Objective: Commercial polymers should be designed for environmental sustainability. Desirable traits are biodegradability and production from cost-effective raw materials with sustainable sources. Our goal is to investigate the following parameters of a potentially biodegradable polymer created from sustainable raw materials:

•Physical, chemical and structural properties

•Degradability and environmental impact

•Usefulness as a replacement technology

What are we working on?Area of study: Polyglycerol Tartarate (PGT)

Because our team members are not the only ones investigating this material, it was agreed that we would focus on materials created from glycerol and tartaric acid cooked above 80 °C. Last year’s team determined the optimal reaction stoichiometry as a 3:2 tartaric acid to glycerol molar ratio. Thus, our main variables are the cooking time and temperature.

What are its application?Housing insulation

•Because the product foams naturally, insulation presents a natural course to begin investigating applications•Commercial insulation is cheap, so we have some pretty tough parameters to beat.•First we had to figure out how to make an insulator:

Why is this special?Foaming Phenomenon

•A major consequence of higher cooking temperature is ‘foaming’Water byproduct escapes as steam until the viscosity of the material becomes so high that it instead forms bubbles that cannot escape•Investigations in this phenomenon have included chemical additives and time-lapse photography

What did we do?Test Method

•A few ASTM tests say that if after six months 70% of a material’s carbon has been converted to CO2, the material can be classified as biodegradable•Because the timeframe for ASTM tests are exceed the scope of this course, a modified test was designed under the mentorship of Dr. Christine Kelly.•To encourage the material to biodegrade, we will put the material in the presence of Return Activated Sludge (RAS) from Corvallis’ municipal water treatment facility. (see right)

How did we do it?Implementation

Two forms of the polymer were tested:•Water soluble material cooked at 120 °C•Water insoluble material cooked at 140 °C

Tests will be done against three controls:•RAS with nothing added•RAS with un-biodegradable polymer (HDPE from a milk jug)•RAS with compostable polymer (Polylactic Acid)

All 5 tests were done in triplicate, for a total of 15 runs (see left)

Data acquisition

•For all 15 runs, bi-daily air samples were taken via a 1-ml syringe (see right)• The samples were analyzed by gas chromatographer and then, GC outputs were converted to CO2 percentage based on the constructed calibration curves of air and CO2

The results:InconclusiveThese samples were cooked for 22 hours in a vacuum oven using silicone muffin cups. The only

difference is their cooking temperature.

88 °C 120 °C

Shake flask tray holding what will be our 15 runs.

Taking a sample from a flask with modified stopper

It’s brown and smelly, but it’s not what you think it is. Really folks, it’s just microbes.

The percent carbon originally in the sample vs. carbon dioxide percentage vs. elapsed time. In this analysis, all carbon dioxide in the head space of the flask was assumed to come from the added polymer, even though it may have instead originated as yeast or glucose. CB, polylactic acid was added in to the pre-treated sludge a week after other test batches were added.

• Operating temperature• Particle size of polymers• Measurement method• Duration of experiment

Recommendations

Is it a polymer?Intrinsic Viscosity

Intrinsic viscosity, [η], is a vital parameter that tells us whether or not the material is a polymer in solution. A polymer in solution will have an intrinsic viscosity greater than one

The viscosity of the sample cooked at 88 °C dissolved in water was investigated for different concentrations. (see graph) The intercept can be estimated to be [η].

Viscometry of sample

cooked at 88 0C.

[η] = 1.27 ± 0.11

0 0 0

1[ ] lim lim limsp s

redC C CsC C

Thermo-gram of percent weight vs. temperatureMeasurements of three different samples cooked at different temperatures were made and compared with glycerol. Around the temperature glycerol starts decomposing at 160 0C, none of the three samples loose any mass and decompose yet.

TGA

DSCThermo-gram of heat flow vs. temperatureThe heat flow is plotted against the temperature change. From the second run of the sample, there is Tg observed at 100.6 0C. From the first run of the glycerol, there is a reaction observed around 180 0C.

Rheometry

Shear modulus (G’) and loss modulus (G’’)

Starting material was prepared with (3:7.5 mass ratio of glycerol and tartaric acid. Starting material and cooked sample behaves very similar up to 120 0C.

G’ and G’’ of the sample sheared at 120 0C and 1400C.

A reaction may be occurring between these temperatures.

1st Attempt

2nd Attempt EPS insulation (left) and PGT 2nd attempt (right)

Comparison of of properties of EPS and PGT: Experimentation with blowing agents may yet produce properties closer to commercial insulation.

Acknowledgements:Thanks to Dr. Skip for his direction, guidance and instruction, lending us a viscometer, and letting us use the vacuum oven and polymer characterization equipmentThanks to David Hackleman and Don Jackson for their experience and adviceThanks to Christine Kelly for her expertise and design ingenuityThanks to Heather Paris, Birdie Cornyn and Jan Trinkel for sharing samples and experienceThanks to Staci Van Norman for training us on lab equipmentLastly, thanks to Dr. Harding for his guidance and support