24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects
in PP/EPR/HDPE
Christelle Bergeon 1, Christophe Mavon 1, Franck Berger 1, Zohra Lounis-Mokrani 2,
Patrick Delobelle 3, Michel Fromm 1
1: Laboratoire de Chimie-Physique et Rayonnement - Alain Chambaudet (LCPR-AC)
UMR CEA E4, Université de Franche-Comté. 16 route de Gray. F-25030 Besançon Cedex
2
: Laboratoire de Dosimétrie, Centre de Recherche Nucléaire d’Alger, BP 399, Alger Gare 16000, Algeria
3
: FEMTO ST-LMARC. UMR 6174. 24, chemin de l’épitaphe. 25030 Besançon cedex
France.
This paper mainly deals with changes in surface properties of an industrial polymer due to irradiations
with gamma photons, electrons and alpha particles.
In the second part of the presentation a discussion is presented that aims at comparing the dose
(electrons, photons) effects with the fluence (alphas) effects, based on simple track structure theory.
Radiation Induced Damage
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
The Polymer Under Study : PP / EPR / HDPE
Plastics have become an important material for industrial applications,
particularly in the automobile sector. Nowadays, plastics make up on average
more than 15% of a vehicles’ weight.
Polypropylene is the most commonly used polymer base. This material is the object of
this study. Plastic parts are usually coated with paint and/or varnish. Workers in the
industry have been trying to improve the coatings’ adherence properties for years.
They often try to improve adherence by using a
flaming treatment or a plasma technology.
What are the effects of ionizing radiations on
PP / EPR / HDPE surface and bulk properties ?
Radiation Induced Damage
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
The Polymer Under Study : PP / EPR / HDPE
is a ternary blend : isotactic polypropylene / ethylene-propylene rubber / high density polyethylene
isotactic polypropylene
polyethylene
Scanning Electron Microscopy of the PP/EPR chemically etched
in potassium permanganate in an acid medium
Radiation Induced Damage
Brandon JP, Ph-D Thesis, University of Besançon, N° 245, 1991.
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Irradiations
b
g
a
Electrons: 10 to 106 Gy, 2 MeV, In air (Van de Graaf accelerator, Aerial, Strasbourg, France)
Gammas: 10 to 106 Gy, 1.17 et 1.33 MeV, In air (60Co source, Alger, Algeria )
Alphas : 1011 to 1016 He+.cm-2, 400 keV, Under vacuum (Ion implantation, Lyon, France)
The samples are exposed to electrons and gamma photons in air, as
for the alpha particles, irradiation is performed under vacuum !
Radiation
Quality
Electron and gamma photon irradiations can be considered as
uniform which is not the case for alpha particles (track structure
and dependance on the fluence)
The depth at which the incomming particles deposit their energy is
very different as well as their stopping power :
Radiation Induced Damage
Oxygenation
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Analytical methods
Irradiated samples have been analysed by means of:
-FT-IR / ATR (Functional groups)
-Contact angle (Surface energy, polarity, dispertion, … )
- Nano-Indentation (Young’s modulus & Hardness)
-Differential Scanning Calorimetry (Melting enthalpy & temperature)
Swelling (Swelling ratio and soluble fraction)
Radiation Induced Damage
Surface
properties
Bulk
properties
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Results :
Surface chemical modifications: FT-IR/ATR spectroscopy
CH3 H2
C
C
H2
C
O2
H2
C
CH3 H2
C
C
O
O
u.a.
H2
C
H2
C
H
OH
CH3 +
+
1709 cm-1 :
Carbonyl bond
C
O
Gedde et al.,
J. Appl. Polym. 1990
Gamma (9*105 Gy)
Absorbance
-1
2916 cm
1375 cm-1
2950 cm-1 2871 cm-1
2839 cm-1
O2
1456 cm-1
0.05
Electrons (9*105 Gy)
1165 cm-1
3100
2700
2300
1900
-1
Wavenumbers (cm )
1500
1100
Vacuum
Spectrum of the
pristine material
+
He (10
3100
2900
2700
2500
14
+
-2
He .cm )
2300
2100
1900
-1
1700
1500
1300
Wavenumbers (cm )
A. Chapiro,
NIM B. 1988
H2
C
H2
C
Radiation Induced Damage
-H2
H
C
H
C
H
C
H
C
1630 cm-1 :
vinylic function
1100
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Results (alphas only) :
Surface modifications: Contact angle
Surface free energy versus fluence
gS (mJ.m-2)
47
45
43
41
39
Untreated
Untreated
37
35
10
11
12
13
+
14
-2
15
log(fluence (He .cm ))
Radiation Induced Damage
There is a correlation between the increase in surface free energy
and the loss of hydrogen (vinylic bond formation).
16
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Results :
Electrons and photons: Hardness & Young’s Modulus.
Whatever electrons or photons were used the results
obtained are similar when compared as a function of Dose
Hardnes s and YoungХs modulus measured on the untreated
and electron-irradiated (D = 9105 Gy) sample Хs surface.
100
H (MPa)
2.2
E (GPa)
90
2
80
9105 Gy
1.8
70
9105 Gy
60
Untreated
1.6
Untreated
1.4
50
1.2
40
30
1
0
500
1000
1500
2000
h (nm)
Radiation Induced Damage
2500
3000
3500
0
500
1000
1500
2000
h (nm)
2500
3000
3500
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Results :
Nano-indentation curves for alpha & electron irradiated samples.
P (mN)
14
P (mN)
14
9105 Gy
12
10
10
The visco-elastic behaviour
does not remain after irradiation
16
+
-2
He .cm
12
The visco-elastic behaviour remains
9104 Gy
10
Untreated
8
8
1015 He+ .cm-2
6
6
1014 He+ .cm-2
4
Untreated
2
4
2
0
0
0
500
1000
h (nm)
1500
2000
0
500
1000
1500
2000
2500
3000
h (nm)
The material was more fragile after the ion treatment since the analyzed surface
is a hard film (the irradiated part is 2.3 µm) on a soft substrate (the untreated part).
Alpha particles gradually lose the ir energy as they penetrate the PP/EPR up to about
2.3 µm. For samples irradiated with electrons, H and E remain constant within the
domain of the studied indentation depth. In deed, in this case, we can consider tha t
the e lectrons regularly lose the ir energy up to h = 3000 nm.
Radiation Induced Damage
3500
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Results :
Swelling for gamma & electron -irradiated samples.
In order to study the crosslinking of the PP /EPR, the samples were analyze d using
the s welli ng technique. Swelli ng was performed in two different liquids.
First, the studied samples were dipped into 1,2-dichorobenzene, a PP/EPR solvent ,
at 130ЎC for about one hour. Thus, the crosslinking network, insoluble in the solvent,
could be studied.
Some samples were also dipped into hexane in order to obtain information about the
PP/EPR samples that were either untreated or irradiated at weak doses and
fluences. This liquid is not a PP/EPR solvent but it has a good affinity with him.
Immersion in 1,2 -dichlorobenzene
after irradiation at an electron dose
of 9 . 105 Gy.
We observe the crosslinking effect.
Radiation Induced Damage
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Results :
Swelling in hexane for gamma & electron -irradiated
samples.
m 2  m1

m1
m1 is the sampleХs mass
after one day of swelling
and hexane evaporation;
and m2 is the sampleХs
mass after a second
swelling in hexane during
a period of 46 days.

0.23
0.22
Untreated
0.21
0.2
0.19
0.18
Electron
Gamma
0.17
0.16
0.15
0
1
2
3
4
log(Dose (Gy))
Radiation Induced Damage
5
6
7
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Results :
Differential Scanning Calorimetry
mW/mg
0
-0,2
PEHD
-0,4
-0,6
PP
Endo
-0,8
-1
5
9.410 Gy
-1,2
5
410 Gy
-1,4
-1,6
0 Gy
-1,8
80
100
120
140
160
180
Temperature (ЎC)
Melting peaks for the two main components
of the compound, i.e. PP and HDPE
Radiation Induced Damage
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Results :
Differential Scanning Calorimetry
170
165
T melting PP (ЎC)
Untreated
165
T melting PP (ЎC)
164
Untreated
163
160
162
155
Electron
Gamma
150
161
160
145
159
158
140
0
1
2
3
4
5
6
13
7
13.5
H
80
-1
melting
14
14.5
15
15.5
log(fluence (He+.cm -2 ))
log(Dose (Gy))
H
75
PP (J.g )
melting
PP (J.g-1)
Untreated
65
75
Untreated
70
55
65
45
Electron
Gamma
60
35
25
55
15
50
0
1
2
Radiation Induced Damage
3
4
log(Dose (Gy))
5
6
7
13
13.5
14
14.5
+
15
-2
log(fluence (He .cm ))
15.5
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Comparison :
Critical doses and fluenc es where the studied properties are
greatly modified
(: electrons, : gamma photons, : alpha particles).
Young's modulus
Young's modulus
Hardness
Hardness
Swelling
Swelling
Melting temperature
Melting temperature
FT-IR/ATR
FT-IR/ATR
0
1
2
3
4
log(Dose (Gy))
Radiation Induced Damage
5
6
7
10
11
12
13
14
15
+
-2
log(Fluence (He .cm ))
16
17
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Dose & Fluence :
The changes in the compound properties were observed from a
critical dose ( 105 Gy) or a critical fluence ( 51013 He+.cm-2).
For the ion irradiation, the track overlapping can explain most of the observed effects:
1011 ions.cm-2
1012 ions.cm-2
1013 ions.cm-2
scale: 20 nm/division
See the work by Yamauchi
But, is there a way to transform a dose into a fluence or reciprocally ?
Radiation Induced Damage
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Dose - Fluence Relation ?
Equivalent Dose Calculation for  = 5 .1013 He+.cm-2
In Polyethylene
E
D=
 1000
R
1.5107 J.kg-1
With electrons
and gammas
in air,
we find
TEL (keV.µm-1)
300
250
-1
 LET = 199 keV.µm-1, or 1.99106 keV.cmD
200
150
100
50
0
0
100
200
300
400
Energy (keV)
LET  
D=

Radiation Induced Damage
1.8107 J.kg-1
= 105 Gy
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Dose - Fluence Relation ?
Deposited dose by an helium ion (400 keV) in
the po lypropylene versus the distance to the
track cent er r and versus the particle energy E.
The latent track
rt
1
0
10
10
2
3
10
10
Dose

( 106 Gy)
4
r (nm)
20
R
40
60
80
C
o
r
e
4
3
halo
2
t
r
a
c
k
a
1
(a)
(b)
0
5
r (nm)
100
x (µm)
10
15
0
300
100 200
E (keV)
400
Matlab calculation based on:
Vareille, J.C. PhD Thesis, University of Limoges, Limoges, France, 1982.
Radiation Induced Damage
Waligorski, M.P.R.; Hamm, R.N.; Kat z, R. Nucl
Tracks Radiat Meas 1986, 11(6), 309-319.
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Dose - Fluence Relation ?
 = 5 .1013 He+.cm-2
Dose inside the latent track
Covered surface fraction
Deposited total dose (%)
110
1
100
90
0.8
80
0.6
70
r = 5 nm
60
0.4
50
40
0.2
30
0
1
2
3
4
5
r (nm)
6
7
8
9
0
9
10
11
12
13
+
14
15
-2
log(fluence (He .cm ))
With the MATLAB software, the deposited total dose along the ionХs
range can be estimat ed: D  3107 Gy. To be compared with
Radiation Induced Damage
D = 105 Gy !
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Conclusions
Radiation Induced Damage
24th ICNTS, Bologna, 1-5 September 2008
Electron, Gamma Photon and Ion Irradiation Effects in PP/EPR/HDPE
Radiation Induced Damage