Enhanced Photothermal Based-Heat Retention in Regenerated Cellulose Fibers via Ceramic Particles and Polyelectrolyte Binders-Based Surface Functionalization

Abstract

There has been growing interest and increasing attention in the field of functional clothing textiles, particularly in product and process development, as well as innovations in heat-generating, retaining, and releasing fibers to maintain a healthy body temperature without relying on unsustainable energy sources. This study, for the first time, reports the various physio-mechanical properties of surface-functionalized regenerated cellulose fibers (RCFs) coated with ceramic particles. The coating imparts photothermal conversion-based heat generation and retention properties with the aid of polyelectrolyte binders. In this design, ZrC enables the conversion of light energy into thermal energy, providing heat for the human body. A feasible coating process was employed, utilizing industrially feasible exhaustion methods to deposit the ZrC particles onto the RCF surface in conjunction with two distinctive polymeric binders, specifically polyethyleneimine (PEI) and polydiallyldimethylammonium chloride (polyDADMAC). The morphological characteristics and tensile properties of the coated RCFs were analyzed via scanning electron microscopy (SEM) and single-fiber tensile testing. Heat retention and release behaviors of a bundle of fiber samples were assessed using infrared (IR) imaging and an IR emission lamp setup. The SEM results confirmed the successful coating of the ZrC particles on the surface of the RCF samples, influencing negligible on their physical-mechanical properties. The heat retention of the coated RCFs with ZrC and both binders was higher than that of reference regenerated cellulose fibers (RCFs), demonstrating their effective heat generation, retention, and heat release properties. Based on the highlighted prominent results for the coated RCFs, these findings highlight the suitability of the developed functional clothing textiles for targeted applications in non-extreme thermal conditions, ensuring thermo-physiological comfort by maintaining body temperature within a tolerable thermal range (36.5-37.5 °C), in contrast to studies reporting significantly higher temperatures (50-78 °C) for extreme thermal conditions.

Keywords: RCFs; ZrC; ceramic particles; heat generation and retention; regenerated cellulose fibers; surface functionalization; zirconium carbide.

Figure 1

Schematic representation of the RCF coating process using two distinctive polymeric binders and ZrC particle adsorption. (1) Preparation of the coating medium in a glass beaker with a magnetic stirrer at room temperature. (2) Immersion of RCF bundles into the prepared solution. (3) Coating using the Labomat device. (4) Squeezing and padding of wet RCF samples between rotating rollers at ambient temperature. (5) Drying of coated samples in a laboratory oven.

Figure 2

Schematic diagram (a) and the measuring apparatus (b) of the testing setup.

Figure 3

SEM micrographs of the reference RCF (CV) on the left and ZrC (Z) particles on the right, captured with a scale bar of 2 µm.

Figure 4

SEM micrographs of coated fibers prepared using aqueous PEI (a,a₁,a_1.1), polyDADMAC (b,b₁,b_1.1), and a CMC and CaCl₂ mixture-assisted polyDADMAC coating (bx,bx₁,bx_1.1), with and without ZrC particles. Images (a,b,bx) depict the fiber surfaces without ZrC particles, while (a₁,a₂,b₁,bx₁) correspond to coated RCF samples before rinsing. The images (a_1.1,a_2.1,b_1.1,bx_1.1) represent ZrC-coated fiber samples after the rinsing step.

Figure 5

High-resolution XPS spectra of reference RCFs (CV), PEI-coated RCFs (a₁), and PEI-coated RCFs with 30% w/v ZrC (a₂).

Figure 6

Infrared (IR) thermographic images (left and middle) and corresponding sample photos (right) of 1 g bundles of RCFs, including reference RCFs (CV), PEI-coated RCFs (a), and PEI-coated RCFs with 10 w/v % ZrC (a₁: unrinsed, a_1.1: rinsed) and 30 w/v % ZrC (a₂: unrinsed, a_2.1: rinsed). Images were taken at room temperature (RT, left) and after 20 min of heating (middle).

Figure 7

Dynamic curves of heat retention and release generated by IR radiation on RCF (CV, Viscose), PEI-coated RCFs (a), and PEI-coated RCFs with ZrC particles (a₁, a_1.1, a₂, and a_2.1), measured before and after IR irradiation using an IR lamp.

Figure 8

Infrared (IR) thermographic images (left,middle) and corresponding sample photos (right) of a 1 g bundle of RCFs (CV), polyDADMAC-coated RCFs (b), polyDADMAC-coated RCFs with 10 w/v % ZrC (b₁: unrinsed, b_1.1: rinsed), pre-coated RCFs with a CaCl₂ + CMC mixture (bx), and the pre-coated RCFs (bx) with additional poly-DADMAC-coated fibers and 30 w/v % ZrC particles (bx₁: unrinsed, bx_1.1: rinsed). Images were taken at room temperature (RT, left) and after 20 min of heating (middle).

Figure 9

Dynamic curves of IR heat retention and release of RCFs (CV, Viscose) and coated RCFs with polyDADMAC (b), polyDADMAC-coated RCFs with ZrC (b₁, b_1.1), and pre-coated RCFs with a CaCl₂ + CMC mixture followed by polyDADMAC coating (bx), with and without ZrC (bx₁, bx_1.1 and bx).