Influence Of Inorganic Additives On Properties Of Poly Vinyl Alcohol/Xylan Composite Films

Xylan,as one of the main hemicelluloses,is a kind of abundant,degradable and renewable resource.As the polar polymer,xylan endows films with good intrinsic barrier properties against apolar migrants?oxygen or aromas?.The application of xylan in the packaging field is one of the main research topics in the high value-added utilization of hemicleluloses.However,xylan performs the poor film-forming ability due to its unique molecular structure and physicochemical properties.Films prepared from xylan showed poor mechanical properties and moisture barrier property.In order to broaden the application of xylan films in food packaging industry,xylan was employed to prepare composite films with poly vinyl alcohol?PVA?which has good film-forming ability in this paper.The influences of several non-toxic inorganic additives on the properties of PVA/xylan composite films were investigated.1.A series of PVA/xylan composite films were prepared by cast method using beech xylan and PVA as degradable raw materials using ammonium zirconium carbonate?AZC?as the inorganic additive.The influences of the AZC amount on PVA/xylan composite films were discussed.The research results showed that xylan could improve the degradability and moisture barrier property of composite films.AZC had the great compatibility with PVA and xylan,and it mainly played a role as a plasticizer in improving the mechanical properties of composite films.With increasing the AZC amount to 15%,the tensile strength and elongation at break of films increased rapidly to 22.10 MPa and 218.0%.Moreover,the addition of AZC could enhance the barrier properties and thermal ability.2.In order to improve the strength of PVA/xylan composite films,and to endow the composite films with ultraviolet?UV?shielding performance,nano-TiO₂ was added into the PVA/xylan matrix.The dispersion performance test of nanoparticles indicated that modified TiO₂-KH550 nanoparticle were dispersed well in the 0.04% sodium hexametaphosphate?SHMP?solution under the ultrasonic and stirring treatment.Investigations on the properties of films showed that nano-TiO₂ had the positive impact on improving the strength,moisture and oxygen barrier properties of the composite films.The maximum tensile strength?27.3 MPa?,the minimum water vapor permeability(2.75×10^-11 g·m^-1·s^-1·Pa^-1)and oxygen permeability(4.013 cm3·m-2·24h^-1·0.1MPa^-1)were obtained under the addition of 1.5% TiO₂-KH550.The strength of nano-TiO₂ loaded composite films was increased by 70% than that of the pure PVA/xylan composite film,and the water vapor and oxygen permeability were decreased by 31% and 41%,respectively.Moreover,the UV transmittance was almost zero under 400 nm in the TiO₂-KH550 amount range of 1.5².5%,indicating nano-Ti O₂ endowed the PVA/xylan composite films with the excellent UV shielding performance.3.A series of PVA/xylan composite films with different amounts of nano-ZnO and nano-SiO₂ were successfully prepared.Results showed that the addition of nano-ZnO and nano-SiO₂ could effectively improve the strength,moisture and oxygen barrier property and surface hydrophobic properties of the composite films.When adding 3% of nanoparticles,the tensile strength of the films increased to the maximum values of 20.4 and 22.5 MPa,respectively,while the water vapor permeability(3.14 and 3.03×10^-11 g·m^-1·s^-1·Pa^-1)and oxygen permeability(5.28 and 5.003 cm3·m-2·24h^-1·0.1MPa^-1)decreased to the minimum value.Besides,the contact angles of the films reached up to 101 o and 78 o when the amount of nano-ZnO and nano-SiO were 3% and 4%,respectively.It was found that the addition of nano-ZnO in composite films exhibited a UV shielding performance,while the nano-SiO₂ loaded composite films maintained a close light-transparency compared to pure PVA/xylan composite film.4.To enhance the moisture barrier property of nano-TiO₂ hybrid PVA/xylan composite films,crosslinking method using STMP as crosslinking agents and emulsion method with SA as emulsified lipids were employed to synthesize crosslinking films and emulsifying films.Results showed that the moisture barrier property for the two types of films were enhanced when adding 10% STMP or 6% SA,of which the the water vapor permeability values were 2.88×10^-11 g·m^-1·s^-1·Pa^-1 and 2.06×10^-11 g·m^-1·s^-1·Pa^-1,respectively.