Polymer-Ceramic Composite Film Fabrication and

Characterization for Harsh Environment Applications

Santiranjan Shannigrahi

OUTLINES:

Polymer-ceramics composites

Basic applications

Current pain

Case study

Conclusions

GRAPH OF MATERIALS PRODUCTION

Source: CES EduPack, University of Cambridge/Granta.

Polymer – ceramic composites

APPLICATIONS OF POLYMER COMPOSITES

CURRENT PAIN

Harsh environment:

• Light/heat

• Moisture,

• UV illumination.

Significant Impact on polymer matrices

CASE STUDY

Composites: 1. Epoxy matrixTemperatureMoistureReversibility

2. PE matrix

UV and temperature

COMPOSITE FILM FABRICATION

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UV-Chamber

UV-VIS characterization

UV-3101 PC

UV-VIS-NIR-spectrophotometer SHIMADZU, (90-2500 nm)

Mechanical testing

Flexural testing using three point bending set up

Humidity chamber (90% Rh & 90oC

Specimens

HARSH ENVIRONMENTS AND CHARACTERIZATIONS

The total UV energy is 84.30 W/m2

EXPERIMENTAL DESIGN (EPOXY)

• Three factors can affect the properties of the epoxy in hygrothermal environment

1. Elevated temperature •Relaxation of polymer matrix

2. Moisture ingression• Changed interchain hydrogen bonding force & plasticization

3. Chemical reaction • Bond scission on main chains (backbones)

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0 10 20 30 40 50220

225

230

235

240

245

Gla

ss T

ran

siti

on

Tem

p

No. of Days

Tg of 90°C /90H

Glass Transition Temperatures of Aged Epoxies

Variation of glass transition temperature (Tg).

0 5 10 15 20 25 30 35 40 45 50

3.7

3.8

3.9

4.0

4.1

4.2

4.3

4.43 Point Flexural Test

Ave Flexure S

tress (MP

a)

Ave

You

ng M

odul

us (G

Pa)

Number of Days

100

110

120

130

140

150

160

170

180 60 oC, 90% humidity

90 oC, 90% humidity

Young’s modulus and Flexural stress variation.

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THERMO MECHANICAL PROPERTY VARIATIONS

AVERAGE WEIGHT GAIN %

• No equilibrium of moisture absorption after 90 days – Non-Fickian behavior (I)

• Irreversible process (Chemical reaction).

Moisture has significant effect on the interfacial mechanics and is strongly correlate with the oxidation of CNF surface

Two classes of carbon fiber surface are consideredNo surface modification (Model-I)Modified with –OH (Model-II)

The interactions across the interface are purely non-bonding, i.e., VDW + electrostatic interactions.

Added water plays a role of plasticizer at the CNF/epoxy interface, and it leads to wider attraction region.

After moisture ingression, interfacial force is enhanced with strong fluctuation. Possible reason: enhanced hydrogen bond interaction. Local stress may break some hydrogen bonds (cluster) and leads to the fluctuation.

MOISTURE EFFECT ON INTERFACIAL ADHESION

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SIMPLIFIED MODEL SYSTEM

The barriers are very high. → Hydrolysis (Chemical aging) is very slow in the neat epoxy resin!

(1) Reaction I

(2) Reaction IIHN

OH

+ H2O

OH

+HN

OH

• C-O bond breaking for C from aliphatic and benzene are:– Ea ≥ 265 kJ/mol and ≥ 259 kJ/mol respectively

• C-N bond breaking: Ea ≥ 191 kJ/mol

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• A structure (97% crosslinked) contains ~550 C-N bonds in the main chains(328 from curing reaction and others from initial structure). Meanwhile, it contains only ~ 80 C-O bonds (side chains are neglected).

• Bond scission on C-N bonds is more crucial for mechanical property degradation.

EFFECT OF C-N BOND BREAKING • Structures with different percentages of broken bonds

– 0.0%, 4.0%, 7.0%, 10%, 15%– 3 configurations for each degree of bond scission

Creating broken bonds leads to decreased density

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Assuming that Young’s modulus is linearly correlated with the degree of bond broken, there exists a critical degree at which the epoxy resin breakdown completely.

Percolation Threshold?

cnf/water/epoxy cnf-OH/water/epoxy

H2O

Water at interface

Water embedded into bulk

HYDRATED MODELS

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EXPERIMENTS – REVERSIBILITY

Objective: To study reversibility of epoxies after ageing → Chemical ageing

After drying the wetted epoxies at 90°C for 48h, the following experiments have been conducted

3-Point Bending DMA FTIR

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REVERSIBILITY: TG

No. of days

Tg (°C)

0 238.22

42 234.29

50 235.20

82 234.59

Tg declines weakly with ageing duration – Weak chemical degradation?

0 20 40 60 80

234

235

236

237

238

239

Gla

ss T

ran

siti

on

Tem

p (

oC

)

No. of Ageing Days

60 oC, 90% RH

Decline in Tg of 20°C from as-received (dry) to 49 days (wet) is due to the lowering of intramolecular hydrogen bonding forces and increased moisture concentration which acts as ‘plasticizers’.

Wetted

Re-dried

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REVERSIBILITY: FTIR RESULTS

Bands (cm-1) Assignment

3600-3100 OH stretching

3000-2850 CH stretching of the alkyl

1600-1585 C-C stretching in aromatic ring

1500-1400 C-C stretching in aromatic ring

1335-1250 C-N stretching (aromatic amines)

1250-1020 C-N stretching (aliphatic amines)

1320-1000 C-O stretching (aromatics)

1600 1400 1200 1000 8000.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Ab

so

rba

nce

Wavenumber (cm-1)

0-day + 2 day of drying 50-day + 2 day of drying 90-day+ 2 day of drying 110-day + 2 day of drying

C-C stretchesin aromatic rings

C-N

*

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4000 3800 3600 3400 3200 3000 2800 26000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Ab

so

rba

nc

e

Wavenumber (cm-1)

0-day + 2 day of drying 50-day + 2 day of drying 90-day+ 2 day of drying 110-day + 2 day of drying

O-H Stretching

C-H Stretching

N-H

• Weakly increased O-H stretching peak

— There is residual moisture inside the sample even after 2-days of drying.

Irreversible effect due to chemical ageing

UV BARRIER POLYMER-CERAMIC COMPOSITES

Patent no. 2014/123488 A1

Lead-free transparent ceramic; Thickness 0.8 mm

500 1000 1500 2000 2500 3000-5

0

5

10

15

20

25

30

35

40 +00.00 kV/cm +06.25 kV/cm +12.50 kV/cm +18.75 kV/cm +25.00 kV/cm -12.50 kV/cm -18.75 kV/cm

Tra

nsm

ittan

ce (

%)

Wavelength (nm)

UV

- re

gion

IR r

egio

n

Transparency window

Tunable ~55% Transmittance

capability

FEATURES OF THE CERAMIC FILLERS

Potential applications: Complete UV absorption; UV absorption indication through color change; Optical Coating and filter for UV; Tunable electro optic ceramics; etc.. Advantages: Nontoxic, robust and thermally stable, block UV, transparent to NIR, low thermal conductivity, electro optic tunability

POLYMER-CERAMIC COMPOSITE

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E N

eat

5%

10%

20%

Ceramic amount

Film

Film thickness is ~ 160

UV-VIS SPECTROSCOPY ANALYSIS

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WEATHERABILITY TEST CONDITIONS

Specimens kept in UV chamber for a 40 h and tested for their physical (crack) and chemical (degradation) properties.

Q: How long will it take to reproduce 5 years of sunlight artificially?

A: Assuming that sunlight in Singapore is similar to sunlight in South Florida (both are sub-tropical environments) and 1 Y of total UV (295-400nm) in Miami is 280MJ.

The formula is: kJ = irradiance x 3.6 x N hours

So the 1080 hours 1 year. To duplicate 5 years of weathering, the total time would be 5400 h or 225 days. This is a crude assumptions for a guide.

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MECHANICAL PROPERTIES OF THE COMPOSITE FILMS BEFORE AND AFTER UV ILLUMINATION

Sample

Max Tensile strength after UV irradiation

Neat 8% decrease

5% 14% increase

10% 18% increase

20% 11% increase

CONCLUSIONS:

In epoxy based composite immersed in moisture and

temperature, their properties become irreversible,

which is due to chemical ageing

In PE based composites, UV absorbing ceramic fillers

improve the mechanical properties, UV resistance and

suitable for harsh environment applications.

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Thank you!