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CHARACTERIZATION OF PI - BASED ADHESIVES INTRODUCTION 0,0 0,2 0,4 0,6 0,8 1,0 50 100 150 200 250 300 350 Heat Flow (W/g) Temperature (°C) 6 th International Conference on Structural Adhesive Bonding, AB2021 Porto, Portugal 8 – 9 July 2021 • Three endothermic peaks occur when the paste samples are heated. The first and the second peaks are due to the decomplexation reaction of the solvent (N-methyl-2- pyrrolidone, NMP). The third peak is relative to the imidization reaction. The thermal profile of the cured paste sample (red curve) no longer shows any peak, indicating the cure takes place completely during the first heating run. • TGA/FT-IR analysis of uncured sample BR ® 680-3 detected the presence of solvent molecules (ethanol, EtOH and NMP) and H 2 O from condensation reactions (imidization), whereas they are absent in the cured polyimide. After 48 min of analysis in both samples it is observable the absorbance of CO 2 molecules due to decomposition reaction of the polymer chain. • At the end of the degradation process the mass of BR ® 680-3 sample residue is equal to 39 wt.% highlighting that the polyimide-based adhesive has good thermal stability. • E a obtained for BR® 680-3 is equal to 34 kJ/mol, a lower energy value in comparison to obtained for the BR ® 680-3 at higher conversion values (124 kJ/mol). Object : study of the thermal stability of high-temperature-resistant polymeric adhesives for the innovative hybrid friction stir welding (FSW)-bonding technique. For the FSW- bonding technique it is necessary to use polymeric adhesives with a high thermal resistance. The best ones to this purpose are (mono- or bi-component) epoxy-based and polyimide-based systems. In particular, polyimides (PI) are characterized by high thermal, thermo-oxidative and chemical stability as well as good mechanical properties. Various polyimides are used as structural adhesives for high and low temperature applications (automotive, aerospace, shipbuilding, etc) for bonding metals such as stainless steel, titanium, aluminum. They show excellent properties also as coating and thin film. The high-temperature-resistant polymeric adhesives investigated were characterized by thermal analytical techniques. PI-based adhesives during the polymerization process release volatile substances which were analyzed through thermal gravimetric analysis, TGA, coupled with FT-IR spectroscopy. Indeed, TGA measures the change in weight of a sample as a function of temperature or time. The accurate measurement of the loss of weight provides one piece of information, but it does not identify what is changing. In the hyphenated technique FT-IR spectroscopy is used to identify the evolved gases and help in determining sample characteristics. KINETIC MODELS FINAL REMARKS -5,0 -4,0 -3,0 -2,0 -1,0 0,0 50 150 250 350 450 550 650 750 DTG (%/°C) Temperature (°C) 20°C/min 15 °C/min 10 °C/min 5 °C/min 1 °C/min Heating rate (°C/min) T 5% (°C) T onset (°C) T p (°C) m (%) W (%) 20 121 540 586 61 39 15 120 539 576 60 40 10 117 534 569 60 40 5 98 524 550 62 39 1 85 503 522 63 37 0,0 0,4 0,8 1,2 1,0 1,3 1,5 1,8 2,0 2,3 2,5 Log β 1000/T (K-1) -3,0 -2,5 -2,0 -1,5 -1,0 1,0 1,3 1,5 1,8 2,0 2,3 2,5 Log dα/dt 1000/T (K-1) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 40 80 120 160 0,0 0,2 0,4 0,6 0,8 1,0 Ea (kJ/mol) α OFW Friedman • uncured sample (black curve) • cured paste (red curve) Sample T peak (°C) ΔH (J/g) BR ® 680-3 I peak 104 II peak 165 III peak ~210°C 80 67 The sample cured at 200 °C shows a low intensity peak (dotted line) due to the imidization reaction in the range of temperature between 200°C and 250 °C Sample T g (°C) BR ® 680-3 cured 280°C 350 BR ® 680-3 cured 250°C 338 0,0 0,1 0,2 0,3 0,4 25,0 125,0 225,0 325,0 425,0 Heat Flow (W/g) Temperature (°C) cured 280°C cured 250°C cured 210°C cured 200°C T g T g -4 -3 -2 -1 20 40 60 80 100 0 10 20 30 40 50 60 70 Derivative weight (%/m) Weight Loss % Time (min) Name D 20 40 60 0,005 0,010 0,015 0,020 0,025 0,030 0,035 0,040 0,045 0,050 0,055 Mins Abs PI uncured 4000 3500 3000 2500 2000 1500 1000 0 10 20 30 40 50 60 70 Wavenumber Mins -0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45 0,50 Abs CO 2 H 2 O C-H -C=O -C-O Sample T D onset (°C) T v max (°C) Residual (p%) BR ® 680-3 I step 96 III step 550 I peak 114 II peak 184 III peak 575 37 -5 -4 -3 -2 -1 0 20 40 60 80 100 0 10 20 30 40 50 60 70 Derivative weight (%/m) Weight Loss % Time (min) 20 40 60 -0,000 0,005 0,010 0,015 0,020 0,025 0,030 0,035 0,040 Mins Abs PI cured Sample T D onset (°C) T v max (°C) Residual (p%) BR ® 680-3 I step 563 I peak 593 57 4000 3500 3000 2500 2000 1500 1000 0 10 20 30 40 50 60 70 Wavenumber Mins 0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16 0,18 0,20 0,22 0,24 Abs CO 2 -C-O condensation reaction: solvent (NMP, EtOH) and/or volatile products polyimide decomposition Determination of the energy of activation E a for the degradation of BR ® 680-3 sample according to the OFW and Friedman equations. E a ~34 kJ/mol E a ~124 kJ/mol This work was realized thanks to the PhD scholarship granted by the Regione Liguria under the Operational Program Liguria Region - European Social Fund POR-FSE 2014-2020. Acknowledgement : DSC traces after curing at different temperature BR ® 680-3 uncured BR ® 680-3 cured 30 50 70 90 Weight Loss (%) 20°C/min 15 °C/min 10 °C/min 5 °C/min The sample was heated from 50°C to 340°C at a heating rate of 10 °C/min The sample was heated at a rate of 10 °C/min from 40 to 700 °C under a N 2 flow and from 700 to 850°C under a O 2 flow. BR ® 680-3 sample was heated at five different heating rates: 1, 5, 10, 15 and 20 °C/min.
Transcript of Presentazione standard di PowerPoint - web.fe.up.pt
CH
ARA
CTERIZ
ATIO
N O
F P
I-B
ASED
AD
HESIV
ES
INTRO
DU
CTIO
N
0,0
0,2
0,4
0,6
0,8
1,0
50 100 150 200 250 300 350
He
at F
low
(W
/g)
Temperature (°C)
6th International Conference on Structural Adhesive Bonding, AB2021 Porto, Portugal 8 – 9 July 2021
• Three endothermic peaks occur when the paste samples are heated. The first and the second peaks are due to the decomplexation reaction of the solvent (N-methyl-2-pyrrolidone, NMP). The third peak is relative to the imidization reaction. The thermal profile of the cured paste sample (red curve) no longer shows any peak, indicating the curetakes place completely during the first heating run.
• TGA/FT-IR analysis of uncured sample BR® 680-3 detected the presence of solvent molecules (ethanol, EtOH and NMP) and H2O from condensation reactions (imidization),whereas they are absent in the cured polyimide. After 48 min of analysis in both samples it is observable the absorbance of CO2 molecules due to decomposition reaction of thepolymer chain.
• At the end of the degradation process the mass of BR® 680-3 sample residue is equal to 39 wt.% highlighting that the polyimide-based adhesive has good thermal stability.
• Ea obtained for BR® 680-3 is equal to 34 kJ/mol, a lower energy value in comparison to obtained for the BR® 680-3 at higher conversion values (124 kJ/mol).
Object: study of the thermal stability of high-temperature-resistant polymeric adhesives for the innovative hybrid friction stir welding (FSW)-bonding technique. For the FSW-bonding technique it is necessary to use polymeric adhesives with a high thermal resistance. The best ones to this purpose are (mono- or bi-component) epoxy-based andpolyimide-based systems.
In particular, polyimides (PI) are characterized by high thermal, thermo-oxidative and chemical stability as well as good mechanical properties. Various polyimides are used asstructural adhesives for high and low temperature applications (automotive, aerospace, shipbuilding, etc) for bonding metals such as stainless steel, titanium, aluminum. Theyshow excellent properties also as coating and thin film.
The high-temperature-resistant polymeric adhesives investigated were characterized by thermal analytical techniques. PI-based adhesives during the polymerization processrelease volatile substances which were analyzed through thermal gravimetric analysis, TGA, coupled with FT-IR spectroscopy. Indeed, TGA measures the change in weight of asample as a function of temperature or time. The accurate measurement of the loss of weight provides one piece of information, but it does not identify what is changing. In thehyphenated technique FT-IR spectroscopy is used to identify the evolved gases and help in determining sample characteristics.
KIN
ETIC
MO
DELS
FIN
AL R
EM
ARKS
-5,0
-4,0
-3,0
-2,0
-1,0
0,0
50 150 250 350 450 550 650 750
DTG
(%
/°C
)
Temperature (°C)
20°C/min15 °C/min10 °C/min5 °C/min1 °C/min
Heating rate
(°C/min)
T5% (°C) Tonset (°C) Tp (°C) m (%) W (%)
20 121 540 586 61 39
15 120 539 576 60 40
10 117 534 569 60 40
5 98 524 550 62 39
1 85 503 522 63 37
0,0
0,4
0,8
1,2
1,0 1,3 1,5 1,8 2,0 2,3 2,5
Log β
1000/T (K-1)
-3,0
-2,5
-2,0
-1,5
-1,0
1,0 1,3 1,5 1,8 2,0 2,3 2,5
Log
dα/d
t
1000/T (K-1)
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0
40
80
120
160
0,0 0,2 0,4 0,6 0,8 1,0
Ea (
kJ/m
ol)
α
OFW Friedman
• uncured sample (black curve)• cured paste (red curve)
Sample Tpeak
(°C)
ΔH
(J/g)
BR® 680-3
I peak104
II peak165
III peak~210°C
80
67
The sample cured at 200 °C shows a low intensity peak (dotted line) due to the imidization reaction in the range of temperature between 200°C and 250 °C
Sample Tg
(°C)
BR® 680-3 cured 280°C 350
BR® 680-3 cured 250°C338
0,0
0,1
0,2
0,3
0,4
25,0 125,0 225,0 325,0 425,0
He
at F
low
(W
/g)
Temperature (°C)
cured 280°C cured 250°C
cured 210°C cured 200°C
Tg
Tg
-4
-3
-2
-1
20
40
60
80
100
0 10 20 30 40 50 60 70
De
riva
tive
we
igh
t (%
/m)
We
igh
t Lo
ss %
Time (min) RMS Intensity Profile (PI_10°Cmin_2rep.spp)
Name Description
20 40 60
0,005
0,010
0,015
0,020
0,025
0,030
0,035
0,040
0,045
0,050
0,055
Mins
Abs
PI uncured
4000 3500 3000 2500 2000 1500 10000
10
20
30
40
50
60
70
Wavenumber
Min
s
-0,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
0,40
0,45
0,50
Abs
CO2
H2OC-H
-C=O
-C-O
Sample TD onset
(°C)
Tv max
(°C)
Residual
(p%)
BR® 680-3
I step96
III step550
I peak 114
II peak 184
III peak 575
37
-5
-4
-3
-2
-1
0
20
40
60
80
100
0 10 20 30 40 50 60 70
De
riva
tive
we
igh
t (%
/m)
We
igh
t Lo
ss %
Time (min)
RMS Intensity Profile (PI cured_10.spp)
Name Description
20 40 60-0,000
0,005
0,010
0,015
0,020
0,025
0,030
0,035
0,040
Mins
Abs
PI cured
Sample TD onset
(°C)
Tv max
(°C)
Residual
(p%)
BR® 680-3I step
563I peak 593 57
4000 3500 3000 2500 2000 1500 10000
10
20
30
40
50
60
70
WavenumberM
ins
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
0,16
0,18
0,20
0,22
0,24
Abs
CO2
-C-O
condensation reaction: solvent(NMP, EtOH) and/or volatile products
polyimide decomposition
Determination of the energy of activation Ea forthe degradation of BR® 680-3 sample according tothe OFW and Friedman equations.
Ea ~34 kJ/mol
Ea ~124 kJ/mol
This work was realized thanks to the PhD scholarship granted by the Regione Liguria under the Operational Program LiguriaRegion - European Social Fund POR-FSE 2014-2020.
Acknowledgement:
DSC traces after curing at differenttemperature
BR® 680-3 uncured BR® 680-3 cured
30
50
70
90
We
igh
t Lo
ss (
%)
20°C/min15 °C/min10 °C/min5 °C/min
The sample was heated from 50°C to 340°C at aheating rate of 10 °C/min
The sample was heated at a rate of10 °C/min from 40 to 700 °C under aN2 flow and from 700 to 850°Cunder a O2 flow.
BR® 680-3 sample was heated at five differentheating rates: 1, 5, 10, 15 and 20 °C/min.
