The role of twist in dry spun carbon nanotube yarns

Twist densification as a method of carbon nanotube (CNT) yarn manufacture has been widely studied. The load transfer between individual nanotubes in the twisted yarns is a result of the combined action of van der Waals attraction and the friction between the nanotubes, both of which increase in magnitude with the level of twist applied to the yarn during manufacturing. To isolate these effects, the twist in the initially twisted yarn was removed by untwisting to produce a twistless yarn. With the disappearance of compressional forces between CNTs originated from the presence of twist, load transfer between individual CNTs in the twistless yarn relies on the van der Waals contact established in the initial twisting stage. Despite the considerable decrease of nanotube packing density in yarn after the removal of twist, 80% of the specific strength and nearly 100% of the specific modulus and specific electrical conductivity of the CNT yarn were maintained.