High-strength Polyethylene Research Articles

Thermal Expansion Coefficient of Unidirectional High-Strength Polyethylene Fiber Reinforced Plastics at Low Temperature

High-strength polyethylene fiber (Dyneema®, DF) has a negative linear thermal expansion coefficient in the direction of the fiber. Thermal expansion coefficients of fiber-reinforced plastics are of important applications in cryogenic use. The purpose of this study is to construct the engineering technology for the thermal strain of DF reinforced plastics (DFRP) for cryogenic engineering. In this study, we investigate the thermal expansion coefficient of unidirectional high-strength DF reinforced plastics (UD-DFRP) in which DFs with different tensile moduli (15–134 GPa) and thermal expansion coefficients are used. Furthermore, using the thermal expansion coefficient and tensile modulus of each DF fiber and the matrix resin, the thermal expansion coefficients of the DFRPs are estimated by the rule of mixtures and are compared with the measured values. The results indicate that the thermal expansion coefficient of UD-DFRP behaves in a similar way to that expected from calculations based on the rule of mixtures. In addition, relationships concerning the difference between the calculated and measured values, the difference in the thermal expansion coefficient of the fiber and the resin, and the surface treatment of the fiber (adhesivity), as well as the diameter of the fiber (the area of the interfacial bonding) are studied. The results show that all of these influence the thermal expansion coefficient of UD-DFRP. The design of negative thermal expansion coefficient of UD-DFRP is established.

The effect of γ‐irradiation on thermal strain of high strength polyethylene fiber at low temperature

AbstractTo understand the contribution to negative thermal expansion by the length of the molecular chains in high‐strength ultra‐high‐molecular‐weight polyethylene (UHMW‐PE) fiber, the thermal expansion coefficient in the range of low temperature was investigated for high‐strength UHMW‐PE fiber (Toyobo, Dyneema®; hereinafter abbreviated to DF), irradiated by γ‐rays (γ‐rays treatment) that induce the molecular scission. The molecular weight of DF decreased by γ‐ray treatment. X‐ray diffraction behavior did not change by γ‐ray treatment. The melting behavior observed by DSC showed the main chain scission of DF by γ‐ray treatment. The DFs, with and without γ‐ray treatment, expand by cooling down (negative thermal expansion). The change of negative thermal expansion of DF by γ‐ray treatment was small. It is suggested that negative thermal expansion does not change by only the molecular chain scission. These results suggested that the effect of negative thermal expansion of DF in the temperature range from 213 to 303 K by the molecular chain scissions is small and that the length of extended molecular chains contributes to a negative thermal expansion a little. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 204–209, 2006

Chain Orientation in Polyethylene Fibers Prepared by Ethylene Nanoextrusion Polymerization

Ethylene nanoextrusion polymerization has been demonstrated to be a novel nanofabrication concept for the preparation of polyethylene (PE) fibers directly from ethylene monomers without any post-processing procedures. For PE fibers, chain orientation is a critical parameter that affects performance and application of the fibrous materials. In this communication, we report an investigation on chain orientation in PE fibrous samples prepared through nanoextrusion polymerization using a two-dimensional wide angle X-ray diffraction (2D WAXRD) technique. Two types of fibrous samples, including individual microfibers and microfiber aggregates, were sampled randomly and studied. For individual PE microfibers, anisotropic diffraction patterns were observed, suggesting chain orientation along the microfiber axial direction. Some microfibers showed the most desired diffraction pattern often found in high-modulus high-strength PE fibers. These samples possessed a very high degree of chain orientation along the fiber axis. Owing to a random aggregation of anisotropic microfibers, microfiber aggregates exhibited isotropic diffraction patterns. This work provided further experimental evidence for the proposed nanoextrusion polymerization concept.

Structural Transitions in Manufacture of High-Strength Polyethylene Fibres by the Gel-Technology Method

Structural Transitions in Manufacture of High-Strength Polyethylene Fibres by the Gel-Technology Method

Thermal conductivity of high strength polyethylene fiber in low temperature

AbstractHigh strength polyethylene fiber (Toyobo, Dyneema® fiber, hereinafter abbreviated to DF) used as reinforcement of fiber‐reinforced plastics for cryogenic use has a high thermal conductivity. To understand the thermal conductivity of DF, the relation between fiber structure and thermal conductivity of several kinds of polyethylene fibers having different modulus from 15 to 134 GPa (hereinafter abbreviated to DFs) was investigated. The mechanical series‐parallel model composed of crystal and amorphous was applied to DFs for thermal conductivity. This mechanical model was obtained by crystallinity and crystal orientation angle measured by solid state NMR and X‐ray. Thermal conductivity of DF in fiber direction was dominated by that of the continuous crystal region. The thermal conductivity of the continuous crystal part estimated by the mechanical model increases from 16 to 900 mw/cmK by the increasing temperature from 10 to 150K, and thermal diffusivity of the continuous crystal part was estimated to about 100 mm2/s, which is almost temperature independent. The phonon mean free path of the continuous crystal region of DF obtained by thermal diffusivity is almost temperature independent and its value about 200 Å. With the aforementioned, the mechanical series‐parallel model composed of crystal and amorphous regions could be applied to DFs for thermal conductivity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1495–1503, 2005

Thermal strain of high strength polyethylene fiber in low temperature

AbstractHigh strength polyethylene fiber (Toyobo, Dyneema® fiber: hereinafter abbreviated to DF) has a negative thermal expansion coefficient. Relation between fiber structure and thermal strain of DF used as reinforcement of DF reinforced plastic (DFRP) for cryogenic use was investigated. The crystallinities and orientation angles of several kinds of polyethylene fibers having different modulus from 15 to 134Gpa (herein after abbreviated to DFs) were measured by NMR and X‐ray. We obtained the parameters of the mechanical series‐parallel model composed of crystal and amorphous by crystallinity and modulus. Thermal expansion coefficients of DFs were estimated by mechanical series‐parallel model. All DFs having different modulus showed negative thermal expansion coefficients in the temperature range from 180 to 300K, and absolute values of those markedly increased by increasing tensile modulus of DF. The estimated thermal expansion coefficients showed negative values, and thermal strains showed a similar curve to observed ones mostly. Average thermal expansion coefficients in the temperature range from 180 to 300K estimated by mechanical model agreed with the observed ones. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2918–2925, 2004

04/00732 Preparation of porous carbon and characterization of carbon filter: Oh, W.-C. and Bae, J.-S. Kongop Hwahak, 2003, 14, (1), 29–34. (In Korean)

This paper presents an experimental study of the composite properties of cement based- and alkali-activated ground-granulated blast furnace slag (GGBS) based composites reinforced by high-strength polyethylene fibers and a discussion of the different behaviors of the two types of binder-based composites. A series of experiments, including those to test the density, compression, and uniaxial tension, was performed to characterize the mechanical properties of the composite. The test results indicated that an alkali-activated GGBS composite shows a higher tensile strain capacity with smaller crack widths and crack spacings than a cement-based composite, although the alkali-activated GGBS composite showed lower compressive and lower tensile strength than the cement-based composite with the same water-to-binder ratio. It was also observed that the alkali-activated GGBS-based composite has higher ratio of the tensile strength to the compressive strength than the cement-based composite.

高強度ポリエチレン繊維強化複合材料からなる超電導コイルボビン(S08-3 超電導材料システム,S08 極低温・超電導材料システムの強度・機能特性)

高強度ポリエチレン繊維強化複合材料からなる超電導コイルボビン(S08-3 超電導材料システム,S08 極低温・超電導材料システムの強度・機能特性)

Dependence on winding tensions for stability of a superconducting coil

The purpose of this study is to manufacture a high performance superconducting pulse coil by using high strength polyethylene fiber (DF; Dyneema ® fiber) reinforced plastic (DFRP) or Dyneema–glass hybrid composite fiber reinforced plastic (DGFRP) as material of a coil bobbin, which has negative thermal expansion, low frictional coefficient and high thermal conductivity. Description in this paper is as follows. First, thermal strains of several kinds of FRP pipes made by filament-winding (FW) method are measured, and the measured results well agreed with calculated ones by our proposed calculation method about thermal strains of a FW-pipe form. This shows that thermal expansion can be controlled by the proposed design technique of a DGFRP FW-pipe. Moreover, frictional coefficients of FRP plates using as coil structural material are measured and frictional heats are calculated for respective material when contact forces are changed. From these results, we find that the lower winding tension of a coil generates the smaller frictional heat when the frictional coefficient of the coil structural material is low. Furthermore, we systematically measure quench characteristics of many specimens of small superconducting coils using DFRP or DGFRP bobbins with different thermal expansions. From the results of quench tests, we find that the higher winding tension’s coils tend to decrease quench current when the coil’s bobbin expanded to a direction of circumference during the cooling down to cryogenic temperature, and suitable values of winding tension in a coil are located in region of 2–4 kg/mm 2. Finally, we design and manufacture 100 kJ class superconducting pulse coil by using a DGFRP bobbin, which wound in winding tension of 4 kg/mm 2. In addition, we prepare another 100 kJ class coil with the higher winding tensions of 8 kg/mm 2, and the quench characteristics of the coils are compared. The quench currents in the coils exceed the 95% rating on the load line for critical current value of a conductor, and a coil with winding tension of 4 kg/mm 2 is more stable.

Change in the Properties of High-Strength Fibres under the Effect of Soil Microorganisms

The resistance of high-strength para-aramid and polyethylene terephthalate fibres to soil microorganisms was investigated. It was found that the curve of the fibre strength versus the duration of exposure to soil microflora is monotonically diminishing. The elongation at break of the fibres also changes monotonically, with the exception of Kevlar. The change in the strength and elongation at break as a function of the duration of exposure in the soil is approximated by exponential equations can be used to predict the change in these indexes. The values of the coefficients in the equation are found. A comparison of the features of the change in the mechanical characteristics with the features of the molecular and supramolecular structure allows assessing the role of both the plasticizing effect of water and microbiological degradation. The increase in the deformation characteristics with a simultaneous decrease in the strength of para-aramid fibres, especially SVM, can probably be attributed to the effect of plasticization and the lability of their structure under the effect of moisture.

Coil bobbin composed of high strength polyethylene fiber reinforced plastics for a stable high field superconducting magnet

High field superconducting solenoid magnets sometimes quench by wire motion induced by electro-magnetic force. High strength polyethylene fiber reinforced plastic (DFRP) has a negative thermal expansion coefficient and a low frictional coefficient. DFRP pipes made by filament winding method could be constructed so as to expand in the circumferential direction when cooled to low temperature with an appropriate selection of winding angle and shape of the pipes. In the case of a superconducting coil wound on a DFRP bobbin, it is expected that wire motions in high field are decreased by expansion of the coil bobbin. In this work, sample coils wound on DFRP bobbin and stainless steel (SUS) bobbin were prepared. The sample coil voltages were measured during increasing current in background external field. The coil using SUS bobbin showed many sharp peaks in tap voltage induced by quick wire motions. In contrast, those using DFRP bobbin showed no peaks. These results suggest that the quick wire motions were constrained by DFRP bobbin which had a negative thermal expansion coefficient and a low frictional coefficient.

New potentialities in producing composites reinforced with high-strength high-modulus polyethylene fibers

A concept of physical and chemical stages of interaction between the matrix and reinforcing fibers during the production of composite materials is introduced. A strong bond between these constituents is formed at the stage of chemical interaction, which is characterized by a certain value of activation energy. The activation energy of such an interaction for high-strength high-modulus polyethylene fibers used for reinforcing composites is estimated. Based on these estimates, conditions for fiber activation with “cold” plasma are found. The application of plasma-activated polyethylene fibers for reinforcing an epoxy matrix allows one to produce light-weight composites with high physicomechanical indices. The failure mode of such composites points to a high strength of the bond between the fibers and matrix. The data on treating the fiber surface with “cold” plasma above the activation energy of chemical interaction may be utilized to create new types of organic composites from other kinds of organic fibers and matrices.

410 高強度ポリエチレン繊維強化複合材料を用いた超電導コイルボビンの開発

410 高強度ポリエチレン繊維強化複合材料を用いた超電導コイルボビンの開発

Scale model of a new midwater trawl system for sampling pelagic larval and juvenile fish

SUMMARY: A new midwater sampling trawl was designed to collect pelagic larval and juvenile fish. It has a rigid square frame of 2.25 m2, with a 12.5 m high strength polyethylene net. The cambered V-type depressor with a camber ratio of 15%, aspect ratio of 6.0, and dihedral angle of 20° was hung to the bottom of the frame with four slings based on the principle of the parallelogram. A 1/5 scale model net of the prototype was made to examine the towing performances in a circulating water tank. The depth of the net and the attack angle of the depressor were measured at various flow velocities ranging from 30 to 100 cm/s with warp lengths of 260, 310, 360, 410 cm. The depressor held the setting angle closely, and the fluctuating range of the net depth was only 2% for the longest warp length over a wide range of flow velocities. This sampling trawl could maintain near constant depth under various flow velocities by the results of model experiment.

Coil bobbin composed of high-strength polyethylene fiber reinforced plastics for a stable high-field superconducting magnet

High-field superconducting solenoid magnets sometimes quench by wire motion induced by electromagnetic force. Fiber reinforced plastic [Dyneema fiber reinforced plastic (DFRP)] pipes composed of high-strength polyethylene fiber by filament winding method could be constructed so as to expand in the circumferential direction when cooled to low temperature with an appropriate selection of winding angle and shape of the pipes. In the case of a superconducting coil fabricated with a DFRP bobbin, it is expected that wire motions in high field are decreased by expansion of the coil bobbin. In this paper, tap voltage between both ends of the coils fabricated with DFRP bobbin and stainless steel (SUS) bobbin were measured with increasing current. The coil using SUS bobbin showed many sharp peaks in tap voltage induced by quick wire motions. In contrast, those using DFRP bobbin showed only a few small peaks. These results suggest that wire motions were constrained by DFRP bobbin. The training effects were observed in both cases.

Morphology and Orientation of Crystallites of Simultaneous Biaxially Stretching Ultra-High Molecular Weight Polyethylene Films Prepared by Gelation/Crystallization from Solutions

Simultaneous biaxially stretching was carried out using ultra-high molecular weight polyethylene dry gel films which were prepared by crystallization from solutions. The concentrations were 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 g/100 mL. The maximum draw ratio was dependent upon the concentration of the solutions. The greatest significant drawability could be realized at 0.9 g/100 mL which is much higher than the optimum concentration of 0.45 g/100 mL assuring the draw ratio > 300-fold for uniaxially stretching. Young’s modulus of the biaxially stretched film was much lower than that of uniaxial films with the same draw ratio (70-fold), although the Young’s modulus of the film with the maximum draw ratio was much higher than that of commercial films. To address this problem, the orientation function of crystallites was determined from the orientation of the reciprocal lattice vectors of the crystal planes. As the result, it turned out that the c- and a-axes are oriented predominantly to the film surface but the orientational degree of the c-axis is not remarkable in spite of high draw ratio of 8.7×8.7. The second order orientation factor was estimated from birefringence by subtracting the crystalline contribution from the total birefringence. These results indicated that the preferential orientation of the c-axis to the stretching direction is mainly due to the rotation of crystallites around their b-axis leading to straining of tie molecules. Furthermore, the ultimate value of Young’s modulus was estimated by assuming an ideal simultaneous biaxially stretching film with 100% crystallinity and the perfect orientation of the c-axis parallel to the film surface. Even so, the predicted value was less than 10 GPa, when the elastic compliance of a crystal unit by Odajima and Zehnder were employed. This indicates the difficulty in producing high modulus and high strength polyethylene sheets in terms of theoretical aspects.

極低温用負膨張コイルボビンの開発 高強度ポリエチレン繊維／アルミナ繊維系混合強化複合材料からなるパイプの弾性率及び熱歪特性

Hybrid composite pipes reinforced with high-strength polyethylene fiber (DF) and alumina fiber (AlF) were prepared to develop the coil bobbin for stable superconducting coils. The bobbin in which the circumferential thermal strain expands with cooling and in which the circumferential Young's modulus is large would be effective for stable coils. The unidirectional hybrid composite (ADFRP) showed 0 thermal expansion coefficient when the ratio between DF and AIF volume was 5/5 in fiber direction, and its Young's modulus was larger than that of DF reinforced plastic (DFRP) both in parallel and perpendicular to fiber direction. The circumferential and longitudinal Young's moduli of ADFRP pipe were larger than those of DFRP pipe. The average value of inner and outer circumferential thermal strains with cooling down showed 0 with a filament winding (FW) angle of 90deg when the ratio between DF and AIF volume (D/A) was 5/5. When D/A equals 5/5, the calculated thermal strain with cooling of the pipe showed good agreement with the average of observed inner and outer thermal strains. The circumferential thermal strain showed an expansion with a FW angle of 50-90deg, and an absolute value was smaller than those of DFRP. The inner and outer circumferential thermal strains were different. The difference decreased with an increase of the ratio inner diameter/thickness, and the differences were smaller than those of DFRP with a decrease of the degree of anisotropy of thermal expansion coefficients in UD-FRP. The experimental data were obtained to make it possible to devise a coil bobbin with negative thermal expansion coefficient by ADFRP.

A novel, efficient route for the crosslinking and creep improvement of high modulus and high strength polyethylene fibres

A new route is presented for the chemical crosslinking of solution-spun, ultra-drawn Ultra-High-Molecular-Weight Polyethylene (UHMW-PE) fibres. UHMW-PE fibres with a range of draw ratio's, Young's moduli and tensile strengths were impregnated with a radical initiator using supercritical carbon dioxide as a carrier. After impregnation, the drawn fibres were crosslinked with ultra-violet light and fibres with a high gel content (> 90%) were obtained. It was found that the chemical crosslinking strongly reduces the plateau creep rate of the fibres and that the threshold stress for irreversible creep is enhanced. Simultaneously, the high Young's modulus and the high tensile strength of the drawn fibres are preserved which illustrates that the long term properties of the fibres (i. e. creep) are improved without a large sacrifice short term mechanical properties such as Young's modulus.

A novel, efficient route for the crosslinking and creep improvement of high modulus and high strength polyethylene fibres

A novel, efficient route for the crosslinking and creep improvement of high modulus and high strength polyethylene fibres

The Crystallization and Impact Properties of High Strength Polyethylene Fibre Reinforced LLDPE Composites

The Crystallization and Impact Properties of High Strength Polyethylene Fibre Reinforced LLDPE Composites