What is Hot Glue? Hot Melt Types and Usage Areas
Hot melt is a solvent-free industrial adhesive that is solid at room temperature, becomes fluid by heating in a controlled manner, and forms a bond mostly upon cooling after being applied to the surface. Families such as EVA, PO, PUR, PSA, PA and APAO; The surface is selected according to line speed, open time, application temperature and strength expectation.
Hot glue is a group of adhesives used in industrial production when fast adhesion, solvent-free operation and compliance with the process speed are expected. These products, known as hot melt adhesive and in English, are solid at room temperature; It is fluidized by heated in a controlled manner in the application equipment and forms a bond after being transferred to the surface.
But the “best hot glue” is not a single product. The operating behavior and final performance of different hot melt adhesive families such as EVA, PO, PUR, PSA, PA and APAO differ from each other. Making a selection based only on the product name without considering conditions such as surface type, line speed, application temperature, open time, appearance expectation, humidity and heat exposure may not give correct results.
What is hot glue?
Hot glue; It is an adhesive that is stored in solid form, melts and becomes fluid under the influence of heat, and forms a bond through cooling or chemical reaction after being applied to a surface. For this reason, it is different from classical systems that wait for a solvent to evaporate. After application, the first adhesion may occur in a short time so that the line can continue; Ultimate strength may develop over a different period of time depending on the product family and process conditions.
In industrial hot glue applications, equipment setting is as important as the product itself. Tank or cartridge temperature, hose and nozzle temperature, weight given to the surface, application interval, printing time and cleanliness of the surfaces directly affect the bond quality. Therefore, the current technical data sheet (TDS) and safety data sheet (SDS) should always be taken as basis for product code-specific values.
How does hot glue work?
- Fluidization: The solid product is heated in a controlled manner within the recommended operating range of the machine. Excessively high temperatures may increase the risk of discoloration, smoke, odor or thermal degradation.
- Application and wetting: Fluid glue is transferred to the surface with a nozzle, roller or a suitable applicator. The cleanliness of the surface, temperature, and surface energy affect how well the glue wets the surface.
- Bond formation: In standard hot melt products, a significant part of the bond is formed by cooling. In reactive PUR hot melt products, chemical curing may occur with moisture; Open packaging, equipment maintenance and operating procedure for these products must be managed separately.
As the application speed increases, the time the glue can remain on the surface decreases. On the other hand, the joining temperature of the parts, printing time and open time requirement may vary. Sample production and process recording should be part of the selection process, as the same product will not work with the same setting on different machines and materials.
Hot glue types
Hot melt adhesives are divided into different families according to the resin structure and targeted performance. The following summary provides guidance for initial assessment; Product code selection should be verified by application testing and current TDS.
________ ________EVA hot glue
EVA-based products are used in numerous production lines with different viscosities, colors, open times and application windows. In processes such as edge banding and packaging, fast initial adhesion, clean application and compliance with machine speed may come to the fore. Decisions should not be made based solely on the name "EVA" without considering the tape back surface, panel material, application temperature and actual line speed together.
PO hot glue
Polyolefin based hot glues; It can provide alternatives in topics such as visible glue line, color, heat behavior and compatibility with some tape surfaces. Especially for low surface energy tapes, back surface treatment, primer and surface cleaning should be checked before product selection. When adhesion problems occur, increasing the temperature alone is not a reliable solution.
PUR hot glue
Since PUR hot melt products may react with moisture after application, a different maintenance and storage discipline is required than standard thermoplastic hot melt products. Open packaging time, management of remaining product in the tank and hose, protection of the nozzle and manufacturer's procedure are important. PUR selection should be made by verifying the suitability of the machine for this system along with the targeted strength.
Where is hot glue used?
Hot glue technology appears in many different production areas due to its advantages of fast cycle and compatibility with automation:
- Furniture and woodworking: Binding of PVC, ABS, PP, PMMA, melamine or wooden edgebands to the panel; Installation of profiles, laminate and decorative parts.
- Packaging: High line speed gluing of box closures, cases, trays, cartons and some flexible packaging components.
- Automotive and transportation: Assembling trim, textiles, felt, filters and auxiliary parts according to material combination.
- Textiles and hygiene products: Controlled fixing of fabrics, nonwovens, elastic parts and multilayer structures.
- Electrical and electronics: Applications with product-specific heat and insulation requirements in cables, coils, components and protective parts.
- Filter and technical lamination: Layering of filter media, felt, foam and different carriers, taking into account surface compatibility.
The same hot glue should not be expected to give the same performance in each of these areas. The porosity of the material, surface energy, thermal sensitivity, time under pressure and usage environment should be evaluated.
How to choose the right hot glue?
Defining the application before searching for the product code allows finding the correct product family faster. The following questions provide a practical starting framework for technical evaluation:
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