PTFE fiberglass is widely used as an anti-stick covering and insulating material. It therefore makes a perfect interlayer between the heat sealing band and the underlay. It allows the heat sealing band to slide in case of linear expansion without sticking to the underlay. The PTFE is adhered directly to the underlay, which is made of silicone, for instance.
Cover strips are PTFE fiberglass with a non-adhesive zone which are used directly on the heat sealing band. The non-adhesive zone is located above the heat sealing band, which can be fastened to the bar with the adhesive zone. Once again, the heat sealing band can slide in case of linear expansion but the film is prevented from sticking to it.

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