In recent years, low-cost carbons derived from recycled materials have been gaining attention for their potentials as filler in composites and in other applications. The electrical and mechanical properties of polymer composites can be tuned using different percentages and different kind of fillers: either low-cost (e.g., carbon black), ecofriendly (e.g., biochar), or sophisticated (e.g., carbon nanotubes). In this work, the mechanical and electrical behavior of composites with biochar and multiwall carbon nanotubes dispersed in epoxy resin are compared. Superior mechanical properties (ultimate tensile strength, strain at break) were noticed at low heat-treated biochar (concentrations 2–4 wt %). Furthermore, dielectric properties in the microwave range comparable to low carbon nanotubes loadings can be achieved by employing larger but manageable amounts of biochar (20 wt %), rending the production of composites for structural and functional application cost-effective.

In this paper, we report the comparison of physical properties of 19.68 Tex (30 Nec)/1 Siro spun yarns and fabrics manufactured from 100% cotton, virgin polyester, and recycled polyester in 50:50 blend ratio with cotton fibers. Tensile analysis revealed that recycled polyester-cotton siro spun yarns exhibited comparable tensile strength to the virgin polyester-cotton yarns. The evenness and structural uniformity of the recycled polyester-cotton yarn was also equivalent to the polyester-cotton siro spun yarns. Plain weave (1/1) fabrics were manufactured from the obtained yarns. Recycled polyester-cotton blended fabrics depicted comparable tensile, tear, and ball bursting strength to the virgin polyester-cotton blended fabrics, and exhibited better wettability, air permeability, and were less prone to pilling when compared with the polyester-cotton blended fabrics. Recycled polyester-cotton fabrics also exhibited good drape properties and less shear stiffness in the Kawabata analysis when compared to their counterparts. Based on the results obtained, it may be safely concluded that the recycled polyester fibers can be used as an alternative to virgin polyester fibers in siro spun medium-count yarns and consequent fabrics.