Process of preparation and properties of ultra-high strength polyethylene fibers

Abstract

High molecular weight polyethylene can be processed into fibers with tensile strengths at break of about 5 GPa and Young's moduli upto 200 GPa by either applying the 'surface growth" technique or a combination of gel-spinning and hot-drawing. The mechanism of the piplecular process in both techniques involves the oriented crystallization:-ytretching of an entanglement network. The high strength levels are only achieved either by crystallizing the stretched network or by drawing the semi-crystalline gel at relatively high temperatures in order to transform the elastically ineffective chain ends of the entanglement network into the strong backbone structure. Evidence is presented for the presence of entanglements in the ultra-strong polyethylene fibers and for the necessity of entanglement in achieving high strengths by hot-drawing. High fiber production rates of the order of 270 rn/mm. can be attained by adding 1 wt.% of aluminium stearate to the paraffin oil solution. This additive avoids the adsorption of polyethylene on the wall of the die and suppresses meltfracture during extrusion. 'N '6.Aeq.Aeq.5'y 'ss'1 'L17 'j27

Influence of draw ratio on morphological and structural changes in hot-drawing of UHMW polyethylene fibres as revealed by DSC

“…Obviously this is only a rough estimate, because we did not take into account the broad molecular weight distribution in the UHMWPE. Nevertheless this result is very similar to the value of 2.3 entanglements per molecule as obtained from swelling experiments on a hot-drawn fibre, which was crosslinked by means of 6~ y-irradiation [27]. In the original 5 wt.…”

“…In the original 5 wt. % spinning solution each molecule was involved in about 12 entanglements [27], which clearly shows that in the drawing process a great many entanglements were smoothed away. Since the main defects in the fully drawn crystalline fibre are likely to be due to the 2.5 entanglements and of course 2 chain ends per .…”

High performance polyethylene nanocomposite fibers

“…For this combination of properties it is used in several industrial applications, such as piping systems, bags, bottles, ropes and fibers. polyethylene fibers has been one of the challenges for polymer scientist and engineers for a very long time [24,25]. One possible way to obtain high performance polyethylene fibers is through melt spinning and subsequent drawing.…”

Structural Aspects of the Damage Tolerance of Spectra Fibres and Composites

“…Melt spun and very high molecular weight solution spun fibres [13] show different creep behaviour. The latter fibre, the preparation of which involves an intermediate porous structure [13], exhibits a very low plateau creep rate at high stresses.…”