Study of castor oil‐based auxetic polyurethane foams for cushioning applications

Anticandidal action of polyurethane foam: a new modifier with functionalized isothiouronium group

A novel sorbent of isothiouronium polyurethane foam, PUF-SC(NH2)2, was synthesized from low-cost raw materials (a commercial polyurethane foam). The prepared PUF-SC(NH2)2 was characterized with different tools, the infrared spectra and Boehm test demonstrated the presence of several active groups in the material matrices of PUF-SC(NH2)2. The diffraction analysis and images of the scanning electron microscope showed that the surface structure was amorphous, and Cu(II) salt crystals were embedded on its surface. The polyurethane foam, as a modifier, was applied to enhance antimicrobial activity, and its anticandidal action was studied against Candida albicans ATCC 10,231. Agar well-diffusion test showed a significantly biocidal action of PUF-SC(NH2)2. The anticandidal action was dependent on PUF-SC(NH2)2 dose, while the microbial inhibition increased with increases in PUF-SC(NH2)2 dose and the microbial growth stopped at 26 μg/mL. The PUF-SC(NH2)2-treated yeast was studied by transmission electron microscope (TEM). TEM micrographs showed severe morphological changes in the yeast cells including the disruption of the cell membrane structure and the appearance of large vacuoles as well as separation between cell membranes and cell walls. The results indicated that this green synergy of PUF-SC(NH2)2 may have a promising potential in antifungal therapy as an effective biomaterial and other biomedical applications.

Graphical Abstract

Effects of Braid Angle and Material Modulus on the Negative Poisson’s Ratio of Braided Auxetic Yarns

Fibers and textiles are ubiquitous in our daily lives, with mechanical properties that match the design specifications for the task for which they are intended; the development of yarns with a negative Poisson’s ratio (NPR) is a hot topic of current research, owing to their potential for use in high-performance textiles (e.g., military, sports, etc.). This study described a simple approach to constructing braided, helically interlaced yarns. When a torque is applied, the yarns prevent the wrapped component from dislodging from the core. The geometry and auxetic behavior of the braided helical structure was analyzed for two different combinations of core materials with similar wrap materials and different braiding angles. Two elastomeric materials (polyurethane (PU) and polyester) served as monofilament cores, while two stiffer multifilament wrap yarns (ultrahigh molecular weight polyethylene (UHMWPE) and polyethylene terephthalate (PET)) served as wrap yarns. In addition, the behavior of yarns braided at seven different angles was investigated to determine the materials’ response to the applied braided configuration’s NPR. The NPR was influenced by the core and wrap materials used and the braiding angle. The NPR value was greater for a core comprising more excellent elasticity (e.g., PU versus polyester); a smaller wrap angle and a slower braiding speed also led to a higher NPR value. The maximum NPR value of −1.70 was obtained using a PU core wrapped at a 9° angle and a strain value of 0.5.