M I Shahzad1, M Giorcelli1, N Shahzad1,2, S Guastella1, M Castellino1, P Jagdale1 and A Tagliaferro1

1Department of Applied Science and Technology (DISAT), Polytechnic of Turin, Turin-10129, Italy. 2Center for Space Human Robotics, Italian Institute of Technology (IIT), Turin-10129, Italy.

Corresponding Author: Muhammad Imran Shahzad Carbon Group, Department of Applied Science & Technology, Polytechnic of Turin, Turin-10129, Italy

Email: imran.shahzad@polito.it, URL: www.polito.it/carbongroup

FABRICATION OF PDMS-MWCNTs COMPOSITE FILMS

. Schematic of Steps Involved in the Fabrication of PDMS-MWCNTs Composite Films FESEM Images of MWCNTs from Cheaptubes®

The commercial MWCNTs (diameter~10-30nm and

length~20-30μm) from CHEAPTUBES®, produced by

catalyzed chemical vapor deposition are used in this

work. MWCNTs are highly entangled due to Van der

Waals attractive forces.

FTIR Spectra summarizes the positions of IR

absorption bands of the chemical groups found

in the PDMS-MWCNTs composites. There is a

minor shift in the peak at 930 cm−1 with

increasing concentration of CNTs in PDMS. In

addition the ratio between the two

transmission values at 900 cm−1 and 930 cm−1

decrease with increasing CNT content.

Raman spectroscopy is performed using a

green laser source (λ~532nm). The D-peak and

the G-peak are the characteristic peaks of

CNTs. The intensity of these peaks is increasing

proportionally with the increase in CNTs inside

polymer, proving good dispersion of CNTs and

uniformity of films. The other peaks in Raman

spectra are attributed to the PDMS structure.

RAMAN SPECTROSCOPY FTIR SPECTROSCOPY

Embedding CNTs in the PDMS matrix can open new fields of application for this well established polymer. The morphological study proved reasonably well dispersion

and random orientation of CNTs into the PDMS composite films. The Raman Spectroscopy as well as FTIR analysis demonstrated the bonding between CNTs and

polymer. The optical characteristics established that PDMS-MWCNTs composite films are promising materials to extend performance of optical limiting devices and

this effect depends on the quantity of CNTs.

9-13 October, 2012 Islamabad, Pakistan

UV-VIS SPECTROSCOPY OF PDMS-MWCNTs COMPOSITE FILMS

These results suggest that,

through a tuning of the

specular transmittance, these

films might be of interest in

laser technology as optical

absorbers to tune the laser

beam power density.

Absorption A=100-(Rd+Rs)-(Td+Ts)

Absorption Coefficient α=1/t *log(1-R)/T

Transmittance

Reflectance

Optical Density OD = log (1/T)

Diffusivity D = (Td+Rd)/(1-A)

Absorption Coefficient vs Weight % of CNTs in PDMS

Transmittance vs Weight % of CNTs in PDMS

For the comprehensive study

of optical behavior of these

polymeric films, optical

characteristics are measured

both for direct as well as

diffused light. The important

parameters are shown here. 200 300 400 500 600 700 800

0

10

20

30

40

50

60

70

80

90

100

Specular (Ts) + Diffused (Td) PDMS_0.0

PDMS_0.5

PDMS_1.0

PDMS_1.5

PDMS_2.0

PDMS_2.5

PDMS_3.0

Tra

nsm

itta

nce

T(%

)

Wavelength (nm)

---------- Specular (Ts)

200 300 400 500 600 700 800

3

4

5

6

7

8

9

10

11

12

13

200 300 400 500 600 700 800

3

4

5 PDMS_0.0

PDMS_0.5

PDMS_1.0

PDMS_1.5

PDMS_2.0

PDMS_2.5

PDMS_3.0

To

tal R

efl

ecta

nce R

(%)

Wavelength (nm)

Sp

ecu

lar

Refl

ecta

nce R

S(%

)

Wavelength (nm)

500 1000 1500 2000 2500 3000 3500

Ra

ma

n In

ten

sit

y (

a.u

.)

PDMS_0.0

PDMS_0.5

PDMS_1.0

PDMS_1.5

PDMS_2.0

PDMS_2.5

PDMS_3.0

0

Si-

C A

sym

me

tric

Str

ech

ing (

787

cm

-1)

CH

3 S

ym

me

tric

Ro

ckin

g (

862

cm

-1)

Si-C

H3 S

ym

me

tric

Ro

ckin

g (

687

cm

-1)

Raman Shift (cm-1

)

Si-

C S

ym

me

tric

Str

ech

ing (

708

cm

-1)

Si-

O-S

i S

ym

me

tric

Str

ech

ing (

488

cm

-1)

D P

eak M

WC

NT

s (

136

2cm

-1)

G p

eak M

WC

NT

s (

158

2 c

m-1)

CH

3 A

sym

me

tric

Be

nd

ing (

141

2cm

-1)

CH

3 S

ym

me

tric

Be

nd

ing (

126

2 c

m-1

)

CH

3 A

sym

me

tric

S

tre

ch

ing (

296

5 c

m-1

)

CH

3 S

ym

me

tric

Str

ech

ing (

290

7 c

m-1

)

G' pe

ak M

WC

NT

s (

271

1 c

m-1)

0 2 4 6 8 10

2900 3000600 700 800 900 1000 1100 1200 1300 1400 1500

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0.96

0.97

0.98

PDMS_0.0

PDMS_0.5

PDMS_1.0

PDMS_1.5

PDMS_2.0

PDMS_2.5

PDMS_3.0

-CH

3 S

ym

me

tric

Satr

etc

h(2

90

0)c

m-1

-CH

3 A

sym

me

tric

Satr

etc

h(2

96

0)c

m-1

Tra

nsm

itta

nc

e (

a.u

)

Wave Number (cm-1)

Si–

O–

Si S

ym

me

tric

al D

efo

rma

tio

n (

101

0)c

m-1

-CH

3R

ockin

g P

ea

ks (

785

-81

5)c

m-1

Si–

C B

and

s (

83

5-8

55

)cm

-1

(90

0-9

30

)cm

-1

–C

H3 S

ym

me

tric

De

form

atio

n (

12

58

)cm

-1

–C

H3 A

sym

me

tric

De

form

atio

n (1

41

0)c

m-1

Pe

ak

Ra

tio

MWCNTs (wt%)

Ratio of Transmission Peaks

at 900 cm-1and 930 cm-1

200 300 400 500 600 700 800

0

20

40

60

80

100

PDMS_0.0

PDMS_0.5

PDMS_1.0

PDMS_1.5

PDMS_2.0

PDMS_2.5

PDMS_3.0

Ab

so

rpti

on

(%

)

Wavelength (nm)

300 350 400 450 500 550 600 650 700 750

0.0

0.5

1.0

1.5

2.0

PDMS_0.0

PDMS_0.5

PDMS_1.0

PDMS_1.5

PDMS_2.0

PDMS_2.5

PDMS_3.0

Op

tic

al D

en

sit

y (

A.U

)

Wavelength (nm)

0

300 350 400 450 500 550 600 650 700 750

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55 PDMS_0.0

PDMS_0.5

PDMS_1.0

PDMS_1.5

PDMS_2.0

PDMS_2.5

PDMS_3.0

Dif

fusit

ivit

y

Wavelength (nm)

0.0 0.5 1.0 1.5 2.0 2.5 3.0

at 300 nm

at 400 nm

at 500 nm

at 600 nm

at 700 nm

at 800 nm 0.0

---------- Specular

Specular + Diffused

MWCNTs (%)

Ab

so

rpti

on

Co

eff

icie

nt

(cm

-1)

2.0x102

0.5 x102

1.0x102

1.5x102

2.5x102

6 5 4 3 2

PDMS_0.0

PDMS_0.5

PDMS_1.0

PDMS_1.5

PDMS_2.0

PDMS_2.5

PDMS_3.0

Ab

so

rpti

on

Co

eff

icie

nt

(cm

-1)

Energy (eV)

4x102

1x102

2x102

3x102

0

- - - - - Specular

Specular + Diffuse 5x10

2

0 0.5 1 1.5 2 2.5 3

0

20

40

60

80

100

Tra

nsm

itta

nce (

%)

MWCNTs (wt%)

at 300nm

at 400nm

at 500nm

at 600nm

at 700nm

at 800nm

---------- Specular

Specular + Diffused

INTRODUCTION The breakthrough of carbon nanotubes (CNTs) has got remarkable progress in various fields of research and applications due to their peculiar structural, electrical,

mechanical and optical properties. CNTs can be up to millimeters long with diameters in the 1-100 nm range, leading to very high aspect ratios. This combination of these

properties allows better interaction in composite matrices, resulting in improved properties and performance.

The incorporation of CNTs into the polymer can enhance the properties of material by increasing mechanical strength and electrical conductivity. However the formation

of aggregates and low dispersions of CNTs in the polymer matrix are the major cause of poor and inhomogeneous composites. Successful integration of CNTs in polymer

matrices could result in different types of lightweight and strong materials for flexible electronic devices and sensors. So, for the exploitation of the potential of CNTs, the

issues regarding economical and controlled fabrication of well dispersed reinforced composite materials has to be tackled and solved. We report here an efficient and

inexpensive process of incorporating carbon MWCNTs into a PDMS (Polydimethylsiloxane) matrix. Furthermore, we focused on their structural and optical properties.

In order to prepare MWCNTs-PDMS composites, different percentages of CNTs has been added to the PDMS

monomer and dispersed by means of mechanical stirring (1000 rpm for 10 min). After the addition of hardener,

the matrix is mixed again. The final step to achieve a uniform dispersion of MWCNTs is sonication (ultrasonic

frequency 37 KHz for 15 min).The composite films with an average thickness of 70 micrometers and different

weight percentages of MWCNTs (from 0.0% to 3.0%) were prepared on glass by Doctor Blade Technique. After

thermal curing at 70°C for 4 hours, the films were detached from the glass surface.

CONCLUSION

FESEM micrographs of PDMS with different weight percentages of MWCNTs a). 1.0 wt% b). 2.0 wt% c). 3.0 wt% at 100kx magnification

FESEM micrographs of PDMS-MWCNTs (3.0 wt %) at a). 10kx b). 50kx c). 200kx

SURFACE MORPHOLOGY OF PDMS-MWCNTs COMPOSITE FILMS