Partially carboxymethylated feather keratins. 2. Thermal and mechanical properties of films.
Free cysteine thiol groups of keratin extracted from chicken feathers were partially carboxymethylated with iodoacetic acid (25-76% cysteine modification). Stable dispersions were used for the preparation of films by solution casting. Glycerol was used as a plasticizer (0.05-0.47 g/g of keratin), and films were stored at a constant relative humidity (20, 30, 50, 70, or 90%). The degree of crystallinity in the films was higher when more cysteine residues were carboxymethylated. The films displayed an optimum in mechanical properties at approximately 50% cysteine carboxymethylation. The tensile strength at this optimum was 25 MPa, the E modulus, 350 MPa, and the elongation at break, 50%. Probably, this optimum was the result of both a decreasing amount of disulfide bonds and an increasing degree of crystallinity for higher degrees of cysteine modification. The influences of a higher amount of glycerol and of different storage conditions on the mechanical properties of films from keratin with a defined degree of cysteine modification were also investigated.
Schrooyen
P M
PM
Department of Chemical Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Dijkstra
P J
PJ
Oberthür
R C
RC
Bantjes
A
A
Feijen
J
J
D000818:Animals; D001696:Biomechanical Phenomena; D002152:Calorimetry, Differential Scanning; D002645:Chickens; D003545:Cysteine / Q000737:chemistry; D005241:Feathers / Q000737:chemistry*; D005990:Glycerol / Q000008:administration & dosage; D019807:Iodoacetic Acid / Q000737:chemistry; D007633:Keratins / Q000737:chemistry*; D015394:Molecular Structure; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D014867:Water
D014867:Water; D007633:Keratins; D003545:Cysteine; D005990:Glycerol; D019807:Iodoacetic Acid