processability and thermal characterization of atard epoxy rtm resin

PROCESSABILITY AND THERMAL PROCESSABILITY AND THERMAL CHARACTERIZATION OFCHARACTERIZATION OF

ATARD EPOXY RTM RESIN ATARD EPOXY RTM RESIN

Peter J. Joyce

U.S. Naval Academy

Robert F. Boswell and Neil A. Graf

Naval Air System Command

Sept. 12, 2001 ASC 16 Technical Conference

ObjectiveObjective

Thermally characterize the selected SI- ZG-5A epoxy resin, formulated by A.T.A.R.D. Laboratories resin characterization cure modeling

SI-ZG-5A selected by AMIPC partner Boeing Anhydride curing epoxy resin system Properties similar to leading epoxy systems Low viscosity Wide process flexibility


Manufacturer’s Cure CycleManufacturer’s Cure Cycle

Time (hrs)

Tem

pera

ture

(C

) 176°C

65°C

4 hrs

6 hrs

0.54°C/min.


Baseline Thermal AnalysisBaseline Thermal Analysis

Differential scanning calorimetry (DSC),TA Instrument Model 2920

Thermogravimetric analysis (TGA), Rheometric dynamic analysis (RDA)

Rheometrics Scientific RDA II analyzer 25-mm aluminum parallel plates with a gap setting of 0.8 mm

Oscillated at 1.0 Hz frequency while a constant 10% strain was applied


Differential Scanning CalorimetryDifferential Scanning Calorimetry

0

50

100

150

200

250

300

0 200 400 600 800 1000 1200 1400

Time (min)

Tem

pera

ture

, (C

)

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Hea

t Fl

ow (

mW

)

Heat Flow

Temperature

(Manufacturer’s rec. cure cycle 50:50 mix ratio)

Tg = 207°CHR = 350J/g


Rheometric Dynamic AnaylsisRheometric Dynamic Anaylsis

0.01

0.1

1

10

100

1000

10000

100000

1000000

10000000

0 50 100 150 200 250 300 350

Time (min)

G' (

dyn/

cm2)

G

" (d

yn/c

m2)

20

40

60

80

100

120

140

160

180

Tem

p (C

)

G'G"

Eta* PTemp

Min Viscosity: 2.4 cP, 79 min

Gel Pt.227 min


Thermogravimetric AnalysisThermogravimetric Analysis

Measured an 8-10 % weight loss.Reduced to ~6% with degassing.Due to the volatility of the catalyst.

Part A - < 4% weight loss (25-180°C @ 3°C/min.)Part B - ~ 98% weight loss


Cure Cycle ModificationCure Cycle Modification

208206205201

170175

180185

190195

200205

210215

220

0 1 2 3 4 5 6 7 8

Hold time (hrs)

Gla

ss tr

ansi

tion

tem

per

ature

(dC)

Eliminating initial 65°C hold exhibited negligible effect.Reducing 176°C from 6 hrs to 3 hrs, little effect.


Varying Mix RatioVarying Mix Ratio

00

228

211

207206203

224

180

185

190

195

200

205

210

215

220

225

230

30 40 50 60 70

Fraction component A

Gla

ss tr

ansi

tion

tem

pera

ture

(dC)


Cure Kinetics AnalysisCure Kinetics Analysis

Variable heating rate method (Duswait, 1974)Heating rates:

0.2C/min.0.5C/min.1.0C/min.5.0C/min.10.0C/min.20.0C/min.


Dynamic DSCDynamic DSC(5(5°C/min.)°C/min.)


Summary Dynamic DSC testingSummary Dynamic DSC testingHEATING RATE

(º C/min)PEAK HEIGHT

(º C)ENTHALPY

(J/g)

0.2 86.8 272

0.5 100.1 298

1.0 113.5 316

2.0 127 373

5.0 143 393

10.0 158 362

20.0 175 288



To calculate the activation energy,

A plot of the log-heating rate versus the reciprocal of the absolute temperature at a constant conversion will have a slope of 0.457 E/R.

The constant conversion point was taken at the peak exotherm.

d

d KE R

log

( / ). /

1

0 457


Arrhenius PlotArrhenius Plot

y = -3.7115x + 9.6146

R2 = 0.9996

-1

-0.5

0

0.5

1

1.5

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9

1000/[Temperature (K)]

Log

[Hea

ting

Rat

e (C

/min

.)]

E = 64 kJ/mol



The Arrhenius frequency factor can be calculated from the equation:

A = 7.36 min-1

AE

RT

E

RT

2



Assuming a first order reaction, the rate constant, k, may be calculated from the equation

ln lnk AE

RT



0

0.5

1

1.5

2

2.5

0 50 100 150 200 250

Temperature (ºC)

Rat

e C

onst

ant

(1/m

in)


Cure Kinetics AnalysisCure Kinetics AnalysisBy utilizing the rate constant, percent

conversions were calculated.

0

10

20

30

40

50

60

70

80

90

100

0 0.5 1 1.5 2 2.5 3 3.5 4

Time (hr)

Per

cen

t C

onve

rsio

n (

%)

65ºC

100ºC

175ºC


ResultsResults DSC

Tg = 207°C, HR = 325-375 J/g (3501-6/474 J/g) RDA

min= 2.3 cP after 79 min. @ 65°CGel point ~ 4 hrs

Cure cycle modifications Initial hold @ 65°C can be eliminated 2nd hold @ 176°C can be reduced from 6 hrs to 3 hrs

Cure kinetics analysisActivation Energy, E = 64 kJ/molLog frequency factor, A = 7.36 min-1


Cure ModellingCure Modelling

Lee, Loos, and Springer (1982)Calculate total heat of reaction,

Calculate the amount of heat, H, released up to time, t

dtdt

dQH

ft

R

0

dtdt

dQH

t

0



The degree of cure, , is defined as

Calculate the rate of degree of cure, d/dt

RH

H

RHdtdQ

dt

d


Cure ModellingCure ModellingCurve fit

54

44

33

24

1 KKKKKdt

d

70 75 80 90 100 115 120

K1 -3.63E-04 -6.17E-04 -3.82E-04 -1.92E-03 -4.27E-03 -5.66E-03 -1.55E-03K2 6.85E-04 1.14E-03 3.79E-04 3.88E-03 8.49E-03 1.08E-02 -8.78E-04K3 -6.16E-04 -9.46E-04 -4.38E-04 -3.24E-03 -6.86E-03 -9.39E-03 -2.97E-04K4 2.67E-04 3.68E-04 3.59E-04 1.20E-03 2.42E-03 3.89E-03 2.21E-03K5 2.75E-05 5.94E-05 8.54E-05 7.63E-05 2.16E-04 3.78E-04 4.55E-04R2 9.97E-01 9.93E-01 9.84E-01 9.96E-01 9.97E-01 9.91E-01 9.75E-01



5 4, 3, 2, 1, ,1

)ln()ln(

5 4, 3, 2, 1, ,exp

iTR

EAK

iRT

EAK

iii

iii

Ongoing. . .


AcknowledgementsAcknowledgements

ONR, Dr. Ignacio PerezMr. Roland CochranMr. Stan NgDr. Reza Malek-Madani

processability and thermal characterization of atard epoxy rtm resin

Documents

selected si zg

thermogravimetric analysis

ta instrument model

amipc partner boeinganhydride

naval academyrobert

mix ratiotg

aluminum parallel plates

hz frequency