Milkweed Fibers

Milkweed fibers are fibers grow in the seed part of Asclepia syriaca plants. They are also known as vegetable silk due to their shiny appearance. The Asclepia syriaca plant, which grows widely in the Northern Hemisphere, does not require irrigation, unlike cotton. According to the studies, the length of milkweed fibers varies depending on the geographical area where they grow, but it is generally between 20−30 μm. The most important physical feature of milkweed that makes it interesting is its huge hollow lumen. The hollow lumen constitutes 90% of the fiber diameters. Milkweed fibers consist of cellulose, hemicellulose, and lignin.

Figure 1. Asclepia syriaca is pollinated by butterflies during its bloom season.

One of the important features of Milkweed fibers is hydrophobicity. The surface of milkweed fibers is covered with a natural wax, in other words Milkweed fibers have a hydrophobic−oleophobic surface. The waxy layer gives them better water-repellent properties. In studies conducted to measure the hydrophobicity of fibers, it was emphasized that the contact angle between water and Milkweed fiber was 140°. In addition to having a hydrophobic feature, the fibers were used as filling material in life jackets during the Second World War because of their low density.

Figure 2. Seed formation of Asclepia syriaca

Another important feature of Milkweed fiber is flexural strength. The lightness of composite materials is one of the crucial criteria. Thus, low-density hollow cellulosic fibers are frequently used in composite applications. A study was conducted to compare the performances of Milkweed and kenaf fibers in composite applications. As a result of the study, it is reported that PP composites reinforced with milkweed fibers have almost three times higher flexural strength than composites reinforced with kenaf fibers.

Figure 3. Milkweed fibers.

To investigate the possibilities of these natural fibers, a nonwoven made from milkweed was produced as a sanitary napkin end product. The sanitary napkin show that Milkweed fibers not only hold more moisture but also have a vertical wicking feature, which improves user comfort. As electronic textiles have gained importance in recent years, milkweed fibers have started to be used in supercapacitor and scaffold applications. Electrochemical characterizations performed on biobased electrodes reveal that milkweed fibers have very high cycling stability and specific capacitance.

“This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 101023459”