Saint-Gobain CHR K100 is a single-faced pressure-sensitive tape composed of a thermoset aromatic polyimide film backing and a silicone pressure-sensitive adhesive. The product designation places K100 within the CHR polyimide tape family as the silicone-adhesive configuration, separating it from acrylic-adhesive polyimide tapes used in lower-temperature coil-wrapping, flexible circuit, and printed circuit board operations. The polyimide backing is available in controlled film thicknesses, with 25.4 µm and 50.8 µm typical for this product class, and the silicone adhesive is applied as a continuous cured layer on one side. The backing contributes tensile modulus, dimensional stability, and dielectric strength; the adhesive contributes peel adhesion, clean removability, and surface-wetting behavior on passivated metals. Total thickness is measured under ASTM D3652/D3652M-93, peel adhesion to stainless steel under ASTM D3759/D3759M-96, and dielectric breakdown strength under ASTM D149-97a. Surface insulation resistance is commonly evaluated under moisture conditioning at 23 °C and 50 % RH according to ASTM D257-14. Because silicone adhesive formulations differ in coat weight, crosslinker chemistry, and adhesion promoter, K100 should be accepted only against the current Saint-Gobain certificate of analysis, not against generic polyimide tape data. Published data for this specific K100 configuration may be limited, and a vendor lot certificate is the only reliable means of confirming total thickness, adhesion, and dielectric performance for a particular incoming roll.

What Separates a Silicone-Adhesive Polyimide Tape from Acrylic Polyimide Constructions?

The principal differentiation between K100 and polyimide-acrylic constructions is the adhesive response during elevated-temperature exposure. Silicone pressure-sensitive adhesives remain mechanically stable through repeated thermal excursions in the 200 °C to 260 °C band, while acrylic pressure-sensitive adhesives typically soften, lose cohesive strength, generate volatile species, or leave a residue under the same cure conditions. Silicone adhesives also wet low-surface-energy substrates more effectively, which is relevant on passivated metals, silicone-treated surfaces, and certain polymer films. This wetting advantage is accompanied by two trade-offs. First, silicone systems exhibit lower resistance to continuous contact with aromatic hydrocarbons and ketones; short solvent wipes may be acceptable, but immersion can swell the adhesive and reduce cohesive strength. Second, low-molecular-weight siloxane species can transfer to the substrate surface even when no visible adhesive residue remains. Within the CHR polyimide family, the backing supplies dimensional stability, high dielectric strength, and cut-through resistance; the adhesive controls the upper temperature limit, clean removal behavior, and initial adhesion. K100 is specified when the process environment exceeds the practical limit of a polyimide-acrylic tape, not merely to increase room-temperature tack. Table 1 defines the position of K100 relative to common masking and insulating tape constructions.

For coil and busbar insulation, transformer lead anchoring, thermocouple attachment, and motor slot liner retention, K100 is selected to provide a thin dielectric barrier with the polyimide backing oriented toward the conductor. The critical parameter is not ambient peel strength but breakdown voltage under service conditions. Polyimide films in this class can exhibit dielectric strengths in the range of 120 kV/mm to 300 kV/mm depending on thickness and electrode configuration when tested to ASTM D149-97a. These values are thickness-dependent; a thicker polyimide film does not always produce a proportional increase in breakdown voltage if electrode edge effects are not controlled. Procurement specifications should require lot-specific values for breakdown voltage and insulation resistance after conditioning at 23 °C and 50 % RH under ASTM D257-14. Moisture ingress at the adhesive-to-backing interface can depress insulation resistance before visible delamination occurs. In varnished motor assemblies, the tape may be overcoated with an epoxy or polyester impregnating resin. Compatibility with the varnish should be tested because silicone surfaces can inhibit wetting and adhesion of some impregnating resins unless a compatible primer or a post-cure treatment is used.

High-temperature splicing of films, foils, and webs is a further application in which K100 is used to hold the web during dryer or oven passes. The silicone adhesive remains bonded through a hot zone, but splicing performance depends on the liner and web surface energy. On silicone-coated release liners, the adhesive may interact with the release chemistry; lap shear and roll-transit trials should be performed before the splice is introduced into an automated line. Because a failed splice can cause web wrap-ups and lost production, converters often test the splice at the maximum line tension and dryer temperature rather than relying on ambient peel adhesion alone.

Powder Coat Masking, Cure Oven Limits, and Edge Creep

Powder coating lines use polyimide/silicone tape to mask bearing bores, grounding pads, threaded holes, and other features before electrostatic powder application. The tape remains in place through convection or infrared cure ovens. Typical thermoset powder cure schedules operate between 180 °C and 200 °C for 15 min to 30 min, and some polyester or epoxy systems require peak metal temperatures near 220 °C. Under these conditions, the polyimide backing exhibits minimal dimensional change. The dominant failure mode observed on production lines is not backing degradation but adhesive edge creep, which opens a channel between the tape edge and the metal surface. Powder ingress through that channel cures as a hard halo and requires mechanical rework. To minimize edge creep, the tape is applied under uniform tension and burnished at the edges with a rigid but non-marring tool; however, excessive tension can tear the backing at sharp internal corners. A second failure mode is cohesive splitting of the silicone adhesive if the time-at-temperature window is exceeded. Residue transfer is evaluated by measuring peel adhesion before and after a simulated cure soak under ASTM D3759/D3759M-96, followed by visual inspection for adhesive transfer. The K100 silicone adhesive is classified for the powder cure window, but in-process verification on the actual substrate is required because passivation chemistry, surface roughness, and bake schedule all change the clean removal response. Parts with high thermal mass may lag the oven air temperature, while infrared cure can heat the tape surface faster than the metal substrate; both conditions alter the adhesive temperature history and must be included in a masking trial plan.

In surface-finishing operations where the same part is subsequently painted, bonded, or welded, silicone transfer from the pressure-sensitive adhesive can reduce topcoat adhesion and interfere with structural bonding. Even when the tape removes visibly clean, low-molecular-weight siloxane species may remain on the metal surface. K100 should not be specified for surfaces that must pass an adhesion test without an intermediate cleaning step such as plasma treatment, vapor degreasing, or an appropriate solvent wipe. Silicone contamination is particularly problematic in automotive topcoat systems and in structural adhesive bonding. The product is also unsuitable where the adhesive must resist prolonged immersion in strong aromatic solvents or ketones; the polyimide backing and silicone adhesive can survive short-wipe contact, but continuous solvent exposure can swell the adhesive and reduce cohesive strength. When vacuum compatibility is required, the vendor should be requested to supply ASTM E595 outgassing data, because not all silicone pressure-sensitive adhesives meet the same collected volatile condensable material limits.

The polyimide backing provides resistance to many oils, hydraulic fluids, and fluorinated solvents, but strong alkaline solutions can attack the film and reduce tensile strength. In electrical machine manufacturing, exposure to alkaline degreasing baths or aggressive varnish strippers should be evaluated with immersion tests under the actual concentration and temperature. Published data for this specific K100 configuration may be limited; the film supplier’s polyimide exposure guide and the tape vendor’s chemical compatibility recommendations should both be consulted before specifying K100 for a chemical immersion boundary.

When the Application Requires Replacing a Polyester or Glass Cloth Tape

K100 is compared with polyester/silicone and glass-cloth/silicone tapes when thickness, dielectric strength, or edge definition is the deciding variable. Polyester-backed silicone tape is lower in heat stability; the polyester backing begins to lose dimensional stability above approximately 150 °C, whereas polyimide retains mechanical and electrical properties through 260 °C. Silicone-coated glass cloth tape offers high tear resistance and conformability, but its greater caliper and woven texture reduce edge definition and low-profile capability. K100 occupies the band between these materials: the polyimide backing provides a smooth, high-dielectric film, and the silicone adhesive extends the working temperature beyond the acrylic polyimide limit. The principal trade-off is the potential for silicone contamination and the reduced resistance to aromatic hydrocarbon or ketone immersion. Against skived PTFE tapes, K100 typically offers higher cut-through resistance and lower cold-flow under load, while PTFE provides lower surface energy and better chemical inertness. Selection between K100 and PTFE should be based on the required dielectric film thickness, chemical exposure, and contamination control plan, not on temperature resistance alone. For fine-line masking where a hard tape edge profile is required, the polyimide backing supports cleaner die-cut geometries than thicker glass cloth laminates, but the stiffness of the polyimide film limits conformation around compound curves compared with a woven glass cloth.

During wave soldering and hot-air solder leveling, polyimide/silicone tape is used to mask gold fingers, connector pads, or plated through-hole areas from solder contact. The tape experiences preheat exposure at 100 °C to 150 °C followed by brief contact with molten solder at 260 °C to 288 °C. In this transient regime, the polyimide backing resists thermal distortion, while the silicone adhesive remains adhered and must release without residue after the assembly cools. Acrylic polyimide tapes often shift or leave adhesive residue in the same transient solder-contact zone, which is why a silicone system is specified. The time at molten solder temperature is short, so this use relies on transient thermal capacity rather than continuous temperature rating. The tape edge must be inspected after wave solder because flux entrapment under a lifted edge can create a solder bridge or wetting defect. If the tape is exposed to aqueous flux cleaning, the silicone adhesive must tolerate the saponifier chemistry; a lot-specific trial is recommended when the flux cleaning bath is aggressive or maintained at elevated temperature.

In thermal spray masking, the tape is used to protect adjacent surfaces from overspray, but particle impact and localized heating can exceed the polyimide film limit if the spray gun dwell is excessive. Plasma spray and high-velocity oxy-fuel processes generate heat spikes above 260 °C on thin tape edges; K100 should be used only where masking is outside the direct plume or where a trial confirms edge integrity. The silicone adhesive may char at direct strike zones and leave a residue that must be mechanically removed. This limitation is not unique to K100 but is a boundary of thin polyimide-backed pressure-sensitive tapes in high-particle-energy thermal spray environments.

Slitting and die-cutting of K100 require different tooling than polyester-backed tapes. The polyimide backing is harder and generates higher blade wear; carbide or ceramic-coated blades are commonly specified for rotary kiss-cutting. Adhesive edge stringing can occur if cutting is performed at room temperature with dull blades; controlled blade depth and periodic wipe-down of the cutting station reduce the transfer of silicone adhesive buildup to the backing surface. Laser cutting can produce a carbonized edge deposit on polyimide; if laser-converted parts are specified, the edge residue must be evaluated for dielectric breakdown risk in high-voltage applications. In cleanroom assembly operations, converted K100 parts should be inspected for particulate generation at the slit edge, because polyimide fracture can produce microdebris that is not present on polyester-backed tapes.

Compliance under RoHS 2011/65/EU and REACH 1907/2006 is formulation-dependent and must be verified with the current supplier declaration for the exact K100 stock-keeping unit. A silicone adhesive may include controlled crosslinker residues or catalysts that must be documented in the material declaration. For electrical insulation applications governed by UL 510, the final converted part—not only the base tape—must carry the appropriate recognition if the customer requires a listed construction. This is particularly relevant when the tape is slit to narrower widths or die-cut into slot liners and lead pads. An ISO 9001 or IATF 16949 controlled production line should maintain incoming inspection records linking each roll to the vendor lot certificate, including total thickness, peel adhesion after specified thermal cycling, and dielectric breakdown where required.