High-performance Polyethylene Fibres Research Articles

Processing and Characterization of UV Irradiated HDPE/POSS Fibers.

High-performance polyethylene fibers, renowned for their superior attributes encompassing a high strength, modulus, and lightness, are conventionally manufactured through the gel spinning method. However, this method is encumbered by several drawbacks, including the requisite application of a separate process to eliminate solvents from the fibers and the utilization of chemicals deleterious to both the environment and human health. Alternatively, the adoption of the melt spinning method presents a cleaner and environmentally friendly approach to attain high-performance fibers. In the present investigation, high-density polyethylene (HDPE) fibers were produced employing the melt spinning method. After the spinning process, strategic orientation procedures were implemented to enhance the crystallinity of the spun fibers. As a concluding step, seeking to elevate the overall performance of the oriented spun HDPE fibers, a cross-linking treatment was applied via UV irradiation. Notably, this study pioneers the incorporation of polyhedral oligomeric silsesquioxane (POSS) hybrid nanoparticles into HDPE during melt spinning, presenting a novel advancement aimed at further enhancing the mechanical properties of oriented HDPE fibers during UV irradiation. For this purpose, two distinct types of POSS, namely octavinyl POSS (OVPOSS) and methacryl POSS (MACPOSS), both having unsaturated double bonds capable of participating in the network structure of oriented HDPE spun during UV cross-linking, were used. The thermal, morphological, and mechanical properties, as well as the crystal structure of samples with and without POSS molecules, were investigated. The mechanical properties of the fibers exhibited higher values in the presence of OVPOSS. The incorporation of OVPOSS and MACPOSS resulted in a noteworthy improvement in the material's tensile strength, exhibiting a marked increase of 12.5 and 70.8%, respectively. This improvement can be attributed to the more homogeneous dispersion of OVPOSS in HDPE, actively participating in the three-dimensional network structure. After orientation and UV irradiation, the tensile strength of HDPE fibers incorporating OVPOSS increased to 293 MPa, accompanied by a concurrent increase in the modulus to 2.8 GPa. The addition of POSS nanoparticles thus yielded a substantial improvement in the overall performance of HDPE fibers.

Novel, injection molded all-polyethylene composites for potential biomedical implant applications

This study aimed to create a self-reinforced composite material that can be processed by injection molding and other standard thermoplastic processing techniques and can be potentionally used as implant material. Self-reinforcement in biomaterials is desirable because it does not compromise biocompatibility and improves biofunctionality through improved mechanical performance. Self-reinforced composites can be currently processed by specialized, expensive and unproductive methods; hence we aimed to create a simpler processing alternative that works with biocompatible materials. We combined a high-density polyethylene matrix with high-performance polyethylene (Dyneema®) fibers. Before making the composite structure, the fibers were cross-linked by gamma irradiation to prevent their melting and maintain their structural integrity. The cross-linked fibers withstood the compounding by twin-screw extrusion and the subsequent injection molding. The effect of the irradiation dose on the processability, crystallinity, morphology, mechanical performance and cytotoxicity was investigated. We found that adding 20 m% of 200 kGy irradiated Dyneema® fibers increased the tensile modulus by 22.0%, the tensile strength by 71.1%, while both the composite and its constituents were all found to be biocompatible. The 41.1 MPa tensile strength, the 1.62 GPa tensile modulus, and the 64 Shore D hardness is quite similar to those of ultra-high molecular weight polyethylene, which is widely used in implants. Still, the material introduced in this paper shows no issues with the melt flow characteristics. These achievements are similar to other self-reinforcing methods, but the manufacturing method presented here can be economically realized on widely available processing technologies and machines.

Enhancing the interfacial bonding between PE fibers and cementitious matrices through polydopamine surface modification

High-performance polyethylene (PE) fibers possess unique features to develop advanced cementitious composites with superior mechanical properties. Nonetheless, due to their hydrophobic nature, such fibers can develop only a poor interfacial affinity between themselves and the water-based cementitious matrices, which restricts a full exploitation of their intrinsic properties. The work described here is an expeditious and environmentally friendly strategy to enhance the bond strength in PE fiber-reinforced cementitious composites through utilization of polydopamine (PDA) surface modification. Environmental scanning electron microscopy (ESEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), water contact angle, and electrokinetic measurements were applied to characterize the surface properties of the fibers under investigation. Moreover, fiber-matrix interactions were assessed by single-fiber pullout from a cementitious matrix with respect to dopamine concentration and modification time. Compared to the unmodified reference sample, a noticeable increase in maximum pullout load, interfacial shear strength, and fiber pullout energy was achieved with the modified fibers. This was explained by the formation of active hydrophilic groups on the fiber surfaces, which groups enhance the fibers’ wettability and yield better interaction with the cementitious matrix. Furthermore, the modified fibers exhibit increased tensile strength, modulus of elasticity, and suitable stability in a highly alkaline environment as well.

Improvement of Copper Oxides-coated Ultra-high Molecular Weight Polyethylene Fibers Reinforced Rigid Polyurethane Composites in Strength and Toughness

The purpose of this work was to develop the high-performance ultra-high molecular weight polyethylene (UHMWPE) fibers reinforced rigid polyurethane (RPU) composites. UHMWPE fibers were electroless deposited by copper to form the copper oxides on the fiber surface. The results showed that the copper oxides-coated UHMWPE fibers had the positive effects on the mechanical properties of the composites. Compared with neat RPU, the tensile strength, tensile modulus, bending strength, and impact strength of copper oxides-coated UHMWPE fibers/RPU composites were increased by 20.4%, 39.7%, 11.0% and 15.8%, respectively. Interlaminar shear strength (ILSS) was also increased by 14.9%. The dynamic mechanical analysis (DMA) proved the reinforcing effect of copper oxides-coated UHMWPE fibers. Both strength and toughness were increased mainly due to the metal oxides deposited on the fiber surface. On one hand, the copper ions and oxygen ions on the UNMWPE fiber surface could react with oxygen and hydrogen in polyurethane to form chemical bonds. On the other hand, the copper oxides increased the crack propagation path to improve the toughness of the material.

Cover Image, Volume 138, Issue 25

This cover designed by Muhammad Irfan and colleagues shows how High Performance Polyethylene (HPPE) fibers are relatively tougher than carbon fibers and can be used to improve impact tolerance of carbon epoxy composite laminates. Composite laminates containing carbon fibers suffer from delamination upon impact. An interleave of a tough material like HPPE fibers inserted between these carbon fiber plies can reduce the damage due to impact. HPPE fibers do not undergo brittle fracture, rather ductile fracture is observed along with fibrillation. Nonwoven interleaves comprising HPPE fibers can be used to improve impact properties of carbon-epoxy composite laminates for various applications. DOI:10.1002/app.50683

Melting kinetics, ultra-drawability and microstructure of nascent ultra-high molecular weight polyethylene powder

For the production of high-performance polyethylene fibers and tapes by ultra drawing, using solid-state processing of disentangled nascent ultra-high molecular weight polyethylene (UHMWPE), the maximum draw ratio is an important design parameter, as it determines the maximum degree of chain alignment and, therewith, the properties of the final product. It would, therefore, be advantageous to have a fast scanning method to estimate the maximum drawability of reactor powders. In the present work, the melting behavior of nascent UHMWPE reactor powder was studied by differential scanning calorimetry, followed by isoconversional analysis to evaluate the apparent activation energy barrier of melting for the different UHMWPE grades of different level of disentanglement. Powder samples were solid-sate processed into tapes at elevated temperature. Ultra drawing of these tapes at the optimum drawing temperature allowed for the evaluation of the maximum draw ratio (λmax) that is determined by the entanglement density. The morphology of the lamellar structure of the nascent powder was studied by small-angle X-ray scattering and by scanning transmission electron microscopy analyses. A correlation between the melting kinetics, the microstructure and the maximum draw ratio was observed for all grades, suggesting that the apparent activation energy of melting can be used as a screening method to estimate the maximum draw ratio.

Enhanced interlaminar shear and impact performance of woven carbon/epoxy composites interleaved with needle punched high performance polyethylene fiber nonwoven

AbstractIn this study, high‐performance polyethylene (HPPE) fiber‐based needle punched nonwovens were interleaved in cross‐plied woven carbon fabric/epoxy composite laminates to enhance their interlaminar and impact properties. The placement of needle punched nonwoven interleaves exhibited considerable enhancement in interlaminar shear strength (ILSS), impact damage tolerance, and compression after impact (CAI) strength of laminates as evidenced by higher interlaminar strength, less absorbed energy, higher elastic energy, reduced damage degree, reduced out‐of‐plane deformation, higher load‐bearing capacity, and higher residual compressive strength as compared to control sample. In particular, the composite laminate with placement of interleaves in alternating sequence between carbon plies resulted in 205.76% increase in ILSS and 129, 103 and 85% increase in CAI at 10, 25, and 40 J impact energy, respectively. Moreover, damaged surface area and out‐of‐plane deformation reduced to 38.75% and 62.5%, respectively for the same specimen impacted at 40 J energy. These results suggest that the HPPE fiber‐based needle punched nonwoven interleaving can be adopted as a simple and low‐cost approach compared with other interleaving techniques, to enhance the resistance to delamination, impact performance, and damage tolerance of traditional structural laminates.

Influence of Solvent Quality and Crystallization Conditions on the Drawability of Ultra-High Molecular Weight Polyethylene Cast from Solution

The standard route toward high-performance polyethylene fibers involves “ultra-drawing”: large-strain solid-state uniaxial plastic deformation at elevated temperatures of precursor ultra-high molec...

Impact of twisting high-performance polyethylene fibre bundle reinforcements on the mechanical characteristics of high-strength concrete

The quasi-static and dynamic mechanical behaviours of the concrete reinforced by twisting ultra-high molecular weight polyethylene (UHMWPE) fibre bundles with different volume fractions have been investigated. It was indicated that the improved mixing methodology and fibre geometry guaranteed the uniform distribution of fibres in concrete matrix. The UHMWPE fibres significantly enhanced the splitting tensile strength and residual compressive strength of concrete. The discussions on the key property parameters showed that the UHMWPE fibre reinforced concrete behaved tougher than the plain concrete. Owing to the more uniform distribution of fibres and higher bonding strength at fibre/matrix interface, the UHMWPE fibre with improved geometry enhanced the quasi-static splitting tensile strength and compressive strength of concrete more significantly than the other fibres. The dynamic compression tests demonstrated that the UHMWPE fibre reinforced concrete had considerable strain rate dependency. The bonding between fibres and concrete matrix contributed to the strength enhancement under low strain-rate compression.

Comparative evaluation of steel wire mesh, steel fibre and high performance polyethylene fibre reinforced concrete slabs in blast tests

Concrete is the most widely used construction material in the modern construction practice. Due to its relatively low tensile resistance, concrete tends to experience tensile failure and cracking under external loads. To enhance the tensile performance and ductility of concrete material, possible solutions including fibre reinforcement and steel mesh reinforcement are investigated in the present study. Steel fibre, ultra-high molecular weight polyethylene (UHMWPE) fibre and steel wire meshes were mixed with varying volume fraction in the concrete matrix. Static material tests including uniaxial compression and flexural bending tests showed that the steel fibre addition yielded better strength enhancement while UHMWPE fibre provided better material ductility. Concrete samples with hybrid steel fibre-steel mesh reinforcement showed high strength and ductility. Field blast tests are designed to study the behaviour of reinforced concrete slabs under close-in detonations. Different damage profiles are observed from the blast tests. The advantages and disadvantages of using different reinforcing materials are discussed. From the results, the advantages of replacing steel fibre with UHMWPE fibre or steel wire mesh were demonstrated.

Tensile behavior of high-strength strain-hardening cement-based composites (HS-SHCC) made with high-performance polyethylene, aramid and PBO fibers

The article at hand presents an investigation of the tensile behavior of high-strength strain-hardening cement-based composites (HS-SHCC) made with four different types of dispersed high-performance polymer fibers. In particular, high-density polyethylene (HDPE), poly(p-phenylene-terephthalamide) (aramid), as-spun poly(p-phenylene-2,6-benzobisoxazole) (PBO) and high-modulus PBO fibers were examined in respect of their reinforcing effect in a high-strength, finely grained, cementitious matrix. Besides the tension experiments at the composite level, single fiber pullout tests were performed for a micromechanical characterization of each composite material. Furthermore, contact-angle measurements and microscopic investigations were carried out to assess the fibers' ability to be wetted and to explain their interaction with the cementitious matrix.

Interior morphology of high-performance polyethylene fibers revealed by modulus mapping

Abstract This work elucidates the undisturbed interior morphology of commercial ultra-high-molecular-weight polyethylene (UHMWPE) high-performance fibers through atomic force microscopy (AFM) modulus mapping of interior surfaces exposed by a novel focused ion beam (FIB)-notched sample preparation technique. The imaging shows unequivocally the presence of epitaxial crystals in the interior of highly drawn UHMWPE fibers. Overall, AFM observations and measurements were made for three different commercial fiber types, illustrating five basic UHMWPE morphologies: (i) extended chain fibrils (shish), (ii) interlocking and (iii) standalone kebab or epitaxial crystals, (iv) voids or interface between fibrils, and (v) tie chains across voids. Furthermore, microfibrils were bundled into groups separated by voids or amorphous material. Bundled groups of microfibrils group together to form macrofibrils, typically separated by larger voids or amorphous material. Additionally, stretched tie-chain bridges provide connectivity between some fibrils. Each of these five features (extended chain fibrils, interlocking and standalone epitaxial crystals, voids and tie-chains) varies across the three types of commercial fibers, and sometimes across the individual fiber interiors. AFM contact modulus values measured transverse to the fiber draw axis were found to vary considerably within different morphological domains. The distribution of morphology sizing was quantified for each of the examined fibers. The measurement of internal facets have major implications for fiber modeling and processing, such as optimization of draw ratios to affect the extent and arrangement of epitaxial crystalline morphologies and thus improve mechanical performance.

Blast resistance of concrete slab reinforced with high performance fibre material

Concrete is now the most abundantly used material in construction. Despite good compressive strength, concrete is marked with brittleness and low tensile strength. A widely adopted method to enhance the concrete material performance especially the tensile strength and ductility is fibrous material addition. In the present study, concrete mix designs with different fibre additions have been developed, and high-performance polyethylene fibre and micro steel fibre are considered with varying volume fractions in the concrete matrix. Material static properties are obtained from laboratory tests, and further study on the dynamic performance of theses fibre reinforced concrete materials is investigated through field blast tests. Concrete slabs with high-performance polyethylene fibre reinforcement and hybrid steel and polyethylene reinforcement are casted and tested under close-in blast scenarios. Discussion on the structural damage and material performance is briefed based on the test results.

High-Performance Polyethylene Fibers “Al Dente”: Improved Gel-Spinning of Ultrahigh Molecular Weight Polyethylene Using Vegetable Oils

We demonstrate that the major drawbacks of so-called gel spinning and solid-state processing of “virgin”, i.e. never molten or fully dissolved, ultrahigh molecular weight polyethylene (UHMW PE) to produce ultrahigh modulus and ultrahigh strength fibers and films, which are the unfavorably low polymer concentrations in highly flammable solvents typically employed in the former process and low production rates in the latter, can be largely avoided by employing relatively poor—as opposed to good—solvents, including, among others, fatty acids and natural oils omnipresent in, for example, fruits, nuts, and seeds, which have additional major recovery and environmental advantages.

The study of processing parameters on impact behavior of high performance polyethylene fiber cross-ply composites by taguchi method

In this study, the effect of processing parameters such as temperature, pressure, time of compaction process and areal density on high-velocity impact behaviour of high performance polyethylene fibre cross-ply composites were investigated by Taguchi method. Samples were made through high temperature and pressure compacting process and morphology and interlayer adhesive of samples were investigated by scanning electron microscopy “SEM and T-peel test, repectively. Taguchi method was used to plan a minimum number of experiments. Statistical analysis, analysis of variance (ANOVA), was also employed to determine the relationship between experimental conditions and yield levels. ANOVA was applied to calculate sum of square, variance, ratio of factors variance to error variance and contribution percentage of each factors on response. A hemispherical tip type projectile was used for high velocity impact tests and the depth of trauma as the response factor was measured after impacting test. Results showed that when the temperature, pressure, and time of compacting process were 125 °C, 3 MPa, and 30 min for the composite sample with 7.4 kg/m2 areal density, the trauma depth was decreased to its lowest value.

Evaluation of fatigue properties of high-performance fibers based on fixed-point bending fatigue test

The main aim of this article is to introduce a bending fatigue testing apparatus and a new fatigue testing method, which can be used to characterize the bending fatigue behavior of flexible materials by setting the following parameters: pre-tension, bending angle, and bending frequency. The Kevlar 49, poly(p-phenylene benzobisoxazole), Nomex, and high-performance polyethylene fibers are chosen to analyze the bending fatigue properties by the new apparatus. The cyclic stress data, number of cycle bending and bending fatigue photos are recorded during the process of the bending fatigue. The curve of the cyclic stress shows that the stress changes in periods during the cyclic bending process. The curve of the cyclic stress is theoretically analyzed. The S–N and the θ−ln N curves indicate that the pre-tension and the bending angle have significant effects on the bending fatigue life. The morphologies obtained from the digital optical apparatus can be used to explain the bending failure mechanisms of high-performance fibers. It is evident that the new bending fatigue testing apparatus is feasible and accurate in measuring and characterizing bending fatigue properties of fibers. The apparatus could effectively describe the bending fatigue lifetime and bending failure mechanisms of high-performance fibers.

3D FEA of high-performance polyethylene fiber reinforced maxillary dentures

Objective This project studies the effect of high-performance polyethylene (HPPE) fibers on stress distributions in a maxillary denture and the influence of fiber position on improving denture performance. Methods A denture was scanned with a 3D Advanced Topometric Sensor digitizing system. The measuring system converted the images into a 3D digital model. A 3D reverse engineering technology then produced a numerical model which was then refined with Rapidform software. The underlying mucosa and bone were constructed using a freeform system integrated with a PHANTOM haptic device. A fiber lamella reinforcement was incorporated into the denture at different positions (fitting side, mid-palatal plane, polished side) with SolidWorks software. Boundary conditions were constrained at the top of the basal bone while bite force of 230 N was applied to the posterior teeth on both sides. The denture models were analyzed with ABAQUS software. Results Stress concentrations were found at the incisal notch and at the anterior and posterior palatal surfaces of the unreinforced denture. The incorporated reinforcement effectively reduced the stress concentrations at these surfaces. Placement of the fibers at polished side was the best position in reducing stress concentrations. Significance 3D FEM usefully provides a non-laboratory means to reveal the weak areas in the maxillary complete denture, and exhibit the effectiveness of HPPE reinforcement together with fiber positions on enhancement of denture strength.

EXPERIMENTAL STUDY ON IMPROVEMENT OF FLEXURAL REINFORCEMENT BY CONTINUOUS FIBER SHEET FOR REINFORCED CONCRETE BEAM WITH CLADDING OF FIBER REINFORCED MORTAR

In this study, analytical and experimental investigations were conducted to clarify the effect of clad reinforcement by polyethylene fiber reinforced mortar (PEFRM) on flexural characteristics of reinforced concrete (RC) beams strengthened with polyethylene fiber sheets. High-performance polyethylene fibers (PEF) were used for making the PEFRM with high tensile strength. The PEFRM-cladding was performed on the tensile side of the RC beam. The RC beams strengthened with the PEFRM-cladding and the sheets were tested under pure bending. As a result, it was shown that the PEFRM-cladding has a remarkable effect on an improvement of flexural reinforcement by the sheets of the RC beam.

Influence of Hybridisation and Test Geometry on the Impact Response of Glass-Fibre-Reinforced Laminated Composites

This paper describes the results of falling weight impact tests (FWITs) on glass-fibre-reinforced (GRP) laminates and E-glass/Dyneema® hybrid laminates. The test programme consisted of (i) falling weight impact tests to determine the penetration energy and (ii) experiments to determine the influence of hybrid construction on damage development and impact fatigue lifetime under repeated impact conditions at sub-penetration energy levels. The objective of this work was to investigate the effect of hybridisation on the impact behaviour of GRP laminates as well as to find optimal conditions for hybridisation. It was shown that in the case of a rigid test set-up - and hence small deflections - the influence of the Dyneema® on the impact behaviour of hybrid laminates is rather small because damage processes are the result of local contact stresses in the vicinity of the impact body, whereas in the case of a compliant test set-up and large deflections the high energy storage capacity of the ductile Dyneema® fibres is used far more effectively for the protection of hybrid composite laminates. Therefore, it was concluded that in order to fully utilise the potential of high-performance polyethylene fibres it is essential that these fibres are located on the (non-impacted) tensile side of an impacted laminate and that the geometrical test conditions are such that large (bending) deformations are allowed.

Aspects of the Morphology and Melting Behavior of Constrained Polyethylene Fibers

Top of pageAbstract The internal microstructure of a high performance polyethylene fiber, both as received and after heating, has been investigated by electron microscopy following permanganic etching. There is longitudinal fibrosity extending over many μm but, in common with other high performance fibers, this is accompanied by internal lateral cratering on the scale of ~1 μm. The craters, which are a response to preferential penetration by the etchant into regions of reduced density and high free volume related to processing conditions, are centered on the first regions to melt. Melting of constrained fibers is from the hexagonal phase to an ordered melt which relaxes making the hexagonal phase unstable. The internal fiber/melt interfaces then move outwards from these centers towards the higher melting regions. Those which melt last are the intersections of the etched surface with surviving crater walls but appear as spines many μm long. They are almost certainly the remnants of the initial entangled molecular network which sustained the stress of processing in accordance with the new model of fiber structure. Keywords: Morphology; Polyethylene; High Modulus Fibers; Electron Microscopy; Thermal Analysis