Contact Information

Author
  • Michelle Douskey, Ph.D.
  • Lecturer in Chemistry
  • College of Chemistry
  • UC Berkeley
  • 307 Latimer Hall
  • Berkeley, CA 94720-1460
Email
Phone
(510) 643 - 9475
Website

Depolymerization of Poly(lactic acid) Cups to Lactic Acid

Laboratory Procedures (PDF)

Author Contact: douskey@berkeley.edu

Summary

In this lab a potentiometric titration of a sample of the polymer poly(lactic acid) (PLA) with a known NaOH standard was performed, using a pH meter to track changes in the pH of the acid solution as measured volumes of base was added. PLA was depolymerized into lactic acid in basic solution through a saponification reaction, an organic hydrolysis reaction that is used to make soap. The data was represented in the form of a titration curve and the amount of lactic acid in the final solution was quantitatively measured.

This lab demonstrates important principles of Green Chemistry as PLA is a renewable feedstock that can be derived from corn or potato starches and is biodegradable. Furthermore, the solvent ethanol can be reused, thus minimizing waste.

In addition to the experimental methods, a suggested prelab, a guide to calculating equivalence points from titration data, and a worksheet with data and discussion questions are included in this resource as well.

This design of this laboratory exercise was inspired by Hydrolysis of Post-Consumer Polylactic Acid Waste submitted to GEMs by Rich Gurney (Simmons College) in 2008.\"

Summary prepared March 2012 by Sheba Plamthottam at the UC Berkeley.

Source

Douskey, M. Depolymerization of Poly(lactic acid) Cups to Lactic Acid, College of Chemistry, UC Berkeley, 2012

Category Descriptors

Chemistry Concepts
  • Aldehydes/Ketones
  • Aqueous Solution Chemistry
  • Carbonyl Chemistry
  • Lewis Acids/Bases
  • Natural Products
  • Polymerization
  • Reactions of Alcohols
  • Solutions/Solvents
  • Stoichiometry
Laboratory Techniques
  • pH
  • Titration/Volumetric Analysis
Green Chemistry Principles
  • Analyze in Real-Time to Prevent Pollution
  • Avoid Chemical Derivatives
  • Design for Degradation
  • Design Less Hazardous Chemical Syntheses
  • Design Safer Chemicals and Products
  • Increase Energy Efficiency
  • Maximize Atom Economy
  • Minimize the Potential for Accidents
  • Prevent Waste
  • Use Renewable Feedstocks
  • Use Safer Solvents/Reaction Conditions
Chemistry Subdiscipline
  • Analytical Chemistry
  • Interdisciplinary/Multidisciplinary
  • Materials Science
  • Polymer Chemistry
Target Audience
  • Colleges/Universities
  • Secondary Schools
Source
  • Original Contributions - unpublished