Silicone

Using silicone as a seam sealer: This type of sealer is ideal for outdoor gear and clothing made from synthetic materials.
It's waterproof and flexible, making it ideal for sealing seams exposed to rain and other elements.

• Non-Staining

• Highly water repellent

• Highly resistant to weathering and ageing

• Electrically insulating Environmentally friendly, both in its production and in its application

• Resistant to many acids and other chemicals

Read more here: "What is Silicone? and Silicone Adhesive and Sealant?"