Preparation And Research Of Poly (Ethylene-co-vinyl Alcohol)/Montmorillonite Layer-by-layer Composite Film

Ethylene vinyl alcohol copolymer?EVOH?has been widely used as packaging materials due to its good barrier properties,however,the properties are worsen under high humidity.To overcome this weakness,an effective method is to construct multilayer structure composed of alternate EVOH and MMT layer.EVOH/MMT multi-layer composite films were prepared by layer-by-layer self-assembly?LBL?technique under a high voltage parallel electric field.Besides the characterization of EVOH/MMT multi-layer composite films,the mechanical properties,thermal stability and barrier properties were investigated emphasically.The interaction between MMT and EVOH was intermolecular hydrogen bonds.The MMT between the EVOH layers significantly improved the barrier properties of the films.As the number layer of the composite films increased from 10 to 60,the water vapor transmission rate(WVTR,g·m^-2·s^-1)decreased from 1.95×10^-3 to 0.13×10^-3;oxygen gas transmission rate(OTR,cm³·m^-2·d^-1·atm^-1)decreased from 3.06 to 0.15 under a relative humidity?RH?of 0%and from 32.28 to 4.81 at 99%RH,respectively.Using traditional LBL technique,9-layer EVOH/CS-MMT composite films with different MMT contents were prepared.The interactions among EVOH,MMT and CS were intermolecular hydrogen bonds.Besides the enhancement in tensile strength and Young's modulus,the barrier properties?moisture,oxygen and carbon dioxide?of the films were significantly improved.As the MMT contents increased from 0 to 12%,the water vapor permeability(WVP,g·m^-1·s^-1·Pa^-1)of the films decreased from 9.37×10^-11 to 4.87x10^-11;both oxygen permeability(OP,cm³·?·m^-2·d^-1·kPa^-1)and carbon dioxide permeability(CDP,cm³·?m·m^-2·d^-1·kPa^-1)exhibited a trend of decrease following by increase:OP from 2.91 to 0.25,and then to 0.31;CDP from 3.57 to 0.42,and then to 0.48.