IMPROVEMENT OF
NATURAL RUBBER - SILICA INTERACTION
BY SILANE-GRAFTING OF THE POLYMER
KARNDA SENGLOYLUAN, JACQUES W.M. NOORDERMEER, KANNIKA SAHAKARO, WILMA K. DIERKES, ANKE BLUME
DEPARTMENT OF RUBBER TECHNOLOGY AND POLYMER SCIENCE, FACULTY OF SCIENCE AND TECHNOLOGY, PRINCE OF SONGKLA UNIVERSITY, PATTANI CAMPUS, THAILAND
ELASTOMER TECHNOLOGY AND ENGINEERING, DEPARTMENT OF MECHANICS OF SOLIDS, SURFACES AND SYSTEMS (MS3), FACULTY OF ENGINEERING TECHNOLOGY, UNIVERSITY OF TWENTE, ENSCHEDE, THE NETHERLANDS
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NATURAL RUBBER - SILICA INTERACTION
BY SILANE-GRAFTING OF THE POLYMER
OUTLINE
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Introduction
What can we win by using silica technology?
https://www.iea.org/publications/freepublications/publication/TheFutureofTrucksImplicationsforEnergyandtheEnvironment.pdf
Reduction in fuel consumption in passenger car tires: up to 7 %
With courtesy from Apollo Global R&D
https://www.fesports.com.au/blog.php?article=38 ht tp ://w w w .ru b be rn ew s.c o m /a rtic le /2 0 1 80 92 5/ N E W S /1 8 0 92 99 67 /a po llo -ro lls -o u t-fir st-tru ck -tir es -fr om -p la nt -in -h u ng a ry
Road freight transport makes up 32% of
total transport-related energy demand
US: app. 3.3 mb/d of oil-based fuels for
road freight transport
Oil use from road freight vehicles was
close to 17 mb/d in 2015
7% savings = app. 1,2 mb/d worldwide
https://www.iea.org/publications/freepublications/publication/The FutureofTrucksImplicationsforEnergyandtheEnvironment.pdf
Advantages
Renewable resource
Converts solar energy
to raw material
Effective CO
2sequester
Low energy input
Low fertilizer demand
Valuable source of timber
Outstanding properties
Low hysteresis
High tensile strength
High elasticity
Good resilience
Low heat build up
Resistance to abrasion
Resistance to crack growth
Flexibility at low temperature
cis -1,4 polyisoprene
n
C
CH
3CH
2H
2C
H
C
Introduction
Introduction
What makes natural rubber so special?
cis
trans
C
CH
3CH
2H
2C
H
C
2
C
CH
3CH
3H
2C
H
C
n
C
CH
3CH
2H
2C
H
C
C
CH
3CH
2CH
2OH
H
C
2 trans-1,4 isoprene units 1000 – 3000 cis-1,4 isoprene units
proteins Mono- or di-
phosphate group
Introduction
Where’s the problem with silica-silane and tire polymers?
Silica particle
Silica:
hydrophilic
Rubber:
hydrophobic
E Si O Si O Si O Si O Si O Si O O O OH O OH Si Si O tO (CH2)3 (CH2)3 Si O (CH2)3 OEt S S Si OEt EtO (CH2)3 S S S S S SIntroduction
What’s the problem with silica-silane and NR?
Processing and dispersion improves
Deproteinized NR (0,4 %wt proteins) NR (1,3 wt% proteins) Skim rubber (13 %wt proteins)
Flocculation
But: no bond to the polymer!
Pre-treated silica
Introduction
Approaches for silica-silane in NR
Silica particle
Modified natural rubber
Silanes (vinyl-, mercapto-, aminosilanes, TESPT, …)
In-situ polymerization of monomers onto the surface
(styrene, isoprene, butadiene)
Plasma polymerization (acetylene, thiophene)
Epoxidation of NR
Butadiene grafted with mercaptosilane
Silanization
Pre-treated silica
Introduction
Approaches for silica-silane in NR
Silica particle
Modified natural rubber
Silanes (vinyl-, mercapto-, aminosilanes, TESPT, …)
In-situ polymerization of monomers on the surface via
bi-layers of surfactants (styrene, isoprene, butadiene)
Plasma polymerization (acetylene, thiophene)
Alcohols (methanol, hexadecanol)
Epoxidation of NR
Butadiene grafted with mercaptosilane
Melt mixing:
Brabender® 50EHT (Brabender® GmbH & Co.KG, Germany)
140
C, 12 minutes, 60 rpm
Silane:
OTPS: 3-OctanoylThio-1-PropyltriethoxySilane
MPDS:
3-MercaptoPropyl-di(triDecan-1-oxy-13-penta(ethyleneoxide) ethoxySilane
Concentration: 10, 20 phr
Initiator:
1,1′-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane
Concentration: 0.1 phr
Experimental
Grafting of silane onto NR
CH3 CH3 CH3 O O O C CH3 CH3 CH3 O C CH3 CH3 CH3 CH3 CH3 CH3 O O O C CH3 CH3 CH3 2 Fragmentation C CH3 CH3 O CH3 2 2 (I) (II) T
O C
CH
3
CH
3
CH
3
or
CH
3
(I)
(II)
HS C
3
H
6
Si
OCH
2
CH
3
O(CH
2
CH
2
O)
5
C
13
H
27
O(CH
2
CH
2
O)
5
C
13
H
27
S C
3
H
6
Si
OCH
2
CH
3
O(CH
2
CH
2
O)
5
C
13
H
27
O(CH
2
CH
2
O)
5
C
13
H
27
CH
4
or HO C
CH
3
CH
3
CH
3
H
2
C
C
CH
H
3
C
CH
2
n
H
2
C
C
CH
H
3
C
CH
n
Si
OCH
2
CH
3
O(CH
2
CH
2
O)
5
C
13
H
27
O(CH
2
CH
2
O)
5
C
13
H
27
S
C
3
H
6
CH
2
C
CH
2
H
3
C
CH
2
n
C
3
H
6
Si
OCH
2
CH
3
O(CH
2
CH
2
O)
5
C
13
H
27
O(CH
2
CH
2
O)
5
C
13
H
27
S
O C
CH
3CH
3CH
3or
CH
3(I)
(II)
H
2C
C
CH
H
3C
CH
2 nS
CH
2Si
OCH
2CH
3OCH
2CH
3OCH
2CH
3 3C
H
2C
H
3C
O
6S
CH
2Si
OCH
2CH
3OCH
2CH
3OCH
2CH
3 3CH
2C
CH
2H
3C
CH
2 nC
3H
6Si
OCH
2CH
3OCH
2CH
3OCH
2CH
3S
H
2C
C
CH
H
3C
CH
nSi
OCH
2CH
3OCH
2CH
3OCH
2CH
3S
C
3H
6C
H
2C
H
3C
O
6C
H
2C
H
3C
O
6CH
3or
O C
CH
3CH
3CH
3Experimental
Grafting reaction
O C CH3 CH3 CH3 or CH3 (I) (II) HS C3H6 Si OCH2CH3 O(CH2CH2O)5C13H27 O(CH2CH2O)5C13H27 S C3H6 Si OCH2CH3 O(CH2CH2O)5C13H27 O(CH2CH2O)5C13H27 CH4 or HO C CH3 CH3 CH3 H2C C CH H3C CH2 n H2C C CH H3C CH n Si OCH2CH3 O(CH2CH2O)5C13H27 O(CH2CH2O)5C13H27 S C3H6 CH2 C CH2 H3C CH2 n C3H6 Si OCH2CH3 O(CH2CH2O)5C13H27 O(CH2CH2O)5C13H27 S O C CH3 CH3 CH3 or CH3 (I) (II) H2C C CH H3C CH2 n S CH2 Si OCH2CH3 OCH2CH3 OCH2CH3 3 C H2C H3C O 6 S CH2 Si OCH2CH3 OCH2CH3 OCH2CH3 3 CH2 C CH2 H3C CH2 n C3H6 Si OCH2CH3 OCH2CH3 OCH2CH3 S H2C C CH H3C CH n Si OCH2CH3 OCH2CH3 OCH2CH3 S C3H6 C H2C H3C O 6 C H2C H3C O 6 CH3 or O C CH3 CH3 CH3 NR-g-MPDS NR-g-OTPS CH3 CH3 CH3 O O O C CH3 CH3 CH3 O C CH3 CH3 CH3 CH3 CH3 CH3 O O O C CH3 CH3 CH3 2 Fragmentation C CH3 CH3 O CH3 2 2 (I) (II) T Decomposition of 1,1′-di(tert-butylperoxy)-3,3,5-trimethylcyclohexaneExperimental
Compounding & mixing
Mixing procedures Cumulative
time (mins.) Step 1: Internal mixer
- NR and silane-grafted-NR (or NR only) mastication - Addition of first half of silica (and ½ of silane if any) - Addition of second half of silica (and ½ silane if any) and
TDAE oil
- Addition of ZnO, stearic acid and TMQ
2 7 12 15
Step 2: Two roll mill
- Addition of DPG, CBS and sulfur 5
Mixer; Brabender® 50EHT, Mixing chamber volume: 70 cm3 TCU settings: 100°C Dump temperature: 135-150°C Ingredients phr RSS3 100.0 100.0 95.0-80.0 TESPT - 4.7* -Grafted NR** - - 5.0-20.0 Zeosil 1165MP 55.0 55.0 55.0 TDAE oil 8.0 8.0 8.0 ZnO 3.0 3.0 3.0 TMQ 1.0 1.0 1.0 Stearic acid 1.0 1.0 1.0 DPG 1.0 1.0 1.0 CBS 1.5 1.5 1.5 Sulfur 1.5 1.5 1.5
* TESPT 4.7 phr = 8.6 wt% rel. to silica ** OTPS- and MPDS-grafted-NRs were prepared by using silane contents of 10 and 20 phr
Silane contents for straight use were calculated based on silane loading in the non-purified silane-grafted-NR Amount of OTPS/MPDS-grafted NR Total amount of silane (wt% rel. to silica) Grafted with 10 phr of silane 5 phr 10 phr 15 phr 20 phr 0.8 1.7 2.5 3.4 Grafted with 20 phr of silane 5 phr 10 phr 15 phr 20 phr 1.5 3.0 4.6 6.1
Results: TESPT versus OTPS and NR-g-OTPS
Processing, filler-filler & filler-polymer interaction
Silane content (wt% rel. to silica)
Similar filler hydrophobation
Less chemical filler-polymer
coupling for OTPS
Shielding of filler similar for high
concentrations
Suppression of flocculation
independent of concentration
Results: TESPT versus OTPS and NR-g-OTPS
Reinforcement
Better filler-polymer network formation for
NR-g-OTPS compared to straight addition
Similar reinforcing strength
at equal concentrations
Results: TESPT versus OTPS and NR-g-OTPS
Breaking interface topography
no compatibilizer with TESPT at 8.6 wt%
rel. to silica with OTPS at 3.4 wt%
rel. to silica
with OTPS-grafted-NR containing total OTPS of 3.4 wt% rel. to silica
with OTPS at 6.1 wt% rel. to silica
with OTPS-grafted-NR containing total OTPS of 6.1 wt% rel. to silica
Results: TESPT versus MPDS and NR-g-MPDS
Processing, f
iller-filler & filler-polymer interaction
Silane content (wt% rel. to silica)
Similar filler hydrophobation
Less chemical filler-polymer
coupling for MPDS
Similar shielding of filler
MPDS MPDS
MPDS MPDS
MPDS MPDS
Results: TESPT versus MPDS and NR-g-MPDS
Strength & breaking pattern
Strength properties reflected in
breaking pattern
with MPDS-grafted-NR containing total silane of
6.1 wt% rel. to silica with MPDS at 6.1 wt% rel. to silica with TESPT at 8.6 wt% rel. to silica without compatibilizer MPDS MPDS MPDS MPDS
Results: TESPT versus NR-g-OTPS & NR-g-MPDS
Processing, f
iller-filler & filler-polymer interaction
Similar filler
hydrophobation
Better shielding of silica
surface by OTPS
Blocked thioester-group &
triethyl-moeities more
reactive for chemical
coupling
MPDS
MPDS
Results: TESPT versus NR-g-OTPS & NR-g-MPDS
Reinforcement
Better filler-polymer network
formation for OTPS
Final strength comparable
MPDS MPDS
Results: TESPT versus NR-g-OTPS & NR-g-MPDS
Dynamic properties
TESPT gives the best secondary network highest storage modulus
No compatibilization: poor filler-polymer interaction highest loss modulus
Higher Tg for grafted NR more restricted polymer movement
Tan δ at 60ºC for silane grafted onto NR similar to TESPT expected similar reduction in rolling resistance
MPDS MPDS
