What to Consider When Choosing the Right Hot-Press Adhesive Formulation or Blend

Hot-press adhesive manufacturing involves modifying, processing, and mixing/blending raw materials to create a range of adhesive formulations with specific properties and characteristics. Do you want an adhesive that will spread thinly to accommodate a smooth or thin decorative layer, or do you want a thicker adhesive that won’t get lost in the nooks and crannies of a rough surface? Do you need all the ingredients to be expensive synthetic ones or can a nature-based, low-cost extender be used? In the past, this optimization process sometimes included using an adhesive blend, a combination of two or more bonding agents. The resulting mixture improved the product performance by being tailored according to the project’s needs. Recently, single component adhesives, such as BreezeBond^TM, have also become available that can be specifically formulated for a range of wood composite panel applications.

Each application has specific requirements, such as unique substrate materials, environmental conditions, and required bond strength. Failing to consider these factors can result in inadequate bonding, compromising the final product’s reliability. In addition, the wrong blend can lead to costly rework, impacting production schedules and increasing expenses. Conveniently, since BreezeBond^TM can be offered as a single component from the adhesive factory, it can reduce the chance of these types of issues with forest products.

Some customers, however, may feel uncomfortable switching their adhesive completely over to BreezeBond^TM alone, and may prefer to retain some of the properties of their existing adhesive. Other applications may be looking to reduce costs and environmental footprint. In these instances, BreezeBond^TM can be blended with other water-soluble adhesives, acting as an “extender”. This can help customers reduce their exposure to the volatile petroleum markets, while making safer products in the process!

Here is a closer look at the key considerations when selecting the right adhesive formulation to ensure that you get the best possible bonding results:

1. 1. Surface Type and Cleanliness

   Different surfaces can require specific types of adhesives to achieve effective bonding. For example, smooth surfaces like sanded wood or paper may benefit from a lower viscosity adhesive than rough or porous surfaces. Such coarse surfaces may need a thicker, or higher viscosity adhesive mix to ensure adequate material is retained between the layers to be bonded.

   Another important consideration is the cleanliness of the surface. Adhesives usually work best when starting with a clean, dry surface. If the surface is contaminated with dust, grease, or other debris, it can prevent the product from forming a strong bond. In such cases, surface preparation may be necessary, which can include abrasive surface preparation or even a primer for some types of adhesive. Selecting an adhesive blend designed to bond with compromised surfaces may be necessary.

2. 2. Environmental Conditions

   It is necessary to understand the adhesive’s operating temperature range, load/shear requirements, and the application’s intended environment. This will allow selection of a blend or formulation specifically designed to maintain its properties and bonding strength within the required limits. Otherwise, for example, a product that could be exposed to an extreme-temperature environment may result in softened or lost adhesion or cracking due to a mismatch of thermal expansion coefficients. Another common failure mechanism is cracking due to choosing an adhesive that is too rigid for an application where there is a cyclical load like shifting winds pushing on a structural component bolted to the ground. BreezeBond^TM is perfect for composite wood panel products because since it is composed of natural components, its mechanical properties work well in tandem with those of the bonded substrate (wood veneers or plies).

3. 3. Dry and Wet Strength

   Dry strength pertains to the adhesive’s bond strength in dry conditions, while wet strength refers to its bonding capability in humid or wet conditions. Different types of bonds have varying levels of dry and wet strength. In some cases, a moisture barrier such as a sealant is also used.

   While most disposable packaging applications are primarily focused on cost and environmental footprint, some packaging applications may be exposed to damp environments such as occasional exposure to rain or defrosting as with food products. In these instances, blends with high wet strength are required. These may include disposable preformed fiber crates, cartons, or other containers. Otherwise, moisture can weaken the bond and cause the structural integrity of the packaging to break down, resulting in product damage or loss during shipping and handling.

   In other cases such as with toys, electronics, kitchenware, or ornamental collectibles, the dry strength of a molded packaging component is the most important consideration. This is because these parts tend to be nestled on the inside of an outer package. These types of goods also are less likely to be exposed to outdoor conditions.

4. 4. Tack

   Tack refers to the adhesive’s ability to adhere to a substrate quickly and form an instant bond under light pressure. The tack level required for a particular application depends on several factors, such as the substrate material, the application method, and the desired bond strength. It can also be adjusted by changing the formulation or modifying the processing conditions during adhesive manufacturing. Oftentimes, a cold press step is implemented prior to hot-press to ensure sufficient wetting onto the surface of the substrate. Other times, a desirable level of tack can be accomplished by letting the adhesive stand to partially air dry momentarily on the substrate before applying the next layer of veneer. This can help keep the plies in place as they move into the hot-press or this step can function to remove unnecessary excess moisture. This can also reduce the risk of venting or “blowouts” which can be loud and occur unexpectedly, affecting production yield. With a consistently implemented pre-dry step, these occurrences can be eliminated.

5. 5. Hot-Press Temperature

   Hot-press temperature refers to the temperature at which the adhesive is activated and the bonding process begins. Different adhesives have different temperature requirements; some bonds require high temperatures to activate, while others require lower temperatures. If the hot-press temperature is too high, it can cause the adhesive to break down or discolor. This can result in weak bonding or even adhesive failure. High temperatures can also adversely affect the materials being bonded, causing further discoloration, cracking, wrinkling, or even burning. In these instances, it may be necessary to extend the duration of the press at a lower temperature.

6. 6. Press Duration

   The press duration is the amount of time the adhesive and substrate are held together under pressure and temperature during bonding. As is the case with temperature, the duration depends on the adhesive type, substrate material, and total thickness. If the press duration is too short, the adhesive may not crosslink adequately. Conversely, it may break down if the duration period is too long. Sometimes though, as mentioned earlier, it is possible to extend the press duration at a lower temperature to achieve bonding if the product materials are sensitive to elevated temperatures.

Choose Specialty Organics to Find the Formulation Right for Your Product

Specialty Organics is an established, eco-friendly adhesive manufacturer offering a range of products and services, including BreezeBond^TM. We offer BreezeBond^TM in a variety of formulations, from low viscosity to high, and with standard or high wet strengths to tailor its characteristics to meet the needs of your specific application. Specialty Organics also offers toll manufacturing, pilot plant proof of concept, scale-up, and custom synthesis services to meet your adhesive and coating-related needs. We also offer contract manufacturing for businesses looking to outsource their adhesive production or sub-licensing opportunities to become a manufacturing partner.

Contact us today to learn more about our products and services or to find a BreezeBond^TM formulation for your wood composite panel!