Understanding Urea-Formaldehyde Glue, applications and best practices

Urea-Formaldehyde Glue is commonly known as Plastic Resin Glue. It’s a thermosetting resin made from urea and formaldehyde. This resin has been used extensively as an adhesive for plywood, medium-density fiberboard (MDF), particleboard, and molded products. In the wood industry, urea-formaldehyde adhesives are commonly used to bond wood to create useful forms like interior-grade plywood and particleboard. It is the most significant glue used in pressed wood and wood boards.

 

Understanding Urea-Formaldehyde Glue

Urea-formaldehyde resin (UF resin) is a class of synthetic resins made from the chemical reaction of formaldehyde (a methane-derived gas) and urea (a solid crystal produced from ammonia). Plywood, particleboard, and other wood products are mainly glued with urea-formaldehyde resins. UF resins polymerize into permanently interconnected networks, which affect the cured adhesive’s strength. Urea-Formaldehyde resins produce a three-dimensional network as insoluble form after setting and hardening, and they cannot be melted or thermoformed.

 

Applications of Urea-Formaldehyde Glue

Plywood, particleboard, wood panels, and bending laminations all use urea-formaldehyde as an adhesive. Urea Formaldehyde is one of the six best adhesives according to the Woodworkers Institute. If a bonded product is labeled as furniture grade, it is likely to contain Urea Formaldehyde and to be water-resistant. If the adhesive is labeled construction grade, it is most likely phenol-formaldehyde and is completely waterproof. 

In general, urea-formaldehyde glue is water-resistant. However, the glue could deteriorate under warm and humid conditions. It may certainly be used in a dry and protected area but may get wet occasionally. It should be given a paint or varnish to protect the surface.

There have even been cases where people used it in small airplanes and it has withstood the test of time with no issues. Moreover, it is often used in the construction of boats as often mentioned in the Yachting and Boating World Forums. Urea-formaldehyde cannot be the only adhesive used in the construction of a boat, but can be used in conjunction with epoxy or other waterproof glues. Melamine is sometimes used to improve the water-resistance of an adhesive. When a manufacturer advertises improved water-resistance, this is frequently the case.

 

Advantages of Urea Formaldehyde glue

First, the material sets hard and rigid. This is an advantage for bent laminations because it helps to decrease the spring back.

It is easy to use and doesn’t require the same level of joint quality as resorcinol or polyurethane. It is gap filling and load bearing (strong) and sandable after setting, although it must be clamped.

Depending on the temperature and brand, the clamping duration is usually around 6 hours. Urea-formaldehyde has an excellent open time of 20-30 minutes depending on the formulation, and it does not grab like some other wood glues. Furthermore, urea-formaldehyde could be washed away with water while it is still uncured.

Second, it is moisture resistant type II. This means that the adhesive can withstand being repeatedly drenched and dried. With marine plywood glue, some manufacturers even claim that their Plastic Resin Glue is waterproof, however all brands are water-resistant.

Third, it blends well with the wood without the glue lines because it is typically beige. Color, however, may vary by brand, from light brown to beige. In warm temperatures, it will also not deform or crawl.

Urea-formaldehyde has a proven track record of reliability and is widely used both in industrial and smaller scale projects because of its affordable price and excellent adhesion properties.

Lastly, it is very simple to use; it’s usually bought as a powder that is then combined with water. It sets better at a relatively hot temperature with most products having a recommended temperature of 21 degrees celsius.

 

Disadvantages of Urea Formaldehyde Glue

When exposed to water at a high temperature, the cured urea-formaldehyde can hydrolyze and release formaldehyde, which causes the weakening of the glue bond. As a result, it is classified as water-resistant rather than waterproof and is not always recommended for marine plywood.

Since uncured resin is unpleasant and poisonous, urea-formaldehyde must be used in a well-ventilated location. Most uncured modern adhesives come with significant warnings, so this isn’t unusual, but proper education of staff is always recommended.

The shelf life of urea-formaldehyde adhesive is one year but it must be stored in a dry environment, usually in airtight plastic containers.

 

Health Effects of Urea Formaldehyde Glue

Breathing formaldehyde at low levels can irritate the eyes, nose, and throat. Formaldehyde exposure at higher levels may cause skin rashes, shortness of breath, asthma, and abnormalities in lung function. Formaldehyde may be especially toxic to children, the elderly, and persons with asthma or other breathing issues.

 

Safety and Detection 

When it was discovered that urea-formaldehyde insulation (UFFI) was outgassing formaldehyde, it received a poor rap. Because the technique of adding more formaldehyde to assure complete reaction is no longer practiced in recent formulations, this problem is no longer a serious issue. In boatbuilding applications, for example, outgassing is not a significant issue.

The usage of formaldehyde in buildings and facilities makes it necessary to monitor continuously for formaldehyde levels. To guarantee that staff is not exposed to unsafe amounts of formaldehyde in the air, a suitable detection instrument should be used to detect and monitor levels.

Real-time data allows for the detection of potential overexposures as they occur, rather than waiting for laboratory examination. Employees can be evacuated if a harmful amount is found until the risk is mitigated.

Formaldehyde detection and measuring equipment can detect and monitor formaldehyde, temperature, and humidity in real-time. The units can be used as manual, hand-held instruments or as continuous monitoring devices with data logging capabilities of up to one month. The apparatus can also take instantaneous single-point measurements of formaldehyde, temperature, and humidity when used in a manual, hand-held capacity.

Some devices can accurately detect formaldehyde concentrations in parts per million and mg/m3 over a wide range of temperature and humidity, and the built-in memory and real-time clocks allow for the logging of all three parameters and corresponding times for improved monitoring and analysis.

 

Conclusion

Urea-formaldehyde glue is used extensively as a major adhesive for a variety of reasons, including low cost, ease of use under a variety of curing conditions, low cure temperatures, water-solubility, water-resistance, resistance to microorganisms and abrasion, hardness, excellent thermal properties, and lack of color.

The applications of urea-formaldehyde are extensive, such as decorative laminates, textiles, paper, foundry sand molds, wrinkle-resistant fabrics, cotton blends, rayon, corduroy, and other materials. It’s also utilized as an adhesive for wood and making electrical appliance casings, e.g., desk lamps.

 

Global Advance Industries Manufacturing

Since off-the-shelf urea-formaldehyde glue from each manufacturer has a different formulation, our manufacturing plant also provides a research and development (R&D) service to develop a specific formulation for our clients.

For further information, please contact +66 (0) 61-829-4441 or Email: Sales@gain.co.th