Enhancing Gel Spinning of Ultra-High Molecular Weight Polyethylene: Insights into Rheology and Microstructure

In this investigation, we assessed the influence of entanglement density on the gel spinning process for producing ultra-high molecular weight polyethylene (UHMWPE) ultrafine fibers with high tensile strength and modulus. Using a semi-dilute solution spinning technique in paraffin oil and including swelling and thermal drawing stages, we discovered that low-entanglement UHMWPE achieves swelling equilibrium more effectively and swells at a faster rate than highly entangled variants, facilitating enhanced drawability, and reduced entanglement. Rheological testing was used to estimate ultimate draw ratios, revealing that low-entanglement UHMWPE could be drawn up to 101 times, which is 1.8 times greater than fibers from highly entangled materials of comparable molecular weight. The fibers spun from low-entanglement UHMWPE demonstrated a tensile strength of 4.2 GPa and an initial modulus of 163.9 GPa, showing improvements of 18% and 68% respectively, compared to their highly entangled counterparts. With a fiber diameter of 7.1 μm, these results show significant enhancements in swelling and thermal drawing processes achievable with low-entanglement UHMWPE, resulting in superior high-performance ultrafine fibers with exceptional processability.