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

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

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

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

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 shows that the sample underwent dissociation after LAOS experiment.

FT-Rheology

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. 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 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. 11
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 shows that there are no significant difference in nonlinearity between the three samples.