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Characterization of natural rubber cup coagula maturation and its effect on dry rubber properties Jutharat Intapun Prof. Eric Dubreucq, Assoc. Prof. Dr.Varaporn Tanrattanakul, Dr. Laurent Vaysse, Dr. Jérôme Sainte-Beuve, Dr. Frédéric Bonfils
Introduction • • • •
Natural rubber (NR) is one of the major exported products of Thailand. Standard Thailand Rubber (STR), STR 20 Raw materials : field coagula Low consistency of the delivered raw material
Scope of work Physico-chemical environment -temperature - oxygen content -relative humidity
Maturation during storage Biochemical Reactions (microorganisms, enzyme)
Consequences on dry rubber properties? Po, PRI and mesostructure
Objective 1. Characterization of industrial maturation conditions 2. Scaling down : labscale maturation box and mini-process 3. Effect of microorganisms on cup coagula properties
Experimental
1. Characterization of industrial coagula pile maturation 1.1 Maturation conditions inside cup coagula pile 1.2 Cup coagula properties
Drilled stainless steel tubes (external diameter 5.1 cm, thickness 2mm, 5mm-diameter holes, 3000 holes/m2) 7m
3m
Cup coagula pile
20m
depth 0cm RH % Temp °C
50cm 3m
100cm
20cm
150cm 200cm
Digicon HT765232 Humidity/temperature meter probe
Figure1. Coagula maturation pile equipped with two drilled stainless steel tube
10kg
Delivery day
10 kg baskets
0 cm
10kg
50 cm
10kg
100 cm
10kg
150 cm
10kg
200 cm
10kg
Creping of 10 kg sample
Drying of crepe
Po, Po PRI and mesostructure
Processing After 24 days Figure 2. Cup coagula sampling for rubber properties determination
2. Scaling down : mini-process and labscale maturation box
2.1 Setting up of the mini-process Aim: Setting up a mini process leading to a dry rubber with properties comparable with the one produced by industrial process Adjusted parameters : 1. Number of passes in mini-creper 2. Temperature and duration of drying
Sampling 10kg of cup coagula
Industrial Creping Minicreper Creping
6 passes
Drying in Lab 120°C, (2,2.5,3h) Or 125°C, (2,2.5,3h) 130°C, (1.25,1.5,2h)
+7,11,12, or 16 passes Drying in Factory 129°C, 3h
21 passes Figure 3. Cup coagula Processing
2.2 Maturation device at labscale factory pile maturation -conditions -rubber properties
Factory to laboratory
laboratory maturation - Monoclonal coagula -T°, RH, O2 controlled and recorded
3. The effect of micro-organisms on cup coagula properties Clean Latex - Microorganisms controlled by antibiotic adding or various inoculum added
A:inoculum
B:inoculum
(Auto coag.)
(Acid coag.)
Coagula
Coagula
C:antibiotic
adding (Acid coa. Coagula Maturation boxes At 40C for 34 days
Processing and measure of properties
Results and discussion
Results and discussion
1. Industrial coagula pile maturation 1.1 Physico-chemical parameters (a)
40 35 30 25 20
(c)
Oxygen content (%)
o
90 Relative humidity (%)
45 Temperature ( C)
20
100
50
80 70 60 50 40 30
15
10
(b)
20
0
50
100 150 200
5
0
0 50 100 150 200 Depth of coagula pile (cm)
Depth of coagula pile (cm)
0
50
100
150
200
Depth of coagula pile (cm)
Figure 4. Temperature, Relative humidity and oxygen content with depth of the pile Measurements were performed at 8 AM (
), 12 AM (
) and 4 PM (
)
1.2 Properties of cup coagula from maturation pile Po (Po Unit) 5
10
15
20
0
25.9
-50
31.3
25
PRI (%)
30
35
40
45
0
5
10
36.9
-100
38.7
-150
-200
15
-50
40
45
50
47.3
-150
51.1
-200
50.6
45
50
1400
1500
41.6
-150
45.8
600 0
-100
40
36.5
-100
55
41.0 42.5
35
Mw (kg/mol)
Depth of pile (cm)
Depth of pile (cm)
0
35
30
-200
41.6
30
25
21.1
-50
Gel (% w/w) 25
20
25.9
0 Depth of pile (cm)
Depth of pile (cm)
0
700
800
900
1000 1100
1038.2
-100
1158.3
-200
1300
869.7
-50
-150
1200
1439.7
1458.7
Figure 5. Po, PRI, Gel content and Molar mass of cup coagula with depth of the pile
Results and discussion
2.1 Scaling down : the mini-process condition in laboratory
Results and discussion Sampling 10kg of cup coagula Industrial Creping
Minicreper Creping
6 passes
1616passes +7,11, and 18 passes
Drying in in Lab Lab Drying 120°C, (2,2.5,3h) Or 125°C, (2,2.5h,3h) 125oC for 2 hr 130°C, (1.25,1.5,2h)
Drying in Factory 129°C for 3hr
21 passes
50
45
Po (median)
40
35
30
25
20
120-2
120-2.5
120-3
125-2
125-2.5 130-1.25
130-1.5
control
Drying conditions
Po and PRI of cup coagula under various processing conditions 35
PRI
30 25 20 15 10 120-2
120-2.5
120-3
125-2 125-3 125-2.5 Drying conditions
control
2.2 Scaling down : Maturation boxes Nitrogen Tank
Dry Air
Maturation box
Humid air
Figure 6. Maturation device in Laboratory
Data logger
3. Cup Coagula after maturation in labscale device A. Physical aspect
Microorganisms No formic acid No antimicrobial agent
(A)
Microorganisms Formic acid No antimicrobial agent
(B)
Microorganisms (killed) Formic acid Antimicrobial agent
(C)
B. Initial Plasticity P0 and PRI of cup coagula 60
50 40
Po
30 20
P30
10 0
(B)
50 40 30 20 10 0
0
4
15
28
34
0
20 10
4
15
28
34
0
maturation time (days)
100
100
100
75
75
75
PRI
125
50
50
50
25
25
25
0
0
0
4
15
28
34
maturation time (days)
Microorganisms No formic acid No antimicrobial agent
0
4
15
28
34
maturation time (days)
Microorganisms formic acid No antimicrobial agent
4
15
28
34
maturation time (days)
125
PRI
PRI
30
125
0
(C)
40
0
maturation time (days)
PRI
50 Po (red) P30 (green)
(A)
Po (red) P30 (green)
P0 / P30
Po (red) P30 (green)
60
0
4
15
28
34
maturation time (days)
Killed microorganisms formic acid Antimicrobial agent
110
With antibiotic
100
Effect of microorganisms on PRI
90 80
PRI
70 60 50 40 30
With micro-organism
20 10 0 N+F+M+
N+F+M-
N-F+M+
N-F-M+
code
Each Pair Student's t 0.05
Effectof microorganisms initial concentration on PRI 120.0
The drop of PRI is proportional to the initial quantity of microorganisms in latex
3x104 CFU/ml
100.0
5x105 CFU/ml
80.0 PRI 60.0
2x10 CFU/ml 6
40.0
20.0
PRI Na azide (3E+4 cfu/ml) PRI Clean (5E+5 cfu/ml) PRI M (2E+6 cfu/ml) PRI 2M (9E+6 cfu/ml) PRI 4M (2E+7 cfu/ml)
2x107 CFU/ml
0.0 0
1
2
3 4 Maturation time (days)
5
6
Figure 7. The effect of microorganism activity on cup coagula properties
Conclusions (1) 1.Characterization Maturation conditions • Temperature and relative humidity of the air increased with depth. In contrast, oxygen content of the air within the pile decreased as depth increased. • Initial plasticity (P0), plasticity retention index (PRI), gel content and Mw were higher at the bottom of the pile.
Conclusions (2) 2. Setting up of the maturation box and mini-process •
Crepping : 16 passes on mini-creper
•
Drying : 2 hr at 125°C
Conclusions (3) 3. The role of micro-organism on cup coagula properties •
Po, PRI decreased with microorganism content and maturation time (antibiotic prevent those drops) • It was proven that the drop of PRI was proportional to initial quantity of microorganisms in the latex
Perspectives 1. Identify precisely the mode of action of this microorganisms during maturation : pure enzyme testing, isolation and test of specific strains 2. Study the microbial activity and its effect on rubber properties under various controlled conditions 3. Recommandations to improve the maturation on industrial site
Thank you for your attention
Introduction • • • •
Natural rubber (NR) is one of the major exported products of Thailand. Standard Thailand Rubber (STR), STR 20 Raw materials : field coagula Low consistency of the delivered raw material
Scope of work Physico-chemical environment -temperature - oxygen content -relative humidity
Maturation during storage Biochemical Reactions (microorganisms, enzyme)
Consequences on dry rubber properties? Po, PRI and mesostructure
Objective 1. Characterization of industrial maturation conditions 2. Scaling down : labscale maturation box and mini-process 3. Effect of microorganisms on cup coagula properties
Experimental
1. Characterization of industrial coagula pile maturation 1.1 Maturation conditions inside cup coagula pile 1.2 Cup coagula properties
Drilled stainless steel tubes (external diameter 5.1 cm, thickness 2mm, 5mm-diameter holes, 3000 holes/m2) 7m
3m
Cup coagula pile
20m
depth 0cm RH % Temp °C
50cm 3m
100cm
20cm
150cm 200cm
Digicon HT765232 Humidity/temperature meter probe
Figure1. Coagula maturation pile equipped with two drilled stainless steel tube
10kg
Delivery day
10 kg baskets
0 cm
10kg
50 cm
10kg
100 cm
10kg
150 cm
10kg
200 cm
10kg
Creping of 10 kg sample
Drying of crepe
Po, Po PRI and mesostructure
Processing After 24 days Figure 2. Cup coagula sampling for rubber properties determination
2. Scaling down : mini-process and labscale maturation box
2.1 Setting up of the mini-process Aim: Setting up a mini process leading to a dry rubber with properties comparable with the one produced by industrial process Adjusted parameters : 1. Number of passes in mini-creper 2. Temperature and duration of drying
Sampling 10kg of cup coagula
Industrial Creping Minicreper Creping
6 passes
Drying in Lab 120°C, (2,2.5,3h) Or 125°C, (2,2.5,3h) 130°C, (1.25,1.5,2h)
+7,11,12, or 16 passes Drying in Factory 129°C, 3h
21 passes Figure 3. Cup coagula Processing
2.2 Maturation device at labscale factory pile maturation -conditions -rubber properties
Factory to laboratory
laboratory maturation - Monoclonal coagula -T°, RH, O2 controlled and recorded
3. The effect of micro-organisms on cup coagula properties Clean Latex - Microorganisms controlled by antibiotic adding or various inoculum added
A:inoculum
B:inoculum
(Auto coag.)
(Acid coag.)
Coagula
Coagula
C:antibiotic
adding (Acid coa. Coagula Maturation boxes At 40C for 34 days
Processing and measure of properties
Results and discussion
Results and discussion
1. Industrial coagula pile maturation 1.1 Physico-chemical parameters (a)
40 35 30 25 20
(c)
Oxygen content (%)
o
90 Relative humidity (%)
45 Temperature ( C)
20
100
50
80 70 60 50 40 30
15
10
(b)
20
0
50
100 150 200
5
0
0 50 100 150 200 Depth of coagula pile (cm)
Depth of coagula pile (cm)
0
50
100
150
200
Depth of coagula pile (cm)
Figure 4. Temperature, Relative humidity and oxygen content with depth of the pile Measurements were performed at 8 AM (
), 12 AM (
) and 4 PM (
)
1.2 Properties of cup coagula from maturation pile Po (Po Unit) 5
10
15
20
0
25.9
-50
31.3
25
PRI (%)
30
35
40
45
0
5
10
36.9
-100
38.7
-150
-200
15
-50
40
45
50
47.3
-150
51.1
-200
50.6
45
50
1400
1500
41.6
-150
45.8
600 0
-100
40
36.5
-100
55
41.0 42.5
35
Mw (kg/mol)
Depth of pile (cm)
Depth of pile (cm)
0
35
30
-200
41.6
30
25
21.1
-50
Gel (% w/w) 25
20
25.9
0 Depth of pile (cm)
Depth of pile (cm)
0
700
800
900
1000 1100
1038.2
-100
1158.3
-200
1300
869.7
-50
-150
1200
1439.7
1458.7
Figure 5. Po, PRI, Gel content and Molar mass of cup coagula with depth of the pile
Results and discussion
2.1 Scaling down : the mini-process condition in laboratory
Results and discussion Sampling 10kg of cup coagula Industrial Creping
Minicreper Creping
6 passes
1616passes +7,11, and 18 passes
Drying in in Lab Lab Drying 120°C, (2,2.5,3h) Or 125°C, (2,2.5h,3h) 125oC for 2 hr 130°C, (1.25,1.5,2h)
Drying in Factory 129°C for 3hr
21 passes
50
45
Po (median)
40
35
30
25
20
120-2
120-2.5
120-3
125-2
125-2.5 130-1.25
130-1.5
control
Drying conditions
Po and PRI of cup coagula under various processing conditions 35
PRI
30 25 20 15 10 120-2
120-2.5
120-3
125-2 125-3 125-2.5 Drying conditions
control
2.2 Scaling down : Maturation boxes Nitrogen Tank
Dry Air
Maturation box
Humid air
Figure 6. Maturation device in Laboratory
Data logger
3. Cup Coagula after maturation in labscale device A. Physical aspect
Microorganisms No formic acid No antimicrobial agent
(A)
Microorganisms Formic acid No antimicrobial agent
(B)
Microorganisms (killed) Formic acid Antimicrobial agent
(C)
B. Initial Plasticity P0 and PRI of cup coagula 60
50 40
Po
30 20
P30
10 0
(B)
50 40 30 20 10 0
0
4
15
28
34
0
20 10
4
15
28
34
0
maturation time (days)
100
100
100
75
75
75
PRI
125
50
50
50
25
25
25
0
0
0
4
15
28
34
maturation time (days)
Microorganisms No formic acid No antimicrobial agent
0
4
15
28
34
maturation time (days)
Microorganisms formic acid No antimicrobial agent
4
15
28
34
maturation time (days)
125
PRI
PRI
30
125
0
(C)
40
0
maturation time (days)
PRI
50 Po (red) P30 (green)
(A)
Po (red) P30 (green)
P0 / P30
Po (red) P30 (green)
60
0
4
15
28
34
maturation time (days)
Killed microorganisms formic acid Antimicrobial agent
110
With antibiotic
100
Effect of microorganisms on PRI
90 80
PRI
70 60 50 40 30
With micro-organism
20 10 0 N+F+M+
N+F+M-
N-F+M+
N-F-M+
code
Each Pair Student's t 0.05
Effectof microorganisms initial concentration on PRI 120.0
The drop of PRI is proportional to the initial quantity of microorganisms in latex
3x104 CFU/ml
100.0
5x105 CFU/ml
80.0 PRI 60.0
2x10 CFU/ml 6
40.0
20.0
PRI Na azide (3E+4 cfu/ml) PRI Clean (5E+5 cfu/ml) PRI M (2E+6 cfu/ml) PRI 2M (9E+6 cfu/ml) PRI 4M (2E+7 cfu/ml)
2x107 CFU/ml
0.0 0
1
2
3 4 Maturation time (days)
5
6
Figure 7. The effect of microorganism activity on cup coagula properties
Conclusions (1) 1.Characterization Maturation conditions • Temperature and relative humidity of the air increased with depth. In contrast, oxygen content of the air within the pile decreased as depth increased. • Initial plasticity (P0), plasticity retention index (PRI), gel content and Mw were higher at the bottom of the pile.
Conclusions (2) 2. Setting up of the maturation box and mini-process •
Crepping : 16 passes on mini-creper
•
Drying : 2 hr at 125°C
Conclusions (3) 3. The role of micro-organism on cup coagula properties •
Po, PRI decreased with microorganism content and maturation time (antibiotic prevent those drops) • It was proven that the drop of PRI was proportional to initial quantity of microorganisms in the latex
Perspectives 1. Identify precisely the mode of action of this microorganisms during maturation : pure enzyme testing, isolation and test of specific strains 2. Study the microbial activity and its effect on rubber properties under various controlled conditions 3. Recommandations to improve the maturation on industrial site
Thank you for your attention
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