self-healing materials

INVESTIGATION OF SELF-HEALING COPOLYMERS UTILIZING TIME

DEPENDENT RESONANT SPECTROSCOPYNicholas R. Bowers, Physics Major

Kenneth A. Pestka II, Assistant Professor Joseph N. Kistner, Physics Major

Rollins College !

Stephen J. Kalista Jr. Union College

• Idea. Explore self-healing behavior of copolymers by analyzing changes in their acoustic properties over time

• Goal. Determine healing timeframe for different copolymers to identify factors that may influence the healing process

PURPOSE OF INVESTIGATION

• Triggered by sufficient energy transfer

• Three proposed phases of healing

• Instantaneous elastic molten state

• Welding and sealing

• Solid polymer interdiffusion and realignment

• Compositional variation, damage amount and mechanism, and sample age and deterioration may all influence the healing action of these polymers

[1] S. J. Kalista, T. C. Ward, “Thermal characteristics of the self-healing response in poly (ethylene-co-methacrylic acid) copolymers”, Journal of the Royal Society Interface. (2006).

Adapted from [1].

SELF-HEALING BEHAVIOR OF COPOLYMERS

SELF-HEALING COPOLYMERS

• Poly (ethylene-co-methacrylic acid) copolymers (EMAA copolymers)

• Four different materials developed by DuPont which differ in molecular weight, ionic content, and material age

SELF-HEALING COPOLYMERS

SELF-HEALING COPOLYMERS

Nucrel (Non-ionic) Suryln (Ionic)

Greater Molecular Weight

Lesser Molecular Weight

60% of Acid Groups Neutralized by Na

30% of Acid Groups Neutralized by Na

• Prepared samples

• Damaged samples

• Placed samples in scanning cell

• Scanned samples continuously over several hours

SELF-HEALING COPOLYMERS

• Resonance spectrum depends on microscopic structure and sample geometry

• Microscopic structure evolves throughout the healing process

• Expect changes in the resonance spectrum during healing process

• Analyze trends in the time evolution of the spectrum to quantify healing mechanism

ACOUSTIC AND ULTRASONIC TIME DEPENDENT RESONANT

SPECTROSCOPY (TDRS)

• Resonance spectrum depends on microscopic structure and sample geometry

• Microscopic structure evolves throughout the healing process

• Expect changes in the resonance spectrum during healing process

• Analyze trends in the time evolution of the spectrum to quantify healing mechanism

ACOUSTIC AND ULTRASONIC TIME DEPENDENT RESONANT

SPECTROSCOPY (TDRS)

• Resonance spectrum depends on microscopic structure and sample geometry

• Microscopic structure evolves throughout the healing process

• Expect changes in the resonance spectrum during healing process

• Analyze trends in the time evolution of the spectrum to quantify healing mechanism

ACOUSTIC AND ULTRASONIC TIME DEPENDENT RESONANT

SPECTROSCOPY (TDRS)

• Resonance spectrum depends on microscopic structure and sample geometry

• Microscopic structure evolves throughout the healing process

• Expect changes in the resonance spectrum during healing process

• Analyze trends in the time evolution of the spectrum to quantify healing mechanism

ACOUSTIC AND ULTRASONIC TIME DEPENDENT RESONANT

SPECTROSCOPY (TDRS)

EVOLUTION OF RESONANCE PEAKS DURING HEALING

Overlapping Resonance Peaks

Nucrel 960 8x8mm Sample

Damaged by Nail

0.000#

0.020#

0.040#

0.060#

0.080#

0.100#

0.120#

0.140#

0.160#

545# 550# 555# 560# 565# 570# 575# 580# 585# 590# 595#

Energy#(R

ela6

ve)#

Frequency#(kHz)#

#t=0h# #t=0.35h# #t=10.3h#

EVOLUTION OF RESONANCE PEAKS DURING HEALING

Nucrel 960 8x8mm Sample

Damaged by Nail

QUALITY FACTORS OF RESONANCE PEAKSNucrel 960

8x8mm Sample Damaged by Nail

0"

50"

100"

150"

200"

250"

300"

0" 1" 2" 3" 4" 5" 6" 7" 8" 9"

Quality"Factors"

Time"(Hours)"

"563kHz" "572kHz" "580kHz"

EVOLUTION OF QUALITY FACTORS DURING HEALING

Nucrel 960 8x8mm Sample

Damaged by Nail

0"

50"

100"

150"

200"

250"

300"

0" 1" 2" 3" 4" 5" 6" 7" 8" 9"

Quality"Factors"

Time"(Hours)"

"563kHz" "572kHz" "580kHz"

EVOLUTION OF QUALITY FACTORS DURING HEALING

Nucrel 960 8x8mm Sample

Damaged by Nail

Phase 3

0.0# 0.5# 1.0# 1.5# 2.0# 2.5# 3.0# 3.5# 4.0# 4.5# 5.0# 5.5# 6.0# 6.5# 7.0# 7.5# 8.0# 8.5# 9.0# 9.5# 10.0#

Phase#2#

Phase#3#

Time#(Hours)#

925# 960# 8920# 8940#

PRELIMINARY HEALING TIMEFRAMES

Greater Molecular WeightLesser Molecular Weight

Higher Ion ContentLower Ion Content

925

960

8920

8940

PRELIMINARY RESULTS AND SUMMARY

• Preliminary results

• Establish healing timeframe estimates for four EMAA copolymers

• Confirm TDRS is a useful tool for determining healing timeframe

• Are consistent with the three-phase healing model

• Correlation between material composition and healing timeframe

• Correlations between healing timeframes and sample age, size, and damage amount are being explored

ACKNOWLEDGEMENTS• Rollins College Student-Faculty Collaborative

Scholarship Program • DuPont