peroxide crosslinking of elastomers - rubbernews
TRANSCRIPT
Outline
- Polymer Applications for Organic Peroxides
- Classes of Organic Peroxides
- Crosslinking Mechanisms of Sulfur and Organic Peroxides
- Advantages of Organic Peroxides in Crosslinking
- Kinetic Considerations in Peroxide Decomposition
Organic Peroxides
ROOR’RO:OR’
- When Heated, the Peroxide Bond Cleaves
Homolytically to Yield Two
Radicals.
RO• •OR’
- These Radicals are Highly Reactive
(Electrons Don’t Like to be Unpaired)
RO• •OR’
- Peroxides have O-O Bond
Organic Peroxides Uses
Monomers
Polymer
Modified
Polymer
Final
Polymer
Product
Polymerization
Initiation
C CR•
C C•R C C
C CR C C•
C CC C
C C•C CC
C CC C•
C CCC C
C C•
6
Monomers
Polymer
Modified
Polymer
Final
Polymer
Product
Polymerization
Initiation
C CR C C•C
C CC C•
CC C
C C•
Organic Peroxides Uses
7
H
Monomers
Polymer
Modified
Polymer
Final
Polymer
Product
Polymerization
Initiation
Grafting
RO•
ROH•ROH •ROH
X
•
X
•
X•
•
Organic Peroxides Uses
8
•
Monomers
Polymer
Modified
Polymer
Final
Polymer
Product
Polymerization
Initiation
Grafting
Visbreaking
RO• HROH•ROH ••••
Organic Peroxides Uses
9
Monomers
Polymer
Modified
Polymer
Final
Polymer
Product
Polymerization
Initiation
Grafting
Visbreaking
ROH
•
•
Cross-Linking
ROORRO• •OR
HH ROHHOR•• ROHHOR
Organic Peroxides Uses
10
Monomers
Polymer
Modified
Polymer
Final
Polymer
Product
Polymerization
Initiation
Grafting
Visbreaking
Cross-Linking
••
Organic Peroxides Uses
11
Hydroperoxides
1hr Half-Life
Temp (°C)Typical
Structure
Example
Products
Primary
Applications
180 to 200 R-OOH Luperox® CU-80
Luperox® DIBHP
Ketone Peroxides N/A R2-C(OOH)2
et al
Luperox® DDM-9
Luperox® 224
Dialkyl Peroxides 137 to 152 R-OO-R’ Di-Cup®
Vul-Cup®
Luperox® 101
Luperox® D16
Crosslinking
Polymer Modification
Polymer Initiation
Composite Cure
Peroxyketals 112 to 134 Luperox® 230
Luperox® 231
Luperox® 331
Luperox® 531
Peroxyesters 56 to 125 Luperox® P
Luperox® 10
Crosslinking
Polymer Initiation
Composite CureRC-OOR’
O
Monoperoxy
Carbonates
117 to 121 Luperox® TAEC
Luperox® TBECROC-OOR’
O
Diacyl Peroxides 81 to 92 Luperox® A
Luperox® DEC
Luperox® LP
Crosslinking
Polymer Initiation
Composite CureRC-OOCR’
O O
R-C-R’
OO-R
OO-R
Peroxy
Dicarbonates
66 to 69 Luperox® 221
Luperox® 223
Luperox® 225ROC-OOCOR’
O O
Polymer Initiation
Composite Cure
Polymer Initiation
Composite Cure
Crosslinking
Polymer Initiation
Composite Cure
Crosslinking
Polymer Modification
Polymer Initiation
Composite Cure
Polymer Initiation
Composite Cure
Organic Peroxides Uses
Crosslinking Involves the Formation of Covalent Bonds Between Polymer Chains
● Improves High and Low Temperature Properties
● Higher Tensile Strength, Lower Elongation
● Better Fluid Resistance
● Lower Compression Set
● Better Fluid Resistance
● Improved Resistance to Stress Cracking
Polymer Crosslinking
Sulfur vs. Peroxide Cure Mechanisms
Polymer Crosslinking
Sulfur Peroxide
H H H H
S S
S
S
S
S
S S
R O O R’S S
S
S
S
S
S S
S SS
S
S
S
S S
S SS
S
S
S
S S
S SSSS S
S S
S SSSS
S S SH HS SSSS S S SH HS S
SSS
SS SS
S
SS
S
S
SS
S S
SS
S
S
S
S
Sulfur vs. Peroxide Cure Mechanisms
Polymer Crosslinking
S S
SS
S
S
S
S
Sulfur
H H
R O O R’R O• •O R’R O•
•O R’R O•
•O R’R O••O R’ R O••O R’ R OHHO R’• •
Peroxide
Sulfur vs. Peroxide Cure Mechanisms
Polymer Crosslinking
S S
SS
S
S
S
S
Sulfur Peroxide
• •• •• •• •••
- Sulfur becomes the cross-link - The peroxide induces a direct C-C cross-link
- Relatively weak S-S bonding that can
break and re-form.
- Direct C-C bonding that is much more
difficult to break.
Sulfur vs. Peroxide Cure Mechanisms
Polymer Crosslinking
Sulfur Peroxide
S S
SS
S
S
S
S
- Sulfur becomes the cross-link - The peroxide induces a direct C-C cross-link
- Relatively weak S-S bonding that can
break and re-form.
- Direct C-C bonding that is much more
difficult to break.
- Simple Formulation
- Cure kinetics controlled by peroxide selection
and other ingredients (e.g. coagents
and anti-scorch agents)
- Requires activator and accelerator
- Cure kinetics controlled by accelerators
- Not inhibited by open-air curing
Comparison of Cure Properties
Sulfur vs. Peroxide Cure Mechanisms
Polymer Crosslinking
Sulfur Peroxide
S S
SS
S
S
S
S
- Simple Formulation
- Cure kinetics controlled by peroxide selection
and other ingredients (e.g. coagents
and anti-scorch agents)
- Requires activator and accelerator
- Cure kinetics controlled by accelerators
- Not inhibited by open-air curing
Comparison of Cure Properties- Better Heat Aging/Compression Set
- No Discoloration
- Better Clarity
- Able to Co-vulcanize Saturated and Unsaturated
Elastomers
- Better Abrasion Resistance
- Better Hot Tear Resistance
Comparison of Vulcanizate Properties
Polymers that can be Crosslinked with Peroxides
Polymer Crosslinking
Sulfur can only be used to cross-link polymers
that contain unsaturation.
Fully saturated polymers can only be cross-linked by
Peroxides.
Sulfur Peroxide
Other
BR – Polybutadiene
SBR – Styrene Butadiene
NBR – Nitrile- Butadiene
IR - Polyisoprene
NR – Natural Rubber
CR - Polychloroprene
EVA – Ethylene Vinyl Acetate
EPM (“EPR”) – Ethylene-Propylene
EPDM – Ethylene-Propylene-Diene
IIR (“Butyl”) – Butylene-Isoprene
HNBR – Hydrogenated Nitrile- Butadiene
PE – Polyethylene
CM (“CPE”) – Chlorinated Polyethylene
CSM – Chlorosulfonated Polyethylene
ACM – Polyacrylate
MQ – Silicone
ECO – Polyepichlorohydrin
FKM – Fluoroelastomers
BRSBR
NBR IR
NR
EPDM
EPM
EVA
HNBR
PE
IIR
CSM
CM
CR
MQ
ACMFKM
ECO
Some polymers contain additional functionality which
Allows them to be cross-linked by other chemical agents.
Overall, peroxides are the most universal cross-linking agent.
Polymer Crosslinking – Heat Aging
Properties of NBR Compound after Heat Aging (70 hrs at 257°F)
Sulfur Cured Peroxide Cured
Before After Before After
Tensile strength (MPa) 19.3 13.7 21.4 23.1
Elongation, % 380 80 395 215
Compression Set (%) Sulfur Cured Peroxide Cured
70 hrs at 212°F (100°C) 66 20
70 hrs at 257°F (125°C) 82 30
Organic Peroxide Decomposition is a First Order Reaction
● The Rate of Decomposition is Dependent on Temperature
● The Extent of Decomposition is Dependent on Both Time and Temperature
● The Half Life is the Time Required for Half of the Peroxide Groups to Decompose at a Given Temperature
Organic Peroxide Decomposition
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5 6 7 8
Per
cen
t R
emai
nin
g P
ero
xid
e
Number of Half Lives
Percent of Peroxide Remaining with Subsequent Half Lives
50%
25%
12.5%
6.25%3.13% 1.6% 0.8% 0.4%
Organic Peroxide Decomposition is a First Order Reaction
● The Rate of Decomposition is Dependent on Temperature
● The Extent of Decomposition is Dependent on Both Time and Temperature
● The Half Life is the Time Required for Half of the Peroxide Groups to Decompose at a Given Temperature.
Organic Peroxide Decomposition
Half-Life of Di-Cup® DiCumylPeroxide at Various Temperatures
Temperature
Half-Life Time(°C) (°F)
25 77 ~2500 years
40 104 ~140 years
50 122 ~22 years
100 212 ~ 4 days
150 302 ~15 minutes
200 392 ~ 9 seconds
k=A • e -Ea/RT
Arrhenius Rate Equation
Organic Peroxide Decomposition
50°
60°
70°
80°
90°
100°
110°
120°
130°
140°
150°
160°
170°
180°
190°
250°
150°
350°
200°
300°
°C °F
Luperox® 610
Luperox® 10
Luperox® 11
Luperox® DEC
Luperox® A98
Luperox® 231
Luperox® P
Di-Cup® RVul-Cup® R
Luperox® D-16Luperox® DI
Luperox® CU80
1 Hour Half Life
Temperature
The Stability of the Organic Peroxides Varies Greatly
● The Temperature Required for Half of the Peroxide to
Decompose in One Hour is Referred to as the
“1 Hour Half Life Temperature”
● This Provides an Indication of the Stability of the Peroxide
and Can Be Used as a Guide to Select the Proper Peroxide
for an Application.
Temperatures Required for Full Cure in 30 minutes
°C °F
Luperox® 225 90 194
Luperox® LP 100 212
Luperox® 575 110 230
Luperox® 231 135 275
Luperox® TBEC 145 293
Vul-Cup® R 160 320
Summary
Organic Peroxides are Used in Many Industries to Manufacture, Modify, and
Crosslink Polymers.
The Organic Peroxide Crosslink Mechanism Differs Greatly from that of Sulfur
and Offers Many Advantages Over Other Vulcanization Techniques.
The Stability of Organic Peroxides Vary Greatly Depending on the Molecular
Structure.
The Wide Range of Organic Peroxide Stabilities Enables the Selection of an
Appropriate Peroxide for Virtually Every Application.
Disclaimer
The statements, technical information and recommendations contained herein are believed to be accurate as of the date hereof. Since the
conditions and methods of use of the product and of the information referred to herein are beyond our control, Arkema expressly disclaims any
and all liability as to any results obtained or arising from any use of the product or reliance on such information; NO WARRANTY OF FITNESS
FOR ANY PARTICULAR PURPOSE, WARRANTY OF MERCHANTABILITY, OR ANY OTHER WARRANTY, EXPRESS OR IMPLIED, IS MADE
CONCERNING THE GOODS DESCRIBED OR THE INFORMATION PROVIDED HEREIN. The information provided herein relates only to the
specific product designated and may not be applicable when such product is used in combination with other materials or in any process. The user
should thoroughly test any application before commercialization. Nothing contained herein constitutes a license to practice under any patent and
it should not be construed as an inducement to infringe any patent, and the user is advised to take appropriate steps to be sure that any proposed
use of the product will not result in patent infringement.
© 2011 Arkema Inc.
Di-Cup® is a Registered Trademark of Arkema Inc.
Vul-Cup® is a Registered Trademark of Arkema Inc.
Luperox® is a Registered Trademark of Arkema Inc.
Thank You