Preparation And Modification Of Feather Keratin/Polyvinyl Alcohol/Tris(hydroxymethyl)aminomethane Blend Film

Keratin,which is a major component of feathers,wool,etc.,is one of the most abundant and underutilized protein sources.Every year,more than 65 million tons of feathers are produced worldwide,most of which are processed by incineration or landfill.These treatments not only waste resources but also pollute the environment.Therefore,this paper considers making full use of keratin extracted from feathers as raw material to prepare feather keratin-based film and exploiting its use in packaging.Not only the environmental pollution caused by landfill or incineration can be reduced,but also the value of keratin can be increased.Feather keratin?FK?,which was extracted by partial oxidation with peracetic acid,and polyvinyl alcohol?PVA?are used as raw materials,and tris?hydroxymethyl?aminomethane?Tris?is used as a plasticizer.The FK/PVA/Tris blend films were prepared by solution casting.The effects of PVA and Tris content on the microstructure,thermal,mechanical,moisture sensitivity and barrier properties of the blend films were investigated.The results show that there are hydrogen bond interactions between the three materials;the blend films are partially crystallized and phase separated;at a constant Tris content,the elongation at break hydrophilic and oxygen barrier properties of the blend films were enhanced upon PVA content increasing.However,at a constant PVA content,elongation at break,oxygen barrier and hydrophilicity properties were enhanced upon Tris content increasing.At the same time,the addition of PVA and Tris resulted in a decrease in the thermodynamic stability of the feather keratin-based film.The weak hydrogen bonding interaction between the three components of the prepared FK/PVA/Tris blend films lead to phase separation,and the prepared FK/PVA/Tris blend films have poor water resistance and thermal properties.They are cross-linked by glutamyltransaminase?TG?,CaCl₂ and genipin,respectively.It was found that TG and the primary amino group of FK or Tris are covalently bonded to form a monosubstituted?-amide of glutamic acid,Ca²⁺of CaCl₂ is ionically bonded to the carboxyl group of FK,and genipin and the primary amino group of FK or Tris are covalently bonded.They are combined to form a crosslinked three-dimensional network structure,which can inhibit the phase separation of the blend film and improve the performance of the blend film.As the content of cross-linking agent increases,the total soluble mass and water vapor permeability of the cross-linked film decrease,and the contact angle increases,indicating that cross-linking greatly improves the water resistance of the blend film;in addition,the mechanical properties and thermal stability of the blend film are also enhanced by cross-linking modification.The cross-linking modified FK/PVA/Tris blend films have poor barrier properties,especially poor oxygen barrier properties.Nano-modification with montmorillonite sodium?MMT?or TiO₂ to improve FK/PVA/Tris blend film properties.The results show that the MMT is exfoliated,the TiO₂ nanoparticles are uniformly dispersed in the film matrix,and there is strong hydrogen bonding between the nanoparticles and the film matrix.It was observed that FK/PVA/Tris blend films containing MMT or TiO₂,led to an improvement in thermal,mechanical and barrier properties compared with the unfilled material.Specifically,P-40-25 containing 3 wt%MMT showed maximum improvement in properties,and its elongation at break and tensile strength increased by 133.06%and 9.29%,and its WVP and OP decreased by 21.68%and 78.6%.In addition,P-40-25 containing 5wt%TiO₂ showed maximum improvement in properties,and its elongation at break and tensile strength are increased by 434.6%and 36.95%,and its WVP and OP are reduced by 26.86%and 37.52%.It is worth noting that the addition of MMT and TiO₂ can improve the barrier properties of ultraviolet rays and the thermal stability of the blend film.The blend modification of feather keratin with PVA and Tris,and the cross-linking and nano-modification of the prepared FK/PVA/Tris blend film,enhenced mechanical,thermal,water resistance,and barrier properties of keratin-based blend films,which are expected to be used in food packaging fields and other fields.