J Korean Acad Conserv Dent.  2004 Nov;29(6):489-497. 10.5395/JKACD.2004.29.6.489.

Rheological characterization of composites using a vertical oscillation rheometer

• Lee IB
• Cho BH
• Son HH
• Lee ST
• Um CM

• KMID: 2175649
• DOI: http://doi.org/10.5395/JKACD.2004.29.6.489

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 delta, were measured. A dynamic oscillatory test was used to evaluate the storage modulus (E'), loss modulus (E") and loss tangent (tandelta) of the composites as a function of frequency (omega) from 0.1 to 20 Hz at 23degrees C.
RESULTS
The E' and E" increased with increasing frequency and showed differences in magnitude between brands. The E*s of composites at omega = 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 tandelta of composites with increasing frequency were significantly different between brands. The relationships between the complex modulus E*, the phase angle delta and the frequency omega were represented by frequency domain phasor form, E* (omega) = E*e(idelta) = E* 45 degree angle delta.
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.

Keyword

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

MeSH Terms

Composite Resins
Composite Resins

Figure

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  Figure 1-a Diagram of the VOR (vertical oscillatory rheometer)

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  Figure 1-b The geometry of measuring unit

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  Figure 2 The relationship between strain ε(t), stress σ(t) and phase angle δ in dynamic oscillatory test

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  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

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  Figure 4 Storage modulus E' increased with increasing the frequency and showed differences in magnitude between brands

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  Figure 5 Loss modulus E" increased with increasing the frequency and showed differences in magnitude between brands

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  Figure 6 Complex modulus E* increased with increasing the frequency and showed differences in magnitude between brands

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  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

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  Figure 8 Loss tangent as a function of frequency

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  Figure 9 Relative complex modulus of composites normalized to that of Z1 at ω = 2 Hz

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  Figure 10 Phasor presentation of E* and δ, E*eiδ= E*∠δ, of composites at ω = 2 Hz in a polar coordinate system

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  Figure 11 Locus of frequency domain phasor plots, G*(ω)eiδ = ∣ G*(ω) ∣ ∠δ of composites in a complex plane

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