Paula Bermudez

Did you know? Epoxy and Polyurethane Tips

Did you know that exotherm (the heat generated during reaction) is proportional to the gel time and the mass of the casting?

• The faster the gel time the higher the exotherm.
• Thick sections have higher exotherm.
• The higher the mass, the higher the exotherm.

Did you know that it is the responsibility of the user to confirm that all the products they purchase is on the TSCA Inventory (USA) or on the DSL (Canada)?  Assuming that the supplier has the products listed is not an adequate defense with the EPA. Did you know that Epoxies and Polyurethanes are mix ratio sensitive? Unlike Polyester materials, adding more or less hardener will not speed up or slow the reaction but will cause degradation in the cured properties. Did you know that not all epoxies are hard after cure? Epoxies can be formulated to yield a variety of hardness, down to the Shore A range with elongation up to 100%. However, if a product turns out to be softer than indicated on the technical data sheet, there is a good chance that it was not mixed in accordance with the stated mix ratio. Did you know that HDT (heat deflection temperature) and Operating Temperature are not the same thing? The HDT is the temperature where the material begins to lose its mechanical strength however, this is only significant in applications where mechanical strength is required at that temperature. In other cases, such as potting, where mechanical strength may not be necessary at elevated temperatures a material with a lower HDT may be sufficient. Did you know that only 50-60% of the epoxy groups have reacted at the point of gellation? At this point the linear molecules have become large enough to become solid at room temperature, but the product does not have significant mechanical properties. Depending on the product, the gelled material may have developed enough properties to be handled in production but not enough for its intended end use. In addition, a material in its gelled state is vulnerable to stresses caused by thermal cycling. Inadvertent thermal cycling can occur during processing if the part is allowed to cool prior to post cure. Did you know that embedded sharp corners are one of the major causes of cracking? Embedded sharp corners represent areas of concentrated stress. Small cracks are initiated during gellation as the material shrinks. Subsequently, these micro cracks will propagate during thermal cycling. Did you know that temperature has a major impact on processing? The viscosity of epoxy resins decrease rapidly with temperature. Lower viscosity will aid in de-airing products while resulting in shorter pot life and faster gellation. As a rule the curing reaction will double (the pot life is halved) for every 100C rise in temperature. Did you know that soft spots in a cured product are most often the result of improper mixing? Thorough and complete mixing of two component materials is extremely important to avoid either resin rich or hardener rich areas in the mix. Under catalyzed or over catalyzed areas contain excess, un-reacted material resulting in soft spots. If the components are mixed by hand or drill it is important that the material from the sides and bottom of the container is properly mixed in. If the materials are mixed with automated equipment, it is important to have the correct mix head (the correct number of elements) and the mix ratio is checked frequently. Did you know that shrinkage occurs in two ways? The first shrinkage that occurs is during cross-linking as the molecules attach to each other and take up less space. More significantly, the greater shrinkage occurs due to thermal contraction while cooling down from the exothermic reaction. As a rule, slower reacting or products containing large amounts of fillers shrink less. Did you know that epoxies and polyurethanes are brittle immediately after gellation? Almost all epoxy and polyurethane compounds pass through a stage, just before the molecules completely align themselves, during which the product is extremely brittle. Depending on the type of material, this stage is passed either with time or the application of additional heat such as post cure. A component or module will be prone to cracking if subjected to undue stress, thermal cycling or thermal shock immediately after the gellation phase. Did you know that, in order to compare the dielectric strength of two different materials, you must also consider the thickness of the test specimens used to determine the published values? It often happens, during material selection, that a product is ruled out because the published dielectric strength is lower. In fact, the published figure is just about meaningless unless the thickness of the test specimen is also stated. A thin test specimen will always yield higher figures because there are less impurities contained within the structure. In order to compare "apples to apples" the two specimens have to be tested in the same thicknesses under the same conditions. Did you know that some materials are more suited to automated dispense equipment than others? Without question, unfilled product are most suited to automated equipment. However in most cases they are not suitable for the part under consideration due to their inherently higher shrinkage and lower thermal conductivity. Materials containing fillers can be formulated for reduced wear on automated equipment by employing "non-abrasive" fillers. Crystalline fillers will cause the most severe wear in dispense cylinders while "Amorphous" fillers are the least damaging. It is important for the supplier to know how the material will be dispensed in order to provide the most appropriate material for the process at hand.

Polyurethane Adhesives Guide – Uses, Advantages & Differences: Everything you need to know

Polyurethane adhesives are a proven choice for industrial bonding and adhesive requirements. From furniture, and automotive manufacturers to aerospace, construction, and electronics brands – polyurethane adhesives are used by some of the largest businesses across a countless range of industries and sectors.

If you want to learn more, please visit our website Yourun Synthetic Material.

Whether referred to as PU adhesives, polyurethane glues, or polyurethane sealants, polyurethane adhesives offer unrivalled levels of versatility, and can be formulated to accommodate for any number of your adhesive requirements.

This aside, when sourcing polyurethane adhesives, or any industrial/large-scale adhesive supply for that matter, there are many questions that you need answering before you can begin your order. If you’re wondering “what are polyurethane adhesives?” or “what adhesive formulation is best for my application?” – you are in the right place.

In this pu adhesive guide – we cover everything you need to know about polyurethane adhesives. For more information and advice, including order quotes and custom formulations, speak to our friendly experts today.

Quick Guide:

• What are polyurethane adhesives?
• What are polyurethane adhesives used for?
• The differences between one-part and two-part PU adhesives
• Two-part PU systems: The details
• One-part PU systems: The details
• One-part or two-part? Making your choice
• Advantages of PU adhesives
• What influences the properties of PU Adhesives?
• Where to order polyurethane adhesives for businesses?

What are polyurethane adhesives?

Polyurethane adhesives (PU adhesives) are polymer-based glues generally used in high strength bonding applications. Polyurethane systems used for adhesives can be separated into two main classifications, 1K (one-part) and 2K (two-part) systems, which share many similarities. All polyurethane adhesives use the same fundamental chemical reaction, this being a reaction between a diisocyanate and a polyol.

This chemical reaction is known as polymerisation: a process where monomers (such as the diisocyanates and polyols) join to form long polymer chains. The polymerisation of polyurethane glues lends to its trademark adhesive properties, making it an ideal choice for any bonding, joining or adhesion application where strong bonds are required.

Want to learn more? Speak to our experts today.

What are polyurethane adhesives used for?

Polyurethane adhesives can be used to bond a wide variety of substrates. Offering a high resistance to water, PU adhesives are ideal for manufacturing parts and components that are intended for use in outdoor or exterior applications.

Suitable substrates:

• Metals (e.g. aluminum, steel, stainless steel)
• Plastics (e.g. ABS, PVC, polycarbonate)
• Wood (e.g. hardwoods, softwoods, plywood)
• Foam (e.g. polyurethane foam, polystyrene foam)
• Panels (e.g.honeycomb panels, composite panels, insulation panels)

Common uses for businesses:

• Automotive manufacturing: PU adhesives are commonly used in structural bonding for vehicle manufacturing as the systems offer enhanced strength and vibration resistance. Common uses include: Attaching interior / exterior trim and panels; assembling door panels and seating components; bonding structural components in car bodies and truck trailers; sealing and bonding in automotive lighting systems.
• Panel Manufacturing: PU adhesives are the first choice for manufacturers of panels, or businesses producing panelling in house. The adhesives can be used for a wide range of uses, including: Structural Insulated Panels (SIPs); composite panels; honeycomb panels; truck and trailer body panels; Recreational Vehicles (RVs)/motorhome and caravan panels; aircraft interiors and more.
• Construction Industry: Commonly used for: Bonding insulation materials, flooring and building components; Brick slips, cladding and PVC / composite door manufacturing.
• Artificial Turf Installation: Bonding artificial grass to a variety of substrates.
• Aerospace Industry: PU adhesives are widely used in composite bonding, as modern aircraft increasingly rely on composite materials to reduce weight. They can be used for: Assembling interior panels and components; repairing aircraft components and more.

Polyurethane adhesive systems are an ideal choice for a range of business needs. At Chemique, we can provide everything you need to get started, overhaul or improve your adhesive usage, including custom PU adhesives and application equipment. We can build and install manual and automatic application systems for rolling, spraying or beading to maximise your potential.

Need polyurethane adhesives or industrial adhesives for your business? Whether you opt for one of our existing brands (such as Solfre, Turftak or Axil) or a custom manufactured solution, we provide the adhesives you need that fit your business. Speak to us today to discover how we can help.

The differences between one-part and two-part PU adhesives:

Two-part PU systems: The details

Two-part polyurethane systems are manufactured and supplied as separate components. For the polymerisation and crosslinking (curing) reaction to take place, the two primary components (diisocyanate and the polyol) must be mixed just prior to use. The components must be combined in the correct ratio to ensure the polyurethane glues/adhesives have the correct physical properties as required.

What this means for you: Two-part PU systems (2K PU systems) offer fast curing times, excellent control over final properties, and strong, durable bonds that you expect when selecting an industrial-scale adhesive. As they are supplied and stored in separate components, 2K systems generally have a long shelf life (even when opened) with the advantage of not curing unless mixed – this allows you to reduce waste by only using the quantities you require.

If you want to learn more, please visit our website polyurethane crosslinker.

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One-part PU systems: The details

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One-part PU systems (1K PU systems) require water to be present to crosslink/cure, which can be derived from moisture in the atmosphere. Depending on the exact type of 1K system used, a water mist may be required to crosslink the adhesive prior to the second substrate being bonded.

What this means for you:

As the diisocyanates and polyols are pre-mixed, one-part PU systems can reduce the time and labour required for preparing the adhesives for use, simplifying the process. This can also offer certainty that the adhesives are prepared to the correct ratios, maintaining consistency in your use. As one-part PU systems are moisture or water activated, the adhesives must be correctly stored once opened and used within the correct time frame to prevent premature curing in the container/bottle. Depending on the size and scale of your adhesive use, however, this may not be as large of a concern.

One-part or two-part? Making your choice

Most substrates that bond with a one-part system will also adhere with a two-part system and vice versa. Consequently, the choice you make between one-part or a two-part adhesive can depend on your use requirements, and what will benefit your business most.

Two-part systems are guaranteed to achieve full through-cure in a specified time, but the two components will need to be properly mixed in the correct ratio. In contrast, a one-part system may be easier to apply and require no mixing; but could require water-misting. It is important to remember that the cure time will be more affected by ambient conditions. Therefore, the desired application method of the adhesive along with any time constraints will influence which system to use.

At Chemique, we regularly help businesses in their decision between one-part and two-part polyurethane adhesives. Sometimes a business may need a blend of the two systems to suit different areas and uses for adhesive applications. 

If you’re stuck deciding between the two polyurethane adhesive systems, we are on hand to help you. From discussing your operations and adhesive requirements, and custom formulation options, to the impacts on efficiency, product quality, and more, get in touch with our friendly experts to find your solution, today.

Advantages of PU adhesives

There are many advantages to using polyurethane adhesives in your business operations. These include:

• Excellent adhesion to a wide range of substrates
• Cure time and pot life can be varied by formulation changes
• Good flexibility can be achieved in the cured product
• Non-flammable
• Good resistance to solvents when cured
• High resistance to water so can be used for immersed or exterior projects
• Application methods include roller, bead or spray, by manual or automatic systems
• Although they can be solvent borne, they can also be supplied solvent-free
• Heat is not required for cure, but can be used to speed up the process once both substrates are present
• Remain bonded through a wide range of operating temperatures 

What influences the properties of PU Adhesives?

The polymerisation/chemical reaction of the diisocyanate and the polyol in polyurethane adhesives has a significant influence over the physical properties for bonding and adhesion.

Polymerisation greatly increases the molecular weight of the adhesive, with the long polymer chains creating strong intermolecular forces (e.g. van der Waals forces) and strong internal bonds within the adhesive itself. As a result, polyurethane adhesives have high cohesion properties which are crucial for forming durable, strong and long-lasting bonds.

Polyurethane adhesives are often crosslinked, meaning the polymer chains are bonded to each other at numerous points. This produces a strong and rigid network of bonds once cured which greatly increases the adhesive’s strength, durability, and resistance to heat and chemicals.

Additives can also be included in the manufacture of polyurethane adhesives to tailor their specific properties for various applications. From catalysts, plasticisers, and stabilisers to thixotropic agents, colourants, and flame retardants, additives can control and tailor a number of properties, including: curing time; bond flexibility; protection against heat, light, and moisture; viscosity/thickness; colour; fire resistance.

Where to order polyurethane adhesives for businesses?

At Chemique, we have over 35 years of experience as pioneers in polyurethane adhesive systems. We manufacture a complete range of adhesive solutions to supply leading businesses worldwide with high-quality, dependable, and cost-effective products.

From our Solfre panel lamination range to our Turftak artificial turf adhesives, we cater to a complete range of business needs, supplying one-off or repeat orders for any volume you require.

We also offer a Total Service Package offering for businesses which includes: tailor-made/custom adhesive solutions (including custom polyurethane adhesives); full engineering and technical support; comprehensive training; product demos and samples; after sales support and advice, and more.

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