Improvement of Thermal and Mechanical Properties of Polyimide

Improvement of Thermal and Mechanical Properties

of Polyimide Using Metal Oxide Nanoparticles

Ahmad Raza Ashrafϕ,§, Zareen Akhter§, Leonardo C. Simonϕ ϕ Department of Chemical Engineering, University of Waterloo, Waterloo, Canada § Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan

2016 SPE AUTOMOTIVE COMPOSITES CONFERENCE & EXHIBITION (ACCE) September 7-9 2016, Novi, Michigan, USA

1 Overview

• What are polyimides? - History, structure, properties Introduction • Applications - General - Automotive

• Polyimide Synthesis • Polyimide nanocomposites

• Glass transition temperature Results + • Storage modulus Conclusion • Thermal stability

2 What are polyimides?

• High performance polymers • Aromatic polyimides consists of 1. Heterocyclic imide rings and 2. Aryl groups linked by simple atoms or groups

O Imide ring O R

N N

n O Aryl group O R = alkyl or phenyl with or without functional groups

3 History

• The first synthesis of polyimide was performed by Bogert and Renshaw in 1908.

• High-molecular weight aromatic polyimide was synthesized in 1955 by Edward and Robinson.

• Poly(4,4'-oxydiphenylene pyromellitimide) widely known as Kapton® was commercialized in early 1960s.

• After the success of Kapton (Dupont), several other PIs have been synthesized and investigated extensively.

• Commercial examples also include Vespel (Dupont), Upilex (Ube), Meldin (Saint-Gobain).

4 Properties Low Fire and dielectric wear constant resistance Low Chemical moisture and absorption radiation resistance Polyimides

Outstanding thermal Excellent stability mechanical properties High glass transition temperature

5 Why polyimides are so strong???

Charge Transfer Complex

St. Clair, T.L. in Polyimides, Ed. Wilson D., Stenzenberger, H.D., Hergenrother, P. M., Chapman and Hall, New York, 1990, Chapter 2.

6 Applications (General)

• Thin film insulators in electronic packaging.

• Base of flexible white LED strip lights.

• H2O2 sensors.

• Gas separation membranes.

• Lightweight composites of RP46 polyimide and glass fibers are extraordinarily fire-resistant electrical-insulation materials.

7 Applications in automotive industry • Aerospace structures as outer protective covering, engine ducts and bushings.

• The bushings, bearing pads and splines in the 10-stage high-pressure compressor of the Rolls-Royce BR710 turbofan engine are made from Vespel polyimide. These parts are exposed to temperatures up to 274 °C yet need no lubrication.

8 Applications in automotive industry

• Polyimide foams: The winner of NASA's 2007 commercial invention of the year are effective for sound, heat and cold insulation. • Effective thermal insulation from -240 °C to +204 °C • Inherently fire-resistant • Low cost and fast production • Can be molded into different shapes.

• Aerospace ethernet cables comprise of aluminized polyimide shield. 1. Engineered fluoropolymer jacket 2. Braided shield 3. Aluminized polyimide shield 4. FEP filler 5. Color-coded composite dielectric 6. Silver-plated copper conductor.

9 Applications in automotive industry

• Thinner, lighter Vespel® SP-21 thrust washers replace all-metal needle bearings in a new 7-speed AT for rear- drive vehicles.

• Variable stator vane bushings made from Vespel CP are used in the high pressure section of the compressor in a aircraft engine. The laminate withstands temperatures in excess of 675°F.

10 Applications in automotive industry

• DuPont™ Vespel® polyimide bushings offers weight and performance advantages over metal in exhaust gas recirculation (EGR) valves.

• Due to their stiffness, tensile strength & resistance to friction, wear and hot exhaust gases at temperatures up to 220 °C, these bushings have replaced metal components in EGR system used in four and six cylinder stratified-charged petrol engines.

11 Applications in automotive industry

• BWD oil pressure light switch has polyimide film diaphragm.

• Conductive Kapton is used as mirror & seat heaters, engine warmers of cars, wing, floor and satellite heaters in aerospace. (thermo-llc.com)

12 Applications in Automotive Industry

• The circuits of BWD throttle position sensors are printed on flexible polyimide film for excellent dimensional stability and for prevention of electrical performance drift.

• The Dayton audio D250P-8 compression driver features polyimide diaphragm for smooth character and rich detailed sound.

13 Synthesis of polyimide O O O

H2 O O H2N C NH2

O BTDA O MDA 1) DMAc Step 1 2) 25°C 3) 24 hrs stirring

O O O H H H2 N N C

HO OH n O O Polyamic acid

Step 2 70°C (18hr), Thermal Imidization 120°C, 150°C, 200°C, 250°C, 280°C (1hr each), O O O

H2 N N C n O O Polyimide BTDA = 3,3',4,4'-benzophenonetetracarboxylic dianhydride MDA = 4,4'-methylenedianiline 14 Synthesis of polyimide/nanocomposites

MDA DMAc

NPs (Nanoparticles) Sonication

MDA/DMAc/NPs

BTDA Stirring Sonication

Polyamic acid/ Nanocomposite

Thermal Imidization 25 - 280 °C

Polyimide/Nanocomposite

15 Review: Interaction of nanoparticles with polyamic acid

Dang, Zhi‐Min, et al. Advanced Functional Materials 18.10 (2008): 1509-1517

16 Interaction between nanoparticles and polyimide

Hsu, Shou‐Chian, et al. Macromolecular Chemistry and Physics 206.2 (2005): 291-298.

17 Research Results

Polyimide/Al2O3 Nanocomposites

Glass transition temperature (Tg) • Pure polyimide (BM) 0.8 BM displayed glass transition 0.7 BM-Al2O3-3% temperature (Tg) at 272 °C. 0.6 BM-Al2O3-5% BM-Al2O3-7% • Incorporation of Al2O3 0.5 BM-Al2O3-9% nanoparticles increased the 0.4 Tg of polyimide matrix. tan(d) 0.3 • Trend was continued with 0.2 increasing concentration of 0.1 nanoparticles. 0.0 • At 9% loading of 100 150 200 250 300 350 nanoparticles Tg was Temperature (°C) increased from 272 °C to 337 °C. BM = polyimide (BTDA + MDA) 18 Polyimide/Al2O3 Nanocomposites

Storage Modulus • Modulus of pure polyimide (BM) is above 1 GPa up to 250 °C. BM BM-Al2O3-3% 2.50E+009 BM-Al2O3-5% • It decreased sharply around BM-Al2O3-7% glass transition temperature 2.00E+009 BM-Al2O3-9% (Tg = 272 °C). 1.50E+009 • Al2O3 nanoparticles improved the 1.00E+009 modulus. E'(Pa)

5.00E+008 • Modulus value at 50 °C increased from 1.60 GPa to 2.56 0.00E+000 Gpa GPa at 9% loading of 50 100 150 200 250 300 350 nanoparticles. Temperature (°C)

BM = polyimide (BTDA + MDA) 19 Polyimide/Al2O3 Nanocomposites

Polymer Tg (°C) Modulus50 Modulus150 Modulus250 (GPa) (GPa) (GPa) BM 272 1.60 1.21 0.88

BM-Al2O3-3% 300 1.95 1.48 1.08

BM-Al2O3-5% 316 2.20 1.67 1.21

BM-Al2O3-7% 325 2.46 1.70 1.24

BM-Al2O3-9% 337 2.56 2.01 1.64

Tg = Glass transition temperature Modulus50 = Modulus at 50 °C Modulus150 = Modulus at 150 °C Modulus250 = Modulus at 250 °C 20 Polyimide/Al2O3 Nanocomposites

Thermal Stability 100 • Decomposition started after 450 °C. 90 • Temperature of 5% BM weight loss is above 540 80 BM-Al2O3-3% °C. BM-Al2O3-5%

Weight (%) • Shape of curve suggests 70 BM-Al2O3-7% BM-Al2O3-9% one step degradation mechanism. 60 200 300 400 500 600 700 800 • Nanoparticles Temperature (°C) incorporation improved the thermal stability of polyimide.

N2, Ramp at 20 °C/min to 800 °C BM = polyimide (BTDA + MDA) 21 Polyimide/Al2O3 Nanocomposites

Polymer T1 (°C) T5 (°C) T10 (°C) R800 (%)

BM 449 542 572 61

BM-Al2O3-3% 451 545 575 63

BM-Al2O3-5% 453 545 575 64

BM-Al2O3-7% 453 545 576 65

BM-Al2O3-9% 453 552 580 68

T1 = Temperature at 1% weight loss T5 = Temperature at 5% weight loss T10 = Temperature at 10% weight loss R800 = Residue at 800 °C 22 Polyimide/Al2O3 Nanocomposites

Isothermal study at 400 °C for 30 minutes • Polyimides can withstand 100.0 BM elevated temperatures for a BM-Al2O3-3% 99.5 BM-Al2O3-5% certain period of time. 99.0 BM-Al2O3-7% BM-Al2O3-9% • Pure polyimide (BM) showed 98.5 only 2.5% weight loss after 30 minutes of isothermal 98.0 treatment at 400 °C. Weight (%) 97.5 • This was further reduced to

1.9% at 9% loading of Al2O3 97.0 0 5 10 15 20 25 30 35 • Improvement in thermal Time (min) stability in case of

Polyimide/Al2O3 composites Air, Ramp at 50 °C/min to 400 °C is evident from decrease in weight loss. BM = polyimide (BTDA + MDA) 23 Polyimide/Al2O3 Nanocomposites

Polymer W15 (%) W25 (%) W35 (%)

BM 97.81 97.61 97.47

BM-Al2O3-3% 98.26 98.05 97.91

BM-Al2O3-5% 98.32 98.12 97.97

BM-Al2O3-7% 98.38 98.17 98.02

BM-Al2O3-9% 98.46 98.25 98.12

W15 = Weight percent after 15 minutes W25 = Weight percent after 25 minutes W35 = Weight percent after 35 minutes

24 Polyimide/ZnO Nanocomposites

• Pure polyimide displayed Glass transition temperature (Tg) glass transition temperature (Tg) at 272 °C. 0.8 BM BM-ZnO-3% 0.7 BM-ZnO-5% • Incorporation of ZnO 0.6 BM-ZnO-7% nanoparticles increased the BM-ZnO-9% 0.5 Tg of polyimide matrix. 0.4 • Shape of curve at 9%

tan(d) 0.3 loading suggests different 0.2 levels of interactions 0.1 between nanoparticles and 0.0 polyimide matrix. 100 150 200 250 300 350 400 Temperature (°C) • At 9% loading, Tg was increased from 272 °C to BM = polyimide (BTDA + MDA) 360 °C.

25 Polyimide/ZnO Nanocomposites

Storage Modulus • Modulus of pure polyimide 2.50E+009 BM (BM) above 1 GPa up to BM-ZnO-3% 250 °C. 2.00E+009 BM-ZnO-5% BM-ZnO-7% • It decreased sharply around BM-ZnO-9% 1.50E+009 glass transition temperature (Tg = 272 °C). 1.00E+009 E' (Pa) • ZnO nanoparticles improved 5.00E+008 the modulus of parent polyimide matrix both at 0.00E+000 start and around Tg. 50 100 150 200 250 300 350 Temperature (°C) • Modulus value at 50 °C was increased from 1.60 GPa to BM = polyimide (BTDA + MDA) 2.32 GPa at 9% loading of nanoparticles.

26 Polyimide/ZnO Nanocomposites

Polymer Tg (°C) Modulus50 Modulus150 Modulus250 (109) (109) (109)

BM 272 1.60 1.21 0.88

BM-ZnO-3% 280 1.73 1.30 1.06

BM-ZnO-5% 319 1.87 1.39 1.08

BM-ZnO-7% 327 2.14 1.47 1.08

BM-ZnO-9% 360 2.32 1.70 1.26

Tg = Glass transition temperature Modulus50 = Modulus at 50 °C Modulus150 = Modulus at 150 °C Modulus250 = Modulus at 250 °C 27 Polyimide/ZnO Nanocomposites

Thermal Stability • ZnO nanoparticles 100 decreased the thermal stability of polyimide.

90 • T5 was lowered to 460 °C BM from 542 °C. BM-ZnO-3% 80 BM-ZnO-5% • ZnO concentration has no BM-ZnO-7% effect on thermal behavior. Weight (%) 70 BM-ZnO-9% • Shape of curve suggests one step degradation 60 mechanism for pure 200 300 400 500 600 700 800 polyimide and two steps Temperature (°C) for polyimide/ZnO.

N2, Ramp at 20 °C/min to 800 °C BM = polyimide (BTDA + MDA) 28 Polyimide/ZnO Nanocomposites

Polymer T1 (°C) T5 (°C) T10 (°C) R800 (%)

BM 449 542 572 61

BM-ZnO-3% 393 459 504 62

BM-ZnO-5% 404 465 513 63

BM-ZnO-7% 404 468 517 63

BM-ZnO-9% 390 465 514 67

T1 = Temperature at 1% weight loss T5 = Temperature at 5% weight loss T10 = Temperature at 10% weight loss R800 = Residue at 800 °C 29 Comparison between PI/Al2O3 and PI/ZnO

Glass transition temperature (Tg)

Al2O3 360 • Both types of nanoparticles ZnO increased glass transition 340 temperature (Tg).

320 • At 9% loading, ZnO nanoparticles are more 300

Tg (°C) effective in increasing glass transition temperature than 280 Al2O3 counterparts. 260 0 3% 5% 7% 9% Concenteration

30 Comparison between PI/Al2O3 and PI/ZnO

Storage Modulus (E’) at 50 °C

2.6 Al2O3 • Nanoparticles ZnO increased modulus.

) 2.4

• Addition of Al2O3 GPa ( 2.2 changes is more effective than ZnO to 2.0 improve E’.

Modulus (Pa) 1.8

1.6

0 3% 5% 7% 9% Concenteration

31 Comparison between PI/Al2O3 and PI/ZnO

Thermal stability 560

540 • Al2O3 nanoparticles 520 improved the thermal Al2O3 stability at 5% weight loss. 500 ZnO • ZnO decreased thermal stability. T5 (°C) 480

460

440 0 3% 5% 7% 9% Concenteration

32 Conclusions

 Nanoparticles can further improve modulus, glass transition temperature and thermal stability, thus with potential to provide further benefit in automotive applications.

 Thermogravimetric analysis (TGA) showed substantial thermal stability, thermal decomposition started after 450 °C in some cases.

 Isothermal studies with TGA showed that polyimides are capable to withstand at elevated temperatures for longer period of time.

33 Conclusions

 Incorporation of Al2O3 and ZnO nanoparticles increased the glass transition temperature and modulus of polyimide.

 At 9% loading, ZnO nanoparticles increased glass

transition temperature more than Al2O3, but Al2O3 provided better modulus.

 Polyimide/Al2O3 nanocomposites had higher thermal stability than polyimide alone.

34 Acknowledgments

• University of Waterloo, Waterloo, Canada (NSERC Discovery Grant and experimental facilities)

• Quaid-i-Azam University, Islamabad, Pakistan (experimental facilities)

• Higher Education Commission of Pakistan for funding of Ahmad Raza Ashraf under International Research Support Initiative Program (for research visit as graduate student at University of Waterloo, Canada) and Indigenous PhD Fellowship Program at Quaid-i-Azam University, Islamabad, Pakistan.

Thank you!