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Natural Rubber
Chapter 86
Natural Rubber Category: Elastomer, Thermoset
Processing Method: See Ch. 77, Butyl Rubber, for an overview of rubber processing.
General Description: Natural rubber is polyisoprene. Chemical and environmental resistance and mechanical properties are improved through crosslinking (vulcanizing), usually through treatment with sulfur.[1065]
Applications: Tire and other automotive. See Collected Comparative Barrier Properties of Plastics and Elastomers for more information.
Natural rubber is more unsaturated and has fewer methyl groups than butyl rubber causing it to be twenty times more permeable to air. The presence of methyl groups generally serves to reduce the permeability of polymers.[1065]
Permeability Data by Material Supplier Trade Name: See Tables 86-01 through 86-04 and Graphs 86-01 through 86-02.
Table 86-01. Various Gases Through Natural Rubber
Material Family
NATURAL RUBBER
Reference Number
1004
TEST CONDITIONS Penetrant
oxygen
hydrogen
carbon dioxide
nitrogen
46
100
260
17
n/a
n/a
n/a
n/a
PERMEABILITY (source document units) Gas Permeability (based on hydrogen as 100) PERMEABILITY (normalized units) Permeability Coefficient (cm3 · mm/m2 · day · atm)
© Plastics Design Library
Chapter 86: Natural Rubber
484 Table 86-02. Air vs. Temperature Through Natural Rubber
NATURAL RUBBER
Material Family NO. 1 RIBBED SMOKE SHEETS
Product Form Cure
20 min. @ 145°C
Reference Number
298
299
MATERIAL CHARACTERISTICS Shore A Hardness
51 (30 second)
MATERIAL COMPOSITION Stearic Acid
2 phr
Zinc Dimethyl Dithiocarbonate
1.5 phr
Sulfur
2.5 phr
Zinc Oxide
5 phr
Channel Black
20 phr
MT Carbon Black
60 phr
SRF Carbon Black
50 phr
Note
10 phr Flexon 845 oil (Exxon), 4 phr Amberol ST-149 (Rohm and Haas Co.), specific accelerator
0.75 phr Altax
TEST CONDITIONS Penetrant Temperature (°C)
air 40
60
80
23.9
Test Apparatus
65.6
93.3
Aminco Permeability Apparatus
PERMEABILITY (source document units) Permeability Relative to Butyl Rubber (%)
700
Gas Permeability (ft3 · mil/ft2 · day · psi) Gas Permeability (cm3 · cm/cm2 · sec · atm)
11.8 x 10-8
26.8 x 10-8
43.9 x 10-8
1020
2316
3793
0.00436
0.0237
0.0402
496
2696
4574
PERMEABILITY (normalized units) Permeability Coefficient (cm3 · mm/m2 · day · atm)
Chapter 86: Natural Rubber
© Plastics Design Library
485 Table 86-03. Nitrogen Through Natural Rubber
NATURAL RUBBER
Material Family Reference Number
309
TEST CONDITIONS Penetrant
nitrogen
Temperature (°C)
21.1
Test Note
applies to general class of base polymer
PERMEABILITY (source document units) Gas Permeability (cm2/s · atm)
6.12 x 10-8
PERMEABILITY (normalized units) Permeability Coefficient (cm3 · mm/m2 · day · atm)
529
Table 86-04. Various Gases Relative to Butyl Rubber Through Natural Rubber
NATURAL RUBBER
Material Family
GUM VULCANIZATE
Product Form Reference Number
300
MATERIAL CHARACTERISTICS Sample Thickness (mm)
0.51
MATERIAL COMPOSITION Paraffinic Oil
5 phr
SRF Carbon Black
50 phr
TEST CONDITIONS Penetrant
helium
hydrogen
oxygen
Temperature (°C)
nitrogen
carbon dioxide
air
water vapor
25 Tappi Standard T464 M-45
Test Method PERMEABILITY (source document units) Permeability Relative to Butyl Rubber (%)
© Plastics Design Library
357
667
1780
2000
2500
2100
2425
Chapter 86: Natural Rubber
486
air permeability (10-8 · cm3 · cm/ cm2 · sec · atm)
Graph 86-01. Air vs. temperature through natural rubber. �
100
Natural Rubber (20 min. @ � 145°C cure; 51 Shore A; 5 � phr zinc oxide, 1.5 phr zinc � dimethyl dithiocarbonate, � 2.5 phr sulfur, 50 phr SRF black, 0.75 phr Altax; ribbed smoked sheets); penetrant: air; 60°C Reference No.
298
10
1 85
75
65
55
45
35
25
temperature (°C)
H2, O2, N2 permeability (10-8 · cm2/ s . atm)
Graph 86-02. Various gases vs. mineral filler through natural rubber. �
40
Natural Rubber (gum vulcanizate); penetrant: H2 Natural Rubber (gum vulcanizate); penetrant: O2
30
Natural Rubber (gum vulcanizate); penetrant: N2 Reference No.
300
20
10
0
0
10
20
30
40
50
60
70
80
90
mineral filler content (phr)
Chapter 86: Natural Rubber
© Plastics Design Library
Natural Rubber Category: Elastomer, Thermoset
Processing Method: See Ch. 77, Butyl Rubber, for an overview of rubber processing.
General Description: Natural rubber is polyisoprene. Chemical and environmental resistance and mechanical properties are improved through crosslinking (vulcanizing), usually through treatment with sulfur.[1065]
Applications: Tire and other automotive. See Collected Comparative Barrier Properties of Plastics and Elastomers for more information.
Natural rubber is more unsaturated and has fewer methyl groups than butyl rubber causing it to be twenty times more permeable to air. The presence of methyl groups generally serves to reduce the permeability of polymers.[1065]
Permeability Data by Material Supplier Trade Name: See Tables 86-01 through 86-04 and Graphs 86-01 through 86-02.
Table 86-01. Various Gases Through Natural Rubber
Material Family
NATURAL RUBBER
Reference Number
1004
TEST CONDITIONS Penetrant
oxygen
hydrogen
carbon dioxide
nitrogen
46
100
260
17
n/a
n/a
n/a
n/a
PERMEABILITY (source document units) Gas Permeability (based on hydrogen as 100) PERMEABILITY (normalized units) Permeability Coefficient (cm3 · mm/m2 · day · atm)
© Plastics Design Library
Chapter 86: Natural Rubber
484 Table 86-02. Air vs. Temperature Through Natural Rubber
NATURAL RUBBER
Material Family NO. 1 RIBBED SMOKE SHEETS
Product Form Cure
20 min. @ 145°C
Reference Number
298
299
MATERIAL CHARACTERISTICS Shore A Hardness
51 (30 second)
MATERIAL COMPOSITION Stearic Acid
2 phr
Zinc Dimethyl Dithiocarbonate
1.5 phr
Sulfur
2.5 phr
Zinc Oxide
5 phr
Channel Black
20 phr
MT Carbon Black
60 phr
SRF Carbon Black
50 phr
Note
10 phr Flexon 845 oil (Exxon), 4 phr Amberol ST-149 (Rohm and Haas Co.), specific accelerator
0.75 phr Altax
TEST CONDITIONS Penetrant Temperature (°C)
air 40
60
80
23.9
Test Apparatus
65.6
93.3
Aminco Permeability Apparatus
PERMEABILITY (source document units) Permeability Relative to Butyl Rubber (%)
700
Gas Permeability (ft3 · mil/ft2 · day · psi) Gas Permeability (cm3 · cm/cm2 · sec · atm)
11.8 x 10-8
26.8 x 10-8
43.9 x 10-8
1020
2316
3793
0.00436
0.0237
0.0402
496
2696
4574
PERMEABILITY (normalized units) Permeability Coefficient (cm3 · mm/m2 · day · atm)
Chapter 86: Natural Rubber
© Plastics Design Library
485 Table 86-03. Nitrogen Through Natural Rubber
NATURAL RUBBER
Material Family Reference Number
309
TEST CONDITIONS Penetrant
nitrogen
Temperature (°C)
21.1
Test Note
applies to general class of base polymer
PERMEABILITY (source document units) Gas Permeability (cm2/s · atm)
6.12 x 10-8
PERMEABILITY (normalized units) Permeability Coefficient (cm3 · mm/m2 · day · atm)
529
Table 86-04. Various Gases Relative to Butyl Rubber Through Natural Rubber
NATURAL RUBBER
Material Family
GUM VULCANIZATE
Product Form Reference Number
300
MATERIAL CHARACTERISTICS Sample Thickness (mm)
0.51
MATERIAL COMPOSITION Paraffinic Oil
5 phr
SRF Carbon Black
50 phr
TEST CONDITIONS Penetrant
helium
hydrogen
oxygen
Temperature (°C)
nitrogen
carbon dioxide
air
water vapor
25 Tappi Standard T464 M-45
Test Method PERMEABILITY (source document units) Permeability Relative to Butyl Rubber (%)
© Plastics Design Library
357
667
1780
2000
2500
2100
2425
Chapter 86: Natural Rubber
486
air permeability (10-8 · cm3 · cm/ cm2 · sec · atm)
Graph 86-01. Air vs. temperature through natural rubber. �
100
Natural Rubber (20 min. @ � 145°C cure; 51 Shore A; 5 � phr zinc oxide, 1.5 phr zinc � dimethyl dithiocarbonate, � 2.5 phr sulfur, 50 phr SRF black, 0.75 phr Altax; ribbed smoked sheets); penetrant: air; 60°C Reference No.
298
10
1 85
75
65
55
45
35
25
temperature (°C)
H2, O2, N2 permeability (10-8 · cm2/ s . atm)
Graph 86-02. Various gases vs. mineral filler through natural rubber. �
40
Natural Rubber (gum vulcanizate); penetrant: H2 Natural Rubber (gum vulcanizate); penetrant: O2
30
Natural Rubber (gum vulcanizate); penetrant: N2 Reference No.
300
20
10
0
0
10
20
30
40
50
60
70
80
90
mineral filler content (phr)
Chapter 86: Natural Rubber
© Plastics Design Library