymer melt, which then makes it easier to have such an internal failure and consequently have more string-like defects at high shear rates. POLYM. ENG. SCI., 56:650–656, 2016. © 2016 Society of Plastics Engineers

A new extrusion head with integrated ultrasonic device and online process parameters measurements system — design and testing

A new extrusion die with integrated ultrasonic device and online viscosity monitoring system was designed. This new construction was tested in the process of high density polyethylene (PE-HD) extrusion. Ultrasonic vibration is applied at various flow rates of material flowing through the output die channel, making the process more efficient. Under ultrasounds application, extrudate flow rate is enhanced by up to 10 %. Die pressure is reduced by up to 16 % for all the rates studied, being this reduction higher as flow rate is lower. Viscosity values are reduced by between 5 and 8 %, depending on the flow rate applied. Temperature is slightly increased.

Toward halogen-free flame resistant polyethylene extrusion coated paper facings

Abstract Extrusion coating experiments of flame retarded low density polyethylene (LDPE) onto a standard machine finished Kraft paper have been carried out. A pilot extrusion coating line was used in order to investigate the potential of halogen-free flame retardant system based on azoalkanes such as azocyclohexane (AZO) and 4′,4-bis(cyclohexylazocyclohexyl)methane (BISAZO) for fire resistant coating applications. In comparison, experiments were performed using FlameStab ® NOR116, magnesium dihydroxide (MDH) and a brominated additive Luvogard MB81/PE as reference flame retardants. The concentration of azoalkane flame retardants was varied between 0.5 and 1 wt.%. The maximum extrusion temperature was varied between 260 and 290 °C and the coating layer weight from 12.9 to 25.0 g/m 2 . The obtained multilayer facings containing azoalkanes exhibited significantly improved flame retardant properties, especially at the low coating weight of 12.9 g/m 2 . Under all of the used experimental conditions the runnability on the pilot line was flawless for azoalkane formulations. In contrast, our pre-trials using MDH/LDPE (50:50) formulations failed due to poor film quality and visible white aggregates. Moreover, the multilayer facings containing the FlameStab ® NOR116, Luvogard MB81/PE or mixtures thereof, showed inferior flame retardant properties compared to azoalkane based facings.

Experimental and numerical analysis of performance of two fluted mixer designs

In this paper, the effect of the Maddock mixer design on its performance in the single screw extrusion of High-density Polyethylene (HDPE) melt has been investigated experimentally on a special extrusion line equipped with a barrel having several glass windows as well as theoretically using a three-dimensional finite element method simulation. The red–green–blue spectral analysis has been used for the experimental quantification of the mixing efficiency, whereas a generalised Newtonian model (with Carreau–Yasuda viscosity function) and a viscoelastic modified White–Metzner model have been utilised in flow simulations. Based on the performed experimental work, it has been found that the mixer with no undercut wiping flight (‘Closed’ mixer) has a faster mixing/purging but a similar final mixing performance as the mixer with undercut wiping flight (‘Open’ mixer). It has also been revealed that the ‘Open’ mixer creates an unwanted dead zone (in the form of the stagnation layer of material rotating between the mixer and the barrel) at which the polymer melt degradation may take place. It has been found that based on the stress, residence time and pathline calculation, it is possible to predict the experimentally observed tendency of the ‘Closed’ mixer for a faster mixing/purging in comparison with the ‘Open’ mixer as well as the presence of a stagnation layer in the ‘Open’ mixer. The performed theoretical parametric study indicates that the gradual opening of the wiping gap causes the pressure driven flow to become more dominant than the drag flow in shearing as well as in the wiping gap independently of the utilised rheological model. On the other hand, the predicted particle trajectories inside the mixer were found to be shorter for the viscoelastic model, tending to occur mainly in the middle of the channel and thus leaving the mixer a little bit faster in comparison with the purely viscous calculations. Finally, it has been revealed that for the highest tested wiping flight opening, the viscoelastic modified White–Metzner model predicts back flow over the wiping flight, whereas the purely viscous Carreau–Yasuda does not, which can be explained by the elongational viscosity, considered in the viscoelastic modified White–Metzner model. This suggests that the modified White–Metzner model should be preferred more than the purely viscous Carreau–Yasuda model in the mixing element die design optimisation.

Effectiveness of polyethylene extrusion in a single-screw grooved feed extruder

The paper presents a description of a modern direct screw drive carried out by a torque motor of a torque 300 Nm, maximum rotational speed 500 rpm and power 15.7 kW. The operation of the torque, its advantages and disadvantages were described. In the extruder plasticizing system in the feed opening zone and part of the feed zone, an exchangeable smooth sleeve and a grooved sleeve with 6 or 8 longitudinal grooves were used. For research, low density polyethylene of the commercial name Malen E and symbol FGNX 23-D006 was used. In the extruder barrel, a special screw was mounted 25 mm in diameter and L/D = 24, with elements of intensive shearing and mixing, constructionally adapted to the grooved section. The research was conducted in the wide range of rotational screw speeds from 1.67 to 8.33 rps.

Fluoropolymer processing aids in linear-low density polyethylene extrusion: How to improve their efficiency?

Mechanisms of wall coating and wall slippage during extrusion of polyethylene with fluoropolymer based Polymer Processing Aids (PPAs) are reviewed for various types of PPAs. It is shown that the spreading of PPA coating on die surface can be improved by using a wetting agent, like a polyethylene glycol. Wall slip is favored by lowering the entanglement density in the interdiffusion phase between PPA and polyethylene. Finally, the morphology of PPA coating is investigated. It can be explained by the balance between viscosity and interfacial energy.

Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

The in-line development of crystalline morphology and orientation during melt extrusion of low density polyethylene (LDPE) tape at nil and low haul-off speeds has been investigated using Small-Angle X-Ray Scattering (SAXS). The processing parameters, namely haul-off speed and distance down the tape-line have been varied and the resulting crystalline morphology is described from detailed analysis of the SAXS data. Increasing haul-off speed increased orientation in the polymer tape and the resulting morphology could be described in terms of regular lamellar stacking perpendicular to the elongation direction. In contrast, under nil haul-off conditions the tape still showed some orientation down the tape-line, but a shish-kebab structure prevails. The final lamellae thickness ( ∼50 Å) and bulk crystallinity (∼20%), were low at, for all processing conditions investigated, which is attributed to the significant short-chain branching in the polymer acting as point defects limiting lamellae crystal growth.