TYPES OF TPEs
&
SELECTION CRITERIA FOR
END APPLICATIONS
© ANOMITRA CHAKRAVARTY
KPS CONSULTANTS & IMPEX PVT. LTD.
www.kpsimpex.com
ETDS CONFERENCE – DELHI, 5 th. MARCH 2014
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Introduction
> Thermoplastic Elastomers (TPEs) combine the processing
advantages of thermoplastics with the flexible, low-modulus
properties of elastomers.
> Worldwide demand for TPEs is forecast to grow at 5.5 percent
per annum to 5.8 million metric tons by 2017.
> Main growth - automotive components, consumer durables
roofing, adhesive / sealants / coatings, industrial etc.
>
Main growth will come from Asia / Pacific
>
Growth segments TPOs and TPVs
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Some End Applications
Consumer: Toothbrush Handles, Running Shoes, Hand & Power
Tools, Toys, Footwear, Home-ware etc.
Healthcare: Medical - Tubing, Stoppers, Bags & Bottles etc.
Electrical & Electronics: Cable & Wire Jacketing, Connectors &
Plugs, Consumer Appliances etc.
Packaging:
Cap
Liners,
Overmoulded
Caps,
Closures
&
Containers, Films & Sheets (modifiers)
Industrial: Hose & Tubing, Safety Equipment etc.
Building & Construction: Roofing Sheets, Window Sealing etc.
Automotive: Hose & Tubing, Interior, Window Sealing, Cable
Jacketing, Under the Hood components etc.
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TPE FAMALIES
1) Thermoplastic Polyolefin's (TPE-O or TPO)
2) Block Copolymers based on Styrene and Butadiene (TPE-S)
(e.g. SBS & SEBS)
3) Thermoplastic Vulcanizates (TPE-V or TPV)
4) Thermoplastic Polyester Elastomer (TPE-E)
5) Polyether Co-polyamides (TPE-A)
6) Thermoplastic Polyurethanes (TPE-U)
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Thermoplastic Polyolefin's (TPE-O or TPO) are blends of PP with
rubber, mainly ethylene propylene rubber (EPR), fillers and additives
produced by compounding or by reacting in a sequence of reactors.
They can be produced to a hardness down to 75 Shore A. Lower
hardness is difficult to achieve because the oil tends to migrate to the
surface of the pellets or molded parts.
TPE-O Major properties
Good surface appearance
Elastomeric feel
Plasticizer free
Mechanical properties (high elongation at break and tear strength
Paint adhesion
Easy to color
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Polyolefin Plastomers (POP) and Elastomers (POE) - bridge the
gap between elastomers and thermoplastics, with rubber-like
properties and the processability of plastic.
E.g. Affinity® and Versify® from Dow Chemical,
Exact® from Exxon Mobil Chemical
Elastamax® TPO (POE) from PolyOne
Exact plastomers are ethylene alpha olefin copolymers that are mainly
used as polymer modifiers in flexible Packaging (enhance toughness,
clarity and sealing performance), Molded and extruded products
(improve impact strength and flexibility), Foamed compounds (add
durability to lightweight shoe midsoles)
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Block Copolymers based on Styrene and Butadiene (TPE-S or
SBS & SEBS) - produced by anionic polymerization. Styrene monomer
is first introduced in a reactor and polymerized using a catalyst, building
a low molecular weight block. When the styrene has been reacted,
butadiene is added and the polymerization continues and builds a high
molecular weight block of polybutadiene. A coupling agent is then
added and the SBS block copolymer is created.
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The butadiene block can be hydrogenated to give another soft block with
a structure that is close to ethylene butylene random copolymers. The so
formed block copolymer is called SEBS. It has a better thermal stability
than SBS due to the removal of the double bonds of the rubber block.
TPE-S (SEBS) Major Properties
Soft touch
Room temperature compression set
Tear strength
Transparency
Excellent surface appearance
High elasticity
Non slip
Easy to color
Low hardness (down to 5 Shore A)
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Polystyrene and polybutadiene being incompatible, the block copolymers
are two phases systems. The polystyrene is the dispersed phase that ties
the polybutadiene together and behaves like a crosslink.
SBS and SEBS block copolymers are difficult to process. They are
compounded with oil, filler and polyolefin's to make them easy to process
and to adjust their properties to the applications.
SBS compounds are mainly used in the shoe industry. They are used for
low demanding applications where product lifetime is short and long-term
UV and thermal stability are not needed.
SEBS compounds are used for more demanding applications in all
market segments e.g. grips where the soft touch, anti slip properties,
good resistance to oil and grease are needed. TPE-S bond to PP, PE or
PS; special grades bond to engineering resins (PA, ABS, PC)
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TPE-S (SEBS) Major Properties
Soft touch
Room temperature compression set
Tear strength
Transparency
Excellent surface appearance
High elasticity
Non slip
Easy to color
Low hardness (down to 5 Shore A)
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Thermoplastic Vulcanizates (TPE-V or TPV) are blends of PP with
crosslinked rubber, oil and filler produced using a process called
dynamic vulcanization.
Production of such compound requires high shear where a
thermoplastic and a suitable rubber are first intimately mixed before
adding the curatives for the cross linking reaction.
Morphology of the resulting blend is a continuous phase of
thermoplastic with crosslinked particles of rubber finely dispersed; the
smaller the particle size, the better the properties.
TPE-V based on PP and EPDM are well known and replace
crosslinked EPDM, Polychloroprene (CR) and Chlorosulphonated
Polyethylene (CSM). E.g. Santoprene®, Vyram®, Geolast®, Vistaflex®
from ExxonMobil Chemical.
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TPE-V (PP) Major Properties
Soft touch
High temperature compression set
Resistance to oil and grease
Long term stress relaxation
Fatigue resistance
Non slip
Easy to color
TPE-V are probably the TPE that have the closest properties to
thermoset rubber. They have been successfully introduced as rubber
replacement in window profile extrusion, automotive weather seals and
suspension bellows. They are used instead of TPE-S as soft touch
materials when oil resistance is needed in power tools applications for
example.
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Thermoplastic Polyester Elastomer (TPE-E, COPE) is a highperformance rubber replacement solution that exhibits similar
mechanical behavior as rubbers, with the ease of use and recycle of
thermoplastics.
TPE-E are built from soft polyether blocks combined with hard
polyester blocks. By playing on the polyether / polyester ratio a broad
range of hardness can be covered by TPE-E.
TPE-E show a higher thermal resistance than TPE-O, TPE-S and
TPU and are widely used in over-moulding applications, leading to
competitive manufacturing processes where assembly of two different
parts made of two different materials is not a separate step.
Typical industrial applications are shock absorbers, industrial flexible
coupling components, high performance sound dampeners etc.
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Typical automotive applications are: covers for airbags, steering
wheels, armrests; under-the-hood tubes and hoses, constant velocity
joint boots. Typical consumer goods are: soft-grip applications,
mobile phone antennas, electronics protective housings, handles.
TPE-E Major Properties
High chemical resistance
High wear-resistance
Good resilience
Good Thermal resistance
High surface aesthetics
Good paintability
E.g. Arnitel® from DSM, Hytrel® from DuPont
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Polyether Co-polyamides (TPE-A, PEBA) are prepared by reacting a
polyamide bearing carboxylic acid end groups and a polyether diol in
the presence of a catalyst. Various types of Nylon can be used. The
ratio of Nylon to polyether determines the hardness of the TPE-A
formed; the type of Nylon determines the thermal behavior (melting
point) of the TPE-A.
TPE-A are among the most expensive but also the most performing
TPE. They are used in demanding applications where no other TPE can
be used or when dynamic properties are required. One property of
interest is the almost constant value of the modulus over a wide range
of temperatures.
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TPE-A Major Properties
Low density
Chemical resistance
High strength and toughness
Resilience
Outstanding low temperature properties
Very good dynamic properties
Thermal stability
TPE-A are mainly used in end sport shoes, conveyor belts, silent
gears, breathable films etc.
E.g. – Pebax® from Arkema, Vestamid® from Evonik Corp.
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Thermoplastic polyurethane (TPE-U or TPU) is a class of
polyurethane plastics with many useful properties, including elasticity,
transparence and resistance to oil, grease & abrasion. Technically they
are thermoplastic elastomers consisting of linear segmented block
copolymers composed of hard and soft segments.
TPU are formed by the reaction of diisocyanates with short-chain or
long-chain diols (so-called chain extenders). The practically unlimited
amount of possible combinations producible by varying the structure
and / or molecular weight of the three reaction compounds allows for
an enormous variety of different TPU.
TPU has many applications including automotive instrument panels,
caster wheels, power tools, sporting goods, medical devices, drive
belts, footwear, inflatable rafts, electronic devices, variety of extruded
film, sheet and profile applications.
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Main Properties of TPU
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Main Applications of TPU
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Selection Criteria
for End
Applications
Hardness Range Covered by the Different
Families of TPE
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Effect of Hardness on Properties
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Effect of TPE on Hardness / Property Balance
Tensile Strength at Break for 90 Shore A Hardness TPE
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Service Temperature Range
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Compression Set at Room Temperature
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Compression Set at 70°C
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Oil Resistance (ASTM D2000 / SAE J200)
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Resistance to Hydrocarbons
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Resistance to Polar Solvents
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UV Stability
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Abrasion Resistance
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Abrasion resistance of materials vis-à-vis typical TPU compound
Acknowledgements: OMNEXUS
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Thermoplastic Strip Builder™ by REMCO ®
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Thermoplastic elastomers including TPUs, TPRs, TPOs and others
which have physical properties that compare favorably to their
thermoset cousins, add significant additional processing advantages.
• No post-application curing required (energy & time saving)
• Faster application & lower labour cost (as compared to cast TPU &
thermoset elastomer)
• Can be ground to finished diameter after cooling to room temp.
• Reuse of process waste & re-grinds (material & cost saving)
• Same tooling can be used (extruder and strip conveying system
needs to be changed)
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THANK YOU
Mr. Anomitra Chakravarty
Technical & Project Consultancy in the field of
Elastomers, Thermoplastics, Recycling & Composites
www.kpsimpex.com
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