Results References [1].Mendoza, J. D. - PowerPoint Presentation

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Results

References[1].Mendoza, J. D. Lab 9: Dynamic Mechanical Analysis, Iowa State University

Time-Temperature Superposition (TTS) Using DMA

AcknowledgmentsThis laboratory report utilized data from an actual laboratory performed by a previous Mat E 453 class at Iowa State University.

ConclusionsBy testing at different temperatures, a master curve for reference 270 ºC could be generated quickly.The shifting was done to 270 ºC because that is where the glass transition of BECy is known to be. The glass transition temperature can be observed by the differences of slopes of the high temperature and low temperature curves.At higher temperatures, the storage modulus was lower, which agrees with expectations.TTS shifting could also be used to generate a master curve for loss modulus and viscoelastic phase lag at 270 ºCThe TTS shifting was good, but not perfect.To obtain better results, a smaller difference in temperatures could be used.TTS shifting is not an exact method, as lines can overlap in multiple places and a choice of where to calculate shift factor must be made.The shift factors could have been taken from the log(frequency) data, which would result in different shift factors even from the same data.

IntroductionDynamic Mechanical Analysis (DMA) is a method that gives useful information on the viscoelastic properties of polymers. Most materials have a combination of elastic (Hookean) and viscous (Newtonian) behaviors and hence exhibit a phase lag between an applied sinusoidal stress and the strain. [1]This results in the material having a complex modulus which accounts for both behaviors. Rheological measurements are utilized to generate master curves that describe the viscoelastic behavior of a material. Temperature superposition (TTS) is a procedure in which a storage modulus versus frequency master curve is created by making measurements at varying temperatures and a range of frequencies and multiplying the frequencies by a shift factor to shift the curves left or right in the horizontal axis. [1]

Mohammed Alzayer, Chris Clay, Xinhang ShenMat E 453, Department of Materials Engineering, Iowa State University, Ames, IA 50011

Fig 2. Modulus versus frequency at varying temperatures.

Testing ProceduresThe polymer investigated in this lab is bisphenol E cyanate ester (BECy) which has a glass transition temperature of 270 °C (reference temperature).

Fig 3. Log-log graph of modulus versus frequency.

The shift factors were calculated from the raw frequency data, not from the log(frequency) data. The log of the shifted frequencies was then taken and plotted.The shift factor listed for 290 ºC  270 ºC in Table 1 is actually the shift factor for 280 ºC 270 ºC multiplied by the shift factor for 290 ºC 280 ºC.

Sample preparation

: Width and thickness of

BECy

sample measured by caliper.

Clamped the sample in DMA 800 to

obtain a

height of 10mm.

Screen cover placed over the sample.

Software programming:

Thermal Advantage NT software

was

used.Tested Temperatures: 260, 270, 280, 290, and 300 ºCFrequency Range: 1-100 Hz, 11 points per temperature. Amplitude: 5µm; Preload: 0.1N; Force Track: 125%.

Fig 1. Sample in DMA 800

Sample

Fig 4. Log-log graph of modulus versus frequency after TTS shifting

Shift

in Temperature

Shift Factor260 °C  270 °C 21270 °C  270 °C 1280 °C  270 °C 0.1899290 °C  270 °C 0.0753300 °C  270 °C 0.1899

Table 1. Shift Factors used to generate TTS plot