Molecular Weight Polyethylene Fibers Research Articles

Thermal aging behavior and heat resistance mechanism of ultraviolet crosslinked ultra‐high molecular weight polyethylene fiber

AbstractAs advances in heat resistant ultrahigh molecular weight polyethylene (UHMWPE) fiber via ultraviolet (UV) crosslinking, it is worth paying attention to its thermal aging behavior and heat resistance mechanism. UHMWPE fibers in different forms, the fully drawn yarn (FDY) and the UV crosslinked FDY (UVFDY), are subjected to isothermal aging at 135°C. The effects of thermal aging on their surface morphology and mechanical properties are studied and compared initially. The results demonstrate that UVFDY is a kind of a heat‐resistant fiber. Subsequently, to reveal the heat resistance mechanism of UVFDY, its crystalline and orientation structure evolution during thermal aging are further studied. It is indicated that the formation of dense‐packing crystals and disorientation behavior lead to fiber shrink, so that a number of grooves appear on the fiber surface. Since the crosslinked stucture of UVFDY hinders its molecules movement, the crystallization and disorientation behavior of UVFDY are weaker than those of FDY, resulting in UVFDY possesses slighter thermal shrinkage (Ts), fewer grooves and better mechanical properties than those of FDY. Therefore, the heat resistance of the fiber improves effectively after UV crosslinking. This work provides insights into the structure–property relationship of UVFDY during thermal aging, and offers basis data for its application in specific conditions.

Structure and properties evolution of UV crosslinked ultra‐high molecular weight polyethylene fiber during processing

AbstractWith the development of heat and creep‐resistant UHMWPE fiber via UV crosslinking, its structure‐properties evolution during processing needs attention. The structures of UHMWPE fiber in different forms, the pre‐oriented yarn (POY), the full stretch yarn (FDY) and UV crosslinked FDY (UVFDY), obtained from our pilot line were systematically studied with differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and solid‐state 13C NMR. Additionally, the heat and creep resistance of UVFDY were evaluated by the temperature at break (Tb), glass transition temperature (Tg), time at break (tb) for a given aging temperature, and creep elongation (Lc). The results demonstrated that UVFDY possessed high gel content (89.0%), high crystallinity (84.2%), and high orientation (91.7%). These characteristics caused UVFDY not only with excellent mechanical properties but also process extraordinary heat and creep resistance, especially for its much higher Tb (220 °C), Tg (−75.7 °C) and tb (20 h) while lower Lc (7.8%), comparing with FDY (Tb = 158 °C, Tg = −86.8 °C, tb = 1.3 h and Lc = 38.2%). This work provides insights into the structure‐properties relationship of UVFDY, which will aid in the development of UV crosslinked UHMWPE fiber with better heat and creep resistance.

Ultra‐high molecular weight polyethylene micro‐ribbon fibers gel spun using orange terpenes

AbstractToxic, hazardous petrochemical solvents are commonly used for industrial‐scale ultra‐high molecular weight polyethylene (UHMWPE) fiber production, but orange terpenes, a byproduct of orange fruit production, present a bio‐derived, sustainable alternative. In this work, fine UHMWPE fibers were spun using orange terpenes as the spin solvent, hot‐drawn at a draw ratio of 5:1, investigated for their morphology, microstructure, and thermal and mechanical properties. The resulting fibers exhibited a flat, micro‐ribbon cross‐section, which is highly desirable for achieving high fiber volume fractions in UHMWPE‐fiber reinforced composites. After drawing, the fibers possessed 4× greater breaking tenacity than any previously published studies on UHMWPE fibers spun using orange terpenes with a tenacity of 8.6 cN/dtex and tensile modulus of 229.2 cN/dtex. Microstructural analysis via differential scanning calorimetry and X‐ray diffraction revealed that the hot drawing process significantly increased molecular orientation, but crystallinity decreased due to crystallite melting during drawing. Therefore, the mechanical properties of these fibers may be significantly improved with optimization of the fiber drawing process. This work establishes the strong potential of orange terpenes as an environmentally‐friendly alternative solvent for UHMWPE gel spinning and sets a foundation for future parametric optimization of the spinning and drawing of these fibers.Highlights Micro‐ribbon ultra‐high molecular weight polyethylene fibers were prepared using bio‐solvent orange terpenes. Flat profile enables tight packing, aspect ratio maintained after drawing. Drawn fibers were 4× stronger than any previous work with orange terpenes. Near‐melt drawing reduced crystallinity, improved molecular alignment.

An experimental and numerical study on the ballistic performance of a lightweight ceramic composite armor

In this paper, the ballistic limit velocity of 12.7mm armor-piercing incendiary projectile impacting a typical lightweight ceramic composite armor made of boron carbide ceramic and multi-layered composite materials (carbon fiber/aramid fiber/ultra-high molecular weight polyethylene fiber) was obtained experimentally. The process of impact was numerically simulated by the FEM-SPH method, and the results pointed out the characteristics of the penetration and the energy dissipation rule of each component of the ceramic composite armor. On this basis, the influence of thickness changing of the carbon fiber core layer on the ballistic performance of ceramic composite armor was studied with a typical “sandwich” structure, and the results showed that: when the thickness ratio of ceramic tile to the backing panel is about 1.5, the thickness changing of the carbon fiber core layer has the greatest effect on the ballistic performance. Under this thickness ratio, when the ratio of ceramic tile thickness to bullet diameter is greater than 1, the increase of carbon fiber core layer thickness will cause the ballistic performance index (BPI) of the target to decrease while the ratio is less than 1, the BPI increases or holds at first, and then decreases.

Enhanced tensile properties of ultra‐high molecular weight polyethylene fibers by solubility improvement with mixed solvents

AbstractThe tensile properties of ultra‐high molecular weight polyethylene (UHMWPE) fibers obtained from mixed solvents are addressed by virtue of improved solubility. In this work, olive oil (OO) was introduced as a poor solvent for the pre‐swelling of UHMWPE in decalin, and its mass percentage was intended to be 10, 20, 30, and 40 wt% of UHMWPE. Then UHMWPE fibers with high molecular weight retention and low entanglement were prepared with paraffin oil as spinning solvent by gel‐spinning and hot‐drawing. Unlike other samples, there is a more significant molecular chain disentanglement and higher molecular weight retention for UHMWPE fibers as OO addition is 20 wt%. Surprisingly, obtained UHMWPE fibers exhibit tensile strength up to 33.85 cN/dtex and tensile modulus of 1673.27 cN/dtex, with an increase of 24.0% and 32.3%, respectively, compared with that of UHMWPE fibers without decalin/OO pre‐swelling. Furthermore, the obtained UHMWPE fibers are accompanied by a marked improvement in melting temperature, crystallization and orientation.

Влияние гибридизации углеродных волокон арамидными и СВМПЭ-волокнами на ударные свойства гибридных углепластиков

The properties and mechanisms of destruction of hybrid composite materials (HCMs) based on flexible and brittle matrices, reinforced with hybrid fibers made of carbon, aramid and ultra-high molecular weight polyethylene (UHMWPE) fibers were investigated by the method of “impact break” (IB) upon low-velosity impact. The composition of the hybrid fiber and the plasticity of the matrix affect the properties and fracture mode of the HCM. It is discovered that the combination of carbon and aramid fibers in a hybrid fiber for reinforcing a flexible matrix (FM) makes it possible to create a material with delayed fracture. It has been shown that upon impact for the destruction of HCM with a flexible matrix, a load twice as large as for specimens with a brittle matrix is required. The highest strength have hybrids, in which, at all stages of loading, up to fracture, there is a joint deformation of the matrix and the reinforcing fiber. The mechanism of deformation and destruction of anisotropic HCMs upon impact has a stepwise character.

High‐performance fiber‐reinforced composites with a polydopamine/epoxy silane hydrolysis‐condensate bilayer on surface of ultra‐high molecular weight polyethylene fiber

AbstractA bilayer structure with polydopamine (PDA) transition layer and 3‐glycidyl ether oxy‐propyl trimethoxy silane (GOPTS) hydrolysis‐condensate strengthened layer on the surface of ultra‐high molecular weight polyethylene (UHMWPE) fiber is prepared to improve the damage resistance of composites and more efficient stress transmission in composites. PDA is covered on the surface of UHMWPE fiber and then GOPTS is hydrolyzed and condensed to form inorganic ‐O‐Si‐O‐ with epoxy groups on the PDA layer. In addition, the surface activated nano‐SiO2 is dispersed in the epoxy resin to increase the strength of the matrix resin. The results show that the interfacial shear strength (IFSS), the impact strength, the flexural strength and flexural modulus of UHMWPE‐PDA‐GOPTS/EP‐SiO2 increase by 99.1%, 54.1%, 76.8%, and 36.6% respectively compared with unmodified UHMWPE/EP. The chemical compositions of the treated fiber surface are characterized by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy (ATR‐FTIR). With the help of the scanning electron microscopy, the interface failure and reinforcement mechanism of the composites are further explored due to UHMWPE fiber shear yield deformation, UHMWPE fiber fracture, matrix resin cracking and the relative sliding friction between the fiber and matrix.

Effect of ultra‐high molecular weight polyethylene fiber on the early mechanical strength and shrinkage crack resistance of concrete

AbstractThis study investigates the early mechanical strength, and shrinkage crack resistance of ultra‐high molecular weight polyethylene (UHMWPE) fiber concrete with different lengths and contents. The microstructure of UHMWPE fiber concrete is investigated by scanning electronic microscope (SEM) to analyze the distribution and mechanism of action of UHMWPE fiber in concrete. The mechanical strength results indicate that the compressive strength and splitting tensile strength of concrete increase first and then decrease by adding fibers. The maximum compressive strength and splitting tensile strength at age of 28d are 42.9 and 3.32 MPa, which is 41.1% and 55.9% higher than that of the benchmark group. The SEM results show that when the UHMWPE fiber content is small, the fibers are evenly distributed in concrete and tightly bonded to the matrix. While the fibers will agglomerate and entangle with the increase of the fiber content, the results of shrinkage resistance test demonstrate that the 12 mm fiber with 0.24% fiber volume content can obtain the best shrinkage crack resistance.

Influence of Processing in Radio-Frequency Low Pressure Plasma on the Adhesion of Synthetic Fibers to Polymer Binders

The paper presents the results of a study of the effect of radio-frequency (RF) plasma modification on the adhesion of ultra-high molecular weight polyethylene (UHMWPE) and polypropylene (PP) fibers to epoxy-diane (ED), epoxy-urethane (EU) and polyester (PES) binder. To assess the adhesive properties, the wet-pull-out method was used, which makes it possible to determine the normalized value of the destructive load of the microcomposite by the force of pulling out the fiber from the polymer matrix.

Preparation and Properties of a Modified Fe2O3 Pigment for Dope Dyeing Ultrahigh Molecular Weight Polyethylene (UHMWPE) Fibers by Melt Spinning

Preparation and Properties of a Modified Fe2O3 Pigment for Dope Dyeing Ultrahigh Molecular Weight Polyethylene (UHMWPE) Fibers by Melt Spinning

Effect of polyalphaolefin oils as a solvent in gel‐spinning of ultra‐high molecular weight polyethylene fibers

AbstractIn this work, lubricants based on polyalphaolefin with different viscosities were evaluated in the processing of UHMWPE fibers. All fibers were obtained by extrusion with 0.04 to 60 wt% of polyalphaolefin oils with different kinematic viscosities and densities (in ascending order: PAO8, PAO40, and PAO100), under screw speed of 20 to 60 rpm with a nozzle of 1.82 mm diameter. Also, n‐hexane was used to extracting the oils from UHMWPE fibers. The fibers did not undergo the drawing process. It was observed that the fibers that underwent process with PAO40 showed the highest linear density, achieving 3273 tex, indicating the orientation of the crystals in a compact morphology inside the extruder and the higher relaxation after leaving the nozzle, increasing die‐swell. Microscopic analysis revealed roughness in fiber as the insertion of PAO100 oil increased, while fibers with PAO40 proved to be more densified. In addition, the fibers processed with PAO40 have an increase in thermal stability after n‐hexane extraction, with degradation temperature Tmax of 482°C in comparison with 476°C for the neat UHMWPE.

Hybridization of Polyester/Banana stem Fiber and Cow horn particulate composite for possible production of a military helmet

ABSTRACT The production of ballistic composites using polyethylene fibres from ultra-high molecular weight polyethylene (UHMWPE) and carbon fibres are gaining relevance. Although these materials have standard properties, they are very expensive and are not readily available. To develop a military helmet that will be less expensive and protect the safety of the personnel that leads to the development of polyester reinforced banana stem fibres (BSF) and cow horn particulate (CHp) composite. Polyester-15 wt BSF+4 wt% CHp was produced using a hand laying method. The composite was cured at 100°C for 6 h. The microstructure, strength, hardness values, and impact energy were determined using the standard method. Lower weight helmet that will not be too heavy and the same protect the safety of the personnel can be produced from this formulation. 94.66% enhancement in tensile strength and 174.79% of the impact energy were obtained. The values of the impact energy, hardness values, and strength obtained in this work are within the range for the production of military helmet.

Enhanced wear resistance of ultra‐high molecular weight polyethylene fibers by modified‐graphite oxide

AbstractA simple and feasible method to enhance the wear resistance of ultra‐high molecular weight polyethylene (UHMWPE) fibers was reported. The graphite oxide (GO) prepared using improved Hummer's method was surface modified with hexadecylamine to improve its compatibility with UHMWPE. Combined with well‐dispersion of modified‐GO (m‐GO) in dichloromethane and the fact that the viscosity of UHMWPE suspension can be decreased by dichloromethane, the well dispersed m‐GO/dichloromethane was added into UHMWPE suspension to improve m‐GO dispersion in UHMWPE fibers. Finally, UHMWPE fibers with different m‐GO concentration were prepared using gel spinning technology. The effect of m‐GO concentration on the structure and properties of modified UHMWPE fibers were investigated. The results indicated that the melting temperature and crystallinity of m‐GO modified UHMWPE fibers increased with increasing of m‐GO concentration, while the fiber's crystal sizes and orientation increased, thus the tensile strength of m‐GO modified UHMWPE fibers remained almost undamaged. The introduction of m‐GO is beneficial to the formation of smooth transfer film on fiber's surface, which enhanced the self‐lubrication of UHMWPE fibers. Compared with pure UHMWPE fiber, the UHMWPE fiber containing 1.5 wt% m‐GO had enhanced wear resistance by 55.4% and still maintained high tensile strength of 29.98 cN dtex−1.

Composite helical spring with skin‐core structure: Structural design and compression property evaluation

AbstractThe helical spring is an essential mechanical component of automobile and machinery and has been widely used in industrial application. The weight reduction is the requirement of current material design and also the research trend for material development. In this study, a novel composite helical spring with “skin‐core” structure was designed and fabricated with an integrated formation process based on the vacuum‐assisted resin infusion technology. Based on the different function of skin and core, the skin structure was weft knitting tube made of aramid and ultra‐high molecular weight polyethylene fiber, and the core structure was unidirectional carbon fiber. By selecting material for knitting tube and adjusting the volume content of carbon fiber core, the static and fatigue compression properties of composite helical spring were investigated. It has been found that the spring torsion and bending performance can be improved by wrapping the core with the knitting tube as the spring wire. Moreover, the finite element method was applied to further analyze the stress evolution of the “skin‐core” composite helical spring during compression and fatigue. The results of compression test and simulation show that the spring stiffness can be effectively improved by using knitting tube and increasing the content of carbon fiber. The stress of the spring cross section is concentrated in the internal radial region of 180°, and the distribution of the corresponding cross sections is relatively uniform. The “skin‐core” structure with aramid knitting tube as the outer skin and carbon fiber as the spring core significantly improves the load‐carrying capacity and stability of the composite spring. The proposed lightweight helical composite could provide a replacement strategy of existing metal or unidirectional filament reinforced springs used in the engineering applications.

The effect of shrinkage on the structure and properties of ultra‐high molecular weight polyethylene fibers with different concentration

AbstractInterface variation in the extraction and drying process of ultra‐high molecular weight polyethylene (UHMWPE) gel fiber results in different shrinkage at different direction. The essence of shrinkage lies in the crystallization of UHMWPE chains under the effect of interface tension. However, UHMWPE gel fiber prepared with different solution concentration has different chain entanglement points density that can hinder the regular stacking for UHMWPE chains. The restriction for axis shrinkage of UHMWPE gel fiber facilitates the orientation of UHMWPE chains that is beneficial to improve the tensile strength of UHMWPE drawn fiber. Combined with multiple methods of Wide angle X‐ray diffraction, Small‐angle X‐ray scattering, Differential scanning calorimetry and sonic orientation, the structural evolution of UHMWPE fiber with different shrinkage ratio and different concentration was investigated. Meanwhile, the suitability for UHMWPE fibers in production was evaluated by final tensile strength of the fibers. Here, a structural evolution model is proposed to elucidate the correlation between the shrinkage and the structure and properties of UHMWPE fibers prepared with different solution concentration.

Adhesion performance of UHMWPE fiber treated with polyethylene wax grafted methyl methacrylate alone or in conjunction with silane coupling agent

To improve the interfacial adhesion between ultrahigh molecular weight polyethylene (UHMWPE) fiber and epoxy resin, the fiber were treated with polyethylene wax grafted methyl methacrylate (PEW-g-PMMA) alone or in combination with silane coupling agent. The factors affecting the interfacial bond property of fiber, e.g. grafting rate, coating temperature, concentration of silane coupling agent were studied. The single-fiber pull-out tests showed that compared with the pristine UHMWPE fiber, the pull-out strength of 9 wt% PEW-g-PMMA treated fiber had increased by 45.11%, and the pull-out strength of 9 wt% PEW-g-PMMA/12 wt% silane coupling agent treated fiber had increased by 77.97%. The pull-out strength of fiber increased with the increase of temperature and grafting rate. Infrared analysis indicated that several polar groups were introduced onto the fiber surface through coating treatment. SEM analysis showed that the surface of treated fibers became rougher. Contact angle tests manifested that the functional coating was conductive to improve the wettability of fiber. Tensile testing and XRD results showed that the processing procedure almost had no effect on the crystallinity and mechanical properties of UHMWPE fibers. Finite element analysis showed that the presence of functional coating can improve the ability of the interface to resist damage.

Toward an efficient stress transfer with a fully connected hybrid network from epoxy, oxidized UHMWPE fibers, and silane surface modified silicon carbide nanoparticles

AbstractIn this work, a new high‐performance hybrid material was designed targeting excellent static and dynamic mechanical properties. To achieve this goal, the hybrid constituents, namely the ultra‐high molecular weight polyethylene fibers and silicon carbide nanoparticles, were respectively, surface modified to graft the proper chemical species in order to maximize the interactions between the reinforcing phases and the epoxy matrix. The adopted grafting procedures were characterized by vibrational and morphological analyses. The generation a fully connected network resulted in consequent ameliorations in the mechanical and thermomechanical properties. Meanwhile, the effect of various amounts of the treated silicon carbide nanoparticles was also investigated. The finding indicated a gradual improvement in the overall mechanical properties up to 5 wt% for which the tensile strength reached its maximum value of about 477 MPa. The same hybrid materials displayed the remarkable storage modulus of 7.7 GPa at 25°C and a glass transition temperature of about 66°C. The synergistic stress transfer between the constituents was further evidenced by a proper investigation of the sample's fractured surfaces. Overall, the study revealed the great advantage of a fully connected network in developing lightweight and high‐performance materials for exigent applications.

The Failure Mechanisms of Ultra-high Molecular Weight Polyethylene Fibre Composites Under In-plane Compression

The in-plane compressive characteristics of the ultra-high molecular weight polyethylene (UHMWPE) fibre (Dyneema®) reinforced composites, both in 0/90° and ±45° fibre orientations with respect to the loading direction, have been investigated. The composite made from unidirectional high modulus fibres (volume fraction 83%) and low strength polyurethane matrix (volume fraction 17%) is layered in an orthogonally alternating manner. The different failure mechanisms for the composites with 0/90° and ±45° fibre orientations have been detected with the methods of experimental measurement, SEM observation and theoretical analysis. The composites specimens of 0/90° fibre orientation failed with macro-buckling of the high-modulus UHMWEP fibre layers with the matrix damage, whereas the specimens of ±45° fibre orientation failed with the shearing of the soft matrix. Hence, the composite specimens in 0/90° fibre orientation had higher stiffness as well as compressive strength than those in ±45° fibre orientation. The failure criteria of the composites under in-plane compression was employed to characterize the failure mechanism. Compared with the traditional thermoset matrix, the soft thermoplastic matrix leads to lower strength and higher failure strain of fibre reinforced composites under in-plane compression. In addition, the composite specimens cut by waterjet machine exhibited higher stress levels than those cut by bandsaw that introduced more initial imperfections with the temperature rising and tensile shocking. The comparison between the methodologies for cutting the tough composites can provide a valuable suggestion to obtain required composite structures without reducing the mechanical properties.

Действие удара на волокно и композиционный материал на его основе

The low-velosity impact properties and failure mechanisms of ultra-high molecular weight polyethylene (UHMWPE) fiber (Dyneema®SK-75) and a composite material (CM) based on it with the rigid and flexible matrices were investigated by the “Impact Break” (IB) method. A fundamental difference in deformation behavior and failure mechanisms upon impact on the UHMWPE-fiber and on the CM based on this fiber has been investigated experimentally. It is shown that impact has a little effect on the properties of UHMWPE-fiber, since it is an isotropic material. It has been established that upon impact, the properties of a fiber without a matrix were significantly higher than the properties of CM based on it. Impact action stimulates the interaction between CM components (fibers and matrix). Mechanism of stepwise deformation of anisotropic CM is occurred, which begins from the first moment of impact and ends with the destruction of the CM. A “stairway of deformation” behavior is observed in anisotropic materials. Stepwise deformation is the main form of deformation and the basic mechanism of failure of anisotropic composite materials upon impact.

Improved Wear Resistance of UHMWPE Fibers by Modified Nano-Graphite

Single ultra-high molecular weight polyethylene (UHMWPE) fiber was modified by modified nano-graphite (NG) in wear resistance. Wear resistance, tensile strength, thermogravimetric analysis (TGA) were used to characterize the effect of modified NG on the properties of UHMWPE fiber. The results showed that with the increasing content of modified NG, the wear resistance of UHMWPE fiber was enhanced and its tensile strength was decreased. Considering the tensile strength and wear resistance of fiber, the optimum content of modified NG in UHMWPE fiber was around 0.58%. At this content, the wear resistance and thermal decomposition temperature of UHMWPE fiber were increased 1.88 times and 50°C respectively than pure UHMWPE fiber.