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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Bioproducts Research » Research » Publications at this Location » Publication #346465

Research Project: Technologies for Improving Industrial Biorefineries that Produce Marketable Biobased Products

Location: Bioproducts Research

Title: Nucleation and plasticization with recycled low-molecular-weight poly-3-hydroxybutyrate toughens virgin poly-3-hydroxybutyrate

item Cal, Andrew
item GRUBBS, BRIAN - Mango Materials
item Torres, Lennard
item Riiff, Timothy
item Kibblewhite, Rena
item Orts, William
item Lee, Charles

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2018
Publication Date: 1/24/2019
Citation: Cal, A.J., Grubbs, B., Torres, L.F., Riiff, T.J., Orts, W.J., Lee, C.C. 2019. Nucleation and plasticization with recycled low-molecular-weight poly-3-hydroxybutyrate toughens virgin poly-3-hydroxybutyrate. Journal of Applied Polymer Science. 136(17):47432.

Interpretive Summary: Poly-3-hydroxybutyrate (PHB) is a naturally occurring biopolyester that can be used as a biodegradable plastic replacement. Recycling of the polymer is problematic due to its low thermal stability at melt temperature; polymer chain length drop below a critical threshold after only a few processing cycles. We show that low molecular polymer chains, which could be generated from recycled PHB, can be developed as a plasticizer for unprocessed PHB through reactive processing. We were able to incorporate up to 20% of recycled material while increasing the toughness and decreasing stiffness. This is the first demonstration that highly degraded PHB can be used to plasticize and toughen high molecular weight PHB polymer, and offers a route to valorization of PHB waste beyond disposal compost or anaerobic environments.

Technical Abstract: Poly-3-hydroxybutyrate (PHB) is a widely distributed carbon storage molecule in prokaryotes that can serve as a biodegradable plastic replacement. Recycling of PHB is limited by molecular weight loss during processing. To simulate recycling, we thermolysed PHB at elevated temperatures and reactively processed this degraded PHB (dPHB) as a filler in virgin PHB. Incorporation of dPHB plasticized virgin PHB, decreasing complex viscosity. Sample containing dPHB were toughened, had decreased stiffness, and had a reduced melt profile. Processing with dPHB decreased Mn, had little effect on Mw, and increased the Z-average molecular weight, indicating branching. dPHB was found to increase spherulite dimensions and crystalinity. Our results demonstrate a route for recycling of PHB as a plasticizer for virgin PHB.