Improving the Water Resistance and Mechanical Properties of Feather Keratin/Polyvinyl Alcohol/Tris(Hydroxymethyl)Aminomethane Blend Films by Cross-Linking with Transglutaminase, CaCl2, and Genipin

Abstract

The high moisture sensitivity of feather keratin/polyvinyl alcohol/tris(hydroxymethyl)aminomethane (FK/PVA/Tris) blend films hinders their application in the packaging field. Thus, in order to improve the water resistance and mechanical properties of such blend films, we attempted cross-linking the blend film with cross-linking agents such as transglutaminase (TG), CaCl2, and genipin. Obvious differences in the morphology of the blended films were observed by scanning electron microscopy before and after cross-linking, indicating that cross-linking can inhibit the phase separation of the blend film. Conformational changes in the blend films after cross-linking were detected by Fourier transform infrared spectroscopy. Importantly, from examination of the total soluble mass, contact angle measurements, and water vapor permeability tests, it was apparent that cross-linking greatly improved the water resistance of the blend films, in addition to enhancing the mechanical properties (i.e., tensile strength and elongation at break). However, cross-linking was also found to reduce the oxygen barrier properties of the blend films. Therefore, cross-linking appears to be an effective method for promoting the application of FK/PVA/Tris blend films in the packaging field.

Improving the Performance of Feather Keratin/Polyvinyl Alcohol/Tris(hydroxymethyl)Aminomethane Nanocomposite Films by Incorporating Graphene Oxide or Graphene

“…To better understand the dispersion uniformity of the GO and graphene nanosheets in the blend films and the effects of their addition on the microstructure of the blend films, the surface and cross section of the 1%-GO, 3%-GO, 1%-Graphene, and 3%-Graphene nanocomposite films were analyzed by SEM. It can be seen in Figure 2c,e that the surface of the GO-modified FK/PVA/Tris blend films was smoother than that of the P-40-25 film (an SEM image of P-40-25 can be seen in our previous report [10]). Additionally, there were no visible granular protrusions, indicating that the GO was well dispersed throughout the film matrix (i.e., no aggregation), and that the filler was strongly adhered to the matrix.…”

“…Figure 5 shows the TSM values for the P-40-25 film incorporated with different amounts of GO and graphene nanosheets. The results show that the addition of these two types of nanosheets can effectively reduce the TSM of the FK/PVA/Tris blend film, and that the TSM values for the blend film decreased with increasing nanoparticles content, i.e., the percentage decreased from 80.5% (P-40-25) [10] to 75.45% (2%-GO) and 74.78% (2%-Graphene), respectively. These results indicate that nano-modification can reduce the water sensitivity of the blend film and improve the stability of the FK/PVA/Tris blend film.…”

“…These peak position shifts indicate that GO interacts with the film matrix through intermolecular hydrogen bonding; thus, it should have good miscibility with the film matrix [27,29]. When 3%-Graphene was added to the blend film, the 3273.68-, 2929.28-, 1237.65-, and 1039.83-cm −1 FTIR peaks for the P-40-25 control film [10], which respectively correspond to O-H and N-H association, -CH stretching vibration, amide III bands, and C-O stretching vibration, shifted to 3279.38, 2922.62, 1235.2, and 1033.98 cm −1 , respectively (Figure 3e,f). These peak shifts indicate that the addition of graphene hinders the hydrogen bonding of the molecular chain of the film matrix at close vicinity of the graphene surface [30,31], and that there is strong interaction between the graphene and film matrix molecules that is mediated by van der Waals forces.…”

“…It can be seen that the infrared spectrum of each nano-modified blend film significantly differs from that of the P-40-25 film, and that the peak positions are shifted. When 3%-GO was added to the blend film, the 3273.68and 1039.83-cm −1 FTIR peaks for the P-40-25 control film, which respectively correspond to O-H and N-H association, and C-O stretching vibration [10], shifted to 3283.82 and 1036.86 cm −1 , respectively (Figure 3b,c). These peak position shifts indicate that GO interacts with the film matrix through intermolecular hydrogen bonding; thus, it should have good miscibility with the film matrix [27,29].…”

“…However, pure keratin film without a plasticizer is very fragile. In our previous research, we found that blending feather keratin (FK), polyvinyl alcohol (PVA), and tris(hydroxymethyl)aminomethane (Tris) [9] prior to cross-linking modification of an FK-based film with CaCl 2 , transglutaminase, and genipin [10] can improve the mechanical properties, hydrophobicity, and thermal properties of keratin. However, the barrier properties of keratin-based blend films, particularly oxygen barrier properties, are not ideal.…”