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What Are Polyurethane Adhesives?

Polyurethane adhesives are being increasingly utilized in the industrial sector for bonding applications instead of traditional resins due to their composition and benefits.
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The industrial sector is seeing an increase in the use of polyurethane adhesives for bonding purposes rather than traditional resins because of their composition and advantages.


With the aid of this article, you will be able to understand the properties, advantages, chemical composition, curing times, technical aspects, and applicability of polyurethane adhesives.


Table of contents

  • Overview

  • Single or dual-component?

  • WHICH GLUE IS BEST FOR MY INDUSTRY?

  • The function of additional substances

  • How do epoxy resins differ from polyurethane resins?

  • Advice

Overview

Firstly, we will outline the definition of 'polyurethane resin'. This reactive substance adheres perfectly to various substrates. It is adaptable and offers high performance, including versatility and the capability to form a durable, robust connection.


They are considered structural adhesives because they merge entirely with two materials rather than just bonding them together, creating a cohesive unit.


Furthermore, they are famous for their capacity to endure intense mechanical pressure, and in certain situations they can serve as substitutes for conventional joining methods like welds and screws.

Single or dual-component?

Polyurethane resin that expands has two main categories: single-component and dual-component.

Single-component adhesive

These are adhesives that contain a prepolymer (NCO) as the primary ingredient along with other substances like additives and solvents. Upon application, it interacts with the moisture in the substrate and air, creating covalent bonds with the surface of the material.

Dual-component adhesive

Dual-component polyurethane possesses a chemically distinct formula.

It is made up of a polyol mixture (part A) and a curing agent (part B) that, once combined, undergo a reaction resulting in the formation of a urethane bond polymer through polyaddition.

To modify the dual-component adhesive's chemical and physical characteristics, other compounds can be added.

Which Glue Is Best For My Industry?

You may be wondering now if using a single component glue is preferable to using a dual component adhesive.

Environmental conditions

Temperature and humidity are crucial environmental factors that must be considered as they impact how the glue reacts.

Certainly, the reaction speed of the adhesive increases alongside with the environmental humidity and temperature when using a single-component glue.

The Type Of Surface

You might use a 1K adhesive instead of a 2K one, depending on how damp the substrate is. Since moisture promotes a strong connection, single-component adhesives are typically utilized with materials that include moisture, like wood.


A dual-component adhesive is used on dry surfaces like PVC instead of those containing moisture.

Surface thickness

Which type of glue can guarantee the best outcome may be indicated by thickness. In order to prevent undulations brought on by the emission of carbon dioxide, thin materials are typically attached using a dual-component method.

Item size

Keep in mind that when working with large dimensions, the humidity level of the material and the surrounding conditions may produce an improper reaction when utilizing single-component adhesives. To attain a consistent response, the issue can be fixed by applying a two-part adhesive or by damping the surface.

The technology

Some opt for single-component glue because it is simple to apply without the need for complicated tools to spread it on the surface.


A dispensing and dosing machine is needed for dual-component glue, as it mixes the two components before application.

Adhesive reaction times

Find an adhesive that is approximately in line with the compound's reaction times by comparing them to your manufacturing times.

These are the three primary ones you should be aware of.

1. Pot life: the time frame in which the product remains usable following mixing.

This mainly pertains to two-part adhesives, since they require blending prior to use.

2. Glue setting time: the period when the glue can be used to bond the two pieces together.

3. Press time: Is the duration necessary to compress a product, which is an essential process for single-component adhesives, in order to allow the adhesive to reach a polymerisation stage for extraction and initial manipulation.

Press time may change based on the glue's reactivity: the more reactive the glue, the briefer the press time.

Keep in mind that the response times of one-part adhesives can differ because of humidity, while two-part adhesives have a consistent reaction regardless of environmental moisture levels and substrate moisture content.

For individuals who are looking for a consistent and well-defined procedure, a dual-component adhesive can be the best option.

The Role Of Additives

Once the two main categories defining adhesives, surfaces and times, have been explained, we will now examine the chemical makeup in more d

etail.

As previously stated, both adhesives contain additional compounds to alter their properties based on their intended application.

In fact, the majority of adhesives, whether 1K or 2K, include components that enhance their effectiveness, like anti-foaming agents for lowering emulsion, charge dischargers for better blending with fillers, and substances for enhancing adhesion on challenging surfaces like glass.


In addition, fillers (or loads) are employed to minimize shrinkage during drying or polymerization, lower the exothermic temperature during polymerization, enhance cohesive properties, abrasion resistance, flame and smoke suppression, moisture resistance, resistance to chemical agents and corrosion, and achieve specific rheological properties.

Solvents

Solvents, found in small quantities, enhance the consistency of certain chemical characteristics of resin.


They enhance viscosity, leading to better process operability, adhesion on plastic substrates, and wettability while also increasing plasticity in the adhesive.

This raises the question: are adhesives available without solvents?

Yes, even though they can be difficult to locate in stores. Solvent-free adhesives, also known as VOC-free glues, enhance their toxicological properties.

Pigments

The natural color of polyurethane adhesives usually ranges from cream to beige.

If you would rather have a different colored glue, don't let that stop you; you can use pigments to get the color you want.

Epoxy Resins And Polyurethane Resins Differentially?

1. One type of thermosetting polymer that is particularly well-known in the flooring industry is epoxy resin.

2. Despite minor differences in their qualities, they both set quickly and have an excellent chemical resistance.

3. The primary variance concerns the operating temperature, a crucial aspect to consider when discussing repair systems to preserve the compound's quality.

4. Epoxy adhesives can withstand higher operating temperatures, around 150°C, compared to polyurethane glues which can handle temperatures ranging from about -100° to +80°C.

Key analyses – Contrasts in characteristics of epoxy versus polyurethane adhesive

  • First, we must once more look at the bonding material in order to determine if epoxy or polyurethane glue is preferable. Second, we must consider the adhesive's reaction times and the working environment.

  • Selecting one type of glue over another can result from a wet atmosphere or from abrupt temperature changes.

  • For example, epoxy glue is not appropriate if the workplace is exposed to UV rays because of its low resistance to these rays.

  • We can say that the type of bonding is one of the most evident distinctions.

  • Truly, polyurethane glue provides highly flexible adhesion, allowing for greater versatility in its mechanical characteristics, offering the possibility of forming a mixture with different levels of elasticity.

  • Epoxy adhesives are commonly described as rigid and unmalleable, often labeled as 'glassy' adhesives.

  • This is exactly why they are commonly utilized in the building industry, particularly for flooring, in order to guarantee a stable and solid outcome.

  • When examining the bonding material, epoxy glue is typically preferred when the surfaces are identical, whereas polyurethane glue is recommended for bonding two different materials. For example, when bonding a polyurethane panel with PVC, polyurethane glue is the better choice for a stronger bond.

  • Finally, when taking into account the economic aspect - which could have varying degrees of influence - polyurethane systems prove to be more economical.

Advice

Our experts are available to help you choose the right adhesive by carefully examining your business, selecting bonding materials, testing samples, and identifying the best glue.

A bad decision entails several dangers, chief among them being deteriorating the surface's look, shrinking the material, creating air bubbles, and providing short-lived bonding.

Additionally, professionals are available to assist you in selecting the ideal adhesive as well as in storing it to preserve its qualities.

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Contacts

Provide you with the appropriate industrial polyurethane adhesive; we will be pleased to help.
Contact our customer service center by emailing kevinshu@hmpur.com - we will assist you in selecting the appropriate adhesive.
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