Shape Memory Effect of Keratin Fibers

In the past thousands of years, keratin fibers were only considered as textile fibers for excellent fiber performances, such as high strength, acceptable elasticity, good thermal insulation, etc. Only recently, some indications have been obtained that keratin fiber may be a smart natural material that may subvert people’s perception of this matter. The smart attribute displays shape memory effects (SMEs) responsive to many types of stimuli including water, heat, coupled water-heat, redox agents, UV light, etc. These smart functions of keratin fibers are found to be the result of three structural components: crystals, hydrogen bonds (HBs), and disulfide bonds (DBs) among intra-and inter-keratin macromolecules. In this chapter, keratin fibers (such as camel hair) were employed for investigating their SMEs under five types of stimuli, in which the HBs, DBs, and crystals were characterized separately, as well as the fiber shape fixation and recovery ratios, respectively. The whole test results indicated that keratin hair fiber is a type of shape memory polymer and the related SME depends on the contents of the HBs, DBs, and crystalline phase inside the hair.