Circular Melt-Spun Textile Fibers from Polyethylene-like Long-Chain Polyesters

Abstract

As textiles contribute considerably to overall anthropogenic pollution and resource consumption, increasing their circularity is essential. We report the melt-spinning of long-chain polyesters, materials recently shown to be fully chemically recyclable under mild conditions, as well as biodegradable. High-quality uniform fibers are enabled by the polymers' favorable combination of thermal stability, crystallization ability, melt strength, and homogeneity. The polyethylene-like crystalline structure endows these fibers with mechanical strength, which is further enhanced by its orientation upon drawing (tensile strength of up to 270 MPa). In vitro depolymerization by high concentrations of Humicola insolens cutinase underlines the accessibility of the fibers for enzymatic degradation, which can proceed from the surface and through the entire fiber within days, depending on the choice of the fiber material. Fibers and knitted fabrics withstand stress, as encountered in machine washing.

Figure 1

Structures of polymers studied and peak melting points.

Figure 2

(a) Schematic representation of the melt-spinning and fiber drawing process. (b) Schematic representation of crystalline and amorphous regions in the filament of as-spun and stretched fibers. (c) Arrangement of PE-2,18 chains in crystallites and the amorphous region. (d) Spooled PE-2,18 fibers on the bobbin (top) and SEM image of a fiber (bottom). (e) Stress–strain curves of PE-2,18 fibers stretched with a draw ratio of 1:3.

Figure 3

SEM images of PE-2,18 fibers after exposure to high concentrations of Humicola insolens cutinase (HiC). Increasingly severe surface erosion is evident after 8 h (top left), 1 day (top center), and 4 days (top right). Reference of PE-2,18 fiber subjected to the protocol but without the addition of HiC after 4 days (bottom left) and PE-18,18 fiber exposed to HiC after 8 days (bottom center). SEM image of the reference HDPE fiber after exposure to HiC for 8 days (bottom right).

Figure 4

(a) Knitted fabric from the PE-2,18 multifilament. (b,c) SEM images of the PE-2,18 fabric in different magnifications. (d) Blended yarn from the mixture of 79 wt % cotton fiber and 21 wt % PE-2,18 multifilament. (e,f) SEM images of the blended yarn in different magnifications.

Figure 5

(a) Laundry program applied to PE-2,18 fibers and fabric for 10 cycles. (b) Stress–strain curves of washed and untreated PE-2,18 fibers. (c) SEM image of the PE-2,18 fabric after 10 cycles of washing.