Biopolymers & Biocomposites Workshop - August 14, 2012

Depolymerization of Post-consumer Polylactic Acid with Ultrasonics

Gowrishankar Srinivasan and David Grewell
Iowa State University

Despite being biorenewable and biodegradable, Polylactic acid (PLA) as a commercial resin has to overcome concerns regarding contamination of conventional plastic recycling stream and controversial arguments such as ‘food competing with fuel/material’ to achieve complete market acceptance . These arguments drive the need to develop a recycling method that would both improve the long-term viability of PLA and make it more attractive in terms of energy savings. Conventional thermal recycling of PLA has been determined to be unfavorable for the resin as the process deteriorates the resin’s properties and makes the recycled resin unfit for food contact uses. Recent research efforts to address this issue have led to depolymerization of PLA as an approach to recover lactic acid for re-polymerization. Most of these depolymerization techniques employ hydrolysis via a combination of pressure (10MPa), heat (120-200°C), and catalysts/pH which are energy intensive to scale up. This research explores the utility of ultrasonics as a efficient tool to depolymerize PLA and achieve higher recovery rates in order to make recovery of lactic acid viable. This work details the failure of the above hypothesis.