Effects of polylactic acid and rPET minor components on phase evolution, tensile and thermal properties of polyethylene-based composite fibers

High mechanical performance and partially biodegradable PE-composite fibers modified with polylactic acid (PLA) and recycled polyethylene terephthalate (rPET) minor components were prepared using melt extrusion and hot drawing process. Rheological properties, morphology, tensile, and thermal properties were investigated. All blends exhibited shear thinning behavior except for starting PLA and rPET. PLA and rPET dispersed phases appeared as droplets in as-extruded strand, and PLA droplets were mostly larger than those of rPET. The fibrillation of both PLA and rPET domains was achieved after further hot drawing as the fiber. The morphology and tensile properties of the fibers mainly depended on the types and contents of dispersed phases including draw ratios. The ultimate strength of the polymer fibers at draw ratio of 20 was more than 600 times higher than that of the as-spun sample of the same composition. Remarkable improvement in secant modulus and ultimate strength was found for PE-30PLA, but the drawing process of this composition encountered some difficulties and rough surface of the fiber was observed. The stiffness and tensile stress for PE-10PLA-10rPET fiber were clearly improved when compared with PE and PE-10PLA. A decrease in thermal stability of PE/PLA composites was observed with increasing PLA content whereas additional presence of rPET significantly increased the stability of the composites both in nitrogen and in air. PE/PLA/rPET fiber possessing high stiffness with good thermal stability prepared in this work has high potential for being utilized as structural parts for load-bearing applications.