What are hot melt adhesives made of?
Hot-melt adhesives (also known as hot glues) are generally 100% solid formulations based on thermoplastic polymers (no water or solvents are involved). Hot melts are sold at ambient temperature and are ‘activated’ in the melt stage beyond their softening point, which is usually between 80 and 120 degrees.
Hot melt is the name given to any polymer-based glue that is applied in a molten state. The application of the adhesive is usually by which works through either trigger action (i.e. EVA or PO hot melts upon heating, PUR hot melts are moisture-cured) or finger pressure (Pressure-sensitive hot melts at ambient temperature).
How do hot-melts work?
Once melted (in a hot melt tank), the adhesive can then be applied onto a substrate in its liquified or molten state. The hot melt wets the substrate, penetrating the surface (and any cavities), and then it solidifies, ensuring cohesion. This setting/ cooling process takes very little time. Glues that cool and remain tacky are known as pressure sensitive adhesives (PSA) – these we will cover in depth another time.
How Hot Melt Adhesives Are Made?
Hot melt adhesives are thermoplastic materials that are typically composed of various polymers, resins, and additives. The manufacturing process involves several key steps:
1. Raw Material Selection
Polymers: Commonly used polymers include ethylene-vinyl acetate (EVA), polyolefin (PO), and polyurethane (PUR).
Resins: These enhance the adhesive properties and can include tackifiers and waxes.
Additives: Fillers, stabilizers, and colorants can be added to modify performance characteristics.
2. Mixing
The selected raw materials are precisely measured and mixed together. This can be done using high-shear mixers or extruders to ensure a uniform blend.
3. Heating
The mixed materials are then heated to a specific temperature to achieve a molten state. This process allows the components to fully blend and achieve the desired viscosity.
4. Extrusion or Molding
The molten adhesive is then extruded through a die or poured into molds, depending on the desired form (e.g., pellets, sheets, or blocks).
5. Cooling
Once shaped, the hot melt adhesive is cooled rapidly to solidify. This can be done using air cooling or water baths.
6. Packaging
Finally, the solidified hot melt adhesive is packaged for distribution. This can include bulk packaging for industrial use or smaller containers for commercial applications.
7. Quality Control
Throughout the manufacturing process, quality control measures are implemented to ensure the adhesive meets specific performance standards and specifications.
In summary, the production of hot melt adhesives involves careful selection of materials, precise mixing and heating, shaping, cooling, and rigorous quality control to produce a reliable adhesive product.
As more companies aim to 'go green' or enhance the eco-friendliness of their products and services, we guarantee zero formaldehyde and adhere to SGS, CMA, RoHS, and EU standards. Furthermore, we produce a COA (Certificate of Analysis) report for every batch of our hot melt products, which is accessible to our clients at any time.
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Published by TIANJIN SHENG-WANG ELECTRONIC CHEMICAL PLANT
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