Customizing adhesive formulas allows customer needs to drive innovation. As the number of adhesive-using industries grows, the variety of uses for hot-melt solutions is expanding to the point where there is not a one-size-fits-all formula for any industry. From cosmetics to construction, manufacturers and end users are seeking custom formulas that will provide more reliable bonds than what can be purchased off the shelf.
Each adhesive needs to be formulated differently, and their chemistries must consider the varying requirements of the specific application. The combination of factors to consider during the development process is endless, but is largely determined by the following variables: the substrates being bonded, the required strength of the bond, the environmental conditions that the substrates will be subjected to throughout the life of the bond, the method of application, and the skill level of the operator. Manipulating the adhesive formula in anticipation of these variables will ensure a quality bond that behaves as expected. Regardless of the application, customized solutions are the most effective and economic way to ensure a quality bond that meets the customer’s requirements.
The first step of the customization process is to identify the specific needs of the new adhesive. Encouraging customers to provide feedback on current formulas, such as what is properly performing (or not), can open a conversation that sparks innovation and drives a more efficient outcome for the user of the adhesive.
Applications Drive the Development Process
The substrates to be bonded have the largest impact on the durability and strength of a bond. A bond’s strength and durability are ultimately subject to the substrates being joined. The materials being bonded and their condition throughout the life of the bond will help determine if the solution is best suited for an EVA-, polyamide-, acrylic-, SBS-, or APAO-based hot melt.
The base of the adhesive in a particular formula will depend heavily on the necessary temperature resistance of the adhesive throughout the life of the bond. While EVAs will work for most applications, APAO- and polyamide-based adhesives should be used when high heat resistance is required. An acrylic-based formula will deliver a better bond when cold resistance is required.
The environment also plays a big factor in the creation of a new formulation. A bond’s durability is affected by the temperature of the substrates at the time of application. While most adhesive applications occur on the factory floor, others may be applied in a freezer where the temperature is 50° cooler. Typically, the cardboard in a freezer application will also be coated in various moisture-protecting finishes. These coatings make it more difficult for an adhesive to adhere to the substrate, especially when applied in a colder environment.
Wax additives should be limited in these applications. Wax causes the adhesive to have a quicker set time, limiting the amount of time in which the operator can perform the application process as required. In the case of sealing a large box, if the set time is too quick, then the glue may start to set before the flaps can be joined, resulting in an unsecure bond. On the other hand, the longer the open time, the longer it may take the operator to move to the next step, which may slow down the process.
The substrates themselves play a large role in determining which adhesive formula will create the necessary open time. For instance, applications with Styrofoam substrates will not require an adhesive blend creating a long open time, as the Styrofoam will not pull the heat from the adhesive as quickly as a metal substrate. Metal substrates will almost immediately pull the heat from the adhesive, causing a shorter open and cure time. Typically, the longer the cure time, the more durable the bond, so an adhesive blend resulting in a long open and cure time would be recommended for metal applications.
Some adhesives are only used for temporary bonds. In other applications, the adhesive is used as an insulator for electrical parts, in which case the adhesive’s viscosity is an important factor.
Professional dent removal applications in the automotive industry create a unique obstacle for developing adhesive solutions, because there is no one formula that will work effectively in both cool and warm climates. In this application, the temperature variations of the metal substrates are endless, depending on the geographic location and the season in which the application is being performed.
When cool, the metal body of an automotive vehicle will pull the heat out of the adhesive quicker than when the metal is warm. For example, a professional dent remover using a hot-melt adhesive in Texas’s summer heat must use a different formula than the dent remover in Minnesota’s chilly springtime. By blending different base materials, waxes and resins into the formula, manufacturers of adhesives for dent removal can develop different formulas for each application process.
In addition to the environment, for the dent removal process to perform properly, the hot-melt glue must also bond to the applicator stud and be thick enough not to run off the stud prior to placing it into the middle of the dent. After the dent is pulled out, the glue must be able to be removed from both the metal surface and the applicator stud. The dent removal application also has unique requirements for tensile and peel strength. Once the adhesive is applied to the stud, the tensile strength must be durable enough for the operator to pull out the dent. The peel strength, however, is expected to be limited so the adhesive can be removed from the substrate after the dent is removed.
The combination of peel, tensile and shear strengths vary by application, and formulas must be developed in anticipation of their end use. A universal testing machine can be used to test shear, peel and tensile strengths of formulas being created to ensure quality results for the end user.
Customization for Aesthetic Expectations
Other factors to consider during the development process include the customer’s aesthetic expectations and how the solution will be used. Color matching is a large concern for many industries, including construction, cosmetics, and the consumer floral and craft industries. Color matching an adhesive to wood paneling, for example, creates an economic and efficient product to be used in filling knot holes. By applying an adhesive that is close to the color in the wood panels, the customer is able to use wood that otherwise would have been scrapped.
By using machines that can mix varying sizes of adhesive batches, the manufacturer can create small sample batches to test the quality of the solution (such as a color match) and ensure it meets customer expectations. Mixing and blending machines can create different hot-melt formulas and then shape the adhesive to fit the needs of customers’ varying expectations and application requirements.
Efficient and Economic Formulas for All Applications
Customizing adhesive solutions with the application in mind creates the most effective adhesive possible for a specific use and can save valuable resources for the end user by making the entire process more efficient from development to application. In order to maintain a cost-effective development process, manufacturers of adhesives need to pair their technical expertise with blending and mixing equipment that allows small sample batches to be made and tested. This allows each formula to be tweaked until it performs efficiently and meets the customer’s requirements.
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