PI / Polyimide Plastic Machining

Your guide to PI Plastic Machining

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A family of some of the most heat and fire resistant polymers in existence

Ideal material for challenging friction and wear applications

High strength and outstanding wear resistance

Polyimides (PI or often referred to as the brand name Vespel®) are a family of some of the most heat and fire resistant polymers in existence. There can be some challenges when machining so choosing an experienced and skilled CNC machining partner is essential.

This guide will take you through the main attributes, common applications, notes for designers and suitable finishing and treatments, as well as UK stock sizes and property tables. Don't forget to bookmark the page so you can refer back later.

If you are interested in PI machined parts, please scroll to the bottom of the page for more information about our service and to request a quote.

PI Guide: Properties, Applications and Design Considerations

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What is PI plastic?

Polyimides (PI or often referred to as the brand name Vespel®) are a family of some of the most heat and fire resistant polymers in existence. Low wear rates combined with the ability to work under unlubricated conditions and high pV-rates makes it the ideal material for challenging friction and wear applications, extending lifetime and reducing maintenance costs.

There are many different grades of PI/Polyimide, all with varying characteristics. A comparison of the technical properties can be found in the tab below.

PI does come with its challenges when it comes to machining. A good machining finish can be achieved by keeping tool cutting edges sharp, particularly for parts requiring tight tolerances. Many of the same milling operations employed on metal (especially brass) may be used on PI, except that a far higher spindle speed must be used. Heat build up should be avoided by using a suitable coolant.

Precautions need to be taken with holding to avoid distortion through over tightening.

Here at Penta Precision, we specialise in machining parts requiring tight tolerances and have plenty of experience with machining polyimides. Being a more expensive polymer, you want to be sure that you use an experienced machining company for a low chance of material wastage in order to keep costs in check.

You may also see PI referred to as:

Vespel®
TECASINT® (1000, 2000, 4000, 5000 and 8000 series)
Duratron®
Meldin®
Plavis®
Sintimid®
Kapton®
Cirlex®
Imidez®

Typical Components & Applications: Valve and pump seats | Wear parts | Fixtures | Washers, bushings, bearings

Main Attributes:

High strength
Outstanding wear resistance
High dimensional stability, even up to 260°C
Long term thermal stability 300°C
Excellent thermal and electrical insulation

Good machinability
Flame retardant
Creep resistant
Good chemical resistance
Resistance to high energy radiation
Excellent machinability

Note For Designers:

The superior performance properties of polyimides come at a cost. They should therefore only be chosen should the part in question need the advanced properties; they really are amongst the highest performing engineering plastics on the market today.

UK Stock Sizes

PI UK Stock Sizes

Here are the standard stock sizes/colours for PI in the UK. Please note we do not supply stock material, the information provided is purely for design and research purposes.

Grades of TECASINT available:

1011 natural – 1000 series unfilled
1021 black – 1000 series with 15% graphite filler
1031 black – 1000 series with 40% graphite filler
1061 black – 1000 series with 15% graphite/10% PTFE
2011 natural – 2000 series unfilled
2021 black – 2000 series with 15% graphite filler
2031 black – 2000 series with 40% graphite filler
2061 black – 2000 series with 15% graphite/10% PTFE
2391 black – 2000 series with 15% MoS2
4011 natural – 4000 series unfilled
4021 black – 4000 series with 15% graphite filler
4111 natural – 4000 series unfilled
4121 black – 4000 series with 15% graphite filler
5051 grey-grey – 5000 series with 30% glass fibre
8001 yellow-brown – 8000 series with 80% PTFE 20% polyimide
8061 yellow-brown – 8000 series with 60% PTFE 40% polyimide

TECASINT 1011 natural (unfilled) stock sizes

Varying stock sizes for each grade. Here are the stocked sizes that are available for 1011 natural as an example. Our Estimators can advise you further if you require a different grade/size.

PI Rod

From 6.35mm - lengths of 250mm and 250mm
Up to 25.4mm - lengths of 250mm, 500mm and 1000mm

PI Plate

From 6.35mm x 300mm - lengths of 125mm up to 1000mm
Up to 40mm x 300mm - lengths of 125mm up to 1000mm

Technical Properties

PI/Polyimide Technical Properties

Here are the properties for the various grades of TECASINT

TECASINT PI Properties

_{^{Mechanical Properties}}	_{^{1011 (natural)}}	_{^{1021 (black)}}	_{^{1031 (black)}}	_{^{1061 (black)}}	_{^{2011 (natural)}}	_{^{2021 (black)}}	_{^{2031 (black)}}	_{^{2061 (black)}}	_{^{2391 (black)}}	_{^{4011 (natural)}}	_{^{4021 (black)}}	_{^{4111 (natural)}}	_{^{4121 (black)}}	_{^{5051 (grey-green)}}	_{^{8001 (yellow-brown)}}	_{^{8061 (yellow-brown)}}	_^Parameter	_^Norm
Modulus of Elasticity (tensile test)	3600 MPa	4000 MPa			370 MPa	4400 MPa	6300 MPa	3900 MPa	4400 MPa	4000 MPa	4943 MPa	6300 MPa	6600 MPa	5800 MPa			1mm/min, 23°C	DIN EN ISO 527-1
Tensile Strength	116 MPa	97 MPa	65 MPa	77 MPa	118 MPa	101 MPa	65 MPa	63 MPa	95 MPa	130 MPa	93 MPa	100 MPa	34 MPa	94 MPa	15 MPa	13 MPa	50mm/min, 23°C	DIN EN ISO 527-1
Elongation at Break	3.8%	2.8%	2.2%	2.9%	4.5%	3.7%	2.1%	2.7%	2.9%	4.5%	3%	1.7%	0.5%	3.4%	200%	4%	50mm/min, 23°C	DIN EN ISO 527-1
Elongation at Break	6%	4.5%	1.4%	3.6%	6.1%	4.6%	2.2%	3.3%	3.6%	6.0%							50mm/min, 23°C	DIN EN ISO 178
Elongation at Break											3.4%	2.5%	1.8%	3.1%			10mm/min, 23°C	DIN EN ISO 178
Flexural Strength	170 MPa	150 MPa	88 MPa	120 MPa	177 MPa	145 MPa	87.5 MPa	89 MPa	137 MPa	180 MPa	131 MPa	160 MPa	113 MPa	163 MPa		29MPa	10mm/min, 23°C	DIN EN ISO 178
Modulus of Elasticity (flexural test)	3700 MPa	4000 MPa			3600 MPa	4300 MPa	5200 MPa	3490 MPa	4136 MPa	4300 MPa	4200 MPa	6100 MPa	6100 MPa	6625 MPa			2mm/min, 23°C	DIN EN ISO 178
Compression Strength	500 MPa	210 MPa	180 MPa	227 MPa	486 MPa	300 MPa	131 MPa	164 MPa	252 MPa	40 MPa	208 MPa	250 MPa	200 MPa	260 MPa		60MPa	10mm/min, 23°C	EN ISO 604
Compression Strength	190 MPa	175 MPa			170 MPa	160 MPa	124 MPa	142 MPa	180 MPa	185 MPa	163 MPa	250 MPa	183 MPa				10mm/min, 10% strain, 23°C	EN ISO 604
Compressive Strain at Break	45%	20.1%			58%	43%	12.5%	16.4%	35.6%		36%	25%	15%	72%			10mm/min, 10% strain, 23°C	EN ISO 604
Compression Modulus	2000 MPa	1880 MPa			1713 MPa	1900 MPa	2027 MPa	1748 MPa	2200 MPa	2100 MPa	2067 MPa	2500 MPa	2200 MPa	2590 MPa			1mm/min, 23°C	EN ISO 604
Impact Strength (Charpy)	75.8 kJ/m²	35.1 kJ/m²	16.5 kJ/m²	25.8 kJ/m²	87.9 kJ/m²	36.7 kJ/m²	14.2 kJ/m²	19.4 kJ/m²		87 kJ/m²	24.4 kJ/m²	24 kJ/m²	11 kJ/m²	27.3 kJ/m²		5.4 kJ/m²	max. 7.5J, 23°C	DIN EN ISO 179-1eU
Notched Impact Strength (Charpy)	5 kJ/m²	4.8 kJ/m²	3.6 kJ/m²	3.9 kJ/m²	9.3 kJ/m²	2.9 kJ/m²	3.3 kJ/m²	3.2 kJ/m²		9.6 kJ/m²	4.8 kJ/m²	1.1 kJ/m²	1.4 kJ/m²	5.1 kJ/m²		2.5 kJ/m2	max. 7.5J, 23°C	DIN EN ISO 179-1eA
Shore Hardness	90D	88D	85D	85D	90D	87D	84D	84D	90D	88D	86D	90D	87D	92D	65D	70D	Shore D, 23°C	DIN 53505

^{_{Thermal Properties}}	^{_{1011 (natural)}}	^{_{1021 (black)}}	^{_{1031 (black)}}	^{_{1061 (black)}}	^{_{2011 (natural)}}	^{_{2021 (black)}}	^{_{2031 (black)}}	^{_{2061 (black)}}	^{_{2391 (black)}}	^{_{4011 (natural)}}	^{_{4021 (black)}}	^{_{4111 (natural)}}	^{_{4121 (black)}}	^{_{5051 (grey-green)}}	^{_{8001 (yellow-brown)}}	^{_{8061 (yellow-brown)}}	^_Parameter	^_Norm	^_Notes
Glass Transition Temperature	368°C	330°C	330°C	330°C	370°C	370°C	370°C		370°C	260°C	260°C			340°C	- 20°C	20°C			_{^{DMA, maximum loss factor tan d / DIN EN ISO 11357}}
Heat Distortion Temperature	368°C	300°C			319°C	335°C	325°C			360°C		470°C					1.85 MPa	DIN 53 461
Service Temperature															250°C	270°C	long term		^{_{Found in public sources, individual testing regarding application is mandatory}}
Service Temperature														300°C			short term		^{_{Found in public sources, individual testing regarding application is mandatory}}
Thermal Expansion (CLTE)	4.3 10-5*1/K				4.3 10-5*1/K	4.5 10-5*1/K			4.7 10-5*1/K	5.6 10-5*1/K	5.4 10-5*1/K	5.2 10-5*1/K	5.0 10-5*1/K				50- 200°C	DIN 53 752	^{_{Thermal expansion XY/Z axis}}
Thermal Expansion (CLTE)	5.3 10-5*1/K				5.1 10-5*1/K	5.44.3 10-5*1/K			5.7 10-5*1/K	7.6 10-5*1/K	7.3 10-5*1/K	6.9 10-5*1/K	6.6 10-5*1/K				200-300°C	DIN 53 752	^{_{Thermal expansion XY/Z axis}}
Thermal Expansion (CLTE)										11.2 10-5*1/K	10.5 10-5*1/K						300-350°C	DIN 53 752	^{_{Thermal expansion XY/Z axis}}
Thermal Expansion (CLTE)												9.9 10-5*1/K	9.7 10-5*1/K				300-400°C	DIN 53 752	^{_{Thermal expansion XY/Z axis}}
Specific Heat	1.04 J/(g*K)	1.13 J/(g*K)			0.925 J/(g*K)					1.04 J/(g*K)				1.20 J/(g*K)	1 J/(g*K)	1 J/(g*K)
Thermal Conductivity	0.22 W/(k*m)	0.53 W/(k*m)			0.22 W/(k*m)					0.4 W/(k*m)		0.35 W/(k*m)		0.4 W/(k*m)	0.25 W(k*m)	0.25 W(k*m)	40°C	ISO 8302

^{_{Electrical Properties}}	^{_{1011 (natural)}}	^{_{1021 (black)}}	^{_{1031 (black)}}	^{_{1061 (black)}}	^{_{2011 (natural)}}	^{_{2021 (black)}}	^{_{2031 (black)}}	^{_{2061 (black)}}	^{_{2391 (black)}}	^{_{4011 (natural)}}	^{_{4021 (black)}}	^{_{4111 (natural)}}	^{_{4121 (black)}}	^{_{5051 (grey-green)}}	^{_{8001 (yellow-brown)}}	^{_{8061 (yellow-brown)}}	^_Parameter	^_Norm
Specific Surface Resistance	10¹⁶ O				10¹⁵O					10¹⁶ O		10¹⁶ O		10¹⁴			23°C	DIN IEC 60093 / ASTM D 257
Specific Volume Resistance	10¹⁷ O*cm				10¹⁵ O*cm					10¹⁶ O*cm		10¹⁶ O*cm		>10¹⁴ O*cm	10¹⁸ O*cm	10¹⁷O*cm	23°C	DIN IEC 60093 / ASTM D 257
Dielectric Constant					4.2					3.59				3.59			1 kHz, 23°C	DIN IEC 60250 / ASTM D 150
Dielectric Constant					4.1										2.3		10 kHz, 23°C	DIN IEC 60250
Dielectric Constant					4.1												100 kHz, 23°C	DIN IEC 60250
Dielectric Constant	3.5																50 Hz, 23°C	DIN IEC 60250
Dielectric Constant												3.7					1 MHz, 23°C	ASTM D 150
Dielectric Constant	3.1																27 MHz, 23°C	DIN IEC 60250
Dielectric Constant					4.2												100 Hz, 23°C	DIN IEC 60250
Electric Strength DC	20 kV*mm-1				21.8 kV*mm-1					18 kV*mm-1		22.7 kV*mm-1					23°C	ISO 60243-1 / ASTM D 149
Dielectric Loss Factor	1*10^-3																50 Hz, 23°C	DIN 53483-1 / ASTM D 150
Dielectric Loss Factor										1*10^-3							1 kHz, 23°C
Dielectric Loss Factor												0.0013					1 MHz, 23°C	ASTM D 150
Dielectric Loss Factor	3*10^-3																27 MHz, 23°C	DIN 53483-1

^{_{Other Properties}}	^{_{1011 (natural)}}	^{_{1021 (black)}}	^{_{1031 (black)}}	^{_{1061 (black)}}	^{_{2011 (natural)}}	^{_{2021 (black)}}	^{_{2031 (black)}}	^{_{2061 (black)}}	^{_{2391 (black)}}	^{_{4011 (natural)}}	^{_{4021 (black)}}	^{_{4111 (natural)}}	^{_{4121 (black)}}	^{_{5051 (grey-green)}}	^{_{8001 (yellow-brown)}}	^{_{8061 (yellow-brown)}}	^_Parameter	^_Norm	^_Notes
Water Absorption	1.08%	0.51%	0.42%		0.47%	0.44%	1.2%	0.35%	0.53%	0.16%	0.08%	0.08%	0.08%	0.53%	0.70%	1.12%	24 h in water, 23°C	DIN EN ISO 62
Water Absorption	3.29%	1.57%			1.65%	1.55%	2.18%	1.5%	1.58%	0.6%	0.53%	0.2%	0.38%				24 h in water, 80°C	DIN EN ISO 62
Flammability (UL94)	V0	V0	V0	V0	V0	V0	V0	V0	V0	V0	V0	V0	V0	V0	V0	V0	Corresponding to	DIN IEC 60695-11-10	Corresponding means no listing at UL (yellow card). The information might be taken from resin, stock shape or estimation. Individual testing regarding application conditions is mandatory.
Oxygen Index										49%		53%						EN ISO 4589-2
Density	1.34 g/cm³	1.42 g/cm³	1.57 g/cm³	1.48 g/cm³	1.38 g/cm³	1.45 g/cm³	1.59 g/cm³	1.52 g/cm³	1.54 g/cm³	1.41 g/cm³	1.49 g/cm³	1.46 g/cm³	1.53 g/cm³	1.57 g/cm³	1.88 g/cm³	1.68 g/cm³