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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, Mw, 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
Fmax => strain
dmax => elongation
W20% => fracture energy slope => elastic modulus
Woody hemp core
X Fmax
dmax
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= Tgtreated-Tgraw
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:
σmax, E, W
20%,d
maxMaterial 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= Wtreated-Wraw
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
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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
