Silicone Technical Textiles

7/14/2019 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 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

Documents

Silicone Technical Textiles