Relationships between biochemistry, modulation of cell wall viscoelastic properties and fracture behaviour in woody hemp core by correlation study

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Relationships between biochemistry, modulation of cell wall viscoelastic properties and fracture behaviour in

woody hemp core by correlation study

Rahime Bag

To cite this version:

Rahime Bag. Relationships between biochemistry, modulation of cell wall viscoelastic properties and fracture behaviour in woody hemp core by correlation study. IAWS annual meeting 2011, International Academy of Wood Science (IAWS). Victoria, AUS., Aug 2011, Stockholm, Sweden. 22 p. �hal- 02808339�

IAWS- Wednesday August 2

Relationships between

biochemistry, modulation of cell wall viscoelastic properties and fracture behaviour in woody hemp

core by correlation study

Rahime BAG

INRA Reims – UMR FARE

2, esplanade Roland Garros - BP 224 51686 Reims cedex 2 -FRANCE

3

Context

Salmen & Olsson, 1998 Chemistry of the cell wall, interactions

Minor constituants: water, extractives

Tg

4

Glassy state Rubbery state

high interaction low interaction

Tg

+ Interactions + mass

+ Structure of the environnement + reticulation

IAWS- Wednesday August 31 - 2011

Context

Mobility and glass transition Tg

Addition of plasticizers:

Mechanical Properties

- Work on fracture properties of tropical woods function to the % of lignin (Bardet, 2003) - Work on impregnation of cane (Arundo donax L.) by extractives (Obataya,1999)

- Extractives removal affect the mobility of amorphous polymers (Bag et al., Holzforschung, 2011)

5

Aim of the research

?

Mobility Chemical

composition Organization

Macroscopic properties

= f (order, M_w, interactions)

extractives

Mechanism?

By which mechanism these molecules intervene in the environment of the in situ polymers?

Are there any correlations between the different properties?

Plant material – Woody hemp core

• Industrial co-product, huge production

• from separation of hemp stem long fibers

• New application: in composites:

- in buildings

- with thermoplastic matrix ( industrial compounds/automotive)

Epidermis

Primary fibers

Xylem

Vascular cambium Secondary

fibers Gap

Cross-section of hemp stem

B. Chabbert, INRA REIMS

Woody hemp core :

7

Woody hemp core

Extractions:

- 1) Toluene (2v/v) ethanol (Tet) - 2) Ethanol 95% (EtOH)

- 3) Water

- 4) All combined

Biochemical analysis

Extractives

- Hemicelluloses - Lignins

- Proteins - Ash

Experimental set-up overview

Correlations?

Residual

Viscoelastic properties, ΔTg - DMA (lignin)

- DEA (hemicelluloses) Mechanical properties - Four point bending test Piece of woody

hemp core

extracted raw

Thermal Conditions:

- at boiling temperature of solvants (Soxlhet) - at ambiant temperature

-

Polysaccharides (HPLC)

Phenolic compounds( UV)

Proteins (UV)

-

Ashes (gravimetry)

Solvents containing extractives

⇒

Lyophilization Obtained products:

⇒

Quantification of following compounds:

Chemical composition of extractives

extractives

breaking mobility

9

Dynamic mechanical analysis, DMA Lignin relaxation,

Special condition: Ethylene glycol immersion

Stress application γ, strain measurement σ Hemicelluloses relaxation

Special condition: 65% RH

Tension application, current measurement Di-Electric analysis, DEA

Transition vitreuse

glassy

rubbery

Glass transition, Tg

Viscoelastic properties of wood

DEA

DMA

Salmen, 1982

extractives

breaking

mobility

Four point bending test

F_max => strain

d_max => elongation

W_20% => fracture energy slope => elastic modulus

Woody hemp core

X F_max

d_max

slope

extractives

breaking

mobility

Mechanical properties of wood

11

Composition of extractives

Mechanical properties Breaking

Elasticity Viscoelastic properties

Tg Lignin

Tg Hemicelluloses

Approach and analysis of results

?

Principal Component Analysis

All measurements combined

Temperature

P o la rity

Study of solvent effects taking into account the

temperature effects

13

Separating study by extraction temperature

- Tg Lignin <=> breaking

properties of woody hemp core - Tg Hemicelluloses <=> elastic properties of woody hemp core Seperating temp. effects leads to

Research of major correlations

extractives

breaking mobility

?

Cold condition Hot condition

But these correlations don’t exist in cold condition in hot condition

Correlation index

Extractives represent a really low proportion in the dry matter (max 5%)

Less extractives with toluene and ethanol (0.6%)

Essentially (70% of extractives) phenolic compounds (lignins?) extracted with toluene and ethanol

Essentially (30%) inorganic compounds and (35%) neutral sugars (hemicelluloses?) with water extraction

Modulation of extractives in quantity et quality according to solvents and thermal conditions

Chemical composition of extractives

15

Calculation of ∆Tg= Tg_treated-Tg_raw

Higher difference on hemicelluloses

Higher influence on successive extractions

Opposite variations between polymers: link with the existence of interactions?

Variation of glass transition

temperatures of in situ polymers

Correlations: extractives / mobility

Lignin mobility correlated with extraction rate, protein and ashes in cold condition and with lignins extracted in hot condition

Hemicelluloses mobility correlated with lignins extracted in cold case and with all compounds extracted instead of lignins in hot case

Cold condition Hot condition

extractives

breaking mobility

Correlation index

17

Variations of mechanical properties

Experiments => acces to diff. responses:

, E, W

d

Material becomes stiffer

Lignin extracting solvents have a clear impact on breaking

Increase of energy Tol/EtOH et EtOH

No effects observed on

samples extracted with water or including water

Calculation of ∆W= W_treated-W_raw

Lignin extraction has a real impact on breaking

Evidence of an additionnal correlation between extraction yield and elasticy

Correlations : extractives / breaking

extractives

breaking mobility

Cold condition Hot condition

Correlation index

19

Discussions

Clear effect of the extraction on mobility observed

=> Plasticizing or rigidification function to the amorphous phase considered

extractions

extractives Tg increase

lignins

hemicelluloses

extractions

Tg decrease water

IAWS- Wednesday August 31 - 2011

Opposite effects observed on Tg lignin and hemicelluloses:

- Mechanisms different?

- Linkage between both polymers?

Importance of the extraction of a portion of lignin-like components

=> impact on mobility

=> impact on breaking properties

Discussion

⇒ Lignin content governs the stiffness to the plant

⇒ Importance of lignin and its intrinsic properties

More over, elasticity is not a property depending directly on

lignin content but significantly depending on hemicelluloses

content in cell wall.

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Extractives

Phenolic compounds Polysaccharides

Mechanical properties Fracture energy

Elasticity Viscoelastic properties

Tg Lignin

Tg Hemicelluloses

Lignin Mobility

 Breaking

Conclusions

Thanks for your attention

R. BAG

Financial support: Region Champagne-Ardenne / INRA

Relationships between biochemistry,

modulation of cell wall viscoelastic

properties and fracture behaviour in

woody hemp core by correlation study

23

National Institute of Agronomical Research -INRA Material Science Team

Moulin de la Housse, Bât 18 51687 Reims Cedex 2 – FRANCE Rahime.bag@reims.inra.fr