Stabilization of Dynamic Properties Following Ageing

Transcription

ROHSTOFFE UND ANWENDUNGEN
RAW MATERIALS AND APPLICATIONS
Truck tires (skim) passenger tire (tread) loss tangent antireversion agent 1,3 bis
(citraconimidomethyl) benzene ageing
Tire operating temperature is of vital
concern to tire engineers because it relates both service life and power loss in
a tire. Operating temperature therefore is
a limiting factor in the choice of construction materials for truck tires, which
run at much higher temperatures than
do automotive tires. The power loss as
well as hysteresis can be correlated to
loss tangent of the compounds both at
cure and following the service life. The
loss tangent is negatively affected when
the system faces conditions responsible
for degradation. The antireversion
agent,1,3 bis(citraconimido)methyl benzene (Perkalink 900) counteracts reversion and degradation in both truck and
passenger tire tread. Perkalink 900 is
found to stabilize the changes in the dynamic properties following ageing. This
paper examines the effect of Perkalink
900 in truck tire (skim) as well as passenger tire (tread) compounds with respect to the stabilization of dynamic
properties.
Stabilisierung der dynamischen
Eigenschaften beim Reversionsprozess
Lkw-Reifen Pkw-Reifen negativ tan Antireversionsmittel 1,3-bis-Citronimidomethyl-benzol Alterung
Die Nutzungstemperaturen ist bei Reifen
von besonderer Bedeutung, weil davon
sowohl die Lebensdauer als auch der
Leistungsverlust abhaÈngen. Daher ist die
Nutzungstemperatur ein limitierender
Faktor bei der Wahl der Rohstoffe fuÈr
Lkw-Reifen die bei viel hoÈheren Betriebstemperaturen gefahren werden als
die Pkw-Reifen. Die Leistungsverluste
und die Hysterese koÈnnen mit dem Verlustwinkel der Compounds nach der Vulkanisation und waÈhrend des Einsatzes
korreliert werden. Durch Bedingungen
die den Abbau und Verschleiss foÈrdern
wird tand negativ beeinflusst. Das Antireversionsmittel 1,3-bis-Citraconimidomethyl-benzol(Perkalink 900) wirkt gegen die Reversion und den Abbau sowohl in Lkw- als auch Pkw-Reifen. Diese
Verbindung stabilisiert die AÈnderungen
der dynamischen Eigenschaften beim
Reversionsprozess. Der vorliegende Beitrag untersucht die stabilisierenden Effekte von Perkalink 900 in Lkw und Pkw.
350
Stabilization of Dynamic
Properties Following Ageing
R. N. Datta and N. M. Huntink, Deventer (The Netherlands)
The effect of antireversion agent, 1,3
bis (citraconimidomethyl) benzene (Perkalink 900) on viscoelastic properties following ageing has been studied in both
NR and SBR compounds. This paper
provides some interesting feature with regard to stabilization of viscoelastic properties following ageing by using 1, 3 bis
(citraconimidomethyl) benzene (Perkalink
900).
Tires of today are frequently required to
operate at high loads and high speeds
for extended periods of time. These severe operating conditions result in greater
heat build up than would normally be encountered under less demanding service
conditions. As a consequence, the excessive running temperature leads to reversion and consequently loss in dynamic
properties that may in turn lead to reduced tire durability or, in extreme circumstances, to tire failure.
Much effort has been expended over
the years to maintain the dynamic properties of tire compounds during service. An
established and, probably, best known
approach is the use of so-called semi-efficient cure systems comprising reduced
sulfur levels and increased accelerator levels [1]. However, though effective in improving the viscoelastic properties, this
approach is only partially successful
since lowering of sulfur levels negatively
influences other desirable properties
such as tear and flex/fatigue life. Additionally lower sulfur dosage is undesirable
[2] when considering the adhesion criteria
to brass plated steel cord.
Experimental
Compound formulations are shown in the
Tab. 1 and 2. Compound mixing was carried out in a similar manner as described
earlier [3].
Stress strain and tear properties of the
vulcanizates were measured using a
Zwick universal testing machine (model
1445) in accordance with ISO 37 and
ISO 34 respectively. Heat build up was
measured with a Goodrich Flexometer
according to the method described in
ASTM D623. Fatigue to Failure properties
were measured by a Monsanto Fatigue to
Failure tester at 23 8C and 1.67 Hz with
0 ± 100 % extension.
Tab. 1. Formulations (Model skim compound)
Ingredients 96132
01
02
NR
N-326
Silica
Stearic acid
Zinc oxide
NAPCO 105
Resorcin DS
Resimene 3521S
PVI 50
Flectol TMQ
Santoflex 6PPD
Santocure DCBS
Crystex OT 20
Perkalink 900
100
45
15
1.2
8
0.5
2.0
3.0
0.2
1
1
1
5
0
100
45
15
1.2
8
0.5
2.0
3.0
0.2
1
1
1
5
0.75
KGK Kautschuk Gummi Kunststoffe 55. Jahrgang, Nr. 7-8/2002
Stabilization of Dynamic Properties . . .
Fig. 1. Reaction of Perkalink 900 with conjugated dienes
The viscoelastic properties were measured using the Metravib Visco Analyzer
(VA 2000) and the Rheometrics (RDA
700) at a frequency of 10 Hz, temperature
of 60 8C and dynamic strain of 2 %. Details of the testing are described in the
earlier publications [4 ± 7].
The crosslink densities and distribution
of crosslink types were measured following the procedure reported elsewhere
[8 ± 15].
Results and discussions
It is well known that during the process of
reversion, structural changes occur in the
main-chain of the polymer. The formation
of cyclic sulfides and conjugated structures are reported [16]. These main chain
modifications apart from others negatively affect the hysteresis characteristics
of the final product.
It has been reported [17] that Perkalink
900 reacts with conjugated structures as
well as with cyclic sulfides (Fig. 1 and 2
respectively) and forms additional crosslinks which, compensate the loss of sulfidic crosslinks encountered during reversion regime.
The ultimate effect of scavenging the
conjugated as well as cyclic structures
should be translated into better maintenance of dynamic properties during service. The effect of Perkalink 900 is therefore studied in both NR (high sulfur),
which is prone to reversion and SBR
(tread) which is less susceptible to reversion.
Fig. 2. Reaction of Mono-citraconimide benzene (MCI-B) with cyclic
sulfides
Tab. 2. Formulations (SBR, tread)
Ingredients
03
04
SBR EM 1500
N-220
Zinc oxide
Stearic acid
Flectol TMQ
Santoflex 6PPD
Santocure TBBS
Sulfur
Perkalink 900
100
50
3
3
1
1
0.75
1.5
0
100
50
3
3
1
1
0.75
1.5
0.25
Properties
01
02
Delta S, Nm
Scorch safety,ts2, min
Optimum cure time, t90, min
Cure rate, Nm/min
2.54
4.2
22.3
0.230
2.72
4.1
23.5
0.240
Tab. 3. Cure data of the mixes at 150 8C
Tab. 4. Mechanical properties of the vulcanizates (Cure: 150 8C/t90 and 60')
Properties
01
02
Modulus, 100 %, Mpa
Modulus, 300 %, Mpa
Tensile strength, Mpa
Elongation at break, %
Tear strength, kN/m
Fatigue to Failure, kC
Heat build up*, delta T, 8C
Surface
Interior
2.9(2.3)
13.3(13.0)
28.7(24.0)
520(510)
85(60)
160(150)
3.2(2.8)
14.1(14.1)
28.9(25.8)
520(500)
110(80)
155(145)
55(72)
68(90)
44(50)
55(63)
* Starting temp: 35 8C, Duration: 2 h
# values in the parentheses are for the vulcanizates cured for 60 minutes
Tab- 5. Viscoelastic properties (Metravib); Cure 150 8C/t90*1.2
Compounds
E 0 , Mpa
E 00 , Mpa
Tangent delta
01
Unaged
Aged 1d/100 8C
Aged 3d/100 8C
11.9
13.9
14.9
1.26
1.51
1.84
0.106
0.109
0.124
02
Unaged
Aged 1d/100 8C
Aged 3d/100 8C
12.9
13.3
14.0
1.30
1.39
1.51
0.101
0.105
0.108
351
Effect of Perkalink 900 in Truck
tire skim compounds
Fig. 3. Cure characteristics at 150 8C
Tab. 6. Viscoelastic properties (Metravib); Cure 150 8C/t90*2
Compounds
E 0 , MPa
E 00 , Mpa
Tangent delta
01
Unaged
Aged 1d/100 8C
Aged 3d/100 8C
11.9
14.5
14.9
1.41
1.64
1.85
0.121
0.113
0.132
02
Unaged
Aged 1d/100 8C
Aged 3d/100 8C
13.0
13.5
14.6
1.43
1.47
1.54
0.110
0.109
0.105
Tab. 7. Viscoelastic properties (Rheometrics); Cure 170 8C/t90
G 0 , MPa
G 00 , Mpa
Tangent d
Control (03)
Unaged
3.95
Aged 1d/100 8C 4.32
Aged 4d/100 8C 4.88
0.91
1.11
1.32
0.230
0.257
0.272
0.25 phr Pk900
(04)
Unaged
3.90
Aged 1d/100 8C 4.44
Aged 4d/100 8C 4.60
0.89
1.01
1.04
0.228
0.228
0.226
Effect in passenger tire tread
compounds
Tab. 8. Crosslink densities * ± Cure 170 8C/t90
Total
Poly-
Di-
Mono-
C-C
Control
(03)
Unaged
Aged 1d/100 8C
Aged 4d/100 8C
3.64
4.42
5.61
2.56
1.78
0.64
0.70
0.28
0.12
0.34
2.36
4.85
0
0
0
Pk900
0.25 phr
(04)
Unaged
Aged 1d/100 8C
Aged 4d/100 8C
3.58
4.48
5.76
2.61
1.95
0.72
0.81
0.43
0.21
0.16
1.43
3.06
0
0.67
1.72
* (2Mc chem)
352
1
105 gmole/g rubber
The effect of Perkalink 900 in typical truck
tire skim compound (Tab. 1) has been
studied. The loading of Perkalink 900 is
selected based on earlier [18] optimization studies. It is typical that Perkalink
900 reacts when reversion occurs. In
the case of high sulfur compounds, process of reversion and hence formation of
main chain modifications starts earlier
during cure. This allows Perkalink 900
to react during crosslinking process as
evidenced from the extent of crosslinking
(delta S), Tab. 3. The cure kinetics are depicted in Fig. 3.
In order to better correlate and compare viscoelastic properties, physico mechanical properties were determined. The
data are summarized in Tab. 4. These
data are in accordance to our earlier observation [19 ± 28] that perkalink 900 provides the stabilization of compound properties following anaerobic ageing. The dynamic properties (heat build up, hysteresis etc) are vital for tyre performance
point of view. It is remarkable to note
that Perkalink 900 significantly reduces
the heat generation during Flexometer
testing (Fig. 4).
The viscoelastic properties are tabulated in Tab. 5 and 6. As expected, Perkalink 900 reduces the changes in the
tangent delta following ageing. The
Fig. 5 demonstrates this fact. This can
be translated into better maintenance
of properties during service life of the tire.
Although SBR is less prone for degradation, the decline in viscoelastic properties
is not unusual. It is interesting to report
that Perkalink 900 stabilizes dynamic
properties of the compounds following
ageing . The relevant data are summarized in Tab. 7. This stabilization effect is
quite significant as demonstrated in
Fig. 6.
This stabilization effect on tangent delta
can be explained by the changes in the
network structure following ageing. The
data tabulated in Tab. 8 clearly shows
that Perkalink 900 is also active during
the ageing process. The presence and introduction of long, flexible, C-C crosslinks
instead of rigid mono-sulfidic crosslinks
allows the system to behave better with
respect to maintenance of viscoelastic
properties. A comparative distribution between C-C and rigid mono-S crosslinks
are shown in Fig. 7. Although the total
(C-C+mono-S) are the same, the compound containing Perkalink 900 contains
C-C crosslinks instead of mono-S crosslinks.
A probable mechanism for the formation of the C-C crosslinks via Perkalink
900 during the process of degradation
is explained (Fig. 8). This suggests that
conjugated structures are also formed
during service of a tire.
All together it can be concluded that by
using Perkalink 900 it is possible to maintain viscoelastic properties of the compounds during service. The two examples cited above are just extreme examples where the benefits are demonstrated.
Fig. 4. Heat build up characteristics
(Temp. 35 8C; stroke: 4.45 mm; Load: 1Mpa and Frequency: 30Hz)
Summary and conclusions
Fig. 5. Changes in
tangent delta following ageing at
100 8C
(Cure: 150 8C/t90)
The effect of Perkalink 900 has been studied both in NR, skim and SBR, tread
model compounds. The physico mechanical properties as well as viscoelastic
properties were studied. The crosslink
density and distribution of crosslink types
were measured.
The above studies suggest that Perkalink 900 stabilizes changes in viscoelastic
properties as observed during oxidation
ageing process. The network studies dictate [18] that Perkalink 900 forms crosslinks at optimum cure when the system
contain higher level of sulfur as in the
case of skim compound. In SBR tread
compounds, the C-C crosslinks are introduced during ageing process indicating
that Perkalink 900 is reactive at service
conditions.
References
Fig. 6. Changes in
tangent delta following ageing at
100 8C
(Cure: 170 8C/t90)
354
[1] T. D. Skinner and A. A. Watson, Rubber Age 99
(1967) 67.
[2] W. J. van Ooij, Rubber Chem. Technol. 57 (1984)
421.
[3] R. N. Datta, A. G. Talma and J. C. Wagenmakers, Kautschuk Gummi Kunststoffe 50
(1997) 274.
[4] R. N. Datta and M. G. J. Hondeveld, Kautschuk
Gummi Kunststoffe 54 (2001) 308.
[5] R. N. Datta and A. J. de Hoog, Kautschuk Gummi Kunststoffe 54 (2001) 257.
[6] R. N. Datta and A. G. Talma, Kautschuk Gummi
Kunststoffe 54 (2001) 1.
[7] R. N. Datta, A. G. Talma and A. H. M. Schotman,
Rubber Chem. Technol. 71 (1998) 1073.
Fig. 7. Distribution of C-C and monosulfic crosslinks
(Cure: 170 8C/t90)
[8] B. Ellis and G. N. Welding, Rubber Chem. Technol. 37 (1964) 571.
[9] P. J. Flory and J. Rehner, J. Chem. Phys. 11
(1943) 521.
[10] B. Saville and A. A. Watson, Rubber Chem.
Technol. 40 (1967) 100.
[11] M. L. Selker and A. R. Kemp, Ind. Eng. Chem.
36 (1944) 20.
[12] C. G. Moore, J. Polym Sci. 32 (1958) 503.
[13] W. C. Warner, Rubber Chem. Technol. 67 (1994)
559.
[14] R. N. Datta and J. C. Wagenmakers, J. Polym.
Mat. 15 (1998) 379.
[15] R. N. Datta and F. A. A. Ingham, Kautschuk
[16] N. J. Morrison and M. Porter, Rubber Chem.
Technol. 57 (1984) 63.
[17] A. H. M. Schotman, P. J. C. Van Haeren, A. J. M.
Weber, F. G. H. Van Wijk, J. W. Hofstraat, A. G.
Talma, A. Steenbergen and R. N. Datta, Rubber
Chem. Technol. 69 (1996) 722.
[19] R. N. Datta and M. S. Ivany, Rubber World
212(5) (1995) 24.
[20] R. N. Datta, J. H. Wilbrink and F. A. A. Ingham,
Ind. Rubber Journal 8 (1994) 52.
[21] R. N. Datta and W. F. Helt, Rubber and Plastics
News, 1996/1997.
[22] R. N. Datta and W. F. Helt, Rubber World, 216(5)
(1997) 24.
[23] R. N. Datta and M.S. Ivany, Tire Technology International, p100 (1995).
[24] R. N. Datta and J. C. Wagenmakers, Kautschuk
[26] R. N. Datta, A. J. de Hoog and J. H. Wilbrink, L'
Industria Della Gomma 39 (1995) 16.
[27] R. N. Datta, A. G. Talma, J. C. Wagenmakers
and D. Seeberger, Gummi Fasern Kunststoffe
49 (1996) 892.
[28] R. N. Datta, A. G. Talma, B. J. Oude Egbrink and
F. A. A. Ingham, Gummi Fasern Kunststoffe 54
(2001) 179 Kautschuk Gummi Kunststoffe 54
(2001) 257.
The author
Dr. R. N. Datta is Market Development Manager and
Mr. N. M. Huntink is Application Specialist of Flexsys
BV, Technology Center, Holland.
Corresponding author
Dr. R. N. Datta
Flexsys BV
Technology Center
Zutphenseweg 10
NL-7418 AJ Deventer
E-mail: Rabin.n.datta@Flexsys.com
Fig. 8. Formation of C-C crosslinks in SBR compounds during service
355

Stabilization of Dynamic Properties Following Ageing

Transcription

Similar documents

Rubber Chemicals Competitive Cross Reference

Combine the performance of a Rinehart Racing system with the