Polyester (PET) material is very resistant to many different outdoor factors: UV light, water, abrasion, extreme temps, chemicals, etc. It is one of the most durable synthetic substrates. If you need thermal transfer labels for harsh conditions, some of very good choices are: standard polyester which is waterproof and abrasion resistant, chemical-resistant polyester which is perfect for long-term outdoor conditions, gloss-coated plastic labels which are a perfect choice for freezers, retro-reflective polyester which is good for long range barcode scanning, etc.