Abstract:

Objective Thin and lightweight warmth keeping materials are one of the hot spots in the research of cold-proof clothing. Downs play an important role in conventional warmth keeping materials, but the coat bloating runs against people's pursuit of beauty and comfort. Silica (SiO₂) aerogel has a thermal conductivity lower than 0.02 W/(m·K) at room temperature, which has a broad application prospect in the field of warmth. However, when aerogel powder is used as a filler for warmth keeping, uneven dispersion due to agglomeration appears to be problematic, in addition to the short durability of aerogel powder composites due to powder falling.

Method This study creates a stable electrostatic field using the inherent charge differences between polyester fibers and down. By integrating aerogel's ultralight properties with down's 3-D network structure, electrostatic forces precisely position aerogel particles, forming a uniformly structured thermal composite with enhanced warmth keeping synergy. The dispersion and adsorption state of silica aerogel powder inside the material, as well as the influence of down and aerogel powder filling amount on the warmth keeping properties of the samples and their optimization were specifically studied.

Results Observed using an optical microscope, it revealed that SiO₂ aerogel powders and their aggregates were adsorbed on the surface of down filaments and uniformly distributed with the help of down filaments, which was consistent with the constructed model based on the electrostatic adsorption principle. The adsorption and uniform dispersion of the aerogel powder were successfully achieved, solving the problem of SiO₂ aerogel powder on agglomeration when used as a filler. In the ultra-light samples, the Crowe values per unit thickness of the down/aerogel powder composite samples with the same mass were higher than those of the single down-filled samples, in which the Crowe values per unit thickness of the composite samples in the third group of samples were 105.23% higher than those of the single down, indicating that a synergistic warmth keeping effect of mixing the down with the SiO₂ aerogel powder was achieved using the electrostatic field. In the cold-tolerant samples with the increase of SiO₂ aerogel powder filling amount, the Crowe value per unit thickness of the down/aerogel powder composite samples showed a trend of increasing and then slowly decreasing. This is because the adsorption of down filaments on aerogel powder has a saturation value, and the Crowe value per unit thickness of the samples would reach the maximum value when powder saturation was reached. Cyclic washing resistance test showed that after washing for 5 cycles, the mass loss of the sample with the maximum filling volume in the light and thin sample and the extreme cold sample was 0.06 g and 0.08 g, respectively. Owing to the selection of high-density calendared anti-feather coating cloth for the sample, the overall tightness of the sample was good, and the internal hydrophobicity of the sample was maintained during the washing process, which further reduced the leakage of SiO₂ aerogel powder. The addition of hydrophobic SiO₂ aerogel powder makes the samples maintain good warmth keeping performance after repeated washing, and the samples demonstrated excellent washing resistance.

Conclusion The results showed that the adsorption of SiO₂ aerogel powder was successfully achieved by using the electrostatic force generated by the friction between the down and the fabric, and the three-dimensional structure of the down was utilized to achieve the purpose of uniformly dispersing the aerogel powder. Compared with the single down-filled sample, the Crowe value per unit thickness of the sample increased by 105.23% with the addition of SiO₂ aerogel powder, indicating that a synergistic effect exists in the interaction between down and aerogel powder. The sample filled with 10 g of SiO₂ aerogel powder only lost 0.01 g of mass and 0.02 clo of Crowe value after washing for 5 cycles, and the warmth keeping effect was still well maintained after washing. In summary, the proposed down/aerogel powder warmth keeping composite material overcomes the problem of easy agglomeration of aerogel powder as a filler and reduces the thickness of the warmth keeping material on the basis of guaranteeing the warmth keeping effect, which provides a new way of thinking for the design and development of thin and light thermal material.

Key words: down, silica aerogel powder, warmth keeping material, crowe value per unit thickness, electrostatic field, filling density