title: Production of starch foams by twin-screw extrusion: effect of maleated poly(butylene adipate-co-terephthalate) as a compatibilizer.
abstract: Free-radical-initiated grafting of maleic anhydride (MA) onto poly(butylene adipate-co-terephthalate) (PBAT), a biodegradable aliphatic-aromatic copolyester, was performed by reactive extrusion. 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane was used as the free-radical initiator. The peroxide concentration was varied between 0.0 and 0.5 wt % at 3.0 wt % MA concentration; the MA concentration was varied between 1.0 and 5.0 wt % at 0.5 wt % peroxide concentration. The reaction temperature was maintained at 185 degrees C for all experiments. Under these conditions, between 0.194% and 0.691% MA was grafted onto the polyester backbone. Size-exclusion chromatography, melt flow index, intrinsic viscosity measurements, thermal gravimetric analysis, and differential scanning calorimetry were used to characterize the maleated copolyester. Increasing the initiator concentration at a constant MA concentration of 3% resulted in an increase in the grafting of MA while decreasing the molecular weight of the resulting polymer. Increasing the feed MA concentration also increased the grafting percentage. The maleation of the polyester proved to be very efficient in promoting strong interfacial adhesion with high amylose cornstarch in starch foams as prepared by melt blending. Thus, the use of maleated copolyester as a compatibilizer between starch and PBAT allowed the reduction of the density of resulting starch foams to approximately 21 kg/m3 and improved the resilience from 84% to as high as 95%. Also, the resulting starch foams exhibited improved hydrophobic properties in terms of lower weight gain and higher dimensional stability on moisture sorption.
authors.affiliation: Department of Chemical Engineering & Material Science, 2527 E.B., Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Yogaraj
authors.initials: Y
authors.lastname: Nabar
authors.forename: Jean Marie
authors.initials: JM
authors.lastname: Raquez
authors.forename: Philippe
authors.initials: P
authors.lastname: Dubois
authors.forename: Ramani
authors.initials: R
authors.lastname: Narayan
mesh_terms: D001673:Biodegradation, Environmental; D007220:Industrial Waste / Q000517:prevention & control; D008299:Maleic Anhydrides / Q000737:chemistry; D010968:Plasticizers / Q000737:chemistry*; D011091:Polyesters / Q000737:chemistry*; D019064:Product Packaging; D013213:Starch / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D008299:Maleic Anhydrides; D010968:Plasticizers; D011091:Polyesters; C488797:poly(butylene adipate-co-butylene terephthalate); D013213:Starch