User:Andrew Sun/Notebook/LAOS study on physical gelation/2009/05/11

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LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Find the critical gel point

Samples

Gels from 5 wt% PAAc solution (Mv=31000): f=1.73e-3 (f=[Fe(III)]/[COOH])

Instruments

ARES Rheometer

Results

Frequency Sweep

Fig. 1
Fig. 1

It is shown in Fig. 1 that the sample was above but near the critical gel point. After LAOS the sample dissociate and locate below the critical gel point.

FT-Rheology

Fig. 2
Fig. 2

It is shown in Fig. 2 that the 3rd harmonic started to appear from strain amplitude of 300%. There is a curious drop at a mediate strain amplitude in both f values of gel samples, although the nonlinearity of the f=1.73e-3 sample is generally higher than the f=1.30e-3 sample.

LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Find the critical gel point

Samples

Gels from 5 wt% PAAc solution (Mv=51100): f=1.73e-3 (f=[Fe(III)]/[COOH])

Instruments

ARES Rheometer

Results

Freqency Sweep

Fig. 3
Fig. 3

It is shown in Fig. 3 that both f=1.73e-3 and f=1.30e-3 samples are above the critical gel point.

FT-Rheology

Fig. 4
Fig. 4

As is shown in Fig. 4, above the critical gel point, the nonlinearity is higher in the sample nearer to the gel point.

LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Find the critical gel point

Samples

Gels from 5 wt% PAAc solution (Mv=44500): f=1.87e-3 (f=[Fe(III)]/[COOH])

Instruments

ARES Rheometer

Results

Frequency Sweep

Fig. 5
Fig. 5

Fig. 5 shows that the sample underwent dissociation after LAOS experiment.

FT-Rheology

Fig. 6
Fig. 6

There is also a drop at mediate strain amplitude, as seen in Fig. 6.

LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Find the critical gel point

Samples

Gels from 5 wt% PAAc solution (Mv=22900): f=1.73e-3 (f=[Fe(III)]/[COOH])

Instruments

ARES Rheometer

Results

Frequency Sweep

Fig. 7
Fig. 7
Fig. 8
Fig. 8

Dissociation occured after LAOS experiment (Fig. 7). Fig. 8 shows the frequency sweep of f=1.30e-3 and f=1.73e-3 samples.

FT-Rheology

Fig. 9
Fig. 9

Fig. 9 shows that the nonlinearity decreases after a strain amplitude of 1100%. No higher harmonic detected at 1900%. The sample may have been seriously dissociated during LAOS experiment.

LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Find the critical gel point

Samples

Gels from 5 wt% PAAc solution (Mv=22400): f=1.15e-3, 1.44e-3(f=[Fe(III)]/[COOH])

Instruments

ARES Rheometer

Results

Frequency Sweep

Fig. 10
Fig. 10
Fig. 11
Fig. 11
Fig. 12
Fig. 12

Fig. 10 and 11 show that both samples underwent significant dissociation after LAOS experiment. Fig. 12 show that f values of 1.15e-3, 1.30e-3 and 1.44e-3 are below, at, and above the gel point, respectively.

FT-Rheology

Fig. 13
Fig. 13

Fig. 13 shows that there are no significant difference in nonlinearity between the three samples.


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