https://ir.nctu.edu.tw:443/bitstream/11536/11058/1/000245064900034.pdf

Composites of UHMWPE fiber reinforced PU/epoxy grafted interpenetrating polymer networks

The influence of draw ratios (DR) of gel-spun ultrahigh molecular weight polyethylene (UHMWPE) fibers on resultant morphologies, tensile, degrees of orientation, and crystal phase transition properties were investigated using wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The anisotropic crystalline structure with full concentric circular rings originally shown on the WAXD patterns of the as-prepared and drawn UHMWPE fibers gradually transform into oriented fibers with azimuthal spots on the equator as their DR values increase from 1 to 20, in which their orthorhombic crystals, percentage crystallinity, crystalline orientation, and the birefringence values increase significantly. As evidenced by SEM and WAXD analysis, the chain-folded molecules originally present in kebab crystals of the as-prepared UHMWPE fiber specimens gradually transformed into shish-like crystals with relatively high orientation as their DR values increase from 1 to 20. In contrast, the crystallinity and crystal orientation values of the drawn UHMWPE specimens increase only slightly, as their DR values increase from 20 to 40, wherein both crystallinity values of orthorhombic and monoclinic crystals increase slightly. In fact, barely any oriented kebab but only shish crystals were observed on the surfaces of drawn UHMWPE fiber specimens with DR values higher than 20. The birefringence values increase only slightly with further increasing DR values, while crystallinity and crystal orientation values of the drawn UHMWPE fiber specimens remained relatively unchanged as their DR values increase from 40 to 150. In the meantime, the monoclinic crystals gradually grow at the expense of the orthorhombic form crystals as the DR values of drawn UHMWPE fiber specimens increase from 40 to 150. Possible reasons accounting for these interesting properties found for the drawn UHMWPE fibers with varying draw ratios are proposed in this study.

https://ir.nctu.edu.tw:443/bitstream/11536/8620/1/000256928800029.pdf

Investigation of the drawing mechanism of UHMWPE fibers

Impact of some environmental conditions on the tensile, creep-recovery, relaxation, melting and crystallinity behaviour of UHMWPE-GUR 410-medical grade

Effect of pre-heat treatment on the static and dynamic thermo-mechanical properties of ultra-high molecular weight polyethylene

Two surface modification methods—plasma surface treatment and chemical agent treatment—were used to investigate their effects on the surface properties of ultrahigh-molecular-weight polyethylene (UHMWPE) fibers. In the analyses, performed using electron spectroscopy for chemical analysis, changes in weight, and scanning electron microscope observations, demonstrated that the two fiber-surface-modified composites formed between UHMWPE fiber and epoxy matrix exhibited improved interfacial adhesion and slight improvements in tensile strengths, but notable decreases in elongation, relative to those properties of the composites reinforced with the untreated UHMWPE fibers. In addition, three kinds of epoxy resins—neat DGEBA, polyurethane-crosslinked DGEBA, and BHHBP-DGEBA—were used as resin matrices to examine the tensile and elongation properties of their UHMWPE fiber-reinforced composites. From stress/strain measurements and scanning electron microscope observations, the resin matrix improved the tensile strength apparently, but did not affect the elongation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 655–665, 2007

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Surface modification and physical properties of various UHMWPE-fiber-reinforced modified epoxy composites

This study investigated sunlight-simulated ultraviolet (UV) beam irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene (UHMWPE) fibers The tensile results showed that after 300 h sunlight UV irradiation, the tensile properties of the UHMWPE fibers were obviously degraded Investigation of morphology revealed that the crystallinity was slightly increased, whereas the overall orientation and molecular weight of the fibers were decreased SEM observations indicated that the degradation process was nonuniform throughout the fiber and a change from a ductile to a brittle fracture mechanism was found after UV irradiation DMA results showed two β-relaxations and one α-relaxation in the original single filament, and UV irradiation led to the increased intensity of the high-temperature β-relaxation and the lowered position of the low-temperature β-relaxation This indicated that irradiation-induced molecular scission and branching were located primarily in the amorphous and the interface areas of the fiber Changes in the thermal behavior were also examined by DSC © 2003 Wiley Periodicals, Inc J Appl Polym Sci 89: 2757–2763, 2003

Meiwu Shi

Papers

Effects of sunshine UV irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene fiber