Comparing chemistries
What is the difference between polyaspartic and epoxy?
Polyaspartic handles sunlight and slab movement better, epoxy goes down harder and more brittle, and which one suits a floor depends on the floor.
The short version
- Epoxy sets rigid. Polyaspartic and polyurea stay flexible after they set.
- Sunlight ambers clear epoxy. Polyaspartic is built to hold its color in daylight.
- A warm tire pulls at the film as it cools, and a brittle film is the easier one to pull.
- Polyaspartic sets fast, so it goes down in sections and leaves the installer less working time.
- Most systems in this trade use both ideas: a flexible base under a topcoat picked for the room.
How the two behave in sunlight
Clear epoxy ambers. Put it where daylight reaches, a garage with the door open half the summer, a patio, a room with a big window, and it goes yellow over the sun's part of the floor while the shaded part stays where it started. It is the resin reacting to UV rather than a defect somebody caused.
Polyaspartic was built for that exposure. It is the same family as polyurea with the chemistry slowed down so it can be rolled or sprayed, and holding its color in daylight is one of the things it was made to do. That is why so many systems put a polyurea or an epoxy underneath where nobody sees it and a polyaspartic on top.
How they behave on a slab that moves
Concrete moves. It swells in July, shrinks in January, and in the southwest Twin Cities metro it does both hard. Epoxy sets rigid, so when the slab under it moves the film has nowhere to go, and the stress lands on whatever line is weakest, usually a control joint or an old crack.
Polyaspartic and polyurea stay flexible once they have set. They stretch with the slab and come back, which is why they get used on a garage over an unheated crawl space, and on exterior concrete that swings through a whole winter.
Warm tires and working time
A tire that has been on the road comes home warm and soft, then sits in one spot while it cools. Warm rubber softens what is under it and grips as it cools, and it pulls at the film in the shape of the tire. A flexible film takes that pull better than a rigid one does, which is part of why the trade moved toward polyurea and polyaspartic in garages.
Working time is the other real difference, and it belongs to the installer rather than to you. Epoxy stays open long enough to spread and back-roll a big floor at a walking pace. Polyaspartic sets fast, so a crew has to work it in sections and keep moving, and a floor stopped in the middle of a section shows a line where it stopped.
Neither chemistry is the answer for every floor. A heated shop floor with no daylight on it is a fine epoxy floor. A garage in this climate, door open, vehicle coming home warm, is the floor polyaspartic was built for. What decides more than the name on the bucket is the whole system.