Multiple-stage Drawn Ultrahigh Molecular Weight Polyethylene/Activated Carbon Fibers Prepared With The Assistance Of Supercritical CO₂

Much effort has been expended in the development of high-performance fibers with tensile tenacity≥20 g/d.Among these high-performance fibers,ultrahigh-molecular-weight polyethylene（UHMWPE）fibers have been the most fast-growing fibers due to their excellent tensile tenacity,light weight,flexibility,chemical and ultraviolet stability properties since1980s.They have been widely used in security,sporting and navigation/sailing equipment,such as bullet-proof vests,ballistic armor,fishing net and etc.Remarkable improved achievable draw ratios（Dras）and ultimate tensile tenacities（σ_ts）of multiple-stage drawn ultrahigh molecular weight polyethylene（UHMWPE）/functionalized activated carbon（FAC）fibers prepared with the aid of supercritical carbon dioxide（scCO₂）were reported.The Dras andσ_ts of single-and multiple-stage drawn scCO2UHMWPE/FAC fibers were considerably higher than those Dras andσ_ts found for the corresponding single-and multiple-stage drawn UHMWPE/FAC fibers spun from gel solutions gelatinized in nitrogen atmosphere.It is worth noting that the largest D_ra obtained for the most proper scCO2UHMWPE/FAC fiber drawn at 130℃ and 20 mm/min in the fifth drawing stage approached 688,which is～40%larger than the D_rafound for the single-stage drawn scCO₂F₁₀₀FAC_0.1^13.5 fiber.Theσ_t found for the most proper five-stage drawn scCO₂UHMWPE/FAC fiber reached an extraordinarily high value of 158 g/d,which is～4.6,～1.6 and～1.4 times of thoseσ_ts found for the optimal single-stage drawn UHMWPE,UHMWPE/FAC and scCO2UHMWPE/FAC fibers,respectively.Considerably smaller lamellar thicknesses and dynamic transition temperatures were detected for scCO₂UHMWPE and scCO₂UHMWPE/FAC as-prepared fibers compared with the equivalent UHMWPE and UHMWPE/FAC as-prepared fibers,respectively.Specific surface area,morphological and Fourier transform infrared analyses of the FAC particles and orientation factor analyses of the single-and multiple-stage drawn UHMWPE,UHMWPE/FAC,scCO2UHMWPE and scCO₂UHMWPE/FAC fibers were performed.The remarkable improved D_ras andσ_ts found for the proper multiple-stage drawn scCO₂UHMWPE/FAC fibers are proposed.