Sikaflex: How to Choose the Right Elastic Sealant or Adhesive

Q: Can Sikaflex be painted?

Yes, most can be painted once cured, unlike conventional silicone; it's worth confirming with the technical data sheet.

Q: What's the difference between a sealant and a mounting adhesive?

A sealant fills and seals a joint with movement; a mounting adhesive bonds and fixes pieces together with much higher initial grab.

Q: Do I need to prime before applying Sikaflex?

Purform® products typically don't need it on common porous substrates, but it's worth checking the technical data sheet for specific materials.

Quick answer: Sikaflex is Sika's range of elastic polyurethane, MS polymer, and silane adhesives and sealants. They are chosen based on three criteria: the movement the joint needs to absorb, whether high initial grab is needed to hold pieces without tape, and whether they are used indoors, outdoors, or on trafficable pavement. Unlike conventional silicone, they can be painted and offer much better structural adhesion.

Which Sikaflex to Choose

Product	Chemistry	Main Use	Highlights
Sikaflex-11 FC Purform®	Polyurethane	Multi-purpose indoor/outdoor adhesive-sealant, expansion joints	Admissible movement ±25%, no primer needed on most materials
Sikaflex-111 Stick & Seal	Silane polymer	Universal indoor/outdoor adhesive and sealant	Isocyanate-free, EMICODE EC1 Plus (very low emissions)
Sikaflex-116 High Grab	MS polymer	Mounting adhesive with high initial grab	Holds parts in place without tape or propping while curing
Sikaflex® PRO-3 Purform®	Polyurethane	Joint sealing on trafficable pavements	Resistant to pedestrian and light vehicle traffic, indoors and outdoors

How to Choose Based on the Situation

Expansion joint on a façade, floor, or between different materials: Sikaflex-11 FC Purform®, for its high admissible movement.
You need to fix a piece (film, trim, profile) without holding it with tape while it cures: Sikaflex-116 High Grab.
You're looking for the option with the lowest volatile compound emissions, ideal for occupied interiors: Sikaflex-111 Stick & Seal.
Joint in a floor or pavement that is walked or driven on: Sikaflex® PRO-3 Purform®, formulated to withstand that traffic.

How to Apply Sikaflex

Clean and degrease the joint; if there is construction residue, use Sika Limpa.
Check whether the material needs priming (most Purform® Sikaflex products don't need it on common porous materials, but always check the technical data sheet).
Apply with a manual or pneumatic gun, filling the joint without leaving air bubbles.
Smooth the surface with a dampened spatula before it skins over.

Frequently Asked Questions

Can Sikaflex be painted?

Yes, most Sikaflex products can be painted once cured, unlike conventional silicone. Confirm this with the product's technical data sheet and the paint you plan to use.

What's the difference between a sealant and a mounting adhesive?

A sealant like PRO-3 is designed to fill and seal a joint with movement. A mounting adhesive like 116 High Grab is designed to bond and fix two pieces together, with much higher initial grab.

Do I need to prime before applying Sikaflex?

Purform® range products are formulated to not require it on most porous substrates, but on very specific materials (certain plastics, metals) it's worth checking the technical data sheet before applying.