APP (Atactic Polypropylene) and SBS (Styrene-Butadiene-Styrene) are both types of modified bitumen membranes used in roofing and waterproofing applications, but they have different properties and applications. Here’s a breakdown of their differences:

APP (Atactic Polypropylene)
1. Composition: APP is a thermoplastic polymer modified bitumen. It is made by adding atactic polypropylene to the bitumen, which enhances its performance.
 
2. Temperature Resistance: APP membranes are known for their high-temperature resistance. They perform well in hot climates and can withstand higher temperatures without losing their structural integrity.

3. Flexibility: While APP is flexible, it tends to become more rigid at lower temperatures compared to SBS. This can make it less suitable for extremely cold environments.

4. Installation: APP membranes are often installed using heat welding techniques. They require a torch or hot air to activate the adhesive properties.

5. Durability: APP membranes are generally more UV resistant and have good weathering properties, making them suitable for exposed applications.

SBS (Styrene-Butadiene-Styrene)
1. Composition: SBS is also a polymer-modified bitumen, but it incorporates styrene and butadiene. This combination gives it unique elastic properties.

2. Temperature Resistance: SBS membranes have excellent flexibility and elasticity, especially in cold temperatures. They can withstand low temperatures without becoming brittle.

3. Flexibility: SBS is known for its superior flexibility and elasticity, making it ideal for applications where movement or temperature fluctuations are expected.

4. Installation: SBS membranes can be installed using cold adhesive, heat welding, or self-adhesive methods, offering more versatility in application.

5. Durability: SBS membranes provide good resistance to UV rays and have excellent waterproofing properties. They are suitable for a variety of climates.

Summary
- APP is better for hot climates and offers high-temperature resistance but can be less flexible in cold conditions.
- SBS is more flexible and elastic, making it suitable for varying temperatures, especially cold climates.

Choosing between APP and SBS will depend on the specific requirements of your project, including climate conditions, installation methods, and performance expectations.