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A Comparison of Elastic Moduli Derived from Theory, Microindentation, and Ultrasonic Testing

Purpose. The objective of our work was to evaluate the elastic modulus through ultrasonic testing of poly(methyl methacrylate-co-methacrylic acid) (PMMA/coMAA), a viscoelastic polymer similar to the commercial Eudragit ® , to calculate this modulus, assuming a regular arrangement of interacting grou... Full description

Journal Title: Pharmaceutical Research 1996, Vol.13(11), pp.1739-1745
Main Author: Lum, Susan
Other Authors: Duncan-Hewitt, Wendy
Format: Electronic Article Electronic Article
Language: English
Subjects:
ID: ISSN: 0724-8741 ; E-ISSN: 1573-904X ; DOI: 10.1023/A:1016465412544
Link: http://dx.doi.org/10.1023/A:1016465412544
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recordid: springer_jour1016465412544
title: A Comparison of Elastic Moduli Derived from Theory, Microindentation, and Ultrasonic Testing
format: Article
creator:
  • Lum, Susan
  • Duncan-Hewitt, Wendy
subjects:
  • microindentation
  • ultrasonic testing
  • elastic modulus
ispartof: Pharmaceutical Research, 1996, Vol.13(11), pp.1739-1745
description: Purpose. The objective of our work was to evaluate the elastic modulus through ultrasonic testing of poly(methyl methacrylate-co-methacrylic acid) (PMMA/coMAA), a viscoelastic polymer similar to the commercial Eudragit ® , to calculate this modulus, assuming a regular arrangement of interacting groups, and ultimately, assess the accuracy of microindentation as a means of evaluating elasticity in very small samples. Knoop indentation testing was performed on cast samples using a Tukon testing apparatus. Solid density and pulse echo testing employing a damped 15 MHz transducer served to quantify the elastic moduli. Using the Hoy method of calculation for molar attraction constants, and assuming pairwise addition, the modulus was calculated and compared with typical experimental values for amorphous and crystalline polymers. Acoustic testing resulted in an average elastic modulus value of 5.67 ± 0.2 GPa for this copolymer, which concurs with literature values for PMMA. Acoustically derived experimental moduli when normalized and plotted against calculated values, resulted in a relationship, /(1 − 2υ) = 17.0 ( + χΔ + 6.9, similar to that predicted in theory. Indentation contact modeling does not adequately describe the real recovery under indentation. In contrast, acoustic testing of pharmaceutical materials affords a simple, reproducible means of characterizing moduli without impairing structural integrity. Acoustically derived moduli further afford insight into the intermolecular interactions, as expressed by the interaction energy terms.
language: eng
source:
identifier: ISSN: 0724-8741 ; E-ISSN: 1573-904X ; DOI: 10.1023/A:1016465412544
fulltext: fulltext
issn:
  • 1573-904X
  • 1573904X
  • 0724-8741
  • 07248741
url: Link


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titleA Comparison of Elastic Moduli Derived from Theory, Microindentation, and Ultrasonic Testing
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descriptionPurpose. The objective of our work was to evaluate the elastic modulus through ultrasonic testing of poly(methyl methacrylate-co-methacrylic acid) (PMMA/coMAA), a viscoelastic polymer similar to the commercial Eudragit ® , to calculate this modulus, assuming a regular arrangement of interacting groups, and ultimately, assess the accuracy of microindentation as a means of evaluating elasticity in very small samples. Knoop indentation testing was performed on cast samples using a Tukon testing apparatus. Solid density and pulse echo testing employing a damped 15 MHz transducer served to quantify the elastic moduli. Using the Hoy method of calculation for molar attraction constants, and assuming pairwise addition, the modulus was calculated and compared with typical experimental values for amorphous and crystalline polymers. Acoustic testing resulted in an average elastic modulus value of 5.67 ± 0.2 GPa for this copolymer, which concurs with literature values for PMMA. Acoustically derived experimental moduli when normalized and plotted against calculated values, resulted in a relationship, /(1 − 2υ) = 17.0 ( + χΔ + 6.9, similar to that predicted in theory. Indentation contact modeling does not adequately describe the real recovery under indentation. In contrast, acoustic testing of pharmaceutical materials affords a simple, reproducible means of characterizing moduli without impairing structural integrity. Acoustically derived moduli further afford insight into the intermolecular interactions, as expressed by the interaction energy terms.
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0Purpose. The objective of our work was to evaluate the elastic modulus through ultrasonic testing of poly(methyl methacrylate-co-methacrylic acid) (PMMA/coMAA), a viscoelastic polymer similar to the commercial Eudragit ® , to calculate this modulus, assuming a regular arrangement of interacting groups, and ultimately, assess the accuracy of microindentation as a means of evaluating elasticity in very small samples.
1Knoop indentation testing was performed on cast samples using a Tukon testing apparatus. Solid density and pulse echo testing employing a damped 15 MHz transducer served to quantify the elastic moduli. Using the Hoy method of calculation for molar attraction constants, and assuming pairwise addition, the modulus was calculated and compared with typical experimental values for amorphous and crystalline polymers.
2Acoustic testing resulted in an average elastic modulus value of 5.67 ± 0.2 GPa for this copolymer, which concurs with literature values for PMMA. Acoustically derived experimental moduli when normalized and plotted against calculated values, resulted in a relationship, /(1 − 2υ) = 17.0 ( + χΔ + 6.9, similar to that predicted in theory.
3Indentation contact modeling does not adequately describe the real recovery under indentation. In contrast, acoustic testing of pharmaceutical materials affords a simple, reproducible means of characterizing moduli without impairing structural integrity. Acoustically derived moduli further afford insight into the intermolecular interactions, as expressed by the interaction energy terms.
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abstractPurpose. The objective of our work was to evaluate the elastic modulus through ultrasonic testing of poly(methyl methacrylate-co-methacrylic acid) (PMMA/coMAA), a viscoelastic polymer similar to the commercial Eudragit ® , to calculate this modulus, assuming a regular arrangement of interacting groups, and ultimately, assess the accuracy of microindentation as a means of evaluating elasticity in very small samples. Knoop indentation testing was performed on cast samples using a Tukon testing apparatus. Solid density and pulse echo testing employing a damped 15 MHz transducer served to quantify the elastic moduli. Using the Hoy method of calculation for molar attraction constants, and assuming pairwise addition, the modulus was calculated and compared with typical experimental values for amorphous and crystalline polymers. Acoustic testing resulted in an average elastic modulus value of 5.67 ± 0.2 GPa for this copolymer, which concurs with literature values for PMMA. Acoustically derived experimental moduli when normalized and plotted against calculated values, resulted in a relationship, /(1 − 2υ) = 17.0 ( + χΔ + 6.9, similar to that predicted in theory. Indentation contact modeling does not adequately describe the real recovery under indentation. In contrast, acoustic testing of pharmaceutical materials affords a simple, reproducible means of characterizing moduli without impairing structural integrity. Acoustically derived moduli further afford insight into the intermolecular interactions, as expressed by the interaction energy terms.
copNew York
pubKluwer Academic Publishers-Plenum Publishers
doi10.1023/A:1016465412544
pages1739-1745
date1996-11