Bonding of Hybo FOAM® Foam
Given the wide variety of adhesives and the numerous materials bonded with HyboFOAM®, it is challenging for us to provide customers with all the information regarding the quantity of each adhesive, bonding methods, drying and curing times. However, we are more than willing to collaborate with end - users and adhesive manufacturers to find practical solutions and customize bonding process plans for each specific product and component. For most bonding issues, HyboFOAM® has solvent resistance and excellent thermal stability even at a thermal curing temperature of up to 180°C. Thus, it can be used with nearly all commercial adhesives.
Before bonding, it is an essential procedure to remove dust from the surface of HyboFOAM® by suction or blowing with oil - free compressed air.
Typically, there are three main types of adhesives: 1. Solvent - based adhesives; 2. Emulsion adhesives; 3. Non - solvent - based bonding systems.
Since it is difficult for solvents to volatilize through the surface of HyboFOAM®, it must be noted that when using solvent - based and emulsion - based adhesives for large - area bonding of HyboFOAM® or bonding HyboFOAM® with other materials, the solvents in the adhesive on the bonding surfaces must be allowed to fully volatilize before applying pressure. Joints bonded with these adhesive systems (usually rubber - based) generally maintain a certain degree of elasticity and thus have high peel strength. If possible, thermally curing the joints will significantly improve the bonding quality.
After applying the adhesive to both surfaces and allowing the solvents in the adhesive on the bonding surfaces to fully volatilize, bond the two surfaces together under pressure at a temperature of 80 - 120°C. The pressure should be controlled at 40% of the maximum compressive strength and held for 1 - 5 minutes at 20°C. When the temperature is lower than 80°C, the bonded materials should be removed.
In certain cases, the adhesive can be applied to only one surface, but the surface material will thicken to some extent. After drying, with voids removed, it can be hot - melted onto the foam. If hot - pressing is not possible, the surface material can be heated sufficiently through a thicker metal plate or fiberboard in a pre - heated gasket.
Non - solvent - based bonding systems include hot - melt adhesives and two - component adhesives such as epoxy resins, polyesters, and methacrylic resins. They cure under sufficient pressure (0.05 - 0.3N/mm²) or have good fluidity during use. Therefore, they can effectively fill the open pores on the foam surface. Curing can be accelerated by heating (up to 160°C), greatly increasing the hardness and rigidity of the bonded area.
When using adhesive films and hot - melt adhesives for bonding, curing is usually achieved by heating. To firmly bond them to the cut pores of HyboFOAM®, the adhesive film must have sufficient thickness (100 - 200g/㎡). Some two - component adhesive films, such as phenolic adhesive films, release volatile substances during curing. Therefore, a gentle pressure should be applied during heating. Before bonding, the press should be briefly opened to allow the volatile substances to escape.
When using hot - melt adhesives, to avoid air bubbles, venting is often achieved by punching holes before bonding. In some difficult cases, to facilitate better venting, grooves can be pre - cut on the surface of the HyboFOAM® board, approximately 1 - 1.5mm deep and 2mm wide.
When bonding HyboFOAM® with other materials, the adhesive is usually selected based on its compatibility with these materials. For example, metals and laminated plastics are bonded with epoxy resins, rubber or polyurethane adhesives; for materials like acrylic glass or methacrylic resins, and for materials like wood, paper, or fiberglass - reinforced polyester boards, polyamine resins, epoxy resins, and polyurethane adhesive systems are used.
To obtain a very flat sandwich structure, both sides of the HyboFOAM® board must be bonded to the skins simultaneously. The two skins must be of the same material and thickness. Uniform heating and cooling of both sides are crucial steps in the manufacturing process of sandwich components.
If the surface of HyboFOAM® is treated with a needle roller before bonding, the resulting bond strength can meet very high requirements.
Due to its certain thermal creep property, to prevent the core material from being compressed or exceeding the specified tolerance range during the heating and pressurization process, we recommend increasing the thickness of the HyboFOAM® core material by 0.5 - 1mm within the original size range before closing the mold and pressing it to the final size using thickness shims.
