Introduction

Kajiwara, Kazuki; McIntyre, J. E.

doi:10.1016/b978-1-85573-182-0.50005-4

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“…Remarkable progress has been made in the improvement of these high performance fibers; however, the highest tensile strengths and moduli achieved for these fibers are still well below the broad range of theoretical tensile strengths and moduli reported for the perfect crystals of these polymers. 1 The highest tenacity of commercially available ultrahigh molecular weight PE (UHMWPE) fibers reaches 45 g/den, which is about 10 times higher than those of steel fibers. 5 However, this strength is still far below the theoretical achievable strength (372 g/den) reported for the perfect PE crystal.…”

Section: Introductionmentioning

confidence: 99%

Drawing properties of ultrahigh molecular weight polyethylene fibers prepared at varying formation temperatures

Yeh

Lin

Jiang

2003

J of Applied Polymer Sci

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ABSTRACT:The values of the percentage crystallinity, melting temperature, birefringence, and cross-sectional area of ultrahigh molecular weight polyethylene (UHMWPE)/ low MWPE (LMWPE) as-prepared fiber specimens are reduced consistently as the formation temperatures decreased from 60 to 0°C. Much more sparse structures with significantly larger voids are found on the fractured surfaces of those as-prepared fibers that were prepared at higher formation temperatures than those prepared at lower formation temperatures. The cross sections of the as-prepared fiber specimens gradually change from an oblate to a nearly circular to an uneven circular shape as the formation temperatures are reduced from 60 to 10 to 0°C, respectively. It is worth noting that the achievable draw ratios (D ra ) of the as-prepared fibers reach maximum when they are prepared at an optimum formation temperature of 10°C. Moreover, the D ra values of the as-prepared fiber (UL 10 ) specimens can be further improved by using a two-stage drawing process, wherein the temperature used in the second drawing stage (T sec ) is higher than 95°C. In fact, the optimum T sec of the two-stage drawn UL 10 fiber specimens increases significantly from 105 to 115°C as the first-stage draw ratio (D lr ) values increase from 20 to 40, respectively. The birefringence values, tensile strengths, and moduli of one-and two-stage drawn UL 10 fiber specimens increase consistently with increasing draw ratios, although the increasing rate of these values is gradually reduced as the draw ratios are greater than certain values. In contrast, at a constant draw ratio, the two-stage drawn UL 10 fiber specimens drawn at a higher T sec always exhibit higher values of birefringence, tensile strengths, and moduli than those with the same D lr but drawn at a lower T sec . Moreover, at a constant draw ratio, the birefringence values, tensile strengths, and moduli of the fiber specimens drawn at a fixed optimum T sec reach the maximum when they are first drawn up to an optimum D lr of about 50. In fact, by using the proper optimum T sec and D lr , the tensile strengths and moduli of the two-stage drawn UL 10 fiber specimens can reach more than 11 and 155 GPa, respectively. The possible mechanisms accounting for these interesting properties are proposed in this study.

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Section: Introductionmentioning

confidence: 99%