DR. R.K. KHANDAL

DIRECTOR

NANOCOMPOSITES FOR OPTICAL PLASTIC MATERIALS

SHRIRAM INSTITUTE FOR INDUSTRIAL RESEARCH19, UNIVERSITY ROAD, DELHI - 110007

OUTLINE OF PRESENTATION

OPTICAL APPLICATIONS

OPTICAL PLASTICS

NANO COMPOSITES

METAL CONTAINING PLASTICS

FUTURE OF NANO TECHNOLOGY

An overview presenting, past, present and future options in novel materials

OPTICAL APPLICATIONS

BIOMEDICALS ENGINEERING INSTRUMENTATION INFRA STRUCTURE

OPHTHALMICLENSES

AUTOMOTIVE

AVIATION

SPACE

RADIATION SHIELDING

TELESCOPE

BINOCCULAR

CAMERA

SENSORS

OPTICS

COMMUNICATION(Fibre Optics)

SIGNALS(Railways, Aviation, Road, transport etc.)

SHIELDING

Glass is the most conventional material used in all the above applications; Plastics are viable alternatives

SPECTCLE

CONTACT

INTRAOCULAR

BIO-MEDICAL APPLICATIONS

Optical Devices Parameters Materials Used

Spectacle lenses Refractive index, optical Glass, Polythiourethanesclarity, Abbe number, Polyacrylates, Polycarbonates

Sun glasses Refractive index, UV- Glass, Polyacrylatesresistance, aesthetics

Contact lenses Refractive index, clarity, Polyacrylates and modifiedbiocompatibility, softness/ acrylates, silicones andrigidity modified silicones

Intraocular lenses Refractive index, Polyacrylates and modifiedtransparency acrylates and siliconesbiocompatibility,

Glass has been completely replaced by plastics

Development of newer plastics is the key

INSTRUMENTAL APPLICATIONS

Optical Device Parameters Materials Used

Binocular lenses Magnifying power, Glass, Polyacrylates,Refractive index, clarity Polycarbonates

Telescopes lenses Magnifying power, Glass, Polyacrylates,Refractive index, clarity Polycarbonates

Magnifying glass Magnifying power, Glass, Polyacrylates,Refractive index, clarity Polycarbonates

Tailoring of available materials for achieving varying refractive index Plastics

Plastics provide flexibility and options

INFRASTRUCUTRE APPLICATIONS

Optical Device Parameters Materials Used

Optical waveguides Refractive index, Lithium niobate (LiNbO3), absorbance / Potassium titanyl transmittance phosphate (KTiOPO4)

in polyacrylate

Optical fibres Refractive index, Glass, Polyacrylatesrate of light Metalstransmission

Research is going on for alternate plastic materials for the above applications

Conventional materials would not have been adequate to meets the demand

ENGINEERING APPLICATIONSOptical Device Parameters Materials Used

Optical modulators Refractive index, Lithium niobate (LiNbO3), total internal reflection, Potassium titanyl phosphateinfrared absorbance (KTiOPO4)

Optical demodulators Refractive index, Lithium niobate (LiNbO3), total internal reflection, Potassium titanyl phosphateinfrared absorbance (KTiOPO4)

Optical interconnectors Refractive index, Lithium niobate (LiNbO3), total internal reflection, Potassium titanyl phosphateinfrared absorbance (KTiOPO4)

Liquid crystal dislays Refractive index, Glass, Polyacrylates(LCD) absorbance / transmittance

Use of plastic materials leads to the development of effective, less cumbersome technology

GLOBAL STATUS : PLASTIC LENSES

CHARACTERISTICS

800-850 million lenses per year

7-8 billion in sales

Lens replacement frequency : 2-3 years

Indian requirement is met by imports only

10%

17%

33%

45%

55%

98%

0%

20%

40%

60%

80%

100%

120%

Latin America United States Canada Western Europe Asia Pacific Japan

Countries

% a

s s

ha

re o

f to

tal

len

se

sMARKET FOR ANTI-REFLECTING LENSES

Lens market breakdown by material

Plastic lenses, medium, high

indexes (>1.5 index)

22%

Plastic lenses <1.5 index

42%

Glass lenses36%

MATERIALS USED : LENSES

Clear picture of the gaining popularity for optical plastics

Major plastics is polycarbonate

INDIAN STATUS : LENSES

140 million pieces per year

Export = 112 million pieces per year

Domestic = 28 million pieces per year

Complete requirement is met by imports

Indigenous technologies are required for increase in Indian market demand

Optical plastic industry is engaged in job work

DESIGN CRITERIA FOR OPTICAL PLASTICS

Evaluation of the environment in which the plastic is to be used

Physical and optical properties of the plastics

Physical properties to be considered are density, hardness, rigidity

Service temperature, thermal expansion, electrical and thermal conductivity

CLASSIFICATION OF OPTICAL MATERIALS

Gradient index materials : Glass & Polyacrylates

Low Refractive Index : < 1.5 (CR 39, PMMA & Crown glass)

Medium Refractive Index : 1.5-1.6 (Polycarbonates)

High Refractive Index : > 1.6 (Polythiourethane)

Infrared refractive materials : Fused silica and polycarbonates

Ultra-violet refractive index : Fused silica, polycarbonatesmaterials and Glass

Materials used are fused silica, polycarbonates and glass

OPTICAL PLASTICSPAST

Material : Polymethyl methacrylate (PMMA)

Applications : Spectacle lenses, Contact lenses, Camera lenses, Binocular lenses

Features : High rigidity leading to eye-discomfort in internal wear such as contact lenses. Poor aesthetics leading to bulge eye look.

Poor shatter resistance leading to delicate handling

Availability of the right type of materials was a constraint

PRESENT

Material : Modified acrylates and silicones, Thiourethanes, polycarbonatyes

Applications : Flexible intraocular lenses, Extended wear contact lenses Contact lenses of variable wear

Features : Fixed optical properties Easy to use Economic Better customer appeal

OPTICAL PLASTICS

With newer materials, novel applications have become possible

FUTURE

Material : Organic/ Inorganic hybrid materials, Polymer composites

Applications : Lenses, Optical waveguides,

Optical fillers, Optical transmitters

Features : Wide range of refractive index,Improved stability and hardness,Tailor-making of optical properties possible

OPTICAL PLASTICS

Nano composites have a great potential for future

Advantages Disadvantages

Light weight Soft surfaceImpact resistance Limitation of refractive index

Good machineability Ultra high & low refractive index not possible

Good aesthetics

Good processability

All the above disadvantages can be overcome by only nanocomposites

OPTICAL PLASTICS

Nanocomposites can be designed

NANO MATERIALS : CROSS-SECTIONAL AND INTERDISCIPLINARY APPROACH

AutomotiveComponents

Paper

Cosmetics

Textiles

Displays

Coatings

Emulsions

Dispersions

Plastics

Films

Powders

Science

Chemistry

Physics

Analytics

MaterialScience

Biology

Applications End Products

Materials/Intermediates

Nano-materials

Developing Nanomaterials is a challenge !

TYPES OF NANO-COMPOSITES FOR OPTICAL APPLICATIONS

METAL-GLASS COMPOSITES

METAL-POLYMER COMPOSITES

Areas of application include sensors, wave guides, optical fibres, etc.

Complementary and synergistic compositions for extraordinary effect

TYPES OF NANOCOMPOSITES FOR OPTICAL APPLICATIONS

METAL-GLASS COMPOSITES

Incorporation of metal nanoparticles (Ag, Au) in glass leading to colored glass

Good absorption of incident light: negligible scattering

Concept used since 15th century

Colloidal dispersions of metals in inorganics was an established way

METAL-POLYMER COMPOSITES

Transparency is achieved

Substantial reduction in intensity loss which is size dependent

Refractive index above 2.5 (ultra-high) and refractive index below 1.25 (ultra-low) is possible only with nanocomposites

TYPES OF NANOCOMPOSITES FOR OPTICAL APPLICATIONS

A novel idea of imparting advantageous features of metals to plastics for better

METAL CONTAINING GLASS

Chronology Materials

Potable gold, Potable silver

Prepn. of colored glass by theincorporation of purple, violet, brown or black colloidal powders

Use of colloidal gold powders for the painting of enamel

Detailed analysis of color of gold colloids

Formation of ruby glass using gold particles

Coloured glass with unique features

15th Century

16th Century

17th Century

18th Century

19th Century

20th Century

PRESENT

Materials : Preparation of dichroic films of gelatin and Os, Rh, Ag, Au, P, Hg, As, S, etc. Dichroic films of PVA-Au, Ag & HgSilver add crystallites in ramie, hemp, bamboo, silk, wool, viscose, (5-14nm)

Applications : Eye-wear lenses, cameras, binoculars, sensors, solar applications, filters, transmitters, wave guides, reflectors, etc.

METAL CONTAINING POLYMERS

Metal containing polymers are a novel idea !

FUTURE OF METAL-CONTAINING POLYMERS

NANOPARTICLE

Electronics

Multiuse

Chemical Industries

Defence

OpticsConsumers

Medical/Biology

Solar Cells Sensors

Electrocatalysis

Photocatalysis

For any application, nanotechnology is a blend of the science of physics, chemistry and biology

Field of optics has seen a lot success with nanotechnology; coatings and

diagnostics

As the scale goes down, the activity rises mainly due to the lowering distances at which theinterparticle interactions occur leading to evolution of energy.

Emulsion

High surface energy, Non-homogeneous, unstable

Thermodynamically

ExtremelyHigh

Irreversible

System Scale Activity RemarksMixtures >micrometer Low

Suspension

Dispersion

micrometer Medium kinetically stable

unstableMicroemulsionSolubilised

nanometer ModeratelyHigh stability probable

Thermodynamic

Macromolecular angstrom High

MolecularAtomic

Very High

Nuclear

Spontaneous

atomic

sub-atomic

Thermodynamically stable

Basis for new materialsSource of energy

SIZE - DEPENDENT PROPERTIES OF MATERIALS

CHANGE OF PROPERTIES AT THE NANOMETER SCALE

Chemical reactivity

Electronic properties

Optical properties (absorption, scattering)

Mechanical properties (hardness)

Transport properties (heat, current)

Bioavailability

In addition to quantum effects, the increased surface-volume ratio at the nanometer scale bring improvements in ;

Nanomaterials have extraordinary features

INCREASE IN SURFACE AREA(at constant volume fraction)

1 m 100 nm 10 nm

No. of particles 1 103 106

Surface AreaPer unit volume

1X 10X 100X

Decreasing Particle Size

Combination of two or more phases where at least one phase is in nanometer range

TYPICAL MORPHOLOGIES

FEATURES OF NANOCOMPOSITES FOR OPTICAL APPLICATIONS

Particle size less than 50-100nm leads to less scattering of

light and therefore improves transparency

By incorporation of inorganic colloids with extreme

refractive index in organic polymers ultra high refractive

is possible

High surface to volume ratio improves reduces scattering

losses

Drawbacks of plastics can be eliminated

Tailor-making of refractive index possible

WORK CARRIED OUT AT SRI Selection of suitable metal salts for dispersion

Ba(OH)2, BaSO4, Ba(NO3)2, BaCl2, PbO, (CH3COO)2Pb, PbNO3, LaCl3, La2O3, La(NO3)3, TiO2

Nb2O3, NbC

Acrylic acid as monomer

Selection of polymerization technique Thermal, Gamma Selection of suitable initiator for thermal polymerization Benzoyl peroxide, Azo bis-isobutyronitile (AIBN)

Selection of suitable dose for polymerization by Gamma radiation

Casting of lenses Eight patents on the product & process

Characterization of cast lenses for various opto-mechanical properties Colour Refractive index Abbe number Shore-D hardness Scratch resistance Haze Pencil hardness Impact resistance Machinability Heat distortion (°C) Specific gravity Transmittance (%) Yellowness index LAB value

1.391.4

1.411.421.431.441.451.461.471.48

0 3 6 9 12 15 18 21 24

% age of metal salt

Ref

ract

ive

ind

ex

M-1 M-2 M-3

EFFECT OF METAL SALTS ON REFRACTIVE INDEX OF ACRYLIC PLASTICS

Metal salts are effective in improving the refractive index of acrylic plastics

EFFECT OF CO-MONOMER 1 ON REFRACTIVE INDEX OF METAL DISPERSED ACRYLIC PLASTICS

1.4

1.42

1.44

1.46

1.48

1.5

1.52

0 2 4 6 8 10 12 14

% age of comonomer-1

Re

fra

cti

ve

ind

ex

Significant increase in refractive index of acrylic plastic is obtained with co-monomer 1

M-1 M-2

M-3

1.381.4

1.421.441.46

1.481.5

1.521.541.56

0 2 4 6 8 10 15 20 25 30 35 40 45 50

%age of comonomer-2

Refr

acti

ve in

dex

EFFECT OF CO-MONOMER 2 ON REFRACTIVE INDEX OF METAL DISPERSED ACRYLIC PLASTIC

M-1 M-2

M-3

Significant increase in refractive index of acrylic plastic is obtained with co-monomer 2

PROPERTIES OF GAMMA RADIATIATED SAMPLES CO-MONOMER 1

Dispersion of metal salts resulted in improved optical and mechanical properties of polyacylates

1.1581.2181.044Yellowness index14.

858287Spectral Transmittance (%)12.

1.281.301.31Specific gravity11.

120120120.0Heat distortion (0C)10.

GoodGoodGoodMachinability9.

PassPass PassImpact resistance 8.

4H3H3HPencil hardness7.

6.80-7.0710.7-10.88.24-8.29Haze6.

Grade-BGrade-BGrade-BScratch resistance5.

78-8070-7570-72Shore-D hardness4.

343435Abbe No.3.

1.581.591.56Refractive index2.

Light YellowDark YellowLight YellowColour1.

M-1 M-2 M-3

Metal dispersed polyacrylateAnalysisS. No.

13. Integrated transmittance 0.5563 0.5575 0.5679

0.1592

90

1.23

>120.0

Good

Pass

3H

---

Grade-B

88-90

38-39

1.5603

0.13920.1263Yellowness index14.

8987Spectral Transmittance (%)12.

1.291.24Specific gravity11.

130>120.0Heat distortion (0C)10.

GoodGoodMachinability9.

PassPassImpact resistance 8.

3H3HPencil hardness7.

---2.75-2.84Haze6.

Grade-BGrade-BScratch resistance5.

80-8285-88Shore-D hardness4.

30-3134Abbe No.3.

1.5741.570Refractive index2.

colourlesscolourlessLight yellowColour1.

M-1 M-2 M-3

Metal dispersed polyacrylateAnalysisS. No.

13. Integral Transmittance 0.5933 0.5822 0.7795

PROPERTIES OF GAMMA RADIATIATED SAMPLES CO-MONOMER 2

STANDARD MATERIAL Vs METAL CONTAINING SAMPLES

>2.02.03.0<1.01-2< 1.0Haze,%7.

9092> 908990-9290-95Transmittance6.

1.20-1.301.241.331.201.322.0-5.0Specific gravity5.

GoodPoorModerateModerateGoodPoorImpact resistance

4.

>85< 65>757588-89>90 Shore-D Hardness

3.

35-385726355850-55Abbe number2.

1.56-1.591.451.661.581.491.80Refractive index1.

PA(SRI)

PAPTU(SRI)

PCCR-39GlassPropertiesS.No

Modified polyacrylates can be a good replacement to the conventional optical materials

STANDARD MATERIAL Vs METAL CONTAINING SAMPLES

0.12-1.20.022750.170.07860.00740.0087Yellowness index

13.

0.5533-0.61520.58450.58580.59060.57911.1548Integrated Transmittance

12.

GoodGoodGoodGoodGoodGoodMachinability11.

3H-4H3H6H3H4H6HPencil hardness

10.

Grade-BGrade-DGrade-BGrade-BGrade-BGrade-AScratch resistance

9.

L=51.38-77.05a=-6.25-7.50

b = 23.7-25.50

L=67.50a=6.30

b=20.30

L=67.90,a = 5.50,b = 23.2

L=67.68,a = 6.15,b = 21.8

L=67.44,a = 6.35,b=20.32

L=67.46,a = 6.35,b=20.48

LAB value8.

PA(SRI)

PAPTU(SRI)

PCCR-39GlassPropertiesS.No

Modified polyacrylates can be a good replacement to the conventional optical materials

CONCLUSIONSMaterials can be designed for desired characteristics

Lenses have been cast successfully with barium ,lead and lanthanum salts.

Tailor making of refractive index of polyacrylates have been achieved between 1.550-1.575 using barium salts; 1.560-1.595 using lead salts; 1.550-1.565 using lanthanum salts.

SRI team has been successful in developing metal dispersed nano-composites of polyacrylate with improved Abbe no., hardness, & scratch resistance.

FUTURE OF NANOTECHNOLOGY

Structuresizes

2040 year1960 1980 2020Based on Bachmann, VDI

0.1 nm

0.1 µm

0.1 mm

Nano

Micro

Macro

Integrateduse of

biological principles,physical laws

and chemical know-howComplex chemistry

Electrical engin.

Electronics

Micro-electronics

Material design

Supramolecularchemistry

Quantum effectsCell biology

Molecularbiology Functional

molecule design

Applicationsof

nano-technology

bottom up bottom up

top down

top down

Chemistry

Coatings,cleaning agents,

composite materials,textiles,

cosmetics,displays

Physics

Biology

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