Heat-Induced Actuator Fibers: Starch-Containing Biopolyamide Composites for Functional Textiles

Abstract

This study introduces the development of a thermally responsive shape-morphing fabric using low-melting-point polyamide shape memory actuators. To facilitate the blending of biomaterials, we report the synthesis and characterization of a biopolyamide with a relatively low melting point. Additionally, we present a straightforward and solvent-free method for the compatibilization of starch particles with the synthesized biopolyamide, aiming to enhance the sustainability of polyamide and customize the actuation temperature. Subsequently, homogeneous dispersion of up to 70 wt % compatibilized starch particles into the matrix is achieved. The resulting composites exhibit excellent mechanical properties comparable to those reported for soft and tough materials, making them well suited for textile integration. Furthermore, cyclic thermomechanical tests were conducted to evaluate the shape memory and shape recovery of both plain polyamide and composites. The results confirmed their remarkable shape recovery properties. To demonstrate the potential application of biocomposites in textiles, a heat-responsive fabric was created using thermoresponsive shape memory polymer actuators composed of a biocomposite containing 50 wt % compatibilized starch. This fabric demonstrates the ability to repeatedly undergo significant heat-induced deformations by opening and closing pores, thereby exposing hidden functionalities through heat stimulation. This innovative approach provides a convenient pathway for designing heat-responsive textiles, adding value to state-of-the-art smart textiles.

Keywords: compatibilization; copolyamide; heat-responsive smart textile; shape memory actuator; starch.

Figure 1

Schematic representation of (a) copolymerization and (b) surface modification of starch with OSA molecules.

Figure 2

(a) Schematic representation of the developed fabric. The top image shows the cross-sectional diagram, and the bottom image presents the layer diagram constructed from the cross-sectional diagram to denote the placement and interlacement of each layer. In all layers, the warp is 100% cotton. In layer 1, the weft is 100% cotton, and the developed actuators, while in the rest of the layers, the weft is Linen-Tencell. (b) Digital image from the top view of the fabric woven with PSMS50 actuators and cotton in the first layer. (c) Digital image of the fabricated smart textile. (d) Image of fabric photographed in a dark chamber showing the effects of glow-in-the-dark yarn stripes interlacing.

Figure 3

(a) FTIR spectra, (b) ¹H NMR spectra, and (c) DSC thermograms of the synthesized homopolymers and copolymer. (d) FTIR spectra and (e, f) SEM images of starch before and after treatment with OSA.

Figure 4

SEM images from cryofracture surface area of (a) neat copolyamide, (b) PSMS10, (c) PSMS30, (d) PSMS50, (e) PSMS70, and (f) PNS50 with 500× magnification.

Figure 5

(a) Typical stress–strain curves, (b) comparison of different mechanical properties of the synthesized copolyamide and biocomposites, (c) photograph of bent PSMS70 biocomposite, (d) storage (E′) and loss (E″) moduli, and (e) loss factor (tan δ) of the synthesized copolyamide and biocomposites versus temperature. The solid and blank symbols represent the storage modulus and loss modulus, respectively.

Figure 6

(a) Storage (G′) and lost (G″) moduli and (b) complex viscosity (|η*|) of the synthesized copolyamide and biocomposites versus angular frequency at a fixed strain rate of 1% and temperature of 160 °C. The solid and blanked symbols represent storage modulus and loss modulus, respectively. (c) Digital photograph of the tensile testing specimens extruded at 160 °C (copolyamide and PSMS50) and 220 °C (PNS50).

Figure 7

Strain/temperature versus time corresponds to the 4 shape memory cycles for (a) copolyamide, (b) PSMS10, and (c) PSMS50. (d) Shape recovery (R_r) and shape fixity (R_f) percentage for the plain copolyamide matrix and PSMS10 and PSMS50 biocomposites.

Figure 8

Actuation of heat-responsive fabric using PSMS50 yarn actuators exposed to an IR lamp. (a) IR and (b) digital images of PSMS50 yarn actuators. (c) IR and (d) digital images of heat-responsive fabric. The fabric undergoes five cycles of heating and cooling. The entire expansion and contraction process is provided in Video S1, Video S2, Video S3, and Video S4.