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Rheological characterization of composites using a vertical oscillation rheometer


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Rheological characterization of composites using a vertical oscillation rheometer

Article information

Restor Dent Endod. 2004;29(6):489-497
Publication date (electronic) : 2004 November 30
doi : https://doi.org/10.5395/JKACD.2004.29.6.489
In-Bog Lee, Byung-Hoon Cho, Ho-Hyun Son, Sang-Tag Lee, Chung-Moon Um
Department of Conservative Dentistry, College of Dentistry, Seoul National University, Korea.
Corresponding author: Chung-Moon Um. Department of Conservative Dentistry, College of Dentistry, Seoul National University, 28 Yoengun-dong, Chongro-gu, Seoul, Korea, 110-749. Tel: 82-2-2072-3953, 2651, Fax: 82-2-2072-3859, inboglee@snu.ac.kr

Abstract

Objective

The purpose of this study was to investigate the viscoelastic properties related to handling characteristics of composite resins.

Methods

A custom designed vertical oscillation rheometer (VOR) was used for rheological measurements of composites. The VOR consists of three parts: (1) a measuring unit, (2) a deformation induction unit and (3) a force detecting unit. Two medium viscous composites, Z100 and Z250 and two packable composites, P60 and SureFil were tested. The viscoelastic material function, including complex modulus E* and phase angle δ, were measured. A dynamic oscillatory test was used to evaluate the storage modulus (E'), loss modulus (E") and loss tangent (tanδ) of the composites as a function of frequency (ω) from 0.1 to 20 Hz at 23℃.

Results

The E' and E" increased with increasing frequency and showed differences in magnitude between brands. The E*s of composites at ω = 2 Hz, normalized to that of Z100, were 2.16 (Z250), 4.80 (P60) and 25.21 (SureFil). The magnitudes and patterns of the change of tanδ of composites with increasing frequency were significantly different between brands. The relationships between the complex modulus E*, the phase angle δ and the frequency ω were represented by frequency domain phasor form, E* (ω) = E*eiδ = E*∠δ.

Conclusions

The viscoelasticity of composites that influences handling characteristics is significant different between brands. The VOR is a relatively simple device for dynamic, mechanical analysis of high viscous dental composites. The locus of frequency domain phasor plots in a complex plane is a valuable method of representing the viscoelastic properties of composites.

Keywords: VOR; Viscoelasticity; Composite; Complex modulus; Frequency domain phasor plot

References

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Article information Continued

Copyright © 2004 Korean Academy of Conservative Dentistry
(open-access) :

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Figure 1-a

Figure 1-a

Diagram of the VOR (vertical oscillatory rheometer)

Figure 1-b

Figure 1-b

The geometry of measuring unit

Figure 2

Figure 2

The relationship between strain ε(t), stress σ(t) and phase angle δ in dynamic oscillatory test

Figure 3

Figure 3

The relationship between storage (real) modulus E', loss modulus (imaginary) modulus E", complex modulus E* and phase angle δ in a complex plane

Figure 4

Figure 4

Storage modulus E' increased with increasing the frequency and showed differences in magnitude between brands

Figure 5

Figure 5

Loss modulus E" increased with increasing the frequency and showed differences in magnitude between brands

Figure 6

Figure 6

Complex modulus E* increased with increasing the frequency and showed differences in magnitude between brands

Figure 7

Figure 7

Phase angle δ of composite. The patterns of the change of δ of samples with increasing frequency showed the different characteristics of the composites between brands

Figure 8

Figure 8

Loss tangent as a function of frequency

Figure 9

Figure 9

Relative complex modulus of composites normalized to that of Z1 at ω = 2 Hz

Figure 10

Figure 10

Phasor presentation of E* and δ, E*eiδ= E*∠δ, of composites at ω = 2 Hz in a polar coordinate system

Figure 11

Figure 11

Locus of frequency domain phasor plots, G*(ω)eiδ = ∣ G*(ω) ∣ ∠δ of composites in a complex plane

Table 1

Phasor presentation of the complex modulus E* and phase angle (δ) of composite resins at various frequencies, E* (dyn/cm2) ∠δ(°)

Table 1

Table 2

Phasor presentation of the complex shear modulus G* and phase angle (δ) of composite resins at various frequencies, G* (dyn/cm2) ∠δ(°)

Table 2