tratamiento de pulpas para su aplicación en materiales...
TRANSCRIPT
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Tratamiento de pulpas para suaplicación en materiales
cementícios
Holmer Savastano Junior
FZEA USP Brasil
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Preparación de la pulpacelulosica
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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
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Ensaio de flotacão - Fibras modificadas com n-octadecil-isocianato
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• 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
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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).
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Short x long pulp fibers
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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
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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
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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
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• 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
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Refining
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Fiber microstructure
Individual filaments
Original sliver
Bunch of individual fibres
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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
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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.
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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
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Surface treatments
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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
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Fibras após modificação com metacriloxipropiltri-metoxisilano (MPTS) e
aminopropiltri-etoxisilano (APTS)
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Tratamento das macrofibrasvegetais
• Propriedades das fibras vegetais• Tipos de tratamento• Alterações nas caraterísticas das fibras
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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 ** ** ** ** ** **
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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
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SEM images of pyrolyzed banana fibers
Banana leaf fiberleft x 200right x 5000
Banana trunk fiberleft x 200right x 5000
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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
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• 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
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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.
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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.