Effect of the ultradrawing behavior of gel films of ultrahigh‐molecular‐weight polyethylene and low‐molecular‐weight polyethylene blends on their physical properties

Abstract

This study examined the effect of the ultradrawing behavior of gel film specimens of ultrahigh-molecular-weight polyethylene (UHMWPE) and UHMWPE/lowmolecular-weight polyethylene (LMWPE) blends on their physical properties. The concentration of a gel film approximated its critical concentration at a fixed drawing temperature; its achievable draw ratio was higher than that of other blend specimens with various concentrations. Noticeably, when about 5 wt % LMWPE was added to a UHMWPE/LMWPE gel film specimen, the achievable draw ratio of the gel film increased, and this contributed to an apparent promoting effect on its anticreeping properties and thermal stability. Therefore, when UL B20.9 was drawn to a draw ratio of 300, the anticreeping behavior was improved to less than 0.026%/day. Moreover, with respect to the thermal stability, when the same specimen was drawn to a draw ratio of 300, the retention capability of its storage modulus could resist a high temperature of 1508C, which was obviously much higher than the temperature of an undrawn gel film specimen (708C). To study these interesting behaviors further, this study systematically investigated the gel solution viscosities, anticreeping properties, dynamic mechanical properties, thermal properties, molecular orientations, and mechanical properties of undrawn and drawn UHMWPE/LMWPE gel film specimens.

Ultrahigh molecular weight polyethylene fibers prepared using conical dies with varying dimensions

“…10 and 11. Similar to those found in our previous investigations [ 25, 26, 49, 50], three distinct transitions (i.e., α, β, and γ transitions) were observed at temperatures near 70°C to 80°C, −40°C to −25°C, and −120°C, respectively, in the tan δ curves of as‐prepared F and F series fiber specimens. It is interesting to note that peak temperatures of α, β, and γ transitions of the as‐prepared F fiber specimens with a fixed draw ratio reach a maximum value, when they were prepared using entry angles near the optimum value at 75°.…”

“…Based on these premises, the transitions found at peak temperatures near −120°C can be attributed to the γ‐transition of UHMWPE molecules of the F and/or F fiber specimens prepared using varying entry angles and lengths of outlet land. As suggested in our previous investigations [ 49, 50], the transitions found at peak temperatures from 95°C to 115°C are attributed to the molecular motions associated with the α transitions of UHMWPE molecules, although the observed transition temperatures are significantly higher than the α‐transition temperatures of melt‐crystallized polyethylenes with regular molecular weights. The particularly high α‐transition temperatures found for F and F fiber specimens are possibly due to their specific microstructures crystallized from UHMWPE gel solutions.…”

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

“…Lemstra and Smith performed experiments by spinning polymer solutions after gelation and observed that PE or PP gels can be spun to very high draw ratios (e.g., 30), forming strong fibers (e.g., with elastic modulus of 108 GPa for PE) . The large deformations of polymers resulted from the reduction of entanglements in the gel and were directly related to the concentration of entanglements …”

Ultradrawing properties of ultrahigh‐molecular weight polyethylene/functionalized carbon nanotube fibers and transmittance properties of their gel solutions

“…In our previous investigation [14, 18–28], the ultradrawing properties of gel‐spun fibers in UHMWPE/CNT blends were studied. Adding CNTs significantly increased the shear viscosities (η s ) of UHMWPE/CNTs gel solutions, reaching a maximum value as the CNTs contents increase up to a specific value.…”