VTC TPE GROUP
TECHNICAL AND PRODUCT
EXPLANATION
TPE Definition
• Thermoplastic Elastomers (TPE’s), have also
been described as Thermoplastic Rubbers
(TPR’s).
• TPE’s are polymer based materials with
similar properties at their service temperature
to vulcanised rubber, but can be processed
and reprocessed at elevated temperatures
like a thermoplastic.
TPE Definition
• TPE’s have also been defined by the classical
elastomer description as materials which after
the application of strain recover to approx their
original shape.
• Using these definitions thus excludes from the
TPE class, hard materials, and it is accepted
materials harder than around 80 Shore A no
longer have elastomeric properties.
TPE COMPARISONS WITH THERMOSET RUBBER
Advantages:
Lower Part Weight
Faster Cycle Time
Waste Eliminated
Processing Energy Reduced
Perfect Parts “Right First Time” (no trimming)
Greater Design Flexibility
Parts 100% Recyclable at End of Life
TPE COMPARISONS WITH THERMOSET RUBBER
Disadvantages:
Limited Heat and Fuel Resistance
Lower Strength Properties
Possibly Higher Material Cost
Established Specification Resistance
HARDNESS OF POLYMERIC MATERIALS
EVA
ABS
TPU
VTC TPE GRADES
THERMOSET RUBBER
PE
FLEXIBLE PVC
0
10
20
30
40
50
SHORE A
60
70
80
PP
90
40
INCREASING HARDNESS
50
60
SHORE D
70
80
TPE COMPARISONS WITH PLASTICS
Advantages:
Improved Low Temperature Resistance
Improved Impact Resistance
Reduced Noise
“Tactile”, Soft Touch Feel
Hard / Soft Design Possibilities
TPE COMPARISONS WITH PLASTICS
Disadvantages:
Possibly Higher Material Cost
Lower Strength Properties
Processing Inexperience / Confidence
TPE PROCESSING ECONOMICS
THERMOPLASTIC ELASTOMER FABRICATION
MATERIALS
FINAL PRODUCT
SHAPING
TPE
THERMOSET RUBBER FABRICATION
MATERIALS
GUM RUBBER
FILLERS
MIXING
SHAPING
VULCANIZE
OILS
ADDITIVES,
ETC
SCRAP
SCRAP
FINAL
PRODUCT
SCRAP
NEED
TO R/C
TPE Compositions
TPE’s are either polymers or more commonly compounds
based on polymer(s) and additives.
TPE’s which are often used as polymers without
compounding are:
Urethane Thermoplastic Elastomers (TPU),(eg “Estane”)
Copolyester Thermoplastic Elastomers (TPC),(eg “Hytrel”)
Polyamide Thermoplastic Elastomers (TPA),(eg “Pebax”)
TPE Compositions
• TPE’s which are commonly compounded materials are:
–
–
–
–
–
–
Olefinic Thermoplastic Elastomers, (TPO)
TPO’s are blends of elastomer such as EPDM and plastic such
as PP or PE
Styrenic Thermoplastic Elastomers, (TPS)
TPS’s are blends of elastomeric polymers such as SBS or
SEBS and plastic such as PS or PP
Thermoplastic elastomer vulcanisates, (TPV)
TPV’s are dynamically vulcanised elastomer blends such as
EPDM blended with plastic such as PP
Performance vs Cost
Performance
Vitaprene+Dryflex
Cost Per Tonne
Fields of Application
Only Western Europe
Field of Application
TPE-S TPE-O TPE-V TPE-U TPE-E TPE-A
Automobile Industry
5
72
8
10
1
2
Wire/Cable
4
1
7
2
0
Shoes
35
1
0
5
2
1
Polymer Modifications
30
2,5
2,5
1
0,3
0,2
Tubes
2
1,5
2
2,5
1,3
1
Frequent Moulding
3
6,5
7
9
1,5
1
Parts in TPE
Bitumen Modifications
40
0
0
0
0
0
Field of Construction
3
0
2,5
0,5
0
0
Glue/Coating Material
20
0
0
12,5
0,2
Film/Foil
0,5
1
0,2
4
0,3
0
Miscellaneous (incl.
6,5
1,4
0,7
1
3,4
0,4
Medicin)
Total
145
89,9
23,9
52,5
12
5,7
Source: Christian Thomas/RAPRA
Total
98
14
44
36,5
10,3
28
40
6
32,8
6
13,4
329
• TPO’s
TPE Compositions
These are normally mechanical blends (without crosslinking), of EPDM rubber and a polyolefin plastic such as
PP and / or PE. Additives such as heat stabilisers
(Irganox), process aids (stearates or amides), fillers
(talcs or calcium carbonate), softeners (paraffinic oil),
colours (carbon black, titanium dioxide); are normally
added to modify properties such as flexibility,
mouldability & extrudability.
TPE Compositions
• TPO’s
Advantages: tend to have very low densities (around
0.88), consistent quality, harder grades more popular,
mid to low price.
Disadvantages: low hardness grades difficult, tend to
have poor flow properties at lower hardness, poor
recovery properties at moderate and especially elevated
temperatures, cost / performance profile not very good.
Applications: Harder grades used for auto bumpers,
airbag covers.
TPE Compositions
• TPS’s
There exists some confusion regarding TPS’s as SBS
and SEBS polymer manufacturers tend to promote
their pure polymers as “thermoplastic elastomers”.
However it is extremely rare that these polymers are
used to fabricate finished parts without compounding.
TPE Compositions
• TPS’s
SBS (Styrene – Butadiene – Styrene) block
copolymers are available in different S to B ratios
(higher S giving stiffer products), different molecular
weights (higher MWt giving poorer flow but better
recovery properties), and “clear” or oil extended (oil
extension tending to give easier processing, better
dispersion compounds). Typical compounds use PS
(polystyrene) as a flow / hardness / process
enhancing plastic additive. SBS has inherently poor
weathering resistance and this can be improved by
additions of other polymers such as EPDM rubber,
EVA (ethylene vinyl acetate), and SEBS
TPS BLOCK COPOLYMER -- PHASE STRUCTURE
ELASTOMER
MIDSEGMENT
POLYSTYRENE
DOMAIN
TPE Compositions
• TPS’s
SBS based compounds;
Other additives such as heat and light stabilisers,
process aids, fillers (talcs or calcium carbonate),
softeners (naphthenic and paraffinic oils), colours are
normally added to modify processing and end use
properties. The following shows an overview of
typical property changes brought about by
compounding additives. These changes are only
general but common to most types of polymer based
TPE’s
Compounding Additive Effects
Material
Increase level
Decrease level
Elastomer
less stiffer, more rubbery,
reduce flow, hinder processing,
increase cost
more stiff, poorer recovery,
increase flow, improve processing,
reduce cost
Plastic
more stiff, less rubbery
increase flow, improve
processing, reduce cost
less stiff, better recovery, reduce
flow, poorer processing, increase
cost
Filler
increase density, reduce
recovery reduce flow rate,
reduce strength reduce mould
shrinkage,reduce cost (less so
volume cost)
reduce density, more rubbery
increase flow, increase strength,
increased mould shrinkage,
increase cost
Softener
reduce stiffness, increase flow,
reduce cost, reduce strength
more stiff, reduce flow, increase
cost, increase strength
EFFECT OF FILLER LEVEL ON COST OF TPE COMPOUND
140
120
100
80
WEIGHT COST
COST
VOLUME COST
60
40
20
0
0.89
1.10
1.26
SPECIFIC GRAVITY
1.40
1.51
TPE Compositions
• TPS’s
SBS based compounds;
•
Advantages: large hardness spread possible (35A
to 60D), low to mid price
•
Disadvantages: poor weathering resistance, poor
recovery properties at elevated temperatures
•
Applications: rubbery articles for moderate
temperature and weathering resistance
TPE Compositions
• TPS’s
SEBS (Styrene – Ethylene – Butylene – Styrene)
block copolymers like SBS are available in different
Styrene, and Molecular Weight levels. Higher MWt
grades give poorer flow but improved recovery
properties. Major advantage of SEBS grades over
SBS based grades are their excellent weathering and
elevated temperature recovery properties.
Typical compounds use PP (polypropylene) as the
plastic additive.
TPE Compositions
• TPS’s
SEBS based compounds;
Due to the very high molecular weight of SEBS it is a
very extendable base polymer, and can be highly
extended with fillers and in particular oil to produce
the widest range of hardness of any TPE family (0A
to 60D)
TPE Compositions
• TPS’s
SEBS based compounds;
•
Advantages: can have very low densities (0.89),
extremely wide hardness range with “jelly” like (0A)
materials possible. Excellent weathering and good
recovery properties up to 70 to 100 Deg C. Fast
moulding cycles
•
Disadvantages; relatively high price base polymer, can
be very shear sensitive, can be difficult to obtain good
dispersion
TPE Compositions
• TPV’s
These are blends, normally of EPDM and PP, which
during mixing, and under the correct high shear
conditions; the elastomer is chemically cross-linked in
very small domains and finely distributed in the PP.
This process called dynamic vulcanisation, enables
improved recovery properties at elevated
temperatures, and better fluid resistance compared to
the TPS compounds.
TPE Compositions
• TPV’s
As the elastomer portion of the TPV is chemically
crosslinked, enough plastic “carrier” must be used to
enable the compound to be thermoplastically
processed. Although oils, and fillers can be added,
this elastomer crosslinking tends to make low
hardness grades (below say 40 A) difficult
THERMOSET RUBBER - PHASE STRUCTURE
Sx
S
S
S
S
Sx
S
Sx
S
Si
RUBBER CROSS-LINKED WITH CHEMICAL LINKAGES
MORPHOLOGY OF THERMOPLASTIC
VULCANIZATES
VULCANIZED ELASTOMER
1 MICRON
PLASTIC MATRIX
RUBBER DOMAINS CROSS-LINKED WITH CHEMICAL LINKAGES
TPE Compositions
• TPV’s
•
Advantages: Excellent weathering resistance, and
good recovery properties up to around 100 to 120
Deg C. “Feel” of vulcanised rubber. Very fast
moulding cycles (can be demoulded quite hot)
•
Disadvantages: relatively expensive
manufacturing process, with smaller mixing “window”
than TPS grades. Low hardness grades difficult. Low
strength at lower hardness’s
TPE Compositions
• Other styles of “TPE’s”
TPZ’s
PVC based compounds in blends with high plastisicer
levels and Nitrile Rubber are promoted by some
companies as TPE’s. These compounds can be low in
price, relatively high in strength, but tend to be of high
density, unstable melt during processing, Halogen
containing, poor recovery properties at elevated
temperatures, can suffer from plasticiser migration, “PVC
odour” and have a Plastic feel.
GENERAL COMPARATIVE PROPERTIES OF TPE TYPES
PROPERTY
TPS
TPS
TPC
TPA
TPZ
SBS
SEBS
(ETHERESTER)
(AMIDE)
FLEXIBLE PVC
15A to 60D
1A to 60D
35A to 60D
60A to 60D
60A to 85D
90A to 70D
60A to 70D
40A to 40D
SPECIFIC GRAVITY
RANGE
0.9 to 1.3
0.89 to 1.3
0.9 to 1.1
0.86 to 1.0
1.05 to 1.25
1.13 to 1.25
1.01 to 1.2
1.2 to 1.35
SERVICE TEMP.
RANGE C
- 60 to + 60
- 60 to + 100
- 60 to + 120
- 60 to + 60
- 60 to + 110
- 60 to + 110
-60 to + 130
-30 to + 70
COMP. SET
GOOD
GOOD
GOOD
FAIR
FAIR
FAIR
POOR
FAIR to GOOD
RESISTANCE
(10 to 30%)
(10 to 20%)
(15 to 25%)
(20 to 30%)
COMP. SET
POOR
FAIR to GOOD
FAIR to GOOD
POOR
FAIR
FAIR
POOR
POOR to GOOD
RESISTANCE
( > 70%)
( > 35%)
( > 30%)
( > 70%)
FAIR to
GOOD
FAIR to
POOR to FAIR
FAIR to GOOD
GOOD to
EXCELLENT
GOOD
GOOD
GOOD
WEATHERING
RESISTANCE
POOR
GOOD to
EXCELLENT
EXCELLENT
EXCELLENT
GOOD
GOOD to
EXCELLENT
GOOD
GOOD to
EXCELLENT
OIL & FUEL
POOR
POOR to FAIR
FAIR
POOR
GOOD to
GOOD
POOR to
GOOD
FAIR to GOOD
HARDNESS
TPV
TPO
TPU
RANGE
AT ROOM TEMP
AT 70C
STRENGTH
RESISTANCE
GOOD
EXCELLENT
VTC TPE GROUP
PRODUCTS
• Dryflex grades designed for injection moulding
• Vitaprene grades designed for extruded products
• Dryflex grades originally developed in Elastoteknik, and
were predominantly TPS based grades. Produced now
in Elastoteknik or VTP
• Vitaprene grades originally developed in VTP, and were
“hybrid” blends of several polymers. Produced now in
VTP or Elastoteknik
• Mediprene grades developed for the Medical industry
only and produced in VTC France
VTC TPE GROUP
PRODUCTS
• Compounding of Dryflex and Vitaprene
The acknowledged most efficient way to mix TPE
compounds is by continuous twin screw extrusion
compounding. These compounders are fed by
particulate polymers and additives by automatic loss
in weight feeders. Another more labour intensive
method is by internal mixer (“Banbury mixer”). This
route can be more flexible, more easily fine tuned,
and can feed baled polymers.
Once compounded the polymer melt is extruded
through a die plate fitted with high speed cutters to
produce pelletised compound of typically 3mm size.
VTC TPE GROUP
PRODUCTS
• Compounding of Dryflex and Vitaprene
VTP have both internal mixers and twin screw
compounders, each on a production scale, and in the
laboratory, where test samples of 1 to 50 Kg can be
produced.
Elastoteknik have twin screw compounders, again in
production and pilot plant sizes.
Both sites are geared to react quickly to sampling
customers with new compound developments, and
continual evaluation of new compounding materials.
VTC TPE GROUP
PRODUCTS
• Property Identification
TPE materials are distinguished by their physical
properties and also by their processing
characteristics.
Development and testing facilities at VTP and
Elastoteknik are excellent and can produce the
“fingerprint” of all our TPE (and any competitors)
compounds by evaluating chemical, rheological, and
physical properties.
VTC TPE GROUP
PRODUCTS
• Property Identification
Elastoteknik and VTP Laboratories are equipped
with single screw extruders to monitor and
develop correct extrudability and die swell.
Both sites have injection moulding equipment to
produce test plaques, and monitor mouldability,
with Elastoteknik having 2K (Two Shot),
overmoulding capabilities and bond strength
testing equipment.
•
VTC TPE GROUP
PRODUCTS
Property Identification
Typical Testing:
DSC, TGA, FTIR, Ash Content, Solvent Extraction, Specific Gravity –
all these can identify base polymer(s), oils, filler types, and
proportions.
Melt Flow Rate, Capillary Rheometry, Spiral Mould Flow – all these
can indicate the “flowability” of a compound, during extrusion or
moulding.
Hardness, Modulus, Elongation at Break, Tensile Strength, Tear
Strength – these physical properties show the flexibility and
toughness of the fabricated compound.
Compression Set, Tension Set, Stress Relaxation – all indicate how
well a material resists and recovers from deformation at different
temperatures.
•
VTC
TPE
GROUP
PRODUCTS
Property Identification
Typical Testing:
Abrasion Resistance, Flex testing – how a product performs in a wearing
environment.
Oil and Fluid Immersion testing -- indicate how a product swells / shrinks
and changes physical properties in contact with fluids at different
temperatures.
UV Weathering and Ozone exposure – quickly show if a material will give
an adequate outdoor service life.
Vertical and Horizontal Burning -- characterise a materials flammability.
Colourmeter testing -- identifies a products colour by a three dimensional
grid number, and not just by the naked eye.
Heat Ageing and Low temperature brittleness -- shows the materials long
term resistance in service to temperature extremes.
Fogging -- identifies if a material is suitable for in car or under glass
applications.
TPE Developments
• The compound database we have, of over 3000 TPE
compounds, includes grades which comply with certain
national and automotive standards. Such standards include
the BSI and RAL glazing gasket requirements,
Underwriters Laboratory flammability testing, and
numerous European and global automotive specifications.
TPE Developments
• Priority Developments currently under way:
Improved Oil and Fuel Resistance TPE grades,
coupled with improved heat resistance, ideally for
under bonnet products
To compete property wise and commercially with
thermoset (NBR) rubber
Fuel Resistance
Volume Swell % 70h @ 23 Deg C Petrol BS7070
100
90
80
70
60
50
40
30
20
10
0
CR
NBR
Vitaprene
EPDM
TPE Developments
• Use of Automotive Post Consumer Waste
in automotive exterior trim applications
Utilising Tyre Crumb at levels between 25 and 50% by
weight of the total compound, and Reprocessed
Polypropylene at 15 to 60%, TPE compounds, with good
physical properties for exterior products, with extremely
high levels of PCW can be produced at VTC
TPE Developments
• Use of Automotive Post Consumer Waste
The tyre crumb used is available from a number of
approved sources in Europe, and has a particle size
around 300 microns (0.300 mm Dia.) The material is
purchased to agreed tolerances on properties such as
sieve analysis, ash content, volatiles
The product has a controlled and accepted level of
“restricted substances” (eg. Heavy Metals)
TPE Developments
• Use of Automotive Post Consumer Waste
The Reprocessed Polypropylene again is available
from several European sources, is supplied as a
specification controlled raw material, with MFR,
Strength, Impact, Melt Temperature, and Ash Content
controlled, and again meeting requirements for
“restricted substances”
TPE Developments
• Use of Automotive Post Consumer Waste
Adjusting levels of Rubber based Tyre Crumb and
Polypropylene, and addition of other compounding
additives such as additional elastomer and plastic,
filler, softener, process aid, stabiliser; gives VTC
technologists the tools to design ranges of
compounds with a wide potential property spectrum
TPE Developments
• Use of Automotive Post Consumer Waste
Typical formulation examples:
80 Shore A
40 Shore D
50 Shore D
Tyre Crumb ~ 50%
~ 40%
~ 25%
Repro PP
~ 15%
~ 35%
~ 55%
Misc. Ingds. ~ 35%
~ 25%
~ 20%
TPE Developments
• Use of Automotive Post Consumer Waste
All PCW compounds are produced to “written in
stone” recipes, using consistent controlled
feedstocks, with all ingredients used within a +/- 1%
weighment tolerance.
Compounds are mixed using identical run to run
mixing cycles, and product tested to customer’s
agreed Quality Plan which can include MFR,
Hardness, S.G. and Stress / Strain parameters.
Despatched lots are accompanied with a Certificate
of Analysis
TPE Developments
• Use of Automotive Post Consumer Waste
Advantages:
Environmentally / ELV logical
Faster moulding cycles
Potential Weight Saving
Tailor Made compounds
Potential Noise Reduction
Improved Impact Resistance, especially at lower temps.
TPE Developments
• Use of Automotive Post Consumer Waste
Disadvantages:
Odour of thermoset rubber
Product finish can reflect level of crumb (Advantage ?)
TPE Developments
• TPV / Hybrid Compounds
VTP has developed initial series of TPV compounds, the “XL”
range, to compete with current market TPV grades, but also to
offer property processing advantages such as
Hopper Ready (No Drying)
Easier to colour
Supply of colour matched compound
Tailor Made compounds to offer optimum price / performance fit
TPE Developments
• TPV / Hybrid Compounds
Good opportunity in Auto Extruded Seals, for glazing,
belt line / body seals
Under bonnet seals, deflectors, shields, grommets,
plugs, damper mounts, boots / bellows
Oil Resistance enhancement required
TPE Developments
• TPV / Hybrid Compounds
Testing of VTC XL grades to Ford WSD-M2D 378-A1/-A2,
379-A1/-A2, 380-A1/-A2, and 381-A1/-A3 specifications for
TPV materials, has revealed compliance results;
except in oil resistance and change in heat aged
stress/strain properties to original.
(Recent Fogging tests carried out at Elastoteknik show all
XL compounds tested gave comfortable compliance)