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CO2 - pulsed laser induced surface grafting of acrylamide onto ethylene - propylene rubber (EPR). II
Radiat. Printed
Phys. Chem. Vol. 42, Nos 1-3, pp. 53-56, in Great Britain. All rights reserved
0146-5724193
1993 Copyright
0
1993
$6.00
+ 0.00
Pergamon Press Ltd
CO2 - PULSED LASER INDUCED SURFACE GRAFIING OF ACRYLAMIDE ONTO ETHYLENE - PROPYLENE RUBBER (EPR). II H.Mirzadch, Polymer Research Center. Tehran, Iran A.A.Katbab, Polymer Engineering Department. Amirkabir University, Tehran, Iran. R.P.Burford, Department of Polymer Science , University of New South Wales, NSW, Australia.
ABSTRACT A line tunable CO2 - pulsed laser (TEA CO2 laser Lumonics - 103-2) which operates at 9.1 - 10.6pm has been employed to induce grafting of acrylamide(AAm) onto the surface of EPR in the presence of Benzophenone (BP) and azobisisobutyronitrile(AZBN) as sensitizer. Characterization has been carried out using ATR-IR(FT), EDXA , and SEM. Grafting of AAm occures providing the system is excited by pulses with the wavelength corresponding to the absorption maxima of the sensitizer. Fractal type of moprphology is formed by the grafted polyAAm .Both graft yield and size of fractals are dependent upon the excitingwavelength and laser pulsing frequency .Results reveal that co-polymerization of AAm occures by vibrational excitation of AAm or the used photosensitizer via multiphoton absorption mechanism.
KEYWORDS COz- Pulsed laser;grafting ;acrylamide; EPR; Benzophenone;
AZBN.
INTRODUCTION The use of both pulsed and continuous laser as exciting sources to initiate polymerization of vinyl monomers appears to increase and several reports have been published dealing with the photosensitized polymerization of acrylic monomers using argon (Parts et al., 1969 Sadhire et al., 1985) , helium - neon (Frigerio et al.,1971) , and nitrogen pulsed laser (Decker.,1983) , and also effects of lasing variables (Hoyle.,1989). Acrylic acid has recently been grafted onto polypropylene using uv - pulsed laser (Kesting .,1990). In previous work (Mirzadeh et al.,1992 ) we have demonstrated the potential of CO2 - pulsed laser to induce grafting of AAm onto the surface of EPR in the absence of photosensitizer at 10.2 and 10.3pm corresponding to the absorption maxima of AAm . In the present article , the sensitizing effect of BP and AZBN upon graft co-polymerization of AAm onto EPR vulcanizate (Vistalon 805 )has been evaluated . Dried extracted samples were put in a special Pyrex reactor equipped with NaCl window and the cell was charged with aqueous solution of AAm (30%) containing the sensitizer (dissolved in acetone). Laser pulses with the fluence of 1.0 j/cm* were directed into the solution .Treated samples were extracted (acetone: H,O 24hrs)and characterized .Water compatibility has been evaluated by measuring water drop contact angle.
53
54
H.
MIRZADEH
et al.
0-l
*Unmodified
I--
1
3
it z
0. I.95
g
0.097s
a
u-l
m
=
0.0
CM-1
1000
Fig.1. Comparison of ATR - IR spectrums of EPR modified with acrylamide in the presence of BP by laser pulses of 10.6pm and repetition rate of, a: 0.2 Hz, b: 0.5Hz.
I<
.o
'FS=l27
‘WEfll:EPR
-6Ltochkd
7+= EbIT5 (GR91)
[email protected]/6WR.92
El%
i . , i
Fig.2. EDXA analysis of EPR samples grafted with acrylamide in the presence of BP by COz - laser pulses of lO.@m with 0.3Hz rate. Table 1. Water drop contact angle (0) of EPR samples modified with AAm by CO2 laser pulses of 10.6pm .
Unmodified Samples 89
Modified in the Presence of BP 55
Modified in the Presence of AZBN 42
8th International
Meeting
on Radiation
Processing
55
m I-
; 3
0.0525
z a
E 0.0175
1000
CM-1
Fig.3. Comparison of ATR - IR spectrums of EPR modified with acrylamide in the presence of AZBN by laser pulses of 10.6pm and repetition rate of, a: O.lHz ,b:O.SHz , c: l.OHz.
Fig.4. EDXA analysis of unmodified EPR samples.
RESULT3 Figure(l) illustrates ATR - IR(FT) spectrums of two EPR samples grafted in the presence of BP and Mohr’s salt(0.005M)by pulses of 10&m (maximum absorption of BP accessible to our CO2 laser ) at repetition rates , 0.2I-k and OSI-Iz for equal lasing time . Comparing the absorption intensity in the region of 1590 - 1666 Cm“(attributed to the CONH;?) for these two samples with the unmodified one shows that grafting of AAm onto EPR surface in the presence of BP has happened . This is in consistent with EDXA analysis given in Fig(Z) for 0.3I-k irradiated sample which shows an average of 25% nitrogen / oxygen (attributed to the grafted PAAm) relative to the unmodified one,
UPC42-l/s-F
56
H.
MIRZADEH
et al.
Fig.5.6. SEM photomicrographs of EPR grafted with AAm in the presence laser pulses of 10.6pm , a:0.2Hz , b: 0.4Hz.
of BPby
with the same surface area, Fig(4). However, the higher peak intensity for the sample irradiated by pulses of OSHz shows the dramatic effect of laser pulsing frequency upon the graft level. Figure(f) also shows the effect of laser repetition rate on the yield of grafting of AAm sensitized with AZBN at 10.6pm (absorption maxima of AZBN accessible to our COZ laser).It is obvious that increasing the rate from O.lHz to 0.5Hz leads to the increase in graft level , but above OSHz the acrylamide characteristic peak intensity decreases The decrease in graft level in the case of O.lHz compared to the 0.5Hz might be due to the lower laser pulses delivered to the system and therefore lower rate of initiation, while above 0.5Hz the decline of graft level could be. attributed to the higher rate of termination of the propagating radicals by the newly initiated radicals (Hoyle et al., 1989). Surface characterization by SEM showed an important phenomenon concerning CO2 - pulsed laser induced grafting o’f AAm, that is the formation of fractals by the grafted polyacrylamide irrespective of the substrate and sensitizer. type. However , the number , size , and shape of fractals was found to depend upon the exciting wavelength as well as repetition rate , Fig(5-6) .We attribute this type of morphology to the combination of CO2 pulsed laser and linear aggregative nature of AAm in aqueous media. REFERENCES Decker,C.;(1983)J.Polym.Chem.Ed.,~2451. Decker,C.;(1983)Polym.Photochem.&l31. Frigerio,G.E.,Stefanini.,A.;( 1971),Lctt.Nuovo,Cimento Soc.Ital.Fis.,2,810. Hoyle,C.E;Chang,C.H;Trapp,M.A;Macromolecule( 1989)&3607-3610. Kesting,W.,Knittel,D.,Schollmeyer,E.,(1990),Angew.Makromol.Chem.182,177-86. Mirzadeh,H.;Katbab.A.A.;Burford,R.P.(1992),under press. Parts,I.P;Feairheller.,W.R.,(1%9) Jr.,US.Pat.3,477,932. Sadhir,R.K;Smith,J.D.B;Casttle,P.M.,(1985)J.Polymer.Sci.,Polym.Chem.Ed.23,41 -
1.
Phys. Chem. Vol. 42, Nos 1-3, pp. 53-56, in Great Britain. All rights reserved
0146-5724193
1993 Copyright
0
1993
$6.00
+ 0.00
Pergamon Press Ltd
CO2 - PULSED LASER INDUCED SURFACE GRAFIING OF ACRYLAMIDE ONTO ETHYLENE - PROPYLENE RUBBER (EPR). II H.Mirzadch, Polymer Research Center. Tehran, Iran A.A.Katbab, Polymer Engineering Department. Amirkabir University, Tehran, Iran. R.P.Burford, Department of Polymer Science , University of New South Wales, NSW, Australia.
ABSTRACT A line tunable CO2 - pulsed laser (TEA CO2 laser Lumonics - 103-2) which operates at 9.1 - 10.6pm has been employed to induce grafting of acrylamide(AAm) onto the surface of EPR in the presence of Benzophenone (BP) and azobisisobutyronitrile(AZBN) as sensitizer. Characterization has been carried out using ATR-IR(FT), EDXA , and SEM. Grafting of AAm occures providing the system is excited by pulses with the wavelength corresponding to the absorption maxima of the sensitizer. Fractal type of moprphology is formed by the grafted polyAAm .Both graft yield and size of fractals are dependent upon the excitingwavelength and laser pulsing frequency .Results reveal that co-polymerization of AAm occures by vibrational excitation of AAm or the used photosensitizer via multiphoton absorption mechanism.
KEYWORDS COz- Pulsed laser;grafting ;acrylamide; EPR; Benzophenone;
AZBN.
INTRODUCTION The use of both pulsed and continuous laser as exciting sources to initiate polymerization of vinyl monomers appears to increase and several reports have been published dealing with the photosensitized polymerization of acrylic monomers using argon (Parts et al., 1969 Sadhire et al., 1985) , helium - neon (Frigerio et al.,1971) , and nitrogen pulsed laser (Decker.,1983) , and also effects of lasing variables (Hoyle.,1989). Acrylic acid has recently been grafted onto polypropylene using uv - pulsed laser (Kesting .,1990). In previous work (Mirzadeh et al.,1992 ) we have demonstrated the potential of CO2 - pulsed laser to induce grafting of AAm onto the surface of EPR in the absence of photosensitizer at 10.2 and 10.3pm corresponding to the absorption maxima of AAm . In the present article , the sensitizing effect of BP and AZBN upon graft co-polymerization of AAm onto EPR vulcanizate (Vistalon 805 )has been evaluated . Dried extracted samples were put in a special Pyrex reactor equipped with NaCl window and the cell was charged with aqueous solution of AAm (30%) containing the sensitizer (dissolved in acetone). Laser pulses with the fluence of 1.0 j/cm* were directed into the solution .Treated samples were extracted (acetone: H,O 24hrs)and characterized .Water compatibility has been evaluated by measuring water drop contact angle.
53
54
H.
MIRZADEH
et al.
0-l
*Unmodified
I--
1
3
it z
0. I.95
g
0.097s
a
u-l
m
=
0.0
CM-1
1000
Fig.1. Comparison of ATR - IR spectrums of EPR modified with acrylamide in the presence of BP by laser pulses of 10.6pm and repetition rate of, a: 0.2 Hz, b: 0.5Hz.
I<
.o
'FS=l27
‘WEfll:EPR
-6Ltochkd
7+= EbIT5 (GR91)
[email protected]/6WR.92
El%
i . , i
Fig.2. EDXA analysis of EPR samples grafted with acrylamide in the presence of BP by COz - laser pulses of lO.@m with 0.3Hz rate. Table 1. Water drop contact angle (0) of EPR samples modified with AAm by CO2 laser pulses of 10.6pm .
Unmodified Samples 89
Modified in the Presence of BP 55
Modified in the Presence of AZBN 42
8th International
Meeting
on Radiation
Processing
55
m I-
; 3
0.0525
z a
E 0.0175
1000
CM-1
Fig.3. Comparison of ATR - IR spectrums of EPR modified with acrylamide in the presence of AZBN by laser pulses of 10.6pm and repetition rate of, a: O.lHz ,b:O.SHz , c: l.OHz.
Fig.4. EDXA analysis of unmodified EPR samples.
RESULT3 Figure(l) illustrates ATR - IR(FT) spectrums of two EPR samples grafted in the presence of BP and Mohr’s salt(0.005M)by pulses of 10&m (maximum absorption of BP accessible to our CO2 laser ) at repetition rates , 0.2I-k and OSI-Iz for equal lasing time . Comparing the absorption intensity in the region of 1590 - 1666 Cm“(attributed to the CONH;?) for these two samples with the unmodified one shows that grafting of AAm onto EPR surface in the presence of BP has happened . This is in consistent with EDXA analysis given in Fig(Z) for 0.3I-k irradiated sample which shows an average of 25% nitrogen / oxygen (attributed to the grafted PAAm) relative to the unmodified one,
UPC42-l/s-F
56
H.
MIRZADEH
et al.
Fig.5.6. SEM photomicrographs of EPR grafted with AAm in the presence laser pulses of 10.6pm , a:0.2Hz , b: 0.4Hz.
of BPby
with the same surface area, Fig(4). However, the higher peak intensity for the sample irradiated by pulses of OSHz shows the dramatic effect of laser pulsing frequency upon the graft level. Figure(f) also shows the effect of laser repetition rate on the yield of grafting of AAm sensitized with AZBN at 10.6pm (absorption maxima of AZBN accessible to our COZ laser).It is obvious that increasing the rate from O.lHz to 0.5Hz leads to the increase in graft level , but above OSHz the acrylamide characteristic peak intensity decreases The decrease in graft level in the case of O.lHz compared to the 0.5Hz might be due to the lower laser pulses delivered to the system and therefore lower rate of initiation, while above 0.5Hz the decline of graft level could be. attributed to the higher rate of termination of the propagating radicals by the newly initiated radicals (Hoyle et al., 1989). Surface characterization by SEM showed an important phenomenon concerning CO2 - pulsed laser induced grafting o’f AAm, that is the formation of fractals by the grafted polyacrylamide irrespective of the substrate and sensitizer. type. However , the number , size , and shape of fractals was found to depend upon the exciting wavelength as well as repetition rate , Fig(5-6) .We attribute this type of morphology to the combination of CO2 pulsed laser and linear aggregative nature of AAm in aqueous media. REFERENCES Decker,C.;(1983)J.Polym.Chem.Ed.,~2451. Decker,C.;(1983)Polym.Photochem.&l31. Frigerio,G.E.,Stefanini.,A.;( 1971),Lctt.Nuovo,Cimento Soc.Ital.Fis.,2,810. Hoyle,C.E;Chang,C.H;Trapp,M.A;Macromolecule( 1989)&3607-3610. Kesting,W.,Knittel,D.,Schollmeyer,E.,(1990),Angew.Makromol.Chem.182,177-86. Mirzadeh,H.;Katbab.A.A.;Burford,R.P.(1992),under press. Parts,I.P;Feairheller.,W.R.,(1%9) Jr.,US.Pat.3,477,932. Sadhir,R.K;Smith,J.D.B;Casttle,P.M.,(1985)J.Polymer.Sci.,Polym.Chem.Ed.23,41 -
1.