There are generally two types of pavement sealers:
Tar-based sealers have been in use for a long time because they perform the best against water seepage and chemical damage (oil and gas for example). They also protect your asphalt the longest (from 3 to 5 years), and have stronger cohesion and adhesion to the underlying pavement. BUT, this prevents flexibility, which causes cracking. They are the least expensive option.
***Tar contains chemicals (PAHs) that are carcinogenic to humans and animals (although the level of danger is widely debated).
Asphalt-based sealers are more compatible with driveways because they are made from the same material. They don’t stain, smell or pollute like tar, and they dry faster. They offer more flexibility, resulting in less cracking. They are however less durable, protecting your driveway for 1 to 3 years, and do not guard well against gas or oil spills. Because they are environmentally friendly, Asphalt-based sealers are more expensive.
– Atlas Seal Team