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Silicones in
Technical TextilesPadmadas Nair
11.12.09,Kusumgar Corporates
Dow Corning Corporation
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Topics
Dow Corning Introduction
Silicone Chemistry
Silicone Coating Chemistry
Silicone Coatings Applications
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Dow Corning Today
The market leader in the silicones industry
More than 7,000 products and services
More than 25,000 customers world-wide
Sales of $5.0 billion in 2008 8,800 employees world-wide
4,600 active patents globally
65 percent of business outside the U.S.
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Industries We Serve
Automotive
Industrial Lubrication
Construction
Power & Utility
Oil & Gas
Personal Care
Household & Cleaning
Products
Rubber Fabrication
Healthcare
Electronics
Compound Semiconductors
Pressure Sensitive
Chemical Manufacturing
Textile & Leather
Imaging
Paints & Coatings
Services
Paper/Labels
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Silicones in Textiles
Fiber Production
Yarn/Thread Production
Fabric Production
Fabric Processing
Apparel or Home/Industrial Textiles
Spinneret Lubes
Spin Finishes
Antistats
Fiberfill FinishesAntifoams
Antimicrobials
Lubricants
Yarn Softeners
Antifoams
Warp Lubricants
Antifoams
Hydrophilic TreatmentElastomer Coatings
Elastomeric Finishes
Antimicrobial
Antifoams
Wetting AgentsAntistats
Softeners
Water Repellents
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Silicone Chemistry
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SiliconeProperties-General
The Silicone Polymer
- viscosity range 0.65 to 1 million cst
Volatiles, Fluids, Gums ,Emulsions, Resins, Solids
Trimethyl end-blocked
O OO
Si Si Si
CH3 CH3CH3 CH3
CH3 CH3
CH3Inorganic Backbone
Organic pending groups
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SiliconeProperties-F lexible Backbone
O OO
Si Si Si
CH3 CH3 CH3 CH3CH3 CH3
Inorganic Backbone
Rotation About the BondsC-C 3.3 kcal/mol
Si-O 0.2 kcal/mol
Bond Angle LengthC-C 112 o 0.154 nm
C-O 111 o 0.142nm
Si-O 130 o 0.163nm
Si-O bond is even and long.
Si-O bond is free to move
Silicone Molecule:- long and strong
- free to move
- no overlapping of chainSilicone has low inter molecular force
Bond StrengthC-C 85 kcal/mol
C-O 81 kcal/mol
Si-O 117 kcal/mol
Si-O bond is stable
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SiliconeProperties-Low Surface Tension
O OOSi Si Si
CH3 CH3 CH3 CH3 CH3 CH3
CH3
etc
Organic pending groups
- Strongly hydophobic
* Low surface tension of Silicone comes from ;1) Low inter molecular forces btn Methyl group => low surface E
2) Flexibility of Siloxane backbone => maximize the effect of Methyl group.
Silicones spread over its own adsorbed film
- complete surface coverage- excellent spreading agent
S.T. (mN/m)
Water 72
Water + Surfactant 30
Ethanol 50
PDMS 20
Hg H2O SoapSilicone
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SiliconeProperties-Summary
Thermal Stability
Low Tg
High Flash Point
Low Polarity
Low Heat of Evaporation
Low Surface Tension
Hydrophobicity
High Compressibility
Physiological Inertness
Low Dielectric Constant
High Gas Permeability
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SiliconeSummary of Character istics
Polydimethylsiloxane Backbone Flexibility Easy orientation
Product Variation
Low Intermolecular Attraction Liquid at high molecular weights
Low friction with polymers
Permeability
High Spreading coefficient
Methyl Pendant Groups
Low surface tension Limited solubility
Hydrophobic surface
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SiliconeI nf luence on Environment & Health
Polydimethylsiloxanes (PDMS) are removed from liquid waste by absorptiononto sewage sludge. They therefore do not contribute to the BOD or COD ofthe effluent.
PDMS does not inhibit bacteria involved in wastewater treatment.
PDMS bound to sewage sludge degrades in soil when sludge is used as afertilizer.
PDMS degradation occurs via an initial chemical reaction catalyzed by clayminerals followed by biological degradation.
The ultimate degradation products of PDMS are carbon dioxide, silica andwater.
Incineration of solid wastes also results in the formation of carbon dioxide,silica and water.
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Silicone Coating Chemistry
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Silicone Coatings
Features/Benefits
Silicone Coatings
Easy to process
(one or two parts)
Chemical
Resistance
Low
shrinkage
Food contact
applications
possible(FDA, BGA)
Good Adhesion
Some Skin
contact application
Water
ResistanceGood Release
properties
Wide temperature
range (-50 to 300 C possible)
Weathering Resistance
cCan be Flame
Resistant
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0100200300400500
0 2 4 6 8 10 12 14 16Exposure Time (days)
ElongationatBreak(%)
Silicone RubberNeopreneNitrileButyl
Elongation at Break After Aging at
150oC
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Classification of Silicone Elastomer
Terminology
HTV (High Temperature Vulcanizing Rubber)
RTV (Room Temperature Vulcanizing Rubber) HCR (High Consistency Rubber)
LSR (Liquid Silicone Rubber)
HCR
LSR
Peroxide cure
Addition cure
Addition cure
RTV
HTV
Silicone
Elastomer
Addition cure
Condensation cure
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Flowable, one-part silicone rubber for fabric coating
Form an elastomeric film on curing at room temperature
Applied by standard coating method
Provides very high and low temperature resistance
Very elastic rubbery coating, up to 400% elongation
Can be food grade
Catalyst Condensation
CH3 CH3 CH3 CH
- Si - O - Si - O - Si - O - Si
CH3 CH3 CH3 CH
CH3 CH3
- Si - O - Si - O Ac + H2O
CH3 CH3
polymer
CH3 CH3
-Si - O - Si - O - H + HO
Ac
CH3 CH3
Silicone Chemistry
RTV Rubbers
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RTV Elastomers
Features/Benefits
RTV Elastomers
Chemical
resistance
Extreme
temperature
stability
Water
resistance
Anti-slip at Low
shore hardness
Very good adhesion to
glass, organic fibers,
metal
100% solids
Some products are
FDA/BGA approved
Very resistant to liquid
water and soapsCan produce flame
resistant elastomers
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What is LSR
Two component, A&B
A pumpable viscous liquid (flowable to thick phase)
Addition cure system based on vinyl containing PDMS and
methylhydrogensiloxane with a platinum catalyst
Mixing ratio of part A &B is most likely 1:1
Can be cured at room temperature to elevated temp.
Injection molding is a typical way to fabricate
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LSRs Features/Benefits
LSRs
Heat cure
Typically two-part
systems
Very good electrical
insulator
Weathering resistance:
flexible after 20 years ofoutdoor exposure
(ATSM D518)Can cure deep
sections Additional cure
chemistry
No humidity
required
Good adhesion to
glass and polyamide
Chemical Inertness
Highly resistant to water,
steam, weak acids and base,
polar solvents and wide
variety of chemicals
Fats, oils, hydrocarbon and
aromatic solvents cause
swelling, but not permanentdeterioration
Attacked by strong
acids and bases
Stiffing point is measured
by ASTM D797
-55C for most LSRs
Some phenyl LSRs can
get down to -100C
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Tensile Strength After Aging at 150oC
0
500
1000
1500
2000
0 2 4 6 8 10 12 14 16Exposure Time (days)
TensileStre
ngth(psi) Silicone Rubber
Neoprene
Nitrile
Butyl
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Material P * 109a
-----------------------------------------------------------------
Collagen 2710 800
Sil icone Rubber 1830 210Epoxy 1480 113
Nylon 6 94
Polystyrene 65 12
Polyethylene 11.3 1.6aln units of cm3.cm/(s.cm2.cm Hg)
* Siloxane chain mobility and free volume are important controlling factors for thepasses of gaseous permeates through silicone rubber.
Permeability to Water Vapor at 25 C
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Oxygen Permeability of Polymers
Polymer P * 109a-------------------------------------------------------------------
Dimethylsi l icone Rubber 60.0
Natural rubber 2.4
Butyl rubber 0.14
Cellulose acetate 0.08Nylon 6 0.004
PTFE 0.0004
* High level of permeability for gases ==> Improved comfort factors
: 25 times more permeable to oxygen than is natural rubber,429 times than butyl rubber.
No through-goingpores
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Typical LSR Coating Line
Knife
Curing Oven
Part A
Pump
Part B
Pump
Static Mixer
Take-up Roll
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LSR Dispensing System
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Silicone and Organic Coating
Comparison
Advantages of SiliconeCoatings
Superior cold resistance (specialty Sigrades can perform as low as -85C).
Better retention of tensile andelongation properties after heat aging.
Relatively high surface friction(useful for some applications).
Easy to process (many coating
systems are 100 percent solids).Less chance of worker sensitizationafter repeated handling, especiallycompared to acrylics and urethanes.
Advantages of OrganicCoatings
Lower cost (except PTFE).
Low dirt pick-up (PTFE, polyurethane,acrylic).
High initial tensile strength.
Good chemical resistance (PTFE,nitrile).
Good heat resistance (PTFE).
Low surface friction (PTFE).Recyclable (PVC).
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Silicone Coating
Applications
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Conveyor roll coating
9050/30P, Syl-
Off SL-5060Base /SRX 212
Catalyst
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LSR 9254, 5050/Bellows for train
Customer: succeeded indeveloping bellows and beingqualified by module maker.
Application: Bellows for train,bus
Fabric: Aramid fabric
Requirement: Basic fabricstrengths, FR (Burning, LOI,gas generation). LOI spec: >40%. Passed spec.
Silicone: LSR(9254+5050)+others
Process: Knife coating on bothsides of fabric
Reference: Attached in the right
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3730A&B/Protective glove coating
Aramid fabric knit with low elongation.
Knife coating trial using 590 EU, 3730 to coat 100~150
gsm.
Both offered similar FR and passed FR test due to high coatweight.
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DY 35-5088/Coating of Electro conductive fabric
Protection of electro conductive agent treated onpolyester fabric using LSR.
Fabric is treated by electro-conductive agent andpolyurethane is not good in terms of washing
durability and electrical property but silicone works
well. Surface handle and adhesion to WR treated
fabric were not easy to overcome. Exothermic (=heat generation)
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Conveyer belt coating
Customer needs: ~1mm silicone coating on different
substrates, such as PET, PU, rubber.
Belts coated with 734 RTV , customer is satisfied
with the performance,
Process: Knife coating on endless belt for 0.8 mm.
Summary Trend
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Summary Trend
Towards Silicone
Environmental issues will have more impact on- production sites, consumers, nature
New techniques and materials will evolve to resolve problems and create
better products,
- Limited room to improve performance of PU, Acrylics, PVCs etc
Cost effective and long service life
Performance at lighter weight and small sized.
Stronger regulation and specification
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Summary
Silicones can bridge the divide between
organics and PTFE coatings.
Dow Corning will work in partnerships with
innovative companies in respective fields toexpand silicone applications.
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Thank You !
Padmadas Nair
Dow Corning India Pvt LtdPhone: +91 9833356006
E-mail: [email protected]
www.dowcorning.com/textiles