Reactive extrusion (REX) is an efficient means of continuously polymerizing monomers as well as chemically modifying existing polymers – it offers “just-in-time manufacturing”. This presentation discusses the use of twin screw extrusion processing to manufacture biobased and biodegradable-compostable polymeric resins for a portfolio of commercial applications. We have developed REX for the ring opening polymerization of epsilon caprolactone and p-dioxanone (1,4-dioxan-2-one) to manufacture biodegradable-compostable polymer resins. The polymerization of monomer to high molecular weight polymer has been achieved in 2-3 minutes using special catalysts and specific screw configurations. Starch, an anhydroglucose polymer, exhibits strong hydrogen bonding and crystallization leading to poor thermal processing since the Tm is higher than the thermal decomposition temperature. We have developed a twin-screw reactive extrusion process in which glycerol transesterifies the starch polymer to make it pseudo thermoplastic and flow. Biodegradable polyesters have been grafted onto this glycerylated thermoplastic starch to provide thermoplastic starch-polyester graft copolymers that can be readily used for blown films and molded product applications. We have designed and engineered a one step, reactive extrusion process using water as the pasticizer and blowing agent along with suitable polymer modifiers to generate cellular starch foams. Water and shear imparted in the extrusion process breaks down hydrogen bonds without significantly reducing molecular weight. Nucleating agents and process aids control the cell structure, and maintain flexibility of the foam material. Reactive extrusion processing has been developed to synthesize maleated and epoxy modified poly(lactic acid) PLA through transesterification and coupling chemistries. These functionalized PLA molecules can be reactively blended with PLA and other biodegradable polyester resins, such as poly(butylene adipate-co-terephthalate) (PBAT), to achieve properties not found in traditional PLA resins — strain hardening properties for blown-film applications, improved processability, heat and impact resistance.

Using reactive extrusion to manufacture greener products – from laboratory fundamentals to commercial scale

253rd National Meeting (2017)

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