Tratamiento de pulpas para suaplicación en materiales

cementícios

Holmer Savastano Junior

FZEA USP Brasil

Preparación de la pulpacelulosica

Algunos tipos de tratamientos

• Modificação mecânica das fibras celulósicas (refino / fibrilação das fibras)

• Branqueamento das fibras celulósicas• Modificação por configurações de micelas• Modificação superficial com silanos• Modificação superficial com isocianatos• Modificações com ácidos e anidridos

Ensaio de flotacão - Fibras modificadas com n-octadecil-isocianato

• Modificação por descargas elétricas e técnicas de irradiação– Descargas tipo corona, descargas de plasma e,

mais recentemente, laser, raios-gama e irradiação ultra-violeta (UV) em vácuo

• Modificação via polimerização por abertura de anéis– Oxipropilação parcial das fibras celulósicas

• Modificação via deposição de nanopartículasinorgânicas/poliméricas– Uso de nanocristais semi-condutores de sulfeto

de cádmio (CdS) e nanopartículas catiônicas poliméricas na superfície de fibras celulósicas para torná-las fotoluminescentes;

– Precipitação de nanopartículas de dióxido de titânio na superfície de fibras para melhorar as propriedades ópticas da celulose

Cement based composites - Problem addressed

The need for low cost fiber-cement with acceptable performance under aggressive climates (durability of the products).

Availability of the raw-materials commonly used in the manufacture of the asbestos-free fiber-cement.

Demand for alternative raw-materials, as appropriate fibers and binders and inert fillers, to substitute traditional ones (high cost and large consumption of energy).

Short x long pulp fibers

Eucalyptus x Pine pulp

Eucalyptus pulp fibres0.83 ± 0.01 mm

Pinus pulp 2.40 ± 0.09 mmless heterogeneous in length

Short fibresHigher number of fibres per volumeor weight

The smaller the fibre length, the easier the fibre dispersion

Effect on flocullation

0369

1215

0.2

- 0.3

0.9

- 1.0

1.6

- 1.7

2.3

- 2.4

3.0

- 3.1

3.7

- 3.8

4.4

- 4.5

5.1

- 5.2

5.8

- 5.9

6.5

- 6.6

Length ranges (mm)

Frac

tion

(%) Eucalyptus pulp

Pinus pulp

05

10152025

20 30 40 50 60Median chord size (�m)

Num

ber f

ibre

s (10

6 /g)

increasing refining

Eucalyptus

Pinus

Results – BSEI SEM

The short Eucalyptusbetter distributed

The higher number of bridging fibers

Increasing MOR and toughness of the composite.

Eucalyptus

Pinus

Summary of different treatmentsto the fibres

Bleaching

Bleaching

Eucalyptus bleachedEucalyptus unbleached

Effect of pulp bleaching

Bleaching extract the fibre components (lignin and extractives from fibre cell wall).

1 m 1 m

Mechanical results

After 28 days of cure Cement composite with Pinuspulp higher mechanical performance

After 200 accelerated ageing cyclesCement composite with Eucalyptus pulp significantly highermechanical performance

0.00 0.02 0.04 0.06 0.08 0.10

0

2

4

6

8

10

12

(MPa

)

(mm/mm)

Eucalyptus unbleached Eucalyptus bleached Pinus unbleached Pinus bleached

28 days

0.00 0.02 0.04 0.06 0.08 0.10

0

2

4

6

8

10

12

(M

Pa)

(mm/mm)

Eucalyptus unbleached Eucalyptus bleached Pinus unbleached Pinus bleached

200 cycles

Mineralization of the fibre

Eucalyptus bleached

Eucalyptus unbleached

Extensive fibre mineralization

Decrease in mechanical properties after accelerated ageing.

0369

121518

28 days 200 cycles

MO

R (M

Pa)

a

0

2

4

6

8

28 days 200 cycles

Toug

hnes

s (kJ

/m2 )

c

• Alkali treatment– dissolves hemicellulose and lignin by hydrolyzing

acetic acid esters and by swelling cellulose

• Acid treatment– The lignin in hardwood species is partly dissolved

by sulfuric acid during the acid hydrolysis

• Pyrolysis treatments– The pyrolysis of lignin occurs in inert atmospheres

at high temperatures

– The thermal decomposition of the lignin is also affected by the acid pretreatment

Refining

Fiber microstructure

Individual filaments

Original sliver

Bunch of individual fibres

Results - AFM

Eucalyptus fibres: more fibrillarstructure.

Pinus fibres: the typical surface structure was granular.

The fibrillar surface structures of the Eucalyptus fibres higher roughness(RMS = 74 ± 18 nm) than Pinus fibres(RMS = 52 ± 10 nm).

Indicative of the higher potential of the Eucalyptus fibres to anchorage in the cement matrix.

Eucalyptus

Pinus

Drainage Parameters

050100150200250

0200400600800

Pulp freeness (CSF mL)

Dra

inag

e ra

te (g

/s)bincreasing

refining

40

60

80

100

32 34 36 38 40Water retention (%)

Solid

s ret

entio

n (%

)

increasing refining

Pinus

Eucalyptusc

Higher number of fibres did not prejudice the drainage rate of the fibre-cement suspensions.

Significant improvement of the solids retention during the dewatering of the suspension (18 mesh = 0.9 mm).

Possible to improve the solids retention of the Pinuspulp increasing the refining.

Refining

Effect of refining

Increase in fibre-matrix anchorage after 28 days of cure;

Decay in toughness after accelerated ageing.

0.00 0.02 0.04 0.06 0.08 0.10 0.120

2

4

6

8

10

12

(M

Pa)

(mm/mm)

200 cycles

Euc unbleached (unrefined) Euc unbleached (CSF 250 mL)

0.00 0.02 0.04 0.06 0.08 0.10 0.120

2

4

6

8

10

12

(mm/mm)

(M

Pa)

Euc unbleached (unrefined) Euc unbleached (CSF 250 mL)

28 days

Surface treatments

Surface treatments

Effect of surface modification of the pulp fibreswith silanes

Decrease mineralization of fibers

Small improvement in the mechanical properties.

Fibretreatment

ConditionLOP (MPa)

MOR (MPa) TE (kJ/m2)

Unmodified 28 days

6.9 ± 1.1 9.9 ± 1.4 0.86 ±

0.25

Modified 6.5 ± 1.0 10.7 ±

1.30.83 ±

0.46

Unmodified 200 cycles

6.3 ± 0.9 7.5 ± 0.5 0.13 ±

0.07

Modified 7.2 ± 0.9 8.0 ± 1.00.30 ±

0.12

Unmodified

Modified

Fibras após modificação com metacriloxipropiltri-metoxisilano (MPTS) e

aminopropiltri-etoxisilano (APTS)

Tratamento das macrofibrasvegetais

• Propriedades das fibras vegetais• Tipos de tratamento• Alterações nas caraterísticas das fibras

Nature of the fiber

Chemical composition (%)

[ ± Cumulative standard deviation]

Elemental composition (%)

Moisture Lignin Cellulose Hemicellulose Extractives C O H N Ash

Coconut coir

13.68

[±0.05]

46.48

[±1.73]

21.46

[±1.44]

12.36

[±2.34]

8.77

[±0.39]

46.22

[±0.03]

40.47

[±0.03]

5.44

[±0.03]

0.36

[±0.002]

1.05

[±0.05]

Coconut sheath

5.90

[±1.84]

29.7

[±4.36]

31.05

[±2.88]

19.22

[±3.46]

1.74

[±0.71]

42.23

[±0.21]

45.57

[±0.23]

5.69

[±0.03]

0.44

[±0.002]

8.39

[±0.03]

Bagasse 5.64

[±1.60]

22.56

[±2.26]

39.45

[±2.41]

26.97

[±2.52]

4.33

[±0.74]

48.6*

**

45.1*

**

6.3*

**

**

**

3.5*

**Banana trunk

(Guad.)

9.74

[±1.42]

15.07

[±0.66]

31.48

[±3.61]

14.98

[±2.03]

4.46

[±0.11]

36.83

[±0.18]

43.62

[±0.22]

5.19

[±0.02]

0.93

[±0.005]

8.65

[±0.03]

Banana trunk

(Brazil)

** 5 63 - 64 19 ** ** ** ** ** **

Banana leaf

11.69

[±0.03]

24.84

[±1.32]

25.65

[±1.42]

17.04

[±1.11]

9.84

[±0.11]

44.01

[±0.22]

38.84

[±0.19]

6.10

[±0.03]

1.36

[±0.007]

7.02

[±0.03]

Arrow Root D1

10.68 26.96 37.73 31.70 2.51 ** ** ** ** **

Arrow Root D2

11.36 22.50 39.99 31.19 3.77 ** ** ** ** **

Sisal ** 7.6 – 9.2 43 – 56 21 – 24 ** ** ** ** ** **

Softwood ** 26-34 40-45 7-14 ** ** ** ** ** **

Fiber Untreated fiber dimensions [st. dev.] Aspect ratio L/wLength (mm) Width (µm) Thickness (µm)

Untreated Pyrolysis Acid Alkaline Silane

Arrow Root (D1)

5.77

[±3.35]

140.48

[±86.14]

83.03

[±38.6]41-70 41 – 82 nd nd nd

Arrow Root (D2)

5.45

[±2.01]

104.17

[±46.98]

64.58

[±29.61]52-85 43 – 59 nd nd nd

Bagasse (B) 3.69

±2.15]

567 .5

[±329.4]

161.25

[±90.75]6,5-23 6 – 23 6-13 4-15 8

Banana Trunk (BT)

1.9

[±0.64]

820.24

[±264.49]

150.29

[±86 .94]2,3-12,6 6 - 23 8-19 10-27 nd

Banana Leaf (BL)

1.70

[±0.91]

834.52

[±245.94]

160.42

[±55 .26]2-11 2 - 16 nd nd nd

Coconut Coir (CC1)

29.35

[±8.17]

331.78

[±198.72]

273.57

[±150.94]88-107 84 - 103 nd nd nd

Coconut Coir (CC2)

2.7

[±2.46]

683.21

[±279.42]

215

[±98.67]4-13 3 -10 nd Nd nd

Coconut Sheath (CT)

5.47

[±3.08]

338.09

±258.23]

177.68

[±134.76]16-31 20 - 35 nd Nd nd

SEM images of pyrolyzed banana fibers

Banana leaf fiberleft x 200right x 5000

Banana trunk fiberleft x 200right x 5000

Tensile strength of treated and untreated fibers

0

100

200

300

400

500

600

700

Acidic treatment Basic treatment Pyrolysis No treatment Treatment of the Fibers

Ten

sile

Str

engt

h (M

Pa)

Bagasse Banana trunk

• Scanning electron micrography of bagasse fibers

•a) Unpyrolyzed fiber b) Pyrolyzed fiber c) Unpyrolyzed fiber treated with silane S1 d) Pyrolyzed fiber treated with silane S1 e) Unpyrolyzed fiber treated with silane S2 f) Pyrolyzed fiber treated with silane S2

Comentários adicionais

• Importância do preparo da fibra.• Destaque para o tratamento de

branqueamento x não branqueamento no caso do Eucalipto.

• Importância do refino para o processo no casoda fibra de Pinus.

• Interesse no processo de pirólise ematmosfera inerte.

Lectura complementar

• G.H.D. Tonoli, H. Savastano Jr., E. Fuente, C. Negro, A. Blanco, F.A. Rocco Lahr. Eucalyptus pulp fibres as alternative reinforcement to engineered cement-based composites. Industrial Crops and Products, 31 (2010) 225–232.

• G.H.D. Tonoli , U.P. Rodrigues Filho, H. Savastano Jr., J. Bras, M.N. Belgacem, F.A. Rocco Lahr. Cellulose modified fibres in cement based composites. Composites: Part A 40 (2009) 2046–2053.

• M.-A. Arsène, K. Bilba, H. Savastano Jr., K. Ghavami. Treatments of non-wood plant fibers used as reinforcement in composite materials. In preparation.