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

Transcription

1 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 Reims cedex 2 -FRANCE IAWS- Wednesday August

2 Context Chemistry of the cell wall, interactions Minor constituants: water, extractives Salmen & Olsson,

3 Glassy state Context Mobility and glass transition Tg Rubbery state high interaction low interaction + Interactions Tg Tg + mass Addition of plasticizers: + Structure of the environnement + reticulation - Extractives removal affect the mobility of amorphous polymers (Bag et al., Holzforschung, 2011) Mechanical Properties - Work on impregnation of cane (Arundo donax L.) by extractives (Obataya,1999) - Work on fracture properties of tropical woods function to the % of lignin (Bardet, 2003) 4

4 Aim of the research Chemical composition extractives Organization Mobility = f (order, M w, interactions) Mechanism?? Macroscopic properties By which mechanism these molecules intervene in the environment of the in situ polymers? Are there any correlations between the different properties? 5

5 Plant material Woody hemp core Epidermis Primary fibers Secondary fibers Vascular cambium Gap B. Chabbert, INRA REIMS 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) Xylem Cross-section of hemp stem 6

6 Experimental set-up overview Woody hemp core Piece of woody hemp core extracted raw Extractions: - 1) Toluene (2v/v) ethanol (Tet) - 2) Ethanol 95% (EtOH) - 3) Water - 4) All combined Thermal Conditions: - at boiling temperature of solvants (Soxlhet) - at ambiant temperature Biochemical analysis Extractives - Hemicelluloses - Lignins - Proteins - Ash Correlations? Residual Viscoelastic properties, ΔTg - DMA (lignin) - DEA (hemicelluloses) Mechanical properties - Four point bending test 7

7 Chemical composition of extractives Solvents containing extractives Lyophilization Obtained products: Quantification of following compounds: - Polysaccharides (HPLC) - Phenolic compounds( UV) - Proteins (UV) - Ashes (gravimetry) extractives mobility breaking 8

8 Viscoelastic properties of wood glassy Transition vitreuse Glass transition, Tg rubbery Dynamic mechanical analysis, DMA Lignin relaxation, Special condition: Ethylene glycol immersion Stress application γ, strain measurement σ Di-Electric analysis, DEA Hemicelluloses relaxation Special condition: 65% RH Tension application, current measurement DEA DMA extractives mobility breaking Salmen,

9 Four point bending test Mechanical properties of wood slope X F max Woody hemp core d max F max => strain d max => elongation W 20% => fracture energy slope => elastic modulus extractives mobility breaking 10

10 Approach and analysis of results Composition of extractives Viscoelastic properties Tg Lignin Tg Hemicelluloses? Mechanical properties Breaking Elasticity 11

11 Principal Component Analysis All measurements combined Polarity Study of solvent effects taking into account the temperature effects Temperature 12

12 Research of major correlations Separating study by extraction temperature Correlation index Cold condition Hot condition Seperating temp. effects leads to - Tg Lignin <=> breaking properties of woody hemp core - Tg Hemicelluloses <=> elastic properties of woody hemp core in hot condition But these correlations don t exist in cold condition mobility extractives? breaking 13

13 Chemical composition of extractives 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 14

14 Variation of glass transition temperatures of in situ polymers 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? 15

15 Correlations: extractives / mobility Correlation index Cold condition Hot condition 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 extractives mobility breaking 16

16 Variations of mechanical properties Experiments => acces to diff. responses: σ max, E, W 20%, d max Calculation of W= W treated -W raw Increase of energy Tol/EtOH et EtOH Material becomes stiffer No effects observed on samples extracted with water or including water Lignin extracting solvents have a clear impact on breaking 17

17 Correlations : extractives / breaking Cold condition Hot condition Correlation index Lignin extraction has a real impact on breaking Evidence of an additionnal correlation between extraction yield and elasticy mobility extractives breaking 18

18 Discussions lignins Opposite effects observed on Tg lignin and hemicelluloses: - Mechanisms different? - Linkage between both polymers? Clear effect of the extraction on mobility observed => Plasticizing or rigidification function to the amorphous phase considered extractives extractions Tg increase hemicelluloses extractions water Tg decrease 19

19 Discussion Importance of the extraction of a portion of lignin-like components => impact on mobility => impact on breaking properties 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. 20

20 Conclusions Extractives Phenolic compounds Polysaccharides Lignin Mobility Breaking Viscoelastic properties Tg Lignin Tg Hemicelluloses Mechanical properties Fracture energy Elasticity 21

21 Relationships between biochemistry, modulation of cell wall viscoelastic properties and fracture behaviour in woody hemp core by correlation study R. BAG Thanks for your attention Financial support: Region Champagne-Ardenne / INRA 22

22 National Institute of Agronomical Research -INRA Material Science Team Moulin de la Housse, Bât Reims Cedex 2 FRANCE Rahime.bag@reims.inra.fr 23