Rubber_Compounding ingredients_Cure system.pdf

Rubber compounding - Vulcanization system of elastomer

1. www.smithersrapra.com
CONFIDENTIAL
Compounding 103:
Cure Systems
Webinar
February 27, 2019
Click hereto access a
recording of the webinar

2. www.smithersrapra.com
CONFIDENTIAL
Today’s Presenters
2
Christine Domer
General Manager, Analytical and
Physical Testing Laboratories
Smithers Rapra
Maggie Olson
Marketing Specialist
Smithers Rapra

3. www.smithersrapra.com
CONFIDENTIAL
Rubber Compounding Webinars
Title Date
Compounding 101: Polymers December 12, 2018
Compounding 102: Fillers & Process Aids January 29, 2019
Compounding 103: Cure Systems February 27, 2019
Compounding 104: Anti-degradant systems March 2019
Compounding 105: Lab Testing April 2019
3

4. www.smithersrapra.com
CONFIDENTIAL
Agenda
•Review: The recipe for an optimized compound
•The five basic systems of a rubber recipe:
–Polymer system
–Filler system
–Oils & plasticizers system
–Cure system
–Anti-degradant system
•Cure Systems
–Vulcanizing agents, accelerators, activators
•Anti-degradants –March Session
–Degradation mechanisms
–Antioxidants, antiozonants, waxes
•Summary –Compounders Toolbox
4

5. www.smithersrapra.com
CONFIDENTIAL
Rubber compound development
5
•Rubber Compounding Ingredients
–Polymer system
–Filler system
–Oils & plasticizers system
–Cure system
–Anti-degradant system
–Specialty
•Processing
–Mixing, extrusion, calendaring, injection, curing process
•Product Performance & Testing
Toughness, tear strength, flex fatigue, abrasion, adhesion,
hysteresis and heat build- up, damping, shock absorption, end use
environment (resistance to O2, O3, UV, aging, solvents, oils, etc.)

6. www.smithersrapra.com
CONFIDENTIAL
Rubber Formula Example: Sulfur
Vulcanizate
Material phr
Raw rubber 100
Filler 50-150
Plasticizer 5-100
Sulphur 0-5
Zinc oxide 5
Stearic acid 2
Accelerator 0.5-3
Antioxidant 104
Other additives 0-
6

7. www.smithersrapra.com
CONFIDENTIAL
Cure Systems

8. www.smithersrapra.com
CONFIDENTIAL
Cure System
•Vulcanization agents or crosslinkers
•Accelerator Activators
•Accelerators
8
Uncured Rubber Crosslinked Rubber

9. www.smithersrapra.com
CONFIDENTIAL
Cure System Definitions
•Vulcanization agents are chemicals that will react with
active sites in the polymer to form connections or cross-links
between chains.
•Activators are materials added to an accelerated
vulcanization system to improve acceleration and to permit
the system to realize its full potential of cross-links.
•Accelerators are chemicals used in small amounts with a
vulcanizing agent to reduce the time of (accelerate) the
vulcanization process. In sulfur vulcanization today,
accelerators are used to control the onset, speed, and extent
of reaction between sulfur and elastomer.
9
Source: Edited by B. Rogers, Rubber
Compounding, Chemistry and Applications,
Copyright © 2004 by Taylor & Francis

10. www.smithersrapra.com
CONFIDENTIAL
Physical Effects of Vulcanization
10

11. www.smithersrapra.com
CONFIDENTIAL
Choice of Cure System
11

12. www.smithersrapra.com
CONFIDENTIAL
Vulcanization Agents
Chemicals that will react with active sites in the polymer to
form connections or cross-links between chains.
•Sulfur
•Peroxides
•Metal Oxides
•Resins
12

13. www.smithersrapra.com
CONFIDENTIAL
Sulfur
S
8 Rings S
X Chains
Rubber Makers Sulfur
Soluble
Insoluble Sulfur
13

14. www.smithersrapra.com
CONFIDENTIAL
Sulfur Crosslinks
14
Source: Rubber Technology, 3
rd
Edition,
Morton, 1987
Bonding Energy kcal/mol
Polysulfide —Sx-- 34
Disulfide —S-S-- 54
Monosulfide—S-- 74

15. www.smithersrapra.com
CONFIDENTIAL
Activators
Materials added to an accelerated vulcanization system to
improve acceleration and to permit the system to realize its
full potential of cross-links.
15
Inorganic Organic
•Zinc Oxide
•Magnesium Oxide
•Lead Oxide
•Stearic Acid
•Lauric Acid
•Amines
•Guanidines
•Ureas, thioureas
•Amides

16. www.smithersrapra.com
CONFIDENTIAL
Accelerators
Chemicals used in small amounts with a vulcanizing agent
to reduce the time of (accelerate) the vulcanization
process. In sulfur vulcanization today, accelerators are
used to control the onset, speed, and extent of reaction
between sulfur and elastomer.
16
Guanidines Slow
Thiazoles Semi-Fast
Sulfenamides Fast-delayed
Thiurams Very Fast
Dithiocarbamates Very Fast

17. www.smithersrapra.com
CONFIDENTIAL
Accelerator Development
1919- 1922: Guanidines, Thiazoles, Thiurams, Dithiocarbamates
1945: Sulfenamides
17
DPG
“Guanidine”
Slow
MBT
“Thiazole”
Semi-Ultra
TMTD
“Thiuram”
Ultra- Fast
ZDCB
“Dithiocarbamate”
Ultra- Fast
CBS
“Sulfenamide”
Fast-delayed Action

18. www.smithersrapra.com
CONFIDENTIAL
Accelerator Classes
18
Source: Edited by B. Rogers, Rubber
Compounding, Chemistry and Applications,
Copyright © 2004 by Taylor & Francis

19. www.smithersrapra.com
CONFIDENTIAL
Common accelerators for sulfur cures
19
Source: The Vanderbilt Rubber Handbook, 14th
Edition, 2010

20. www.smithersrapra.com
CONFIDENTIAL
Accelerator summary
20
http://www.nocil.com/Downloadfile/DTechnical
Note-Vulcanization- Dec10.pdf

21. www.smithersrapra.com
CONFIDENTIAL
Three classes of sulfur cure systems
1. Conventional systems –high S/A ratio
2. Efficient (EV) systems – high A/S ratio
3. Semi-EV systems that are between 1 & 2
21
Bonding Energy kcal/mol
Polysulfide —Sx-- 34
Disulfide —S-S-- 54
Monosulfide—S-- 74

22. www.smithersrapra.com
CONFIDENTIAL
Crosslink Structure and Properties
22
http://www.akrochem.com/pdf/technical_papers/
curing_w_sulfur.pdf

23. www.smithersrapra.com
CONFIDENTIAL
Fatigue Compromise
23
Source: Edited by B. Rogers, Rubber
Compounding, Chemistry and Applications,
Copyright © 2004 by Taylor & Francis
EV

24. www.smithersrapra.com
CONFIDENTIAL
Sulfur Reaction
Schemes

25. www.smithersrapra.com
CONFIDENTIAL
Reaction Scheme –Sulfur Cure System
25
Source: N. J. Morrison, M. Porter,
RUBBER CHEM. TECHNOL. 57, 63 (1984)

26. www.smithersrapra.com
CONFIDENTIAL
Reaction Scheme –Sulfur cured NR
26
Source: Reaction scheme –Mechanism of
crosslinking natural rubber with sulphurand
accelerators, Stelescuet al

27. www.smithersrapra.com
CONFIDENTIAL
Reaction Scheme –Sulfur cured EPDM
27
Source: The Vanderbilt Rubber
Handbook, 14th Edition, 2010

28. www.smithersrapra.com
CONFIDENTIAL
ArrehniusEquation
28
kthe rate coefficient
Aa frequency constant (rxnorder)
E
athe activation energy
Rthe universal gas constant
Tthe absolute temperature

29. www.smithersrapra.com
CONFIDENTIAL
General Rule of Thumb
Sulfur Vulcanization Reaction:
•Reaction rate approximately doubles for every 10°C
increase in temperature
29

30. www.smithersrapra.com
CONFIDENTIAL
Peroxides
30

31. www.smithersrapra.com
CONFIDENTIAL
Peroxide Crosslink Mechanism
31
RO-OR 2 RO
RO + - HC=CH- CH-CH
2-
|
H
ROH + - HC=CH- CH-CH
2-
-HC=CH- CH-CH
2-
-HC=CH- CH-CH
2-
1. Radicals form
2. Hydrogen abstraction
HEAT
3. Carbon-Carbon crosslink
formed between polymer chains.

32. www.smithersrapra.com
CONFIDENTIAL
Peroxide Cured Rubber Features
Carbon- Carbon bond
couples two polymer chains
•C-C crosslink is rigid,
strong
•C-C crosslink is thermally
stable
32
Imparts (vs sulfur)
•lower compression set
•improved heat resistance
•lower tear strength
•lower abrasion resistance
•poor hot tear
Bonding Energy kcal/
mol
Polysulfide -Sx- 34
Disulfide - S-S- 54
Monosulfide-S- 74
Carbon carbon–C--C- 80
-HC=CH- CH-CH
2
-HC=CH- CH-CH
2

33. www.smithersrapra.com
CONFIDENTIAL
Peroxide RO-OR
•Rate of crosslinking is directly proportional to the rate of
decomposition of the peroxide.
•Cure time and cure temperature is related to the half life. Half
life is the time required for half of the peroxide to decompose
at the reaction temperature.
•Peroxide selection based on cure time and temperature
needed and physical properties for the application
Dialkyl> perketal> perester > diarylperoxides
33

34. www.smithersrapra.com
CONFIDENTIAL
Peroxide RO-OR Avoidances
•Avoid heat in storage.
•Avoid acidic ingredients such as non- treated clays and
silicas. Use water-washed clays or silane treated silicas
•Avoid aromatic and naphthenic oil; use paraffinic oil.
•Avoid ingredients that are strong H donors
•Avoid oxygen exposure during curing (autoclave or flash)
•Avoid peroxide curing butyl, halobutyls, polyisobutylene,
polypropylene, epichlorohydrin, and polyvinylchloride.
34

35. www.smithersrapra.com
CONFIDENTIAL
Peroxide Cures with Coagents
•Coagents: multi -functional monomers which lend a hydrogen
to the peroxide radicals and they contain double bonds for
crosslinking.
•Usage: improve processability and modify physical properties
•Coagent can improve properties:
–Heat age resistance
–Increase modulus
–Increase tensile strength
–Increase tear strength
–Improve abrasion resistance
–Improve compression set
–Lower compound viscosity
–Improve adhesion
35
Source: P. Dluzneski(2001) Peroxide
Vulcanization of Elastomers. Rubber Chemistry
and Technology: July 2001, Vol. 74

36. www.smithersrapra.com
CONFIDENTIAL
Peroxide Cure with Coagents
36
http://www.pentasil.eu/images/Fundamentals
%20of%20Curing%20Elastomers%20with%
20Peroxides.pdf

37. www.smithersrapra.com
CONFIDENTIAL
Coagents
37
http://www.crayvalley.com/docs/technical-
paper/fundamentals-of-curing- elastomers-with-
peroxides-and-coagents-part-2-(1).pdf

38. www.smithersrapra.com
CONFIDENTIAL
Metal Oxide cure of CR
38
Source: The Vanderbilt Rubber Handbook, 14th
Edition, 2010

39. www.smithersrapra.com
CONFIDENTIAL
Resin Cure –Novolak
39
https://patents.google.com/patent/EP1016691A1/en
Bayer inc., 1999
R’ form cross links:
Methylene bridges (-CH
2-) or
dimethyleneether (-CH
2-O-CH
2)

40. www.smithersrapra.com
CONFIDENTIAL
40
Source: Edited by B. Rogers, Rubber
Compounding, Chemistry and Applications,
Copyright © 2004 by Taylor & Francis

41. www.smithersrapra.com
CONFIDENTIAL
Summary: Compounder’s Tool Box
•Elastomer properties
•Modifying raw materials (fillers, oils/plasticizers) affecting
cost, processing, and cured properties
•Cure systems
•Antidegradants
•Processing
•Test methods
41

42. www.smithersrapra.com
CONFIDENTIAL
Smithers Lab Locations
Location Services Offered
Akron, Ohio Analytical Lab
Materials Testing
Whole Product Testing
TechnicalConsulting Services
Tire Analysis Reports
Information Services
Ravenna,Ohio WholeTire & Wheel Testing
Lansing, Michigan Whole Product Testing
Package / Distribution Testing
Brimley, Michigan Winter TestingFacility
Tire Traction Testing
Shawbury, UK Analytical Lab
Materials Testing
Whole Product Testing
TechnicalConsulting Services
Leatherhead, UK Whole Product Testing
Package / Distribution Testing
Information Services
Suzhou, China Whole Tire & Wheel Testing
42

43. www.smithersrapra.com
CONFIDENTIAL
Contact
43
Christine Domer
General Manager, Akron Labs
(330) 762- 7441
[email protected]
Jeremy Elliott
Technical Sales Representative
(330) 762- 7441
[email protected]