Starch Graft Poly(methyl acrylate) Loose-Fill Foam:  Preparation, Properties and Degradation

Abstract

Starch graft poly(methyl acrylate) (S-g-PMA) was prepared by ceric ion initiation of methyl acrylate in an aqueous corn starch slurry (prime starch) which maximized the accessibility of the starch for graft polymerization. A new ceric ion reaction sequence was established as starch-initiator-methyl acrylate followed by addition of a small amount of ceric ion solution when the graft polymerization was almost complete to quench the reaction. As a result of this improved procedure, no unreacted methyl acrylate monomer remained, and thus, essentially no ungrafted poly(methyl acrylate) homopolymer was formed in the final grafted product. Quantities of the high purity S-g-PMA so prepared in pilot scale were converted to resin pellets and loose-fill foam by single screw and twin screw extrusion. The use of prime starch significantly improved the physical properties of the final loose-fill foam, in comparison to foam produced from regular dry corn starch. The S-g-PMA loose-fill foam had compressive strength and resiliency comparable to expanded polystyrene but higher bulk density. The S-g-PMA loose-fill foam also had better moisture and water resistance than other competitive starch-based materials. Studies indicated that the starch portion in S-g-PMA loose-fill foam biodegraded rapidly, whereas poly(methyl acrylate) remained relatively stable under natural environmental conditions.

Modification of starch by graft copolymerization

“…Ceric (IV) ammonium nitrate is currently used to initiate the grafting of polymers on starch due to some advantages such as the absence of free radical initiators in the reactive medium, which limits the formation of homopolymer, and the ease of application at room temperature in aqueous medium. The mechanism is based on the reduction of Ce complex from IV to III when reacting with hydroxy groups from starch, leading to the formation of radicals on the polymer backbone (Fig.…”

Recent progress in chemical modification of starch and its applications

“…[57][58][59] Fig. Starch graed with poly (methyl acrylate) was prepared by Chen et al, 60 using ceric ion as an initiator. Starch graed with poly (methyl acrylate) was prepared by Chen et al, 60 using ceric ion as an initiator.…”

Grafting

“…72 The grafted starch is intended for the use as loose-fill foam. At the end of the reaction, an additional small amount of ceric ion solution was added.…”