Comparative evaluation of pyrophyllite-impregnated woven and non-woven natural plant fibers for sustainable thermal insulation applications

Pyrophyllite has emerged as a promising mineral additive in the development of sustainable insulation geocomposites, owing to its characteristic layered silicate structure, notable thermal stability, and chemical inertness. This study presents a comparative investigation of the thermal behavior and impregnation performance of woven and non-woven natural fiber systems treated with pyrophyllite-rich mineral formulations, with a view toward environmentally friendly thermal insulation applications. Woven jute, cotton, and linen fabrics, along with non-woven jute and sisal yarns, were impregnated with sodium silicate-based binder solutions at varying pyrophyllite concentrations. The raw material, sourced from the Pütürge district of Malatya (Türkiye), was characterized through X-ray diffraction (XRD), which identified pyrophyllite as the dominant mineral phase alongside quartz, muscovite, kaolinite, and illite. Morphological examination revealed platy and fibrous particle morphology, and geochemical analysis confirmed a high silica-alumina composition. Thermal performance was evaluated by thermogravimetric analysis (TGA), while impregnation efficiency was quantified through mass uptake measurements.

Pyrophyllite treatment consistently improved the thermal stability of all fiber systems relative to untreated controls. Woven fabrics demonstrated more uniform impregnation and reproducible thermal degradation profiles, a behavior attributed to their regular weave and balanced fiber structure. Among woven substrates, jute fabrics achieved the highest post-treatment residual mass and thermal performance, reflecting strong mineral retention and enhanced char formation, while cotton fabrics recorded the greatest overall mass uptake. Non-woven yarn systems, by contrast, exhibited substantially higher impregnation capacities, as their open and irregular structures facilitated deeper mineral penetration. Higher pyrophyllite loadings improved residual mass values across both fabric types, though excessive concentrations occasionally led to localized mineral agglomeration. Notably, distinct impregnation thresholds were identified in the non-woven systems: jute yarns maintained relatively stable thermal improvement up to approximately 30% mineral loading, whereas sisal yarns showed a threshold near 35%, beyond which further addition yielded diminishing thermal benefits and increased decomposition variability.

To conclude, woven samples offer reproducible and thermally consistent geocomposite performance, while non-woven configurations provide superior mineral uptake capacity. It is also worth noting that non-woven systems displayed distinct impregnation thresholds, beyond which additional pyrophyllite incorporation provided limited thermal benefit and introduced greater variability in degradation behavior. These observations collectively suggest that both fabric architecture and mineral loading must be carefully optimized to achieve the desired balance between impregnation efficiency and thermal homogeneity. Pyrophyllite-impregnated natural fibers therefore represent viable and sustainable candidates for thermal insulation and flame-retardant composite applications within the broader context of green building materials.