Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS).Liquid paraffin (LP) was used as a diluent in the preparation of microporous UH...Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS).Liquid paraffin (LP) was used as a diluent in the preparation of microporous UHMWPE. Small angle laser light scattering (SALLS) and differential scanning calorimetry (DSC) were used to determine the phase separation temperatures,i.e.the cloud points and the dynamic crystallization temperatures,respectively.It was found that the cloudI points were coincident with the cr...展开更多
High-strength and high-modulus ultra-high molecular weight polyethylene（UHMWPE）, named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. Accordi...High-strength and high-modulus ultra-high molecular weight polyethylene（UHMWPE）, named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope（SEM） analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope（TEM） and selective area electron diffraction（SAED） analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry（DSC） analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature（136.4 ℃） is ascribed to the melting of the reinforced phase.展开更多
In this study, the blends of polypropylene (PP) and ultrahigh molecular weight polyethylene (UHMWPE) were prepared by the four-and twin-screw extruders, and ethylene-propylene-diene monomer (EPDM), as the third compon...In this study, the blends of polypropylene (PP) and ultrahigh molecular weight polyethylene (UHMWPE) were prepared by the four-and twin-screw extruders, and ethylene-propylene-diene monomer (EPDM), as the third component, was added to the binary blends. The mechanical.thermal, morphological and rheological properties of these two blends have been investigated.For the materials blended by the four-screw extruder, a 15 wt-% content of UHMWPE corresponds to a maximum lzod impact strength, and the miscibility enhancement effect of EPDM on PP/UHMWPE blends is very remarkable. Mechanical and thermal properties demonstrate that melt blending by the four-screw extruder is a better prcessing method for PP/UHMWPF blends than that by the twin-screw extruder. A co-continuous structure was observed in blends through TEM, and a novel "linear interpenetrating" toughening mechanism is proposed on the basis of this research展开更多
Managing fractures of distal humerus in patients with rheumatoid arthritis (RA) is technically challenging. Total elbow arthroplasty (TEA) is one of the treatment options for these fractures. While elbow motion is lar...Managing fractures of distal humerus in patients with rheumatoid arthritis (RA) is technically challenging. Total elbow arthroplasty (TEA) is one of the treatment options for these fractures. While elbow motion is largely regained by TEA, comminuted condyle fragments are often ignored. Although numerous approaches for repair of condylar fragments around TEA are described, any universal fixation strategy for these fractures has not been established. This report describes, for the first time, application of an ultra-high molecular weight polyethylene (UHMWPE) tape for the treatment of distal humerus fracture in 2 patients with rheumatic elbow arthropathy. The post-operative clinical courses were good. Radiographs showed bony union of the condylar fragments without loosening in two cases. Because of its flat configuration, softness, and flexibility, UHMWPE tape is a promising material for stabilizing fracture of the distal humerus associated with TEA.展开更多
Due to the low density and excellent mechanical proper-ties,high performance fiber reinforced materials have aconsiderable application in the area of high technologyand dally usage.In this paper,the Ultra-high Molecu-...Due to the low density and excellent mechanical proper-ties,high performance fiber reinforced materials have aconsiderable application in the area of high technologyand dally usage.In this paper,the Ultra-high Molecu-lar Weight Polyethylene(UHMWPE)fiber reinforcedPE tape prepared with the method of powder impregnat-ion was studied.The effect of impregnate length and thetensile force of the yarn on the fiber content as well as on the strength and modulus of the tape were discussed.Calculation shows that the strength and the modulus ofthe ULMWPE fiber can keep about 85％ after it undergothe process.展开更多
The three stages in the hot-drawing process of ultrahigh-molecular-weight polyethylene gel films can be detected by x-ray diffraction, infrared spectroscopy, birefringence and scanning electron microscopy. In the firs...The three stages in the hot-drawing process of ultrahigh-molecular-weight polyethylene gel films can be detected by x-ray diffraction, infrared spectroscopy, birefringence and scanning electron microscopy. In the first stage of the drawing process, the lamellae in the gel films rotate and/or slip with the b-axis preferentially perpendicular to the drawing direction. With increased drawing, the c-axis of the lamellae become parallel to the stretching direction while unfolding of the chain begins, and the chains of the amorphous phase also orient along the drawing direction in the strain-chain domain. When the draw ratio is large enough, the lamellar structure is transformed into a fibrillar structure in a two-dimensional fashion.展开更多
The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means ...The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G″) plots at 180 and 200 ℃ versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100 rad/s for Ziegler-Natta catalyzing ethylene-propylene random copolymerization(PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G″(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus(G 0_N) of UHPPH from a certain experimental temperature G″(ω) curve directly. For UHPPH, the G 0_N determined to be 4.28×10 5 and 3.62×10 5 Pa at 180 and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G 0_N has no relation to the molecular weight.展开更多
This paper reports the spinning and drawing behavior of Ultra-high Molecular Weight polyethylene Terephthalate) (UHMW-PET) fibers. The as-spun fibers were produced by dry-jet wet spinning of a 15%-17% solution in 50:5...This paper reports the spinning and drawing behavior of Ultra-high Molecular Weight polyethylene Terephthalate) (UHMW-PET) fibers. The as-spun fibers were produced by dry-jet wet spinning of a 15%-17% solution in 50:50(v:v) trifluroroacetic acid and dichloromethane. Both molecular weight and polymer solution concentration have marked effect on the drawability of the as-spun-fibers. The maximum extension drawing ratio (EDRmax) of as-spun fiber increases with increasing molecular weight, whereas optimal concentration to achieve the EDRmax of as-spun fibers decreases with increasing molecular weight. Drawing speed and temperature during the first step have remarkable effect on the drawability of these fiber during the second step. Relatively lower drawing temperature and drawing speed (19 ℃ , 60 mm/min) during the first drawing step was beneficial to mechanical properties of ultimate fibers. At the range of 210 ℃ to 230 ℃, the draw ratio (DR) during the second step increases with increasing temperature.展开更多
Ultra-high molecular weight polyacrylonitrile (UHMW PAN ) was prepared by aqueous suspension polymerization, and the effect of molecular weight on its rheological behaviors in dimethylsulfoxide (DMSO) and the spinning...Ultra-high molecular weight polyacrylonitrile (UHMW PAN ) was prepared by aqueous suspension polymerization, and the effect of molecular weight on its rheological behaviors in dimethylsulfoxide (DMSO) and the spinning stability were investigated. It shows that,compared with common polyacrylonitrile (C-PAN),UHMW- PAN/DMS0 solution has smaller non- Newtonian index, larger structural viscosity index, much longer maximum relaxation time, and no first- Newtonian region appears in the flow curves under the same experimental conditions. The explanations for these phenomena are given in the view of chain- entanglements. The optimal technology of preparing UHMW-PAN fibers and hollow fiber membranes could be obtained based on the theological study.展开更多
基金supported by Special Funds for Major State Basic Research Projects,China (No.2003CB615705).
文摘Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS).Liquid paraffin (LP) was used as a diluent in the preparation of microporous UHMWPE. Small angle laser light scattering (SALLS) and differential scanning calorimetry (DSC) were used to determine the phase separation temperatures,i.e.the cloud points and the dynamic crystallization temperatures,respectively.It was found that the cloudI points were coincident with the cr...
文摘High-strength and high-modulus ultra-high molecular weight polyethylene（UHMWPE）, named self-reinforced material, was obtained by the elongation of UHMWPE-montmorillonite nanocomposite at melting temperature. According to the scanning electron microscope（SEM） analysis, a great deal of fibrillar texture formed in the direction of elongation, and the tensile fractured surface was similar to that of highly oriented fiber. The transmission electron microscope（TEM） and selective area electron diffraction（SAED） analyses reveal that the reinforced phase of the self-reinforced material is an extended chain crystal and its size is about 50200 nm wide and several microns long, and the montmorillonite layers are broken up to pieces in the size from 100 to 10 nm. The broken layers which have a huge surface area interacting strongly with macromolecules reduces the entanglement density of UHMWPE and induces the chain orientation in flow field. It is supposed that the astriction of montmorillonite layers to polyethylene chains is not only end-tethered but also side-tethered. The differential scan calorimetry（DSC） analysis shows that there are two endothermal peaks for the self-reinforced material, of which the peak at a higher temperature（136.4 ℃） is ascribed to the melting of the reinforced phase.
文摘In this study, the blends of polypropylene (PP) and ultrahigh molecular weight polyethylene (UHMWPE) were prepared by the four-and twin-screw extruders, and ethylene-propylene-diene monomer (EPDM), as the third component, was added to the binary blends. The mechanical.thermal, morphological and rheological properties of these two blends have been investigated.For the materials blended by the four-screw extruder, a 15 wt-% content of UHMWPE corresponds to a maximum lzod impact strength, and the miscibility enhancement effect of EPDM on PP/UHMWPE blends is very remarkable. Mechanical and thermal properties demonstrate that melt blending by the four-screw extruder is a better prcessing method for PP/UHMWPF blends than that by the twin-screw extruder. A co-continuous structure was observed in blends through TEM, and a novel "linear interpenetrating" toughening mechanism is proposed on the basis of this research
文摘Managing fractures of distal humerus in patients with rheumatoid arthritis (RA) is technically challenging. Total elbow arthroplasty (TEA) is one of the treatment options for these fractures. While elbow motion is largely regained by TEA, comminuted condyle fragments are often ignored. Although numerous approaches for repair of condylar fragments around TEA are described, any universal fixation strategy for these fractures has not been established. This report describes, for the first time, application of an ultra-high molecular weight polyethylene (UHMWPE) tape for the treatment of distal humerus fracture in 2 patients with rheumatic elbow arthropathy. The post-operative clinical courses were good. Radiographs showed bony union of the condylar fragments without loosening in two cases. Because of its flat configuration, softness, and flexibility, UHMWPE tape is a promising material for stabilizing fracture of the distal humerus associated with TEA.
文摘Due to the low density and excellent mechanical proper-ties,high performance fiber reinforced materials have aconsiderable application in the area of high technologyand dally usage.In this paper,the Ultra-high Molecu-lar Weight Polyethylene(UHMWPE)fiber reinforcedPE tape prepared with the method of powder impregnat-ion was studied.The effect of impregnate length and thetensile force of the yarn on the fiber content as well as on the strength and modulus of the tape were discussed.Calculation shows that the strength and the modulus ofthe ULMWPE fiber can keep about 85％ after it undergothe process.
文摘The three stages in the hot-drawing process of ultrahigh-molecular-weight polyethylene gel films can be detected by x-ray diffraction, infrared spectroscopy, birefringence and scanning electron microscopy. In the first stage of the drawing process, the lamellae in the gel films rotate and/or slip with the b-axis preferentially perpendicular to the drawing direction. With increased drawing, the c-axis of the lamellae become parallel to the stretching direction while unfolding of the chain begins, and the chains of the amorphous phase also orient along the drawing direction in the strain-chain domain. When the draw ratio is large enough, the lamellar structure is transformed into a fibrillar structure in a two-dimensional fashion.
文摘The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight(UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G″) plots at 180 and 200 ℃ versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100 rad/s for Ziegler-Natta catalyzing ethylene-propylene random copolymerization(PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G″(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus(G 0_N) of UHPPH from a certain experimental temperature G″(ω) curve directly. For UHPPH, the G 0_N determined to be 4.28×10 5 and 3.62×10 5 Pa at 180 and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G 0_N has no relation to the molecular weight.
文摘This paper reports the spinning and drawing behavior of Ultra-high Molecular Weight polyethylene Terephthalate) (UHMW-PET) fibers. The as-spun fibers were produced by dry-jet wet spinning of a 15%-17% solution in 50:50(v:v) trifluroroacetic acid and dichloromethane. Both molecular weight and polymer solution concentration have marked effect on the drawability of the as-spun-fibers. The maximum extension drawing ratio (EDRmax) of as-spun fiber increases with increasing molecular weight, whereas optimal concentration to achieve the EDRmax of as-spun fibers decreases with increasing molecular weight. Drawing speed and temperature during the first step have remarkable effect on the drawability of these fiber during the second step. Relatively lower drawing temperature and drawing speed (19 ℃ , 60 mm/min) during the first drawing step was beneficial to mechanical properties of ultimate fibers. At the range of 210 ℃ to 230 ℃, the draw ratio (DR) during the second step increases with increasing temperature.
基金This work was supported by Shanghai Natural Science Foundation(98ZF14001)
文摘Ultra-high molecular weight polyacrylonitrile (UHMW PAN ) was prepared by aqueous suspension polymerization, and the effect of molecular weight on its rheological behaviors in dimethylsulfoxide (DMSO) and the spinning stability were investigated. It shows that,compared with common polyacrylonitrile (C-PAN),UHMW- PAN/DMS0 solution has smaller non- Newtonian index, larger structural viscosity index, much longer maximum relaxation time, and no first- Newtonian region appears in the flow curves under the same experimental conditions. The explanations for these phenomena are given in the view of chain- entanglements. The optimal technology of preparing UHMW-PAN fibers and hollow fiber membranes could be obtained based on the theological study.
