Cellulose Acetate Thermoplastics with High Modulus, Dimensicnal Stability and Anti-migration Properties by Using CA-g-PLA as Macromolecular Plasticizer

Cellulose diacetate(CDA)can be melt processed to produce numerous and widely-used plastic products.However,due to the high glass transition temperature(Tg)of CDA,the addition of up to 30 wt%of micromolecular plasticizers is indispensable,which significantly reduces the dimensional stability and raises safety concerns from the migration of plasticizers.In this work,a series of CDA-graft poly(lactic acid)(CDA-g-PLA)copolymers were synthesized by ring-opening polymerization of lactide onto the hydroxyI groups of CDA.The resultant CDA-g-PLA copolymers possess adjustable degrees of substitution(DSpua)and side chain length(DPpLa)by controlling the reaction time and feed ratio.The Tgs and thermal flow temperatures(Ts)of CDA-g-PLA strongly depend on DPpA such as the Tgs decrease linearly with the increase of DPA.The CDA-g-PLA copolymers with the DPLA of 3-9 can be directly processed to transparent plastics by melt processing without any external plasticizers,because of their low Tfs of 170-215℃.More impressively.the CDA-g PLA can act as the macromolecular plasticizer.The obtained CDA/CDA-g-PLA has higher storage modulus,flexural modulus and Young's modulus than the commercial CDA plasticized with triethyl citrate.In addition,the CDA/CDA-g PLA exhibits high dimensional stabilty and anti-migration property.During a long term treatment at 80℃ and 60%humidity,the CDA/CDA-g-PLA can retain the initial shape.Therefore,this work not only proposes a facile method for achieving a direct thermoplastic processing of CDA,but also provides a macromolecular plasticizer for CDA to make lightweight,stable and safer biobased thermoplastics.

Multifunctional Films Based on Wheat Gluten and Microencapsulated Thyme Essential Oil

In this work,active and edible films for food packaging were obtained by intensive mixing and compression molding of the wheat gluten(WG)glycerol-plasticized paste.Thyme essential oil(TEO,10 and 15 wt.%)was incorporated as the active component microencapsulated inβ-cyclodextrins(β-CD)and included directly into the biopolymer matrix for comparison.It was found that films incorporating microencapsulated TEO are more soluble in water(total soluble matter(dry method)of about 33%and 36.6%vs.22.4%and 18.6%,for films containing 10%and 15%TEO,respectively)but less rigid than those obtained with free oil(elastic tensile moduli of 6.9 and 3.1 vs.9.9 and 6.8 MPa,for films containing 10%and 15%TEO,respectively),although the water vapor permeability of the former is lower(4.95 10^(−9) and 6.29 10^(−9) vs.8.85 10^(−9) and 11.1310−9 g/Pa^(*)s^(*)m,for films containing 10%and 15%TEO,respectively).Active films containing both free and encapsulated TEO inhibited gram(+)as well as gram(−)bacteria and exhibited enlarged antioxidant properties,with the latter presenting slightly better performance.In addition,encapsulation slowed the release rate of TEO from the films,allowing the bioactive to remain active in the film for much longer.Therefore,the present work revealed that films prepared from TEO/β-CD microcapsules included in compression-molded wheat gluten matrices showed great potential to be used as an active food packaging.