Joshua Mangler1, P.R.Hondred2, M.S. Kessler2 1 Dallas Center-Grimes High School Grimes, Iowa
2Dept. Of Materials Science and Engineering, Iowa State University
Bio-polymers: characterization for self-healing
application.
MOTIVATION
OBJECTIVE
Our objective is to develop bio-based self healing polymers. The
research focuses on the healing agent and how different triflate
catalysts affect the thermal-mechanical properties of tung-oil based
thermosetting bio-polymers. The thermal-mechanical properties
investigated were:
Effective cure rate and temperature
Ideal glass transition temperature
Thermal stability
MATERIALS AND METHODS
BACKGROUND
POLYMERIZATION PROCESS
THERMOGRAVIMETRIC ANALYSIS
DIFFERENTIAL SCANNING CALORIMETRY
CONCLUSION AND FUTURE WORK
Petroleum vs Biorenewables
Cost
Sustainability
Environment
Energy
Polymers made from biorenewables are gaining traction as an effective
and plausible alternative to petroleum based products. Continued
research into their properties and applications may yield sustainable
and cost effective alternatives and subsequently reduce society’s
dependency on oil.
Macrocrack Microcrack
Time
Figure 1. Polymer crack progression over time
I sure wish I’d
presented my
theory with a
poster before I
wrote my book.
Healing Agent Catalyst
Crack forms
in material Crack ruptures
microcapsules
Healing agent
polymerizes
Figure 2. Self-healing concept showing microcapsules and catalyst
Figure 3. Scanning electron microscope images of ruptured microcapsules
+ +
Catalyst
Rare Earth
Triflates
Styrene
Divinylbenzene
Crosslinked Thermoset
Figure 7. Polymerization process
Figure 4. Chosen oil – tung oil
Figure 5. Chosen rare earth
triflates
Samarium
Triflate
Scandium
Triflate
Ytterbium
Triflate
Cerium
Triflate
Procedure: 1) Rare earth triflate added to the
monomers and mixed for one minute
with horn sonicator.
2) Sample was placed into hot water
bath sonicator until cured. Times
varied per triflate.
3) Post cured at 150°C for five hours.
Chemical Ratio of Samples
Monomer
s
47% Tung oil
32% Styrene
16% Divinylbenzene
Initiator 5% Rare earth triflate
Table 1. Composition of monomers and initiator
Viscoelastic Behaviors of Polymers • Complex mechanical modulus
• Glass transition temperature
Testing Conditions Equilibrate at -50°C
Ramp 3°C/min to 150 °C
Figure 11: Storage
modulus of different
tung oil triflate
polymers
Figure 13: Tan
delta of different
tung oil triflate
polymers
Figure 12: Loss
modulus of different
tung oil triflate
polymers
Cerium Scandium Ytterbium Samarium
14.7°C 55.4°C 56.4°C 13.8°C
Testing Conditions Equilibrate at -50°C
Ramp 3°C/min to 200 °C
Glass Transitions of Polymer Cure • Heat flow compared to standard reference
• Glass transition temperature
ACKNOWLEDGEMENTS
Thank you to NSF for funding the summer RET program, Dr. Michael Kessler
for providing the opportunity to work within his polymer composite research
group, the members of the group – especially Danny Vennerberg - for their
support and assistance. A special thanks to Peter Hondred for his mentoring,
direction, and guidance.
Reactivity
Figure 10: DSC cure of bio-polymers
Testing Conditions Ramp 20°C/min to 650 °C
Conclusion: •Effective cure temperature
•Good thermal stability
•Variable glass transition
temperatures
•Phase separation in cerium
triflate catalyzed bio-polymer
Future work: •Characterization of thermal
degradation
•Evaluate adhesive properties
•Evaluate crosslink density
•Characterization of phase
separation
DYNAMIC MECHANICAL ANALYSIS
DYNAMIC MECHANICAL ANALYSIS CONT’D
Table 2: Glass transition temperatures
Figure 8: (Above) Thermal
degradation of bio-polymer in air
Figure 9: (Left) Thermal
degradation of bio-polymer in
nitrogen
VARIABLE
STORAGE
MODULUS
VARIABLE GLASS
TRANSITION
TEMPERATURES
PHASE
SEPARATION IN
CERIUM
CATALYZED
BIO-POLYMER
Thermal Degradation • Monitors weight change as a function of
temperature or time
• Predicts thermal stability
• Monitors decomposition, oxidation, and
dehydration
CBiRC: NSF award EEC-0813570 (PI Shanks)
Figure 6. Tung oil bio-polymer samples catalyzed by rare earth
triflates. Rare earth triflate catalyst (from left to right), cerium,
scandium, samarium, ytterbium.