C

H

L

O

HOW IMPURITIES (HEMICELLULOSES, INK AND LIGNIN)

AFFECT THE FUNCTIONALIZATION OF CELLULOSE FIBRESA. Salvador1, J. Hidalgo1, M. Azpeitia1, P. Orsolini2, P. Tingaut2, T. Zimmermann2 and A. Tejado1

1Tecnalia Research & Innovation, Sustainable Construction Div., Spain

2EMPA, Swiss Federal Laboratories for Materials Science and Technology, Switzerland

CELLULOSE SAMPLES

Objective Cellulosic fibres offer sustainable reinforcement for polymer-based biocomposites (e.g. WPC), but usually require some chemical modification to

achieve good compatibility. Since cellulose reactivity largely depends on pulp characteristics, especially on purity of the samples, the reaction rate of four different pulp

samples, namely bleached softwood kraft (b-SKP), virgin thermo-mechanical (TMP), recycled TMP and acetosolv weat straw, has been compared. Functionalization of

cellulose fibres has been carried out through a set of oxidation reactions expected to benefit fibrillation and thus reinforcing ability.

Conclusions The impurities present on recycled newspapers (mainly ink and inorganic fillers) delay the reactivity of cellulose fibres, apparently by hampering

the diffusion of reactants into the fibre wall and buffering the reaction medium at alkaline pH. Virgin TMP, with no buffering effect, shows a rapid pH evolution and fast

reaction related to the damaged fibres and extensive presence of fines. On the other hand, the hemicelluloses present on wheat straw pulp participate of the reaction

and increase the overall rate due to their ready accessibility. Furthermore, the short and thin-walled WS fibres also collaborate to accelerate the reaction by allowing a

rapid diffusion of reactants into the fibre wall, contrary to the thick-walled non-damaged softwood kraft pulp. Regarding the reaction yield, measured here as total [H+]

generated, hemicelluloses (WS) do contribute to increase the total amount, while lignin (TMP) and impurities (Recycled) reduce the extent of the reaction. This work

also states that the pH range for maximum reaction rate is not significantly affected by the presence of the impurities.

La Compagnie Industrielle de la Matière Végétal, FR (Bouchra Benjelloun) and ECOPulp Oy, FI (Ari Hentonnen),

valuable partners of the INNOBITE consortium, and Smurfit Kappa Nervion, ES (Javier Pérez) are greatfully acknowledged for providing the pulp

samples for this study. Esther Strub and Anja Huch (EMPA, CH) are greatfully acknowledged for the SEM imaging.

Cell-A Cell-B Cell-C Cell-D

b-SKP TMP Recycled WS

Bleached

Softwood Kraft

Virgin Thermo

Mechanical

Recycled

TMP

Acetosolv

Wheat Straw

1000 µm 1000 µm

FUNCTIONALIZATION

Chemistry A well-known and highly efficient

reaction (carboxylation of dialdehyde cellulose)[1]

was used to compare the behaviour of the different

pulps under equal conditions.

Fibrillation (SEM of Cell-A)

Kinetics Oxidation reactions were initially

monitored through pH evolution. Proton (H+)

generation rate and yield were determined.

Effects on fibres The presence of negatively charged groups induces

fibrillation and disintegration of fibres.

Fib

res

be

fore

tre

atm

en

t(S

EM

)

Sample pH for Rmax pH for R>80%

Cell-A 4.2 4.2 - 4.5

Cell-B 4.3 4.2 - 4.5

Cell-C 3.9 3.8 - 4.5

Cell-D 4.2 4.1 - 4.3

Disintegration (Optical Micrographs of Cell-A)

Reaction rate (R) vs pH

Reaction yield vs time1000 µm 1000 µm

IMPURITIES

Highly pure High lignin % ≈30% ink + inorganics High hemicellulose %

FIBRES

Non-damaged Damaged with lots of fines Highly damaged Short and thin-walled

COMPOSITION (%)

(C: Cellulose, H: Hemicellulose, L: Lignin, O: Other impurities)

99.5 58.7 36.2 58.2

0.5 14.3 25.8 40.3

0 26 8.4 1.3

0 1 29.6 0.2

References[1] Tejado et al. 2012

Cellulose 19(3):831-842; Yan

et al. (2012) Langmuir

28:7834-7842; Tejado et al.

(2011) Prov. Patent Appl.

USPTO 61/450,222.

100 µm

200 µm

100 µm1000 µm

Acknowledgements

3

4

5

6

7

8

9

10

0 1 2 3 4 5

Time (h)

15 20

Diffusion of reactants into the fibre wall

pH

pH vs time