Rapid Degradation of Poly(lactic acid) with Organometallic Catalysts

Mayank Garg; Scott R. White; Nancy R. Sottos

doi:10.1021/acsami.9b17599

Rapid Degradation of Poly(lactic acid) with Organometallic Catalysts

Mayank Garg, Scott R. White, Nancy R. Sottos

Research output: Contribution to journal › Article › peer-review

Abstract

Poly(lactic acid) (PLA) is an effective sacrificial material for the creation of vascular networks in thermoset polymers and composites. The high thermal stability of PLA limits its applications as an embedded sacrificial template in higherature-resistant thermoset matrices. Here, we demonstrate faster and more efficient PLA degradation at temperatures lower than previously reported using two organometallic catalysts: tin(II) oxalate (Sn(Oxa)) and tin(II) acetate (Sn(Ac)₂). We process Sn(Oxa) by two separate methods to obtain a significant difference in the specific surface area (SSA) of the catalyst particles and compare PLA degradation performance in a thermogravimetric analysis (TGA) instrument. Changing the SSA of Sn(Oxa) by a factor of â&circ;¼20 reduces the PLA degradation onset temperature by 37 °C. The total degradation time of PLA films also decreases after blending with Sn(Oxa) having a higher SSA. We also find Sn(Ac)₂ lowers the degradation onset of PLA by 53 °C compared to Sn(Oxa) with a similar SSA. In addition, Sn(Ac)₂ decreases the time for complete degradation of PLA films by an order of magnitude compared to Sn(Oxa) at 200 °C. Films with a significantly lower Sn(Ac)₂ concentration compared to Sn(Oxa) degrade much faster at lower temperatures up to 160 °C. Finally, PLA films with different loadings of Sn(Ac)₂ are embedded in an epoxy thermoset matrix and subsequently vascularized at elevated temperatures in a vacuum oven. Microchannel formation is observed at 170 °C using Sn(Ac)₂, reducing the temperature required for vaporization of embedded sacrificial polymer compared to Sn(Oxa) catalyst. Sn(Ac)₂ can potentially reduce the energy, time, and amount of catalyst required for degrading PLA into volatile products for sacrificial applications.

Original language	English (US)
Pages (from-to)	46226-46232
Number of pages	7
Journal	ACS Applied Materials and Interfaces
Volume	11
Issue number	49
DOIs	https://doi.org/10.1021/acsami.9b17599
State	Published - Dec 11 2019

Keywords

VaSC
microchannel
poly(lactic acid) (PLA)
thermal degradation
tin acetate (Sn(Ac))
tin oxalate (Sn(Oxa))
vascular networks

ASJC Scopus subject areas

Materials Science(all)

Online availability

10.1021/acsami.9b17599

Library availability

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title = "Rapid Degradation of Poly(lactic acid) with Organometallic Catalysts",

abstract = "Poly(lactic acid) (PLA) is an effective sacrificial material for the creation of vascular networks in thermoset polymers and composites. The high thermal stability of PLA limits its applications as an embedded sacrificial template in higherature-resistant thermoset matrices. Here, we demonstrate faster and more efficient PLA degradation at temperatures lower than previously reported using two organometallic catalysts: tin(II) oxalate (Sn(Oxa)) and tin(II) acetate (Sn(Ac)2). We process Sn(Oxa) by two separate methods to obtain a significant difference in the specific surface area (SSA) of the catalyst particles and compare PLA degradation performance in a thermogravimetric analysis (TGA) instrument. Changing the SSA of Sn(Oxa) by a factor of {\^a}&circ;¼20 reduces the PLA degradation onset temperature by 37 °C. The total degradation time of PLA films also decreases after blending with Sn(Oxa) having a higher SSA. We also find Sn(Ac)2 lowers the degradation onset of PLA by 53 °C compared to Sn(Oxa) with a similar SSA. In addition, Sn(Ac)2 decreases the time for complete degradation of PLA films by an order of magnitude compared to Sn(Oxa) at 200 °C. Films with a significantly lower Sn(Ac)2 concentration compared to Sn(Oxa) degrade much faster at lower temperatures up to 160 °C. Finally, PLA films with different loadings of Sn(Ac)2 are embedded in an epoxy thermoset matrix and subsequently vascularized at elevated temperatures in a vacuum oven. Microchannel formation is observed at 170 °C using Sn(Ac)2, reducing the temperature required for vaporization of embedded sacrificial polymer compared to Sn(Oxa) catalyst. Sn(Ac)2 can potentially reduce the energy, time, and amount of catalyst required for degrading PLA into volatile products for sacrificial applications.",

keywords = "VaSC, microchannel, poly(lactic acid) (PLA), thermal degradation, tin acetate (Sn(Ac)), tin oxalate (Sn(Oxa)), vascular networks",

author = "Mayank Garg and White, {Scott R.} and Sottos, {Nancy R.}",

note = "Funding Information: The authors acknowledge the funding and technical support from Air Force Office of Scientific Research (AFOSR grant no. FA 9550-16-1-0017, Center of Excellence in Self-healing, Regeneration, and Structural Remodeling). The authors also acknowledge the Imaging Technology Group at the Beckman Institute for Advanced Science and Technology for SEM and EDAX equipment, CU Aerospace for providing a high-speed rotary grinder, Yurun Miao in Prof. Kenneth S. Suslick{\textquoteright}s lab for specific surface area measurements, Prof. Paul V. Braun for providing a centrifuge, and Dr. Xiang Zhang (University of Wyoming) and Prof. Philippe Geubelle (University of Illinois) for the degradation kinetics modeling of PLA. We also extend our gratitude to Prof. Jason F. Patrick (NC State University) and Anthony S. Griffin for helpful discussions. Publisher Copyright: {\textcopyright} 2019 American Chemical Society.",

year = "2019",

month = dec,

day = "11",

doi = "10.1021/acsami.9b17599",

language = "English (US)",

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AU - Garg, Mayank

AU - White, Scott R.

AU - Sottos, Nancy R.

N1 - Funding Information: The authors acknowledge the funding and technical support from Air Force Office of Scientific Research (AFOSR grant no. FA 9550-16-1-0017, Center of Excellence in Self-healing, Regeneration, and Structural Remodeling). The authors also acknowledge the Imaging Technology Group at the Beckman Institute for Advanced Science and Technology for SEM and EDAX equipment, CU Aerospace for providing a high-speed rotary grinder, Yurun Miao in Prof. Kenneth S. Suslick’s lab for specific surface area measurements, Prof. Paul V. Braun for providing a centrifuge, and Dr. Xiang Zhang (University of Wyoming) and Prof. Philippe Geubelle (University of Illinois) for the degradation kinetics modeling of PLA. We also extend our gratitude to Prof. Jason F. Patrick (NC State University) and Anthony S. Griffin for helpful discussions. Publisher Copyright: © 2019 American Chemical Society.

PY - 2019/12/11

Y1 - 2019/12/11

N2 - Poly(lactic acid) (PLA) is an effective sacrificial material for the creation of vascular networks in thermoset polymers and composites. The high thermal stability of PLA limits its applications as an embedded sacrificial template in higherature-resistant thermoset matrices. Here, we demonstrate faster and more efficient PLA degradation at temperatures lower than previously reported using two organometallic catalysts: tin(II) oxalate (Sn(Oxa)) and tin(II) acetate (Sn(Ac)2). We process Sn(Oxa) by two separate methods to obtain a significant difference in the specific surface area (SSA) of the catalyst particles and compare PLA degradation performance in a thermogravimetric analysis (TGA) instrument. Changing the SSA of Sn(Oxa) by a factor of â&circ;¼20 reduces the PLA degradation onset temperature by 37 °C. The total degradation time of PLA films also decreases after blending with Sn(Oxa) having a higher SSA. We also find Sn(Ac)2 lowers the degradation onset of PLA by 53 °C compared to Sn(Oxa) with a similar SSA. In addition, Sn(Ac)2 decreases the time for complete degradation of PLA films by an order of magnitude compared to Sn(Oxa) at 200 °C. Films with a significantly lower Sn(Ac)2 concentration compared to Sn(Oxa) degrade much faster at lower temperatures up to 160 °C. Finally, PLA films with different loadings of Sn(Ac)2 are embedded in an epoxy thermoset matrix and subsequently vascularized at elevated temperatures in a vacuum oven. Microchannel formation is observed at 170 °C using Sn(Ac)2, reducing the temperature required for vaporization of embedded sacrificial polymer compared to Sn(Oxa) catalyst. Sn(Ac)2 can potentially reduce the energy, time, and amount of catalyst required for degrading PLA into volatile products for sacrificial applications.

AB - Poly(lactic acid) (PLA) is an effective sacrificial material for the creation of vascular networks in thermoset polymers and composites. The high thermal stability of PLA limits its applications as an embedded sacrificial template in higherature-resistant thermoset matrices. Here, we demonstrate faster and more efficient PLA degradation at temperatures lower than previously reported using two organometallic catalysts: tin(II) oxalate (Sn(Oxa)) and tin(II) acetate (Sn(Ac)2). We process Sn(Oxa) by two separate methods to obtain a significant difference in the specific surface area (SSA) of the catalyst particles and compare PLA degradation performance in a thermogravimetric analysis (TGA) instrument. Changing the SSA of Sn(Oxa) by a factor of â&circ;¼20 reduces the PLA degradation onset temperature by 37 °C. The total degradation time of PLA films also decreases after blending with Sn(Oxa) having a higher SSA. We also find Sn(Ac)2 lowers the degradation onset of PLA by 53 °C compared to Sn(Oxa) with a similar SSA. In addition, Sn(Ac)2 decreases the time for complete degradation of PLA films by an order of magnitude compared to Sn(Oxa) at 200 °C. Films with a significantly lower Sn(Ac)2 concentration compared to Sn(Oxa) degrade much faster at lower temperatures up to 160 °C. Finally, PLA films with different loadings of Sn(Ac)2 are embedded in an epoxy thermoset matrix and subsequently vascularized at elevated temperatures in a vacuum oven. Microchannel formation is observed at 170 °C using Sn(Ac)2, reducing the temperature required for vaporization of embedded sacrificial polymer compared to Sn(Oxa) catalyst. Sn(Ac)2 can potentially reduce the energy, time, and amount of catalyst required for degrading PLA into volatile products for sacrificial applications.

KW - VaSC

KW - microchannel

KW - poly(lactic acid) (PLA)

KW - thermal degradation

KW - tin acetate (Sn(Ac))

KW - tin oxalate (Sn(Oxa))

KW - vascular networks

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Rapid Degradation of Poly(lactic acid) with Organometallic Catalysts

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