In this study, an alternative composting method of biodegradable polylactic acid was proposed, capable of reducing the molecular weight by over 80% in 90 minutes.
Human Factors of XR: Using Human Factors to Design XR Systems
Effect of UV on PLA Degradation
1. Effect of UV Treatment on the
Degradation of Biodegradable
Polylactic Acid (PLA)!
Catherine Zhang!
Grade 11, Shrewsbury High School!
Presented at National AJAS Conference,
Boston, Feb. 2013!
Catherine Zhang!
3. Motivations!
• Reducing the Growing Landfill Problem!
• Why polylactic acid (PLA)?!
Bio-Based and
Biodegradable!
Versatile and
Strong!
Used in Variety of
Applications!
• Why photodegradation?!
Hydrolysis is well-studied, both energy and time-consuming!
Photodegradation can break bonds of polymers!
UVC Light: Highest Energy Photon!
Catherine Zhang!
4. Introduction of PLA Synthesis and Challenges!
• Synthesis (2-step process):!
• Formation of lactic acid by
fermentation!
• Formation of the PLA by
either direct condensation
or ring-opening
polymerization!
• Challenges:!
• 20% more expensive!
• Low Tg and high WVTR!
• Can only be degraded in an
industrial composting
facility (hydrolysis)!
Natural Biodegradability!
Performance!
Catherine Zhang!
5. Objectives!
Effectiveness of the UVC
treatment!
Effectiveness of mechanical
chopping!
Proposing an economic
alternative composting process!
Catherine Zhang!
6. Hypotheses!
• UVC Treated vs. Untreated!
Longer
Treatment Time!
Accelerated
Degradation!
UVC Light oxidizes and breaks bonds between monomers!
• Chopped vs. Unchopped!
Mechanical
Chopping!
Accelerated
Degradation!
Chopping may help breaking polymer chains!
Catherine Zhang!
8. Results – Visual Observations!
0 Minutes!
30 Minutes!
a)!
b)!
60 Minutes!
90 Minutes!
c)!
d)!
Increasing levels of discoloration and brittleness
over UV treatment time was observed!
Catherine Zhang!
9. Results – Mass Loss!
Unchopped: Mass loss increased
as UV treatment time increased!
Chopped: Mass loss increased
as UV treatment time increased!
Unchopped lost ~ twice amount of mass as the chopped!
Catherine Zhang!
10. Results – Molecular Weight (GPC)!
Unchopped PLA Film:
Chopped PLA Pieces:
Increased treatment time results
in decreased molecular weight
except 90 minute !
Increased treatment time results
in decreased molecular weight!
Catherine Zhang!
12. PLA Degradation!
• PLA degradation:!
• Photo degradation: photooxidation leading to formation of
hydroperoxide derivatives, then degraded to compounds
containing carboxylic acid and unstable diketones!
Catherine Zhang!
13. Results – Mass Loss!
15 Minute Water Soaking of the 60 minute UV treated sample
can further increase mass loss from 2.5% to 31.6%!
Catherine Zhang!
14. 4-Step Alternative Composting Process!
Proposed Industrial Scale of Composting Process!
PLA Waste!
Composting!
Mechanical
Chopping!
UV Treatment
Conveyor Belt
Oven!
Water Soaking
Bath !
Catherine Zhang!
15. Conclusions and Future Work!
• Conclusions:!
• UVC Light can rapidly degrade PLA, but not mechanical chopping!
Level of discoloration and brittleness increased as treatment time
increased!
In order Mass loss decreased linearly as treatment effects, two things
to see any positive environmental time increased!
must occur:!
Unchopped film lost twice as much mass as chopped!
1. Consumers must be educated aboutobserved correctly < 24k)!
Clear molecular weight reduction was how to (113.5k vs.
dispose of their biodegradable plastics.! investigated further!
Inconsistency of the GPC results need to be
2. • Scientistsdegradation process: Photooxidation! effective and
Possible need to continuously innovate more
economic composting processes.!
• A 4-Step alternative composting process was proposed!
• Future Work:!
• Process development of 4-Step composting process!
• Detailed process comparison analysis (hydrolysis vs. 4-Step)!
Catherine Zhang!
16. Acknowledgements!
I would like to thank Professors Julie Goddard and
Shaw Hsu from UMass, as well as Fang Tian, for their
guidance. I would especially like to thank Mr. Sahas
Rathi for conducting the GPC testing, and Professor
Goddard for allowing me to use her lab. I would like to
thank Professor Sakai from Kyoto Institute of
Technology for his advice. I would also like to thank Mr.
Allen King from NatureWorks® for donating PLA
samples. Thanks also go to Ms. Constantine and Mr.
Collins from Shrewsbury High School.!
Catherine Zhang!
18. References!
Beaucage, G. (2005). Determination of molecular weight. Retrieved from http://www.eng.uc.edu/~gbeaucag/
Classes/!
!Characterization/MolecularWeighthtml/MolecularWeight.html!
Brenndorfer, B. (n.d.). Photodegradation of plastics. Retrieved from http://www.fao.org/docrep/X5018EX501.!
Copernicus Institute for Sustainable Development and Innovation. (2009). Product Overview and Market
Projection of Emerging Bio-Based Plastics. Utrecht, The Netherlands: Shen, L., Haufe, J. & Patel, M.K.!
Dell, K. (2010, May 3). The promise and pitfalls of bioplastic. Retrieved from http://www.time.com/time/
magazine/article/0,9171,1983894,00.html!
Groot, W., Krieken, J.V., Sliekersl, O., & Vos, S. (2010). Production and purification of lactic acid and lactide.
In R. Auras, L. Lim, S. E. M. Selke, & H. Tsuji (Eds.), Poly (lactic acid): synthesis, structures,
properties, processing, and applications (pp. 3-26). Hoboken, NJ: John Wiley & Sons Inc.!
Pandey, J. K., Reddy, K. R., Kumar, A. P. & Singh, R. P. (2005). An overview on the degradability of polymer
nanocomposites. Polymer Degradation and Stability, 88, 234-255.!
Sakai, W., & Tsutsumi, N. (2010). Photodegradation and radiation degradation. In R. Auras, L. Lim, S. E. M.
Selke, & H. Tsuji (Eds.), Poly (lactic acid): synthesis, structures, properties, processing, and
applications (pp. 413-421). Hoboken, NJ: John Wiley & Sons Inc.!
Selke, S. E. M. (1990). Packaging and the environment. Lancaster, PA: Technomic Publishing Company Inc.!
Wiles, D. M., & Scott, G. (2005). Polyolefins with controlled environmental degradability. Polymer
Degradation and Stability, 91, 1581-1592.!
Wool, R. P., & Sun, X. S. (2005). Bio-based polymers and composites. Amsterdam: Elsevier Academic Press.!
Catherine Zhang!