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

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 * style="background-color: #EEE"|[[Image:owwnotebook_icon.png|128px]] LAOS study on physical gelation
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 * style="background-color: #F2F2F2" align="center"|  |Main project page


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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

Frequency Sweep
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
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.

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

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

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

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

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

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

Frequency Sweep
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 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.

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

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


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