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Stable Free Radical Assisted Peroxide Vulcanisation:
Cure characteristics and vulcanisate properties
Benny George and Rosamma Alex
Rubber Technology Division
Advanced Center For Rubber Technology
Rubber Research Institute of India
Kottayam, Kerala, India.
IRC & IRRDB Meeting, 29 October to 2 November 20012,
Kovalam, Kerala
Vulcanisation
Viscous raw rubber
Elastic material
Time Line History of Sulphur Vulcanization
Sulphur vulcanization
Vulcanizing agent
Unacclerated sulphur
vulcanization
Thiocarbanilide
Dithiocarbamates
Accelerated sulphur
vulcanization
Diphenyl guanidine
accelerators
2- Mecaptobenzothiazol
2- Benzothiazolyl disulphide
2- Alkylamino thiobezothiazole
(sulphenamide)
Delayed action
sulphur vulcanization
Premature
N cyclohexyl thiophthalimide
vulcanization
inhibitor
Time Line History of Peroxide Vulcanization
Benzoyl Peroxide
Peroxide Vulcanization 1950
Various Peroxides
and co-agents
Advantages
1. No reversion at higher cure temperatures
2. Low compression set
3. Excellent heat ageing resistance
4. Co-vulcanisation of saturated and unsaturated rubber blends
Cure behavior comparison
Time, min
Time, min
Peroxide
Sulphur/accelerator
DCP/TEMPO/ bismaleimide system for
sulphur/ accelerator like scorch control*
Time, min
*Benny George and Rosamma Alex, Delayed action peroxide vulcanisation,
IRC , Mumbai, 2010
Matreials used
PERKADOX14-40B
Di(tert-butylperoxyisopropyl)benzene
TRIGNOX 17-40 B
Butyl 4,4-di(tert-butylperoxy valerate)
Co-agents
SR25 - N,N’-m-phenylene dimaleimide (Type I)
SR350 - Trimethylolpropane trimethacrylate (Type I) 2,2,6,6-tetramethylpiperidine -1- oxyl
Effect of concentration of TEMPO on cure characteristics of
Trignox 17-40B at 1600C
Effect of concentration of TEMPO on cure characteristics of
Perkadox 14-40B at 1750C
rque (dNm 40
Time (minutes)
Perkadox
Comparison of MH-ML value
Trignox 17-40 B
Perkadox 14-40 B
duc
e 10
R
%
Concentration of TEMPO
Effect of cure temperature on on cure characteristics of
Trignox 17-40B* at 0.8 phr TEMPO
rque (dNm
o
Time (minutes)
No Temperature, ML,
Effect of cure temperature on cure characteristics of
Perkadox 14-40B * at 0.8 phr TEMPO
rque (dNm
o
T
Time (minutes)
No Temperature, ML,
Effect of co-agent on cure characteristics of
Trignox 17-40B/TEMPO at 1600C
rque (dNm
o
Time (minutes)
Effect of coagent on cure characteristics of
Perkadox 14-40B /TEMPO at 1750C
rque (dNm 40
Time (minutes)
Mechanism of scorch control
Advatage of using Perkadox14-40B /TEMPO/SR350
1. Excellent scorch safety
2. Easy to release from the Mould
3. Enable to mould thicker articles which requires the
excellent properties offered by peroxide vulcanisation
Cure Characteristics of bulk compound at 1750C
Compound
EPDM Control
25.7 128.2 102.3
EPDM/Perkadox14-
105.0 85.8
40B/TEMPO/SR 350
Vulcanisate properties
Properties
EPDM control
EPDM/Perkado
x 14-40B/
TEMPO/SR 350
Tensile strength, MPa
Modulus,100%, MPa
Modulus,200%, MPa
Modulus,300%, MPa
Tear strength, N/mm
Hardness, Shore A
Compression set,
1000C, 72 h
Conclusions
1. Sulphur accelerator like scorch control in peroxide vulcanisation
can be achieved using a stable free radical/co-agent system
2. Perkadox14 {Di(t-butyl peroxyisopropyl)benzene/TEMPO/SR350
(trimethylol propane trimethacrylate ) system has the potential to
be utilised by the manufacturing industry.
3. The vulcanisate properties of the TEMPO containing vulcanisates
are comparable with that of the control compound.
Thank you

Source: http://clinic.rubberboard.org.in/PDF/ircpdf/RT-08%20Benny.pdf