Urea Formaldehyde Glue also known as Plastic Resin Glue
Urea Formaldehyde glues are the single most important type of glues used in the making of plywood and wood panels.
What is Urea Formaldehyde Glue, also known as Plastic Resin Glue
Urea-formaldehyde resin is a range of synthetic resins produced by the chemical combination of formaldehyde (a gas produced from methane) and urea (a solid crystal produced from ammonia). Urea-formaldehyde resins are used mostly for gluing plywood, particleboard, and other wood products. UF resins polymerize into permanently interlinked networks which are influential in the strength of the cured adhesive. After setting and hardening Urea Formaldehyde resins forms an insoluble, three-dimensional network and cannot be melted or thermo-formed.
Urea Formaldehyde insulation (UFFI) got a bad rap when it was found to be outgassing formaldehyde. This problem is no longer a significant issue because the practice of adding extra formaldehyde to insure complete reaction is no longer done in modern formulations. Outgassing is not a significant problem in boatbuilding applications.
Here is an article that talks about outgassing of formaldehyde gas in wood products.
Any chemistry lover can read this article from the International Journal of Adhesion and Adhesives on Urea-formaldehyde (UF) Adhesive Resins of Wood.
What is Urea Formaldehyde Used For?
Urea Formaldehyde is a widely used glue for plywood, particle board, wood panels and bent laminations.
The Woodworkers institute lists Urea Formaldehide as one of its 6 best Adhesive.
If a glued product is labelled furniture grade it likely has Urea Formaldehyde and is water resistant. If it labelled construction grade the adhesive is likely phenol formaldehyde and is fully waterproof. Here is a link to my page on Phenol Formaldehyde glue.
What are the Advantages of Urea Formaldehyde glue?
- Sets hard and rigid. This is an advantage for bent laminations since it reduces springback.
- It's been in use for a long time and has proved it's reliability over time. It is simple to use and not as demanding as to quality of joints as resorcinol or polyurethane.
- Although it needs to be clamped, it is somewhat gap filling and load bearing (strong) and is sandable after setting.
- Cured Strength UF is superior to that of wood so strength is not an issue.
- Depending on formulation it has a good open time of 20-30 minutes and it does not grab like some other wood glues. Clamp time is usually around 6 hours, depending on temperature and brand.
- Urea Formaldehyde can be cleaned up with water while uncured.
- Type II moisture resistance. This means that the glue resists being soaked and dried repeatedly. In this test it is not boiled as in marine plywood glue. Some brands such as Circa 1850 and Dural claim Water Proof status for their Plastic Resin Glue but almost all brands are water resitent.
- Since it is a mostly beige colour (colour varies with brands, from light brown to beige) it blends well with the wood without pronounced glue lines.
- Will not distort or creep in warm temperature.
- It is not an expensive adhesive.
- Easy to use, usually purchased as a powder which gets mixed with water. Prefers warmer temperatures to set. Most brands specify 70 degrees F.
What are the Disadvantages of Urea Formaldehyde (Plastic Resin) Glue
- Upon addition of water, in high temperature, cured urea formaldehyde can hydrolyse and release formaldehyde, this weakens the glue bond. For this reason it is not considered waterproof but rather water resistant and is not used for marine plywood.
- Urea Formaldehyde must be used in a well ventilated area because uncured resin is irritating and can be toxic. This is not unique as most uncured modern adhesives carry strong warnings.
- Urea Formaldehyde Adhesive has a limited shelf life, one year. It needs to be kept in a dry area so it is usually sold in airtight plastic containers.
So can Urea Formaldehyde be used in Boatbuilding?
Being water resistant Urea Formaldehyde has some uses. Glue deterioration occurs in damp and hot conditions.
It certainly could be used in a protected dry area that will not be submerged but might occasionally get wet. It should get a finish such as paint or varnish.
The homebuilt aircraft people have used it happily for years.
Many boats have been built with it. Here is a link to the Yachting and Boating World Forums on glues. Cascamite, Aerolite, Balcotan etc. come up many times as having been successful boat glues.
It cannot be the only adhesive used in a boat build but it can be used alongside epoxy or other waterproof glues.
If you are veneering on the other hand, you cannot find a better adhesive.
In order to improve the water resistant qualities Melamine is sometimes added. This is usually the case when a manufacturer claims improved water resistance.
I don't claim to be an expert. I'm not an engineer or a chemist. I make mistakes. This page is not a recommendation of products, it is for information and entertainment. IF you want to build a boat with Urea Formaldehyde glue make sure you use the material as instructed by the manufacturer. There are health concerns about uncured resin, so wear gloves and work in a well ventilated area, or wear a vapor mask. Do your homework and be safe.
email me if you find mistakes, I'll fix them and we'll all benefit: Christine