urethane adhesive

Polyurethane Glue – All about Polyurethane Adhesive

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You can find a wide variety of adhesive products available with a range of features that make them well suited to producing strong durable bonds in a number of situations. One such product is polyurethane glue, which stands out with numerous beneficial characteristics. In the guide that follows, we’ll take a closer look at polyurethane adhesive and how to go about finding the type best suited for your needs.



What Is Polyurethane Glue?

Polyurethane glue otherwise referred to as PU adhesive, is used in situations that demand extremely high durability. The degree of elasticity offered allows for use for static as well as for more tactile bonding purposes. These adhesive types are formulated from polymers and commonly have a variety of other types of additives in them too.

Polyurethane adhesive commonly finds usage as a dual-component adhesive, but it can be found in single-component varieties as well. Either relies on the reactivity of several chemical agents for the adhesive properties, which can often make use of a catalyst like moisture, light, or heat in the process. The adhesive often occurs in a rather thick paste and does not shrink once applied. It also offers complete water resistance and allows sanding and painting when it has dried completely. Polyurethane glue can also fill and even out inconsistencies in the surface you use it on. Characteristics like these, and numerous others, make this type of adhesive an essential tool that is well suited for a wide range of bonding applications.

However, it is extremely important not to overlook the level of safety awareness required when using polyurethane glue types. The Chemicals Prohibition Ordinances prevent these adhesives from being purchased by anyone under 18. You will also of course need to take special precautions when using it and we will look at this in detail further on.



Different Types of Polyurethane Glues

You can find polyurethane adhesive in different variants. Whether they are in single, or dual-component form, they are always reliant on the chemical reactivity between the components in their particular formula. Hot melt is another type of adhesive used. Each variant has specific properties which make it well suited for certain purposes. Hot melt adhesive types are incredibly sturdy, however they only provide a small time window in which the glue can be applied. In the guide that follows we will take a closer look at certain qualities of various adhesive types. This will come in handy when choosing a polyurethane glue product for your next project.



Polyurethane Two-Component Adhesives

Dual-component or PU 2K adhesive types rely on the chemical reactivity between the two components to produce the necessary adhesion. In general, it is a hardening agent and a type of resin. Each of these is combined according to a specified ratio and you can find different mix ratios depending on the product and the application type. A widely used adhesive to hardener ratio is 100:15 and also 100:30. Other adhesive solutions for these products are also available, such as epoxy resin adhesives.

Dual-component polyurethane adhesive types can be categorized by their various strength levels:

  • A good level of shear strength is required when the adhesive bond will be supporting a large amount of weight
  • Some adhesive bonds will experience intense shock loads and stretching and require great impact resistance
  • Viscoplastic adhesives are those that possess a combination of these properties at the same time



Dual-component adhesive types are known by the different qualities that a polyurethane adhesive provides:

  • Extremely weather-resistant and offer protection from the elements
  • Lasting durability and strength
  • Impact and shock-resistant
  • Good quality lap shear strength offered
  • Able to excellently bridge between surfaces and even join larger gaps
  • Great adhesive properties for use in larger areas
  • Application is simple, clean, and allows easy processing
  • Suitable for interior and exterior surfaces


Fields of Application

PU adhesive types are well suited for different types of surfaces and application purposes. They are suitable not for metal and wood adhesion, but also for various other types like plastic, plaster, and cork. PUR glue variants are very useful for combination bonds that involve two different surface types.

For instance, if your floor surface at home requires replacing and you need to join parquet flooring or floorboards, a polyurethane adhesive is ideal for this purpose. Obviously, there are also aspects that may cause a certain amount of difficulty if you don’t know your way around them. The price of a polyurethane adhesive product for one is rather high comparatively and during the application process, the glue can lose adhesion strength if you don’t work quickly enough. For this reason, PUR glue types may be more comfortably used by more experienced craftsmen. However, the positive aspects of using polyurethane adhesive types far outweigh the negatives. High-end polyurethane glue is solvent-free, for starters, which avoids you having to ventilate the area for many days after the application before you can safely be there. The strength of the adhesion is excellent, when effectively applied, and can hold up in even the most demanding situations.

PUR glue types are also well suited for the adhesion of natural stone, as they cause no discoloration and leave no greasy residue. They can even be applied to fire-retardant materials such as gypsum plasterboards and fibers.

polyurethane adhesive



Difference between Urethane and Polyurethane?

Both Urethane and Polyurethane are different types of polymers. Polyurethane means that the polymer is formulated from multiple urethane groups.


How to Glue Polyurethane?

When using 2K PU adhesives the procedure is incredibly simple. The first step involves measuring each individual component and then mixing them together. Ensure that you read the product guide carefully. If you deviate from the specified mixing ratio, it will affect the quality of the adhesive and may also alter the curing process. Be careful of air bubbles when mixing the adhesive, as these remain when the adhesive has dried.

These dual-component adhesives can also be found in double compartment packaging which makes it very simple to mix.

A single-sided application is enough to provide effective adhesion. Be sure to completely coat the adhesive surface, however, take care not to apply it too thickly or it may leak through the joints. Keep a cloth nearby, as any leaks will need to be dealt with immediately. A craft knife can be used for removing any dry adhesive if necessary.

Keep in mind that the time you can effectively apply the adhesive is limited, and once this pot life is expended it cannot be used anymore. It can, however, be combined with additives such as inhibitors and accelerants which will decrease or increase this pot lifespan.

The last stage of the drying process finishes in between four and seven days. While the initial curing phase is within the first twelve hours, it will allow you to place and fix your adhesive materials accurately in this period, and you may require clamps for this.



Polyurethane 1K Glue

PU 1K adhesive products contain only a single component. Once applied, the glue absorbs moisture from the air which aids the curing process. An outer shell begins to form in a few minutes, due to this rapid curing rate.

GORILLA Waterproof Polyurethane Glue
  • Incredibly strong and versatile glue that can bond to many surfaces
  • Best for tough repairs on dissimilar surfaces, both indoors and out
  • 100% waterproof and won't break down when exposed to elements
View on Amazon
DAP Polyurethane Construction Adhesive and Sealant
  • Offers superior adhesion to a wide variety of substrates
  • remains permanently flexible, paintable
  • Manufactured in the United States, 50-year durability guarantee
View on Amazon

These single-component polyurethane adhesives are used in factories in a strategic manner. For the home DIY enthusiast, the gun application is more than adequate.



These are some of the beneficial qualities of polyurethane 1K adhesives:

  • Easy application, for the home user with a sealant gun
  • Impact-resistant
  • Retains elasticity after curing
  • Well suited for application in larger areas
  • Certain 1K adhesive types even allow occasional contact with food


Fields of Application

As with dual-component adhesives, single-component adhesive is also well suited for a variety of different application purposes. You can easily take on plastic, wood, metal, and gypsum board. The high elasticity nature of the bond provided by single-component adhesive is the reason it is often used for flooring applications. Should you wish to lay down a parquet or plank floor, this type of adhesive will serve you well.



Ensure the adhesion surfaces have no traces of dust or grease present. You can use solvent and a lint-free cloth for cleaning them before applying the single-component adhesive. To make the adhesive even more effective, you can use sandpaper to lightly texturize the surfaces.

You can now begin applying the glue smoothly on one of the adhesion surfaces. Next, you can place the surfaces together and use clamps to increase the level of adhesion while the glue cures.



Hot Melt Glues

Hot melt adhesive types are formulated using thermoplastic polymers. This allows them to solidify completely at room temperature and become fluid in the presence of heat. You can only apply them while fluid, but once they have cooled and dried they solidify once more. Hotmelt glue can contain a variety of agents such as plasticizers, wax, and antioxidants. Additional substances can be combined to allow other specific qualities.

Hotmelt adhesive does not require a porous surface like single and dual-component urethane glue. The drying process is also reliant on a decrease in temperature rather than a chemical change. There are two main hotmelt adhesive types, PUR and EVA hotmelts, which can be reactivated and re-melted once cured and this allows recycling.

pur glue



Below are some of the beneficial aspects of hotmelts, and the problem areas:


  • Hotmelt adhesive is free of solvents
  • Become solidified extremely rapidly, allowing immediate functionality, which ensures an increased frequency of the production cycle.
  • Allow application on both porous and non-porous surfaces.
  • Regardless of their rapid activation, EVA hot melts can also be reactivated, which allows pre-coating.
  • Well suited for so many different materials
  • The adhesive joins retain elasticity
  • The adhesive surfaces can be detached from one another once more by applying heat
  • Additive agents can increase the strength of base polymers.
  • Solidifies at room temperature, allowing for simplified storage and transportation.


  • You can only apply to substances with effective temperature resistance. The reactive nature of thermoplastics can be convenient in some areas but inconvenient in others.


Fields of Application

Hotmelt glue can be applied in all sorts of different areas. Not only is it used in bookbinding and packaging but also label and cardboard manufacturing, in the assembling of many different products, and also in the motor industry. Hotmelt adhesive allows bonding using an almost endless variety of materials such as plastic, metal, rubber, wood, glass, cardboard, ceramics, cork, and a number of fabrics too. You can even bond leather and felt.

So hot melt glue is used in large-scale commercial applications, home industries, and of course by DIY enthusiasts as well. The health and hygiene and the manufacturing sectors make use of the power of these types of adhesives.

Where home craft and hobbies are concerned, a glue gun is an essential tool that is never too far away.



Hotmelts are generally utilized by home users with a glue gun that dispenses the hot adhesive when pressure is applied to the trigger. The glue is spread over the clean adhesion surfaces which can then be joined. The adhesive cools and sets rapidly, so be sure to work fast. If the glue solidifies you can’t work with it. You can also apply hotmelts with other tools like spiral syringes and extruders. You can find the adhesive in different forms such as blocks, films, granulates, or glue sticks.



Conclusion of the Different PU Adhesives

Despite the marginally higher price tag of polyurethane adhesives, they do offer plenty of worthwhile benefits. They are well suited for use with a variety of different materials, and their strong adhesion allows single-sided application. Polyurethane adhesives are easy to work with, even dual-component products have double canisters for easy mixing purposes. Polyurethane adhesives are also highly resistant to the elements and can endure heavy contact and impact.

polyurethane glue



Storage and Durability of Polyurethane Adhesives

There are certain considerations when you go about storing polyurethane glue:

  • It is recommended that you store PU adhesive in a cool dark room; the optimal storage temperature range is 10 – 25° C
  • Ensure the packaging is protected from any moisture or extreme cold
  • Be sure to first use older glue in the container
  • Inspect the packaging regularly for any sign of damage

Once you have finished with the polyurethane adhesive, ensure that the canister is properly sealed, as this prevents any glue from going hard – which means you won’t be able to use it. The longevity of PUR glue in storage is limited. It depends on the particular product, but it is generally between a few months and up to a few years. For further details, check the included product information.

Used PU containers should always be disposed of discretely. Drop them at a collection point for hazardous waste rather than disposing of them with regular household garbage.



Safety Instructions for Processing PU Glue

If you work with PUR glue types, safety must be your number one priority. Be sure to wear a respirator mask, protective eyewear, and disposable gloves. This reduces the risk of contact with your skin or from inhaling any fumes while working. Certain ingredients of these adhesives could contain carcinogens, so ensure your workspace is well ventilated.

Before proceeding with the application, make sure you have gone through the list of safety precautions supplied, contact an experienced professional should you have any queries.

Should the polyurethane adhesive touch your skin directly, use soapy water to remove all traces right away. A cloth can be used to clear any adhesive that is still fluid. If the residue happens to harden on your skin, seek medical attention immediately – do not attempt to remove it on your own.

Polyurethane adhesive types may be costly, but they allow for extremely high durability bonding. When using them, be sure to always take the necessary safety precautions.


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