HIGHEST HEAT AMORPHOUS THERMOPLASTIC POLYIMIDE BLENDS

Kapil C. Sheth, SABIC Innovative Plastics, Mt.Vernon, IN, USA

Abstract

Novel thermoplastic polyimide blends have been

designed with capability to tailor glass transition

temperatures exceeding 300ºC. These highest heat

amorphous thermoplastic blends offer high temperature

load bearing capability and dimensional stability. These

compositions also demonstrate excellent flame resistance.

Introduction

Aromatic polyimides represent a distinctive class of

materials that are widely used in electronics, aerospace

and many other demanding applications. Aromatic

polyimides have a unique combination of properties

including high glass transition temperatures (Tg),

mechanical property retention at high temperatures, high

thermal stability, good electrical properties and solvent

resistance. However, many such polyimides are infusible,

rendering them impossible to process by conventional

techniques. Lack of melt processability is a big drawback.

Significant efforts have been devoted to the

development of melt processable polyimides, commonly

referred to as thermoplastic polyimides (TPI)1-3

.

Evaluation of new monomer combinations has led to the

introduction of new materials such as amorphous LARC-

TPI resin (Tg~250ºC) and semi-crystalline AURUM*

resin (Tg~250ºC, Tm~388ºC). A related class of melt

processable materials known as polyetherimides (e.g.,

ULTEM** 1000 resin, Tg~217ºC) were also developed.

Another approach to improve melt processablity of

aromatic polyimides is to blend with other easier to

process high temperature crystalline and amorphous

resins. For example, many blends of polyimides with

polyetherimides have been reported4-5

.

Recently a genuine new TPI polymer has been

introduced by SABIC Innovative Plastics. It is the highest

glass transition temperature, amorphous thermoplastic

resin available (Tg ~ 311ºC). Its high Tg and viscosity

limit injection molding applications. However, other

processing techniques such as extrusion and compression

molding can process high viscosity materials such as the

new TPI polymer. In order to improve its injection

moldability, many new TPI blends with good melt

processability have been developed by alloying the new

TPI polymer with other amorphous thermoplastic

polyimides, polyetherimides or semi-crystalline resins.

A series of amorphous TPI blends using the new TPI

polymer has been commercialized as EXTEM** UH

products6-7

. These EXTEM UH TPI blends offer good

dimensional stability, high temperature strength, creep

resistance and best-in-class flame resistance. Another class

of high temperature semi-crystalline blends has also been

introduced by alloying polyetheretherketone resin with the

new TPI polymer8.

Experimental

The new TPI polymer from SABIC Innovative

Plastics was blended with other thermoplastic polyimides

and/or polyetherimides in varying proportions across the

composition space. Blend compositions can be varied to

tailor mechanical, thermal, flow and end-use properties

for a wide-array of applications. Two such TPI blends

have recently been commercialized as EXTEM UH1006

and UH1016 grades.

These TPI blends are melt processable on existing

standard processing equipment. All blends were

compounded on a WP30 twin-screw extruder. Barrel

temperatures varied from 350ºC to 400ºC depending on

blend composition. All ASTM test parts were molded on a

standard 170-ton injection molding machine equipped

with a general purpose screw according to guidelines

recommended in Table 1. Prior to molding, pellets were

dried at 175ºC for 6 hours in a dehumidifying dryer to a

moisture content of 0.02 wt% or lower. All molded part

data were generated according to ASTM guidelines.

Discussion

Figure 1 shows capillary rheology (melt viscosity vs.

shear rates) for the TPI blends in their typical processing

range. The two commercial grades have significantly

different viscosities to enable a variety of end use

applications and part designs. The viscosity can be further

tweaked as needed with the addition of processing aids.

Typical flow lengths for the EXTEM UH1006 grade

are shown in Figure 2. These data were generated using a

spiral flow tool on a 170-ton injection molding machine.

Injection pressure was fixed at 1,378 bar (20,000 psi). The

actual mold temperature was ~165-170ºC. Flow lengths

were measured at three different thickness and three melt

temperatures. Since the UH1016 grade has a lower

viscosity, it demonstrates longer flow lengths under

comparable processing conditions.

Datasheet properties of one of the new TPI blends

(EXTEM UH1006 grade) are compared in Table 2 to a

polyetherimide (ULTEM 1000 resin) and a semi-

crystalline TPI (AURUM PL450C resin). The new TPI

blend shows improved tensile and flexural properties

(modulus and strength) at 23ºC as well as at 150ºC.

Compressive strength is also higher for the new TPI blend.

The new TPI blend has a lower coefficient of thermal

expansion and hence better dimensional stability.

Flammability performance in terms of UL-V0 rating and

limiting oxygen index are equivalent for the new TPI

blend and the semi-crystalline TPI. UL rating of V0 at a

thickness of 0.4 mm without addition of any other

additives demonstrates that the flame-retardant

performance of the TPI blend is significantly superior to

the polyetherimide and other high performance materials.

The semi-crystalline TPI AURUM has a Tg~250ºC

and Tm~388ºC, but it is a slow crystallizing polymer. It is

amorphous and transparent as molded, and the use

temperature is limited to 240ºC9. It requires a secondary

annealing step (>10 hours at 220-280ºC) to develop

crystallinity and improve heat resistance for use above

240ºC. Exposure of molded amorphous parts to

temperatures above 240ºC without any annealing can

cause dimensional stability issues. Annealing of a semi-

crystalline resin can also lead to dimensional changes.

The new TPI blends, however, do not require any

annealing since these are amorphous blends. Molded parts

maintain good dimensional stability even at high

temperatures.

High temperature performance of a commercial TPI

blend (EXTEM UH1006 grade) is highlighted in Figures 3

and 4. The blend shows superior tensile and flexural

strength retention even at 200ºC (Figure 3). Modulus

retention at higher temperatures for the blend also leads to

excellent creep resistance at 150ºC and 200ºC (Figure 4).

Another distinguishing feature of the new amorphous

TPI blends is that the heat resistance (Tg or heat distortion

temperature) is tailorable over a wide range by varying

blend components and composition. The new TPI polymer

can be blended with other thermoplastic polyimides and/or

polyetherimides. Since the new TPI polymer has a Tg ~

311ºC, blends with a Tg greater than 300ºC are feasible.

The commercial TPI blends (EXTEM UH1006 and

UH1016 grades) represent only two of a wide-range of

products which are possible by blending with the new TPI

polymer.

Figure 5 shows an example of a binary blend of the

new TPI polymer and a polyetherimide. The blend

composition was varied by changing the new TPI polymer

content in the 60% to 100% range. The Tg of a miscible

blend can be usually be predicted using the well known

Fox equation10

. The actual Fox equation is shown in

Figure 5. The blend Tg was experimentally measured

using a Perkin-Elmer Differential Scanning Calorimeter at

a heating rate of 20ºC/min under a nitrogen purge. The

predicted and measured Tg for this binary TPI blend are in

very good agreement. Thus, for this particular blend Tg

can be designed to any target by varying the composition

i.e. the content of the new TPI resin.

Conclusions

Two new high heat thermoplastic polyimide blends

with good melt processability have been designed. These

TPI blends offer good dimensional stability, high

temperature strength, creep resistance and excellent flame

resistance. By leveraging the new TPI polymer, it is

possible to design a wide-range of blends with other

amorphous thermoplastic polyimides, polyetherimides or

semi-crystalline resins to target glass transition

temperatures exceeding 300ºC.

References

1. S. Tamai, A. Yamaguchi and M. Ohta, Polymer,

37(16), 3683 (1996).

2. J. de Abajo and J.G. de la Campa, Advances in

Polymer Science, 140, 23 (1999).

3. V.L. Bell, U.S. Patent 4,094,862 (1978).

4. K. Blizard and M. Druy, ANTEC, 53(2), 3124 (1995).

5. S.P. Ma and T. Takahashi, Polymer, 37(25), 5589

(1996).

6. S. Lee, Plastics Technology Magazine, January 2007.

(http://www.ptonline.com/articles/200701fa6.html)

7. EXTEM

Resins from SABIC Innovative Plastics.

(http://www.geplastics.com/gep/Plastics/en/ProductsA

ndServices/ProductLine/extem.html)

8. MAX-Series (http://www.victrex.com/en/peek_poly/

victrex_max-series.php) at Victrex plc website.

9. AURUM Product literature from Mitsui Chemicals.

(http://www.aurumtpi.com)

10. L.A. Utracki, Polymer Blends Handbook, 187 (2002).

Key Words: TPI, thermoplastic polyimide, TPI blend

* trademark of Mitsui Chemicals

**trademark of SABIC Innovative Plastics IP BV

Table 1. Typical Injection Molding Conditions for the TPI Blends

Table 2. Property Comparison of EXTEM UH1006 Grade

Figure 1. Rheology of EXTEM UH Blends

Figure 2. Spiral Flow of EXTEM UH1006 Grade

Maximum Moisture Content % 0.02

Drying Temperature °C 175

Drying Time hr 6

Melt Temperature °C 400 - 415

Nozzle Temperature °C 395-415

Front - Zone 3 Temperature °C 395-415

Middle - Zone 2 Temperature °C 390 - 405

Rear - Zone 1 Temperature °C 380 - 390

Mold Temperature °C 150 - 175

Back Pressure bar 3-5

Screw Speed rpm 40-70

Shot to Cylinder Size % 40 - 70

EXTEM UH1006 / UH1016 Grades

100

1000

10000

100 1000 10000

Shear Rate (1/s)

Viscosity (Pa-s)

UH1006

UH1016

415°C

0

100

200

300

400

390 400 410 420 430

Melt Temperature (ºC)

Flow Length (mm)

3.0 mm

2.3 mm

1.5 mm

1,378 bar (20,000 psi)

Injection Pressure

ASTM Testing Amorphous Amorphous Semi-crystalline

TPI Blend Polyetherimide TPI

PROPERTY Unit EXTEM UH1006 ULTEM 1000 AURUM PL450C

Tensile Modulus - 23°C MPa 3,800 3,200 2,760

Tensile Strength - 23°C MPa 120 105 92

- 150°C MPa 68 50 58

Flexural Modulus - 23°C MPa 3,520 3,300 2940

- 150°C MPa 2,500 - 2550

Flexural Strength - 23°C MPa 175 160 137

- 150°C MPa 109 - 88

Compressive Strength - 23°C MPa 160 130 120

Izod Impact, notched - 23°C J/m 75 53 90

Coefficient of Thermal Expansion ppm/°C 46 50 55

HDT, 1.8 MPa, 3.2mm (as-molded) °C 240 190 238

Density g/cc 1.37 1.27 1.33

UL-V0 Flammability Rating mm 0.4 0.8 to 1.6 0.4

Limiting Oxygen Index % 47 45 47

Figure 3. High Temperature Strength

of EXTEM UH1006 Grade

Figure 4. Creep Resistance of EXTEM UH1006 Grade

Figure 5. Tailoring Tg of the TPI Blends

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Temperature (ºC)

Property Retention (%)

Flexural Strength

Tensile Strength

0.1

1

10

1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02

Time (Hours)

Strain (%)

23°C

150°C

200°C

20MPa Load

0.0 0.2 0.4 0.6 0.8 1.0

New TPI Polymer (wt fraction)

BlendTg(°C)

Predicted

Actual

2g

2

1

1

)(T

w

)()(

1+=

ggT

w

blendT

>200°C

311°C

0.0 0.2 0.4 0.6 0.8 1.0

New TPI Polymer (wt fraction)

BlendTg(°C)

Predicted

Actual

2g

2

1

1

)(T

w

)()(

1+=

ggT

w

blendT2g

2

1

1

)(T

w

)()(

1+=

ggT

w

blendT

>200°C

311°C