Study And Control On Gas Barrier Properties Of Poly (butylene Adipate-co-Terephthalate) Films

A large number of synthetic plastic film products are discarded after disposable use.Thus,"white pollution" problems caused by their difficult degradation in natural environment and long-term accumulation seriously restrict the sustainable development of the society.Such problems can be well solved by using representative biodegradable poly(butylene adipate-co-terephthalate)(PBAT)as alternative materials.However,poor water vapor and oxygen barrier properties,as well as photodegradation property brought from the ester groups dramatically limit its generalized applications.Thus,in this work,targeting the challenges of poor gas barrier and ageing resistance of PBAT,we developed several strategies for fabricating two-dimensional(2D)nanosheets-polymer composite films and multi-layered films.A series of composite films with highly oriented 2D nanosheets are successfully fabricated by orthogonal combination of uni/biaxial orientation and/or scraping.Furthermore,the size,surface properties,orientation and distribution of 2D nanosheets in the composite system varied by different process strategies and their influences on gas barrier and ageing resistance are studied and optimized for high gas barrier film.The main conclusions are showing below:(1)Six species of 2D nanosheets are successfully prepared,including organo-modified montmorillonite(OMMT),graphene oxide(GO),partially reduced graphene oxide(PRGO),highly reduced graphene oxide(HRGO),totally reduced graphene oxide(TRGO)and polydopamine modified totally reduced graphene oxide(PDA-TRGO),among which,OMMT,GO,PRGO and PDA-TRGO demonstrate good compatibility with PBAT.(2)OMMT 2D nanosheets modified with MD2EtOH can be dispersed homogeneously in PBAT matrix,and the resulting composite films show good water vapor and oxygen barrier properties.Blown film containing 13 wt%OMMT shows water vapor permeation(WVP)and oxygen permeation(OP)values of 7.1 × 10-12 g·m·m-2·s-1·Pa-1 and 2.8 × 10-15 cm3·cm·cm-2·s-1·Pa-1,decreasing 56.2%and 75%,respectively,comparing with pure PBAT film.(3)Good dispersion of graphene in PB AT matrix is achieved by adjusting oxygen-containing groups on graphene surface.Gas barrier properties and ageing resistance of PBAT composite films are enhanced simultaneously even at low GO and PRGO content.Specifically,16.0%of OP value can be decreased with 0.35 vol%of GO and PRGO content,47.5%of WVP value can be decreased with 0.21 vol%of PRGO content.(4)High orientation of 2D nanosheets in composite films could be achieved by biaxial orientation with orientation factor of 0.97,showing better gas barrier properties than the values in literature.PBAT composite films containing 0.21 vol%PRGO and 13 wt%OMMT show WVP values of 1.7×10-11 and 3.2× 10-12 g·m·m-2·s-1·Pa-1,decreasing 64.6%and 79.5%comparing with pure PBAT,respectively.Biaxially oriented PBAT film containing 0.35 vol%PRGO shows OP value of 9.4 × 10-15 cm3·cm·cm-2·s-1·Pa-1,decreasing 87.5%comparing with pure PBAT.(5)The gas barrier and ageing resistance of composite films are further enhanced by scraping an oriented nanocoating on the surface.By scraping a nanocoating containing 50 wt%GO on a biaxially oriented film containing 0.21 vol%PRGO,WVP and OP values can be decreased to 1.0 × 10-11 g·m·m-2·Pa-1·s-1 and 6.2×10-16 cm3·cm·cm-2·Pa-1·s-1,which are 80%and 99.2%decrease comparing with pure PBAT,respectively.