Polymers for Modifying Bitumen

CHAN
GING TIMES . . .

CHANGING .
REQUIREMENTS . .

KRATON™ D polymer: the cost effective

modifier in asphalt road paving
Meeting requirements through block, which for bitumen applications is usually made up
of polybutadiene. However, for some applications out
modification of polyisoprene, it is tipped at all ends with polystyrene
end-blocks.
Asphalt is the dominant paving material for roads and Polystyrene and polybutadiene, when mixed together
runways. Polymer modification of the bituminous binder would not form a single-phase blend. In fact they would
has become widespread due to increases in number and behave like water and oil. After blending and if left
severity of requirements. undisturbed, they would again separate in to two distinct
These requirements include: phases. However, the polystyrene and polybutadiene are
chemically united in SBS, which does not allow phase
❖ Heavier loading of roads due to increased amount of
separation to take place.
traffic and its increasing weight.
❖ The increased safety expectations for skid resistance
On a micro-scale however, phase separation does take
and state of the roads surface over its lifetime.
place, and the styrenic end blocks of different molecules
❖ Need to reduce overall cost to authorities and users
associate forming styrene domains. At the other end of
including maintenance costs and delays together with
each molecule the same phenomenon occurs linking into
the insurance related vehicle damage.
a different styrene domain creating a three dimensional
❖ Improved ride comfort for the road user.
and network structure.
❖ Reduced impact on the living environment by,
for instance, noise emission reduction.
❖ Ease and speed of construction, to optimise Effect of SBS block copolymers on
building costs and minimise end product bitumen binders
quality variations.
SBS polymers absorb the ‘oily components’ from the
Because of its suitability to meet these requirements, bitumen increasing their volume to as much as 10 times
Styrene-Butadiene-Styrene (SBS) block copolymer has the polymers volume. The network formed by the styrene
become the leading polymer modifier for bitumen. domains is inflated but can remain intact throughout the
Product capability and market leadership mean that binder giving it elastic properties over a much wider
KRATON polymers products are recognised as the temperature range. This reduces the viscous behaviour at
benchmark in the roads industry. high temperature and the brittle behaviour at low
temperature. Properly formulated SBS - bitumen binder
Styrene Butadiene Styrene block therefore results in:
copolymers
❖ Improved resistance against permanent deformation at
KRATON SBS block copolymers have a molecular high temperature through its high (zero shear) viscosity
structure that is characterised by a rubbery core mid- derived from its polymer network.
❖ Improved crack resistance at low temperature by shifting the critical cracking
temperature to lower levels.
❖ Improved resistance against mechanical and thermal fatigue due to its
increased toughness
❖ Improved fretting resistance by improving the
binders’ toughness.
❖ Improved ageing resistance and resistance against
ageing brittleness, in particular for the exposed binder
in porous asphalt.

The success of SBS block copolymer-modified binders is

related to its performance in these widely varying situations.
The recent introduction of the more advanced performance
specifications in the USA has highlighted the enhanced
performance of SBS-modified binders and has further
accelerated the growth in their use.

KRATON polymer grades used in road and

runway paving
Bitumen is a natural product of widely varying composition even for the same
grade. This depends on parameters such as the crude oils origin, the age of the oil
well, the refinery processing conditions and the blended components used.
Consequently a customised approach is needed using a palette of grades to adapt
to variations in bitumen composition and to the performance specifications or
requirements. But with proper formulation, most bitumens can be used as a basis
for a SBS modified bitumen binder.

The following grades are widely used for road and runway paving applications:
❖ KRATON D1101, the road paving SBS benchmark grade with 31% polystyrene
content.
❖ KRATON D1192 A patented new grade with modified butadiene mid-block
giving a lower viscosity of the bitumen polymer blend, a higher bitumen polymer
compatibility and better ageing properties.
❖ KRATON D1116 A radial, low styrene SBS molecule for blends with a higher
butadiene requirement.
❖ KRATON D1118 A high SB di-block containing granular polymer for use in
combination with vulcanisation agents such as sulphur.
❖ KRATON D1102, A low molecular weight, linear SBS for producing polymer
modified bitumen with a low melt viscosity.
❖ KRATON D1184 and KRATON D1186, for those applications requiring very
high softening points.

Specific applications in emulsions

Emulsions have shown a recent rapid increase in popularity due to their improving
technology and the increasing desire to minimise delays. The advance of polymer-
modified emulsion technology has also brought additional performance benefits to
road paving solutions based on emulsions.
The use of KRATON D1192 which result in a lower viscosity polymer bitumen blend
enables the production of emulsions with a higher polymer content or, on average,
substantially smaller particles in the emulsion.

For emulsions also, KRATON polymers’ wide grade range and

formulation knowledge has greatly benefited customers around
the world.

Road paving examples

There are numerous examples of KRATON polymers used in roads
around the world, from the Californian desert to the extreme
climate of north eastern China. With the appropriate choice of
bitumen and polymers, the formulations can be adapted to hot
climates, cold climates and climates with large temperature
variations.

The advantages of KRATON polymers have again been demonstrated under the
extreme conditions of a Formula One motor racing circuit such as Sepang Malaysia
with its tropical conditions and Magny Court in central France, and also in the UK’s
Rockingham Speedway course. In all these situations aggregate losses due to the
extreme shear forces resulting from the high speeds and adherence of the tyres can
be reduced to a minimum by the increased toughness obtained with the addition of
KRATON polymers.

Another extreme application is airport runways, where shear forces at touchdown

and concentrated vertical loads from the wheels pose extreme demands on the
asphalt mix and pavement design. Here also the toughness and elasticity at
temperatures extremes enables runways to perform, for instance, in the heat and
cold of Almaty in Kazakhstan, the heat of Brunei airport, the cold of Anchorage
(Ted Stevens) airport but also at such busy airports as Schiphol, Amsterdam.

The use of KRATON polymers in bridge decks

Bridge decks of both concrete and steel bridges require
waterproofing and an asphalt mix paving. Both elements are
subjected to extreme conditions due to their un-dampened
temperature exposure and the loading induced strains.

For waterproofing of the bridges’ construction material, special

KRATON polymers modified sealing felts can be applied. Due to
their extreme elasticity, toughness and crack resistance at low
temperature and flow resistance at high temperatures they are
highly suited and widely applied for this application. The high
temperature resistance is necessary to minimise ageing damage
during the applications of the asphalt mix.

The elastic recovery and toughness of a polymer-modified

bituminous binder also applies to the asphalt mix used on the bridge
deck. Use of KRATON polymers not only reduces the risk of cracking damage
due to strains resulting from movements in the bridge, but also the toughness of the
binder assists in preventing delamination among the different asphalt mix layers or
between the asphalt mix and the underlying waterproofing layer.
KRATON products and other The KRATON companies
applications KRATON Polymers LLC and its subsidiaries (known as
KRATON Polymers) comprise a group of companies
KRATON polymers are high performance thermoplastic
operating world-wide. This truly global Business
elastomers engineered to enhance performance
pioneered styrenic block copolymer chemistry more
capabilities within a wide spectrum of applications
than 40 years ago, and remains committed to the
which include:
industry and its customers all over the world.
❖ Polymer modified bituminous felts for roofing and
other waterproofing applications.
Quality product is manufactured in six countries world-
❖ Hot melt and pressure sensitive adhesives such as
wide, and there are five research establishments in
tapes and label adhesives.
Europe, the USA, Japan and
❖ Compounding for enhancing toughness, grip, feel
Brazil. An international workforce
and appearance of products ranging from toys,
of employees service customers in
automotive to packaging.
over 120 countries, and successful
❖ Compounds for applications in shoe soles.
sales, marketing and distribution
❖ Sealants.
networks operate globally
❖ Coatings.

There are currently over a 100 grades of KRATON KRATON Polymers is owned by
a group of investors led by
polymers and compounds comprising:
Ripplewood Holdings LLC, a
❖ Styrene Butadiene Styrene block copolymers (SBS)
US-based investment firm.
❖ Styrene Isoprene Styrene block copolymers (SIS)
❖ Hydrogenated SBS and SIS polymers: Styrene-
Ethylene-Butylene-Styrene (SEBS) and
Styrene -Ethylene-Propylene-Styrene (SEPS)
❖ Hydrogenated polymers with functional groups
❖ Polyisoprene rubber

KRATON Companies contact info

In Europe/Africa/Middle East: Fax: +44 (0) 1829 770961
In the USA: call toll free 1-800-4-KRATON (1 800 457 2866) or +1 832 204 5384 (from outside USA)
Fax +1 832 204 5459
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In Asia Pacific: Japan: fax +81 3 3769 5994 Hong Kong: fax +852 257 14118

E-mail: info@KRATON.com Visit us at www.KRATON.com

or contact your local KRATON Polymers Sales Manager
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