GDR AMC2-22 octobre 2013

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GDR AMC2 - 22 octobre 2013

Guilherme DE OLIVEIRA REIS

Frédéric BONFILS

a

_{, Paul MENUT}

a

_{, Laurent VAYSSE}

a

_{, Yacine HEMAR}

b

_{et Christian SANCHEZ}

a

Coagulation acide du latex d’ Hevea brasiliensis : Agrégation et gélification de particules colloïdales Coagulation acide du latex d’ Hevea brasiliensis : Agrégation et gélification de particules colloïdales

Coagulation acide du latex d’Hevea brasiliensis :

Agrégation et gélification de particules colloïdales

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Guilherme DE OLIVEIRA REIS • GDR AMC2 22/10/2013

₂

Introduction

10 M

Tons/year

30 million people

Reduce the variability of the quality of natural rubber

Socio-economic and environmental issues

Context of Natural Rubber

Goal

Identify and characterize the structuration of the natural rubber

Unique properties

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₄

Polyisoprene

–

Proteins

–

Phospholipids

d ~ 1 µm

pHi ~ 3.2

d

Commercial Natural Rubber Latex

ϕv = 0.6

Dialyzed : TRIS-HCl buffer (pH = 8.5, I = 7 mM)

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Results

Aggregation (Фv, size, pH,…)

Colloidal gel (Rheology, Фv,)

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₆

Acidification :

addition of Glucono- -lactone (GdL)

Glucono- -lactone (GdL)

Gluconic Acid

H

2

O

(7)

Turbidity

DWS

Granulo-polarimetry

_SLS

(8)

₈

SLS

Aggregation : during acidification

(9)

Aggregation : long times

<1 hours

7 days

(10)

₁₀

Aggregation : long times

<1 hours

7 days

14 days

35 days

(11)

Aggregation : long times

<1 hours

7 days

14 days

35 days

SLS

(12)

₁₂

Phase diagram

<1 hours

7 days

14 days

35 days

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Phase diagram

<1 hours

7 days

14 days

35 days

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₁₄

Gelation

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Rheological properties of gel

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₁₆

G’

₀

= f (Фv)

Conditions :

20°C, 4H, 1Hz, 0.5% Strain

G’ (close), G” (open)

Ф

_v

= 0.4

,

Ф

_v

= 0.18 ,

Ф

_v

= 0.1 ,

Ф

_v

= 0.05

, Ф

_v

= 0.025

G’,G” = f (time)

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G’

_{0 α}

Фv

3.35 G’

₀

= f (Фv)

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₁₈

Shih and al.

Physical

Review A, 1990, 42, 4772-4779

Hagiwara et al. Food Hydrocolloids, 1998, 12, 29-36.

5%

Limit strain of linearity

γ

_{0 α}

Фv

-1.77

pH 8.5 (t=0)

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Wu and Morbidelli. Langmuir. 2001. 17, 1030-6

A = 3.35 , B = -1.77 , d = 3 , α = 0 (strong link regime)

x (backbone fractal dimension) = 1.1 to 1.3

Wu and Morbidelli model

D

f

= 1.8

Fractal dimension

G’

_{0 α}

Фv

A

_et

γ

(20)

Non linear regime

20 T.C. Gisler, R.C. Ball, D.A. Weitz, Phys. Rev. Lett. 82 (1999) 1064

Pouzot and al, JCIS. 293 (2006), pp. 376–383

G’

_max

G’

₀

Strain Hardening

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Strain Hardening

G’ max

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₂₂

Strain Hardening

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Strain Hardening

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₂₄

Strain Hardening

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Irreversibility

Hardening of the plateau

Strain Hardening

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₂₆

Irreversibility

Hardening of the plateau

Strain Hardening

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Irreversibility

Hardening of the plateau

Strain Hardening

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₂₈

Irreversibility

Hardening of the plateau

Strain Hardening

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Фv

Interaction

density ??

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₃₀

Conclusion

Aggregation :

phase diagram

(pH, Φ

v

, temps)

Colloidal Gel :

D

f

= 1.8

,

DLCA

and

Strong link

regime

Strain hardening

(Φ

v

, irreversibility)

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Guilherme DE OLIVEIRA REIS

Thank you for your attention

Coagulation acide du latex d’Hevea brasiliensis :

Agrégation et gélification de particules colloïdales