When a buyer asks for “foil laminate for insulation”, the two facings without an insulating core that they usually mean are foil-scrim-kraft, often shortened to FSK, and foil bonded to polyethylene. They look similar on a roll and behave very differently on a job.
Foil-scrim-kraft (FSK)
FSK names a foil face, scrim reinforcement and kraft backing. It does not specify every adhesive, coating or bonding layer. For duct wrap, pipe insulation or board-facing applications, ask for the complete layer sequence and intended installation.
- What to compare: handling stiffness, reinforcement, tear properties, facing integrity and mounting requirements for the exact grade.
- What not to assume: FSK is not automatically polyethylene-free, suitable for high temperatures or impossible to heat-seal. A published heat-sealable FSK example includes a PE layer. That example illustrates variation in market naming; it is not a specification or certification for a Leetaiheng product.
Foil-PE laminate
Solid aluminium foil bonded to polyethylene film, sometimes with PET in between for stiffness. Used where a vapour barrier, a sealable layer or a wipe-clean surface is needed: wall wraps, packaging liners, moisture barriers under floors.
- What to compare: foil and film thickness, layer order, sealability where required, measured vapour transmission and handling properties.
- What not to assume: a foil-PE name does not guarantee a particular barrier value, seal window or service temperature. Adhesives, film grade, joints and installation conditions also need to be specified.
Telling them apart on the roll
Turn the roll over. FSK has a paper back, and the reinforcing scrim shows through the foil face as a faint grid under raking light. Foil-PE has a plastic back with no grid, and the foil face reads as smooth. If a delivery does not match the order, this is the fastest check before anything is cut.
Where the kraft matters
Kraft paper takes up moisture and polyethylene does not, and most of the practical difference between the two families follows from that. FSK is at home where the facing stays dry and is fixed to a board or wrapped around a duct: it holds its shape, takes a staple and does not stretch. It is the wrong choice where the facing will be wet, in contact with the ground, or asked to act as a vapour barrier. Foil-PE goes the other way: the plastic back gives a sealable, wipe-clean layer that shrugs off moisture, but it is more extensible and needs more care in tensioning and fixing. A buyer who specifies FSK for a wet application, or foil-PE where stiffness is required, will get exactly what was ordered and still have the wrong material.
Deciding
- Will it see heat? Give continuous and peak temperatures, exposure duration and the contact surface. Select only against the documented limits of the full laminate, not the FSK or foil-PE label.
- Does it need sealing or a vapour limit? Specify the sealing process, substrate and test method or target value. Confirm supporting data for the offered grade.
- How will it be mounted? State tension, fasteners, backing and moisture exposure, then compare construction-specific handling and mechanical data.
- Does it need a fire class? State the required classification and assembly. Availability of a matching construction and current report must be confirmed; neither family name proves a rating.
One name, many constructions
Neither family name fixes a construction. Two rolls both sold honestly as FSK can differ in foil thickness, scrim count, kraft weight and adhesive, and the same is true of foil-PE. Treat the name as a starting point for the conversation and the layer list below as the specification.
What to put on the order
Foil thickness, carrier (scrim type and weight, kraft grammage, PE thickness), one or two foil faces, perforated or not, roll width and length, and the standard for any fire or vapour-transmission claim.
We supply foil laminates with specified carriers, slit to a confirmed width, including Aluminum Foil, Plain for buyers who laminate in house. Send us the application and we will confirm a proposed construction and the technical documents available for it.