Ultra-high Strength Polyethylene Fibers Research Articles

Fast, Light-Responsive, Metal-Like Polymer Actuators Generating High Stresses at Low Strain

Summary Producing lightweight polymeric actuators able to generate high stresses typical of hard metals and/or ceramics remains challenging. The photo-mechanical responses of ultra-drawn ultra-high molecular weight polyethylene (UHMWPE) actuators containing azobenzene photo-switches with symmetrically attached polyethylene (PE) side chains are reported. Long PE side chains promote dispersion within the apolar UHMWPE matrix, and the ultra-drawn films are highly aligned. The ultra-drawn azobenzene-doped UHMWPE films have high Young's moduli (∼100 GPa) and are viscoelastic at room temperature at strains below 1%. The photo-mechanical response of the films is fast ( 6 × 104 Pa (kg m−3)−1) to UV or visible light at a low strain (∼0.06%). The actuator responds to rotating linearly polarized light, causing a photo-induced stress wave response. Such rapid, high-stress, low-strain, photo-mechanical responses are unique in soft polymer systems with physical values approaching hard metals/ceramics.

Ribbond for Treatment of Complicated Crown Fractures: Report of 3 Cases

Dental trauma is relatively common and can occur secondary to sporting injuries, falls, fights, or accidents. According to the International Association of Dental Traumatology, 50% of children experience dental trauma between the ages of 8 to 12. There are many options for endodontic and restorative treatments of traumatized teeth. Ribbond, which was introduced in the market in 1992, consists of bondable, reinforced ultra-high strength polyethylene fibers. Ribbond may be an option for the treatment of traumatized teeth because of its aesthetic properties; absence of additional tooth preparation; and its high resistance to traction, which allows it to easily adapt to tooth morphology. In this report, we describe endodontic and restorative treatments using Ribbond for 3 female patients with horizontal complicated crown fractures of the maxillary incisors.

Effects of a pulsed XeCl excimer laser on ultra-high strength polyethylene fiber and its interface with epoxy resin

The effects of excimer laser treatment on the changes in the surface topography, the physical and chemical properties of ultra-high strength polyethylene (UHSPE) fibers, and their interfacial property with epoxy resin were investigated. The scanning electron microscopy (SEM) photomicrographs show that UHSPE fibers exhibit a rougher surface after irradiation with the XeCl pulsed excimer laser as a result of intense laser heat and ablation. The wettability and surface chemistry of control and laser-treated UHSPE fibers were monitored by TRI wettability/friction apparatus. The chemical changes on the surfaces of UHSPE fibers were analyzed by Fourier transform infrared spectroscopy (FTIR) in attenuated total reflectance (ATR) mode. The tensile properties of single fibers, before and after laser treatment, were studied using an Instron tensile tester. Interfacial shear strength (IFSS) measurements were performed using the single-fiber pull-out test. The fiber surface becomes polar after the laser treatment with increased acid-base contribution. The strength of laser-treated UHSPE fibers is lower than that of the control fibers. The IFSS results indicate that laser treatment improves the adhesion strength of UHSPE fibers with epoxy resin because of the changes in surface chemistry and enhanced roughness. The results show the potential of the excimer laser as an alternative surface treatment for fibers to enhance their adhesion with epoxy resins.

Surface modification of ultra-high strength polyethylene fibers for enhanced adhesion to epoxy resins using intense pulsed high-power ion beam

The effects of intense pulsed high power ion beam (HPIB) treatment of ultra-high strength polyethylene (UHSPE) fibers on the fiber/epoxy resin interface strength were studied. For this study, argon ions were used to treat Spectra™ 1000 (UHSPE) fibers in vacuum. Chemical and topographical changes of the fiber surfaces were characterized using Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), dynamic wettability measurements, and scanning electron microscopy (SEM). The fiber/epoxy resin interfacial shear strength (IFSS) was evaluated by the single fiber pull-out test. The FTIR-ATR and XPS data indicate that oxygen was incorporated onto the fiber surface as a result of the HPIB treatment. The wettability data indicate that the fibers became more polar after HPIB treatment and also more wettable. Although the total surface energy increased only slightly after treatment, the dispersive component decreased significantly while the acid-base component increased by a similar amount. SEM photomicrographs revealed that the surface roughness of the fibers increased following the HPIB treatment. The single fiber pull-out test results indicate that HPIB treatment significantly improved the IFSS of UHSPE fibers with epoxy resin. This enhancement in IFSS is attributed to increased roughness of the fiber surface resulting in mechanical bonding and in increased interface area, increased polar nature and wettability, and an improvement in the acid-base component of the surface energy after the HPIB treatment.

Excimer laser surface modification of ultra-high-strength polyethylene fibers for enhanced adhesion with epoxy resins. Part 1. Effect of laser operating parameters

The effects of a pulsed XeCl excimer laser (308 nm) on ultra-high-strength polyethylene (UHSPE) fibers and the fiber/epoxy resin interface were studied. SpectraTM 1000 (UHSPE) fibers were treated in air with a pulsed excimer laser with different energy density levels and numbers of pulses. Chemical and topographical changes of the fiber surfaces were characterized using X-ray photoelectron spectroscopy (XPS), dynamic wettability measurements, and scanning electron microscopy (SEM). The fiber/epoxy resin interfacial shear strength was evaluated by the single-fiber pull-out test. The XPS spectra demonstrated that the fiber surface undergoes photodissociation because of the laser treatment, which results in the incorporation of oxygen at the surface. The wettability data showed that the fiber becomes more polar after laser treatment and also more wettable. SEM photomicrographs revealed that the surface roughness of the fibers increases after the laser treatment. The interfacial shear strength (IFSS) results indicated that the laser treatment significantly improves the adhesion strength of UHSPE fibers with epoxy resin. This enhancement in IFSS is attributed to the increased roughness of the fiber surface and increased interfacial area, increased polar nature and wettability, as well as the improvement of the acid-base component of the surface energy after laser treatment.

Effects of oven aging on plasma treated ultra high strength polyethylene

The effects of radio-frequency plasma treatment on ultra high strength polyethylene (UHSPE) fibers using ammonia, oxygen, and argon plasmas were evaluated. The effects of oven aging on adhesion of UHSPE fibers were determined; two methods of oven aging, in air and in water, were used in this study. The effects of aging on the bond between the plasma treated UHSPE and epoxy resin were mechanically evaluated using single fiber pull-out tests. Electron spectroscopy for chemical analysis (ESCA) and wetting force measurements were used to evaluate chemical changes. ESCA results indicate that O-C=0 groups are important for improving IFSS between epoxy and UHSPE.

Acid treatment for functionalizing polyethylene fiber surfaces for enhanced adhesion to epoxy resins

AbstractThe utility of high‐strength, high‐modulus polyethylene fibers in fiber‐reinforced composites is limited due to its poor interfacial adhesion to various polymeric matrices. One way to overcome this limitation is to introduce reactive functionalities on the fiber surface capable of covalently bonding to matrix resins. Ultra high‐strength polyethylene (UHSPE) fibers were treated with chlorosulfonic acid. The surface acid groups were found to considerably improve the interfacial adhesion between polyethylene fibers and epoxy resins as shown by the microbond test. These surface functionalities were found to improve the fiber wettability, as shown by contact angle measurements using the Wilhelmy balance method. Colorimetric measurements of methylene blue absorption were used to quantify the surface concentrations of the acid groups. It was possible to functionalize the UHSPE fiber surfaces using this method to obtain fibers that formed a stronger adhesive bond with epoxy resins; this was achievable without sacrificing other fiber mechanical properties.

The influence of short branches on the α, β and γ‐relaxation processes of ultra‐high strength polyethylene fibers

AbstractDynamic mechanical measurements were conducted for several kinds of ultra–high‐strength polyethylene fibers with different methyl branch contents. As is the case with conventional polyethylene materials, UHSPE fibers also exhibit α, β, and γ‐relaxation dispersions. Each relaxation process is the function of both the tensile moduli and the branch contents of UHSPE fibers. It was also found that the γ‐process of UHSPE fibers is dominated mainly by the localized molecular motion in the crystalline part, such as a dislocation mode of crystallite defects, which is very sensitive to the branching content. From the time and temperature superposition of the frequency dispersion experiments, it was found that activation energies for both the α2‐process and α3‐process increase proportionally to the methyl branch content, while the α1‐process is not so affected by the branch content. This result shows that the incorporated branch sites in the crystalline part effectively hinder the chain‐to‐chain slippage; meanwhile, they have not hindered the slippage at the grain boundary so far, which also enables us to explain the creep improvement of UHSPE fibers through branch incorporation with the same mechanism. © 1994 John Wiley & Sons, Inc.

Plasma-treated ultra-high-strength polyethylene fibres improved fracture toughness of poly(methyl methacrylate)

Use of ultra-high-strength polyethylene (UHSPE) fibres in composites has been limited by problems with adhesion to the matrix. The present study presents a gas-plasma treatment of UHSPE staple fibres (Spectra 900 and 1000) to improve adhesion to poly (methyl methacrylate). The gases used were nitrogen, argon and carbon dioxide for treatment times of 0 and 1 min. No significant differences were observed in flexural stresses, and only modest improvements were seen in the flexural modulus and the stress-intensity factor by reinforcing the cements with surface-modified UHSPE fibres. At least a sixfold improvement in the toughness index (fracture energy) was observed by reinforcing the cements with carbon dioxide treated fibres with a fibre index, l/d, of 776 at 1 wt %. The fibres added reinforcement by a crack-bridging effect that significantly improved the toughness index. The plasma treatment altered the fibre surface sufficiently to cause significant differences in the susceptibility to plastic flow during the fibre pull-out process.

Photoinitiated surface grafting of synthetic fibers, I. Photoinitiated surface grafting of ultra high strength polyethylene fibers

AbstractPhotoinitiated surface grafting of acrylic monomers has been carried out onto high strength polyethylene (HSPE) yarn by means of a continuous process. The grafting reaction is initiated by UV irradiation of the yarn after presoaking in an acetone solution of initiator and monomer. Four initiators, benzophenone (BP), 4‐chlorobenzophenone (4‐CBP), 2‐hydroxy‐2‐cyclohexylacetophenone (HHA), and 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA), and two monomers, acrylic acid (AA) and acrylamide (AM), have been used. After short irradiation time (10 to 20 s) successful grafting is obtained, as shown by ESCA and IR‐ATR spectra, dye adsorpotion from aqueous solution, and measurements of adhesion of single filaments to epoxy resin. Grafting efficiency of 74% has been reached for AA as monomer (26% is homopolymer). The tensile strength and modulus of the HSPE yarn are retained in the grafting process. The degree of surface grafting is mainly a function of structure and concentration of monomer and photoinitiator in the presoaking solution and of the irradiation conditions used. Increasing irradiation time gives increasing amounts of grafted polymer up to a certain limiting value. The reactivities of the four initiators have been compared showing the highest grafting yields of AA with BP and of AM with 4‐CBP as photoinitiator. AA grafted HSPE yarn can be dyed to rather deep color by dipping in an aqueous solution of Crystal Violet. Increased dye absorption by a factor of up to seven has been measured for yarn grafted with AA to the maximum level obtained. The filaments of the grafted yarn show increased adhesion to epoxy resin by a factor of up to five compared with the ungrafted filaments.

Plasma-treated ultra-high strength polyethylene fibers. Part II. Increased adhesion to poly(methyl methacrylate)

The use of ultra-high strength polyethylene (UHSPE) fibers in composites has been limited by problems with adhesion to the matrix. The present study presents a gas plasma treatment of UHSPE fibers (Spectra ™ 900 and 1000) to improve adhesion with poly(methyl methacrylate) bone cements. The gases used were nitrogen, argon, and carbon dioxide for treatment times of 0, 1, 5, and 10 min. Significant improvements in the interfacial shear strength and fiber pull-out energies were achieved with only modest changes in the tensile strengths. Increased adhesion was attributed to improved wettability of the fiber surface. Increased fiber pull-out energies were attributed to enhanced propensity for surface peeling causing higher forces needed for fiber pull-out, based on SEM photomicrographs and fiber pull-out curves. No significant differences in interfacial shear strengths and energies were observed among fibers exposed to the three gases. One-minute exposure times were sufficient to cause significant improvements ...

Plasma-treated ultra-high strength polyethylene fibers. Part I. Characterization by electron spectroscopy for chemical analysis

Use of ultra-high strength polyethylene (UHSPE) fibers in composites has been limited by problems with adhesion to the matrix. In this study we present a gas plasma treatment of UHSPE fibers (Spectra 900™ and 1000™) to improve adhesion in poly(methyl methacrylate). The gases used were nitrogen, argon, and carbon dioxide for treatment times of 0, 1, 5, and 10 min. Significant improvements in fiber wettability were attributed to the addition of polar groups to the surface, as characterized by ESCA. No change in surface topography was seen at magnifications up to 2000 x .

Ammonia plasma treatment of ultra-high strength polyethylene fibres for improved adhesion to epoxy resin

A study of the effect of plasma treatments on the mechanical properties and adhesion of ultra-high strength polyethylene fibres to epoxy resin is reported. Fibres were treated with ammonia plasma under various time and power conditions. The fibre/matrix interfacial shear strength was measured using load and fibre pull-out data obtained in a single-fibre pull-out test. The debonding was optically as well as acoustically monitored. Optical birefringence patterns were visible at the fibre debond region. Acoustic emission signals generated from debonding and stick-slip processes were also detected. A more than four-fold increase in the interfacial shear strength was achieved by plasma treating the fibres at the discharging condition of 30 W and 0.5 torr for 1 min. The birefringence patterns showed, qualitatively, that the shear in the matrix around the fibres increased for treated fibres and extended further into the matrix material. Surface topography of the pulled out fibres showed that the failure mode was unchanged by the treatment.

Photocrosslinking of ultra high strength polyethylene fibers

AbstractUltra high strength polyethylene (HSPE) fibers have been successfully photocrosslinked using benzophenone as photoinitiator. The introduction of photoinitiator without disturbing the fiber structure is a difficult problem which was solved by vapor absorption at elevated temperature while keeping the fiber under constant strain. The crosslinked fiber showed no decrease in mechanical properties at room temperature as is the case when fibers are crosslinked by other reported methods such as radiation and chemical crosslinking. The crosslinked fiber showed enhanced high temperature resistance as well as much lower creep rate on prolonged stressing. Photocrosslinking of HSPE fiber is superior to other crosslinking methods reported in the literature.

Temperature-dependent fracture mechanisms in ultra-high strength polyethylene fibers

The influence of the temperature on the mechanical properties of gel-spun hot-drawn ultra-high molecular weight polyethylene fibers has been investigated.

Comments on "Effects of Strain Rate and Gauge Length on the Failure of Ultra-High Strength Polyethylene Fibers"

Comments on "Effects of Strain Rate and Gauge Length on the Failure of Ultra-High Strength Polyethylene Fibers"

Stochastic strength and size effect in ultra-high strength polyethylene fibres

Abstract A modified Poisson/Weibull probabilistic scheme is shown to yield accurate predictions for the mechanical strength of several types of ultra-high-strength polyethylene fibres. Strong diameter effects observed in such fibres are also conveniently modelled the proposed scheme. This new approach is shown to be at least as satisfactory as previously proposed models for diameter effects based on linear elastic fracture mechanics (LEFM). Moreover, it provides a simple solution to a current problematic issue inherent to the Weibull/weakest-link model, namely the conflicting values generally obtained for the Weibull shape parameter as calculated from Weibull plots and weakest link predictions respectively.

Cross-linking of ultra-high strength polyethylene fibres by means of electron beam irradiation

Ultra-high strength polyethylene fibres, with a tensile strength at break of 3.0 and 3.4 GPa, were irradiated, at various temperatures in a hydrogen atmosphere, by means of high energy electrons. When the fibres were not annealed, the tensile strength at break was found to decrease upon irradiation, while the Young's modulus remained unchanged. A maximal obtainable tensile strength of 22 GPa was calculated from the decrease in tensile strength and the gel-sol measurements. Gel contents upto 100% were obtained for fibres irradiated in the hexagonal phase.

Effects of Strain Rate and Gauge Length on the Failure of Ultra-High Strength Polyethylene Fibers

Ultra-high strength polyethylene filaments taken from a single spool of yarn were examined for strain rate and gauge length effects. As noted in previous research, high strength polyethylene exhibits pronounced strain rate effects that may be seen in strength changes, stress-strain behavior, and and topography of the fracture zones. Unlike most polymeric fibers, ultra-high strength polyethylene seems to exhibit no gauge length effects over the range from 10 to 200 mm, holding the strain rate constant. This latter effect, if true in general, would be a substantial advantage for polyethylene fibers, because scaling effects would be minimized.

Effect of chlorosulfonation of ultra-high strength polyethylene fibres on mechanical properties and bonding with gypsum plaster

Ultra-high strength polyethylene fibres were chlorosulfonated according to Kanig's technique. It has been found that the tensile strength of the fibre decreases during chlorosulfonation, whereas the Young's modulus can be increased by more than fifty percent of its original value. The interfacial bond-strength between polyethylene and gypsum plaster could be improved at least 4.8 times, amounting values of 6.3 MPa, making these fibres very suitable for use as a reinforcing material in gypsum plaster. SEM indicated that this improvement could be described to surface roughening of the fibre, due to chemical degradative stress-cracking during constrained chlorosulfonation.