Polyurethane vs. Vinyl Vacuum Bags
Which material is right for your shop?

For many years, most woodworkers didn't give much attention to polyurethane vacuum bags for one simple reason - the cost. We've argued in the past that polyurethane wasn't worth three times more money than vinyl. Though there are many characteristics of polyurethane material that make it better than vinyl, it was still not worth the added expense. But things have changed!

Polyurethane bagging material has become much more affordable, and vinyl prices have increased significantly. Polyurethane is now within the reach of many hobbyist woodworkers and small cabinet shop owners. Additionally, polyurethane vacuum bags are even more flexible now and can withstand greater pressure and heat. With so many advantages, we would bet that most people who try a polyurethane bag will never switch back to vinyl.

How Good Is It?
Before a durability comparison can be made between vinyl and polyurethane, a standard has to be set. Both materials come in several grades, which can affect their performance and durability. A high grade of vinyl can be more durable than a low grade of polyurethane. For the purpose of this article, let's assume that this comparison is between a high grade of vinyl and a high grade of polyurethane, and both are a 30 mil thickness

Simply put, polyurethane vacuum bags are significantly more durable than vinyl bags. With everyday use, vinyl has a tendency to develop tears and pinholes (which can be repaired). A polyurethane bag can withstand much more use and abuse because it is chemically engineered to be elastic. This elasticity is what makes it more puncture resistant than vinyl. Additionally, polyurethane has a much greater "memory". In other words, it goes back to its original shape after being stretched. And unlike many other polyurethane materials, our VS Elite™ and Extreme™ polyurethane bags can also be repaired and patched.

A New Generation of Polyurethane
We worked with several manufacturers to find a polyurethane film that meets the requirements that are crucial to professional and hobbyist woodworkers. It had to be ultra-resilient and durable, but also affordable. Other important factors include clarity, bondability, and resistance to veneer glues and some epoxies. The truth is that finding the right combination of these characteristics is like solving a Rubik's Cube while wearing a blindfold. It took a lot of time and testing to find a polyurethane for woodworkers who only want the best.

Here's What You Should Know
Strength and Resilience - You'll find that polyurethane stretches more than vinyl, and this can be an important factor for some applications. When pressing a wickedly curved project, you may find that the polyurethane conforms to the shape of the project much more readily than vinyl. In fact, VS Elite™ and Extreme™ polyurethanes can stretch up to 6 times their width/length and still return to their original shape and size even after years of use. If you opt to build a frame press or vacuum press table, polyurethane is critical because it allows you to use it with projects of varying thicknesses.

Cost - Polyurethane bags had cost 3 to 4 times more than vinyl several years ago. The expense was hardly worth the increased life of the bag and the additional ease of use. However, the cost of vinyl has increased substantially since 2020. Polyurethane has not increased as much as vinyl, so the gap between the costs of these materials is now much smaller. We think this makes polyurethane an easy decision, and it could soon make vinyl obsolete for vacuum bagging.

Weight - There is little difference in weight between vinyl and polyurethane of the same thickness. But since 20 mil polyurethane is much more durable than 30 mil vinyl, it is better to compare them in that configuration. With 20 mil polyurethane, you get a more durable product that weighs 33% less than 30 mil vinyl.

Adhesive Resistance - There is a wide array of chemicals that can be used to alter the performance of polyurethane films. One additive that makes the VS Elite™ and Extreme™ polyurethane easier to use is the non-transferring lubricant. It prevents glues and some epoxy types from sticking to the inside of the bag. It also makes it easier to slide the project and/or platen into the bag. As an added benefit, this lubricant adds significant life to the vacuum bag because it also helps block UV light.

Bond-Ability - The ability to chemically bond polyurethane to itself is a characteristic that allows the user to make a custom vacuum bag. This important property eluded nearly every manufacturer who helped us find the ideal polyurethane material. After several months of tests with dozens of potent adhesives and countless polyurethane concoctions, we found something that made it possible to chemically weld polyurethane to itself with vinyl cement. This felt like a small miracle, and it's a feature not found in many other polyurethane films. Polyurethane is not as easy to bond as vinyl, but smaller bags can be built with the right technique.