Surfboard Foam: Polyurethane or Polystyrene Core?
What type of surfboard foam should you choose for your next shred stick— polyurethane or polystyrene? Those words bang around the surfboard industry, design forums and in the shaping room, but most surfers are confused about their meaning. The decision used to be simple. The long-defunct Clark Foam ran the market on surfboard blanks up to 2005 with their top-dog formula for polyurethane blanks. Polyurethane foam was cheap and available, so it was the industry standard. End of story. But the abrupt loss of Clark Foam left a vacuum which sent the surfboard world scrambling for alternatives. Suddenly epoxy resin and polystyrene foam floated to the top of the options. Neither was anything new, but they helped fill the void and drew the next generation of innovators into the fray.
When you read about PU boards, you are reading about polyurethane foam blanks which are the most common blanks still among both daily surfers and pros.
- PU foam is easily shaped and airbrushed.
- It’s known for being more responsive in its performance but it also (over time) absorbs water and yellows.
- Polyurethane surfboard blanks can be glassed with either polyester or epoxy resin, making it versatile in terms of giving riders more options.
- Polyurethane blanks are also easily shaped, thus making surfboards less expensive than polystyrene since it takes less time to shape and finish each board.
- The biggest downside of building PU boards is their impact on the environment since they contain carcinogens and are essentially impossible to recycle once in surfboard form.
- The big bonus: PU surfboards are the cheapest option.
While there are different degrees of expanded polystyrene foam, it is regarded as lighter and more buoyant foam than polyurethane. However, there are some aspects that you should keep in mind:
- Polystyrene is not as easily shaped and cannot be used with polyester resins due to temperature/chemical sensitivity.
- It does not react well to polyester resin’s hot chemical reaction and will melt. Therefore, epoxy resin is the only option with polystyrene.
- Many surfers find epoxy/polystyrene boards have less “life”, lacking flex energy, which is probably why most of the top pros still ride PU boards.
- Polystyrene foam cores sealed with epoxy resin, last much longer and emit fewer toxic gasses, so the idea is that the combination is better overall for the planet.
Expanded Polystyrene VS. Extruded Polystyrene
You have two main choices when it comes to polystyrene foam. Expanded Polystyrene (EPS) and Extruded Polystyrene (XPS). Open-celled polystyrene is beaded foam similar to a styrofoam cooler, but the open cells suck up water if dinged. Besides the aforementioned lack of flex and memory along with high water absorption, another drawback is that open-celled polystyrene is difficult to shape, paint or airbrush.
Closed cell polystyrene (called extruded polystyrene foam), on the other hand, is more expensive to produce but absorbs very little water and will remain white and “full of life” for much longer. Closed cell polystyrene is durable and lightweight and said to be more flexible than expanded polystyrene foam surfboards, thus containing that elusive flex energy. And similar to traditional polyurethane foam, due to its closed cells, extruded surfboard foam is easy to airbrush and paint; however, it does often delaminate very easily because closed cell polystyrene builds gas that forces the sealed resin to separate from the foam. Epoxy Pro has developed “Thermovent” technology which uses small vents that allow the gas to escape and thus avoid delamination.
The Bottom Line
If you are on a strict surfboard budget and are an intermediate/advanced surfer, stick to the old school polyurethane foam core boards with polyester resin. They start out light and responsive but will wear out faster than the other options (just rip in the interim). If you have a little more cash on hand, pony up for an epoxy polystyrene model. If you are a beginner who just needs a solid board for learning that will be beaten for the next few years, after a cheap used board, Epoxy/EPS is probably your best bet since you need something that will last.