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Properties and Curing Kinetics of Epoxy Resins Cured by Chitosan

Balasubramani, Praveen Kumar
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1480328803855009

Abstract Details

2016, MS, University of Cincinnati, Engineering and Applied Science: Materials Science.
Toxicity of commercially available curing agents for epoxy resins pose a severe environmental threat. There is therefore a need for alternative non-toxic curing agents for epoxy resins. In this research, Chitosan, a biomaterial, was employed as an environmentally friendly curing agent for crosslinking Diglycidyl Ether of Bisphenol A (DGEBA) resins. Properties such as cross-linking behavior, viscoelastic behavior, and thermal stability were investigated.

Curing behavior of diglycidyl ether of bisphenol A resin using chitosan was studied by Fourier Transform Infrared (FTIR) Spectroscopy. Degree of crosslinking, correlated with the epoxy fractional conversion (α), was determined by following the change in area of oxirane ring peak at 914 cm-1. Four molar ratios (Epoxy:Chitosan) 1:1, 1:2, 1:3, and 1:4 cured at three isothermal curing temperatures 160°C, 180°C, and 200°C for 5 hours, were used to determine the effect of temperature and concentration of chitosan on the epoxy fractional conversion (α). It was found that the value of `α’ increased over curing time, curing temperature, and chitosan concentration. The maximum epoxy fractional conversion of 70% was obtained for molar ratio of 1:4 at 200°C.

A four parameter kinetic model with two rate constants was employed to simulate the experimental data obtained from FTIR analysis. Total order of the reaction was found to be about 2.8 and the activation energy was in the range of 27-48 KJmol-1. Result obtained shows that cure reaction is autocatalytic in nature, and does not follow simple nth order cure kinetics. Avrami analysis was performed on the curing reaction and parameters such as Avrami exponent (n), rate constant (k) and activation energy (Ea) were determined. At 200°C, the value of n, k and Ea were 0.87, 8.88 and 24.21 KJmol-1 respectively for molar ratio of 1:4 (Epoxy:Chitosan).

Dynamic Mechanical Analysis (DMA) was used to study the viscoelastic properties of the chitosan cured epoxy resin films. Glass transition temperature (Tg), determined from peak of tan δ plot, was found to be 30±4°C for chitosan cured epoxy resin films, 55±4°C for neat epoxy films and 165±3 °C for neat chitosan film. In addition, two other transitions at ≈85°C and ≈180°C were observed for chitosan cured epoxy resin films. Films cured with molar ratio of 1:4 (Epoxy:Chitosan) showed an increase of about 5% and 33% in glassy region storage modulus and rubbery region storage modulus respectively, when compared to that of neat epoxy film. Damping ability, studied from tan δ plot, was found to decrease with increase in chitosan concentration.

Thermogravimetric analysis was performed on chitosan cured epoxy resin films, neat epoxy resin film and neat chitosan film. Temperatures at which the samples experience 5% weight loss (T5%), 80% weight loss (T80%) and maximum weight loss (Tmax) were determined and correlated with their thermal stability. It was found that thermal stability of chitosan cured epoxy resin films increased with increase in cross-link density. Films cured with molar ratio of 1:4 (Epoxy:Chitosan) showed an increase of 86°C, 101°C and 126°C for T5%, T80%, and Tmax respectively when compared to that of neat epoxy resin film.

Jude Iroh, Ph.D. (Committee Chair)
Relva Buchanan, Sc.D. (Committee Member)
Raj Manglik, Ph.D. (Committee Member)
143 p.
Materials Science
epoxy; chitosan; cure kinetics; crosslinking; Dynamic Mechanical Analysis; Fourier Transform Infrared Spectroscopy

Recommended Citations

Citations

  • Balasubramani, P. K. (2016). Properties and Curing Kinetics of Epoxy Resins Cured by Chitosan [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1480328803855009

    APA Style (7th edition)

  • Balasubramani, Praveen Kumar. Properties and Curing Kinetics of Epoxy Resins Cured by Chitosan. 2016. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1480328803855009.

    MLA Style (8th edition)

  • Balasubramani, Praveen Kumar. "Properties and Curing Kinetics of Epoxy Resins Cured by Chitosan." Master's thesis, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1480328803855009

    Chicago Manual of Style (17th edition)

ucin1480328803855009
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© 2016, some rights reserved.Creative Commons License Properties and Curing Kinetics of Epoxy Resins Cured by Chitosan by Praveen Kumar Balasubramani is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.