Hot Melt Adhesive Technical Specifications: Key Information and Selection Guide

Hot melt adhesive technical specifications help production teams match an adhesive to the substrate, application equipment and finished product. Viscosity, softening point, open time and setting time should be reviewed together. This guide explains the main terms, the differences between common adhesive families and the information to collect before a production trial. Always use the current technical data sheet (TDS) for the exact grade being considered.

What is hot melt adhesive?

Hot melt adhesive is applied in a heated, flowable state. Conventional thermoplastic grades develop a bond as they cool. Reactive grades, such as moisture-curing PUR hot melts, also undergo a subsequent curing reaction. Cooling and final curing are therefore different stages when evaluating a reactive product.

Common hot melt adhesive families

EVA hot melt adhesive

EVA stands for ethylene vinyl acetate. EVA-based formulations are used in a range of bonding applications. The polymer and other formulation ingredients influence flow, working time and bond behavior. Select a specific grade using its documented properties instead of assuming that all EVA adhesives share the same operating range.

Polyolefin hot melt adhesive

Polyolefin, often abbreviated PO, describes another family of hot melt formulations. When comparing a PO grade with EVA or another adhesive, review the actual substrate, application method and service requirements. The family name alone does not establish adhesion to a particular coating or resistance to heat and moisture.

Reactive PUR hot melt adhesive

PUR means polyurethane reactive. Moisture-curing PUR hot melts develop initial strength during cooling and continue to cure through reaction with moisture. Ask the supplier about handling strength, final cure time and suitable equipment. Follow grade-specific instructions for moisture protection, shutdown and cleaning.

Key hot melt adhesive technical specifications

1. Viscosity and measurement conditions

Viscosity describes resistance to flow and is commonly reported in mPa·s or cP. A useful specification includes the test temperature and measurement method. Compare values under equivalent conditions, and check compatibility with the pump, nozzle, roller or coating system. A single viscosity value does not describe performance at every operating temperature.

2. Softening point

Softening point is determined using a specified test method. It should not be treated as the recommended application temperature or a guarantee of the bonded product’s maximum service temperature. Review the relevant heat-performance data and test the finished assembly under representative conditions.

3. Open time

Open time is the working interval available to bring the surfaces together after applying adhesive. It must match the distance and timing between application and assembly. Adhesive quantity, substrate temperature and surrounding conditions can affect the usable interval on the production line.

4. Setting time and handling strength

Setting time concerns how quickly the bond develops sufficient strength for the next handling step. Confirm the supplier’s test conditions and the compression time available on your machine. For reactive adhesives, initial handling strength does not mean that final curing is complete.

5. Application temperature

Use the recommended range for the chosen grade and compatible equipment. Check the settings for the melter, hoses and applicator where applicable. If flow or bonding is inconsistent, review the process with the supplier before increasing temperature or changing the formulation.

6. Melt flow index and tack

If melt flow index or melt flow rate is listed, request the test temperature, load, units and method before comparing results. It is not interchangeable with a viscosity measurement. Instron’s overview of melt flow testing describes the measurement methods used for MFR and MVR. Tack describes surface stickiness under defined conditions; confirm how it is assessed for the intended application.

7. Thermal stability and usable time in the melter

Ask how long the product may remain heated under the specified conditions and what maintenance or shutdown procedure is required. Where a supplier uses terms such as pot life or heat stability, request the exact definition and test conditions. These limits are product-specific.

How to compare grades for your production line

1. Identify the substrate: record material, coatings, print, recycled content and surface condition.
2. Describe the equipment: note the applicator, line speed, bead or coat pattern and compression time.
3. Define the end use: include storage, transport, temperature exposure and required bond performance.
4. Review comparable data: compare hot melt adhesive technical specifications using the same test conditions wherever possible.
5. Run a documented trial: use actual materials, record settings and inspect bond consistency across multiple samples.

For packaging applications, see our guide to selecting hot melt adhesive for carton boxes. Repeat the trial when the board, coating, equipment or production conditions change.

Storage and technical support

Follow the product label, TDS and safety data sheet for storage and handling. Protect material from contamination and follow the equipment manufacturer’s procedures. Share your substrates, process settings and acceptance criteria with TECHBOND so the technical team can advise on a suitable grade and trial.

TECHBOND MFG (VIETNAM) CO., LTD.
Hotline: 0866 15 37 68
Email: info@techbond.com.vn