A technical guide to selecting machined polyimide grades for electro-optical systems, vacuum equipment, semiconductor technology and demanding sensor applications.
Introduction
Some components have to keep their exact dimensions while everything around them changes. In electro-optical systems, vacuum equipment and high-end sensor technology, insulating and guiding parts operate close to lasers and heat sources, under vacuum, under radiation and through repeated thermal cycling. Polyimide is one of the few machinable polymer families built for this combination, provided the right grade is selected. This guide explains how.
Why Electro-Optical and Vacuum Systems Challenge Material Selection
Typical specifications combine temperatures of approximately 250 to 300 °C near heat sources, vacuum conditions in which the material must not release condensable substances, the risk that outgassing products contaminate lenses and sensor surfaces, a demand for low thermal expansion so that optical paths remain aligned, electrical insulation, radiation exposure, tight tolerances and small production quantities. Metals usually need additional insulation measures in these positions, many standard thermoplastics reach their thermal limits, and ceramics are costly to machine and sensitive to impact.
Why Polyimide Is Used
Polyimide maintains its mechanical integrity over a wide temperature range, with continuous use up to approximately 300 °C depending on grade and load. The compression-moulded polyimide grades described here have no conventional melting point. Selected grades show low outgassing, which has made polyimide an established choice in vacuum, semiconductor, aerospace and demanding sensor environments. Polyimide parts for these requirements are produced by CNC machining from stock shapes. For every vacuum application, the selected grade is verified against the application-specific outgassing requirements; no grade is assumed suitable without this check.
Polyimide Grades and Their Functions
- Comco-Polyimide N (equivalent to Plavis-N and Vespel® SP-1): unfilled base grade with the highest purity. Best electrical insulation of the family and very good chemical resistance. First choice for insulators and electrically critical precision parts. Not filled for friction duty.
- Comco-Polyimide G15 (equivalent to Plavis-G15 and Vespel® SP-21): 15 percent graphite filled, self-lubricating. The grade for friction and wear positions such as moving contacts and guide surfaces. The graphite filler reduces electrical insulation compared with the unfilled grade.
- Comco-Polyimide G40 (equivalent to Plavis-G40): 40 percent graphite filled, with the lowest thermal expansion of the family and maximum dimensional stability. Used where alignment must be preserved over temperature. Electrically less insulating than the unfilled grade.
- Comco-Polyimide MoS: filled with molybdenum disulphide for vacuum tribology, where graphite-based lubrication is less effective. Used for friction positions in high vacuum.
- Comco-Polyimide ESD: electrostatically dissipative grade for components near sensitive electronics, where controlled dissipation is specified instead of full insulation.
Selecting Polyimide for Vacuum Applications
Grade selection for vacuum follows the specification, not the datasheet headline. The relevant inputs are the required vacuum level, operating temperature, mechanical load, the required outgassing values, electrical requirements, friction and wear conditions and the required dimensional stability. The chosen grade is verified against these values case by case. Not every polyimide grade is automatically suitable for every vacuum application.
Typical Components
Insulators, spacer rings, mounting elements, valve seats, guide components, sealing components, friction and wear components, electro-optical precision parts and sensor-related components.
Available Stock Shapes and CNC Machining
Polyimide is available as sheets and rods, cut to size or CNC-machined into finished parts. Since polyimide for these applications is shaped by machining, prototypes, single parts and small series are produced directly from stock shapes, without tooling.
Why Source Through Plastix Factory?
Plastix Factory provides digital material selection, technical material information, stock availability, cut-to-size ordering and access to CNC-machined parts in one platform, backed by the polyimide manufacturing experience of COMCO EPP. Specialised grades and vacuum-specific requirements are reviewed by the technical team before ordering.
Summary
Polyimide solves the combination of high temperature, vacuum, radiation and tight tolerances that stops most other machinable polymers. The unfilled grade insulates, the graphite grades manage friction and expansion, MoS covers vacuum tribology and ESD covers dissipative requirements. The grade decision is made against the specification, and the parts are machined from stock shapes in any quantity from one.
Check Polyimide Availability and Order Online
Special polyimide grades, vacuum-specific requirements and CNC-machined parts can be submitted to the technical team.
Vespel® is a registered trademark of DuPont.