Silicone Technical Textiles

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role of silicone in technical textile

Text of Silicone Technical Textiles

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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