In every corner of life and production, adhesives play a crucial role, and Hot Melt Adhesives, as one of the widely used types, have garnered significant attention for their unique characteristics. From the manufacturing of daily necessities to the precision assembly in high-end industries, hot melt adhesives have become an indispensable material due to their convenience and efficiency. So, what are the different types of hot melt adhesives, and how can you choose the right product?

The Diverse Family of Hot Melt Adhesives

Hot melt adhesives are not a single category but a large family of adhesives. Their common feature is that they are solid at room temperature and need to be heated to a molten state for use, solidifying quickly upon cooling to achieve a strong bond. Common types of hot melt adhesives include PUR reactive polyurethane hot melt adhesives, PA polyamide hot melt adhesives, PO polyolefin hot melt adhesives, and EVA (ethylene-vinyl acetate copolymer) hot melt adhesives. For ease of distinction, types other than PUR are generally referred to as conventional hot melt adhesives.

(1) Polyethylene Hot Melt Adhesive

Polyethylene hot melt adhesive is made by polymerizing ethylene with a small amount of α-olefin or other monomers. It has excellent bonding properties, is cost-effective, and is particularly good at bonding with porous materials. It is widely used in packaging of cardboard boxes and paper boxes, sealing of food packaging containers, manufacturing of non-woven fabrics, carpet seaming, automotive carpet backing, and clothing interlining bonding.

(2) Polypropylene Hot Melt Adhesive

Polypropylene hot melt adhesive is a thermoplastic resin made from the polymerization of propylene, with amorphous polypropylene as the main component. It bonds well with low surface energy materials and is often mixed with low molecular weight polyethylene or crystalline polypropylene to improve curing speed and temperature resistance. It plays a significant role in paper packaging, carpet backing, and paper lamination, ensuring the quality and stability of products.

(3) EVA Hot Melt Adhesive

EVA hot melt adhesive is produced by high-pressure bulk polymerization or solution polymerization of ethylene and vinyl acetate. It boasts many excellent properties, such as superior adhesion, softness, heat flowability, cold resistance, chemical resistance, and weather resistance. It is widely used in bookbinding, woodworking, and the packaging industry, serving as a key material to ensure product quality and aesthetics.

(4) Polyester Hot Melt Adhesive

Polyester hot melt adhesive is prepared from saturated polyester. It not only has excellent electrical insulation properties but also offers high bonding strength. It performs well in impact resistance, water resistance, heat resistance, cold resistance, chemical resistance, and elasticity, and bonds well with a variety of materials. It is widely used in the apparel, electrical, footwear, and construction industries, meeting diverse needs across different fields.

(5) Polyamide Hot Melt Adhesive

Polyamide hot melt adhesive has repeating amide groups in its molecular main chain. It has excellent heat resistance, cold resistance, electrical properties, oil resistance, chemical resistance, and medium resistance. It is odorless, colorless, cures quickly, and bonds a variety of metals and non-metals. Even at high temperatures (149°C), it remains highly stable and is commonly used for bonding metal parts, ensuring product reliability in complex environments.

Key Performance Indicator - Temperature Resistance

Among the many properties of hot melt adhesives, temperature resistance is a key indicator that directly affects their performance in different environments. Temperature resistance is mainly reflected in two aspects: softening point and high-temperature strength.

Softening Point

The softening point is the temperature at which a substance begins to soften and is commonly measured using the ring-and-ball method. The specific procedure involves placing a steel ball of a certain mass on a metal ring filled with the sample. Under specified heating conditions, the temperature at which the steel ball contacts the underlying metal plate is recorded as the softening point of the hot melt adhesive, typically expressed in degrees Celsius (℃). Although the softening point can reflect the temperature resistance of hot melt adhesives to some extent, it is not equivalent to the maximum temperature that the adhesive can actually withstand and should not be the sole criterion for judging temperature resistance.

High-Temperature Strength

High-temperature strength measures the ability of hot melt adhesives to maintain bonding strength under high-temperature conditions. Different types of hot melt adhesives exhibit varying high-temperature strength, depending on their chemical composition and molecular structure. In practical applications, it is essential to consider both the softening point and high-temperature strength when selecting the appropriate hot melt adhesive product based on specific usage environments and requirements.

How to Choose the Right Hot Melt Adhesive

When faced with a wide array of hot melt adhesive products, how can you select the one that best suits your needs? Here are four key steps:

1. Clarify the Bonding Method: Determine the specific bonding method, such as potting, dispensing, or spraying, as well as the size of the bonding area. Different bonding methods have varying requirements for the adhesive's flowability and curing speed, which are the primary factors to consider when choosing a hot melt adhesive.

2. Understand the Bonding Materials: Identify the types of materials to be bonded, such as metals, plastics, wood, or fabrics. The surface characteristics and chemical properties of different materials can significantly affect the bonding performance of hot melt adhesives. For example, plastics can be categorized into high and low surface energy materials, with the latter requiring specially formulated adhesives. Additionally, consider whether the material surface needs pre-treatment, such as sanding, cleaning, or applying a primer, to enhance bonding strength.

3. Consider Process Requirements: Analyze the existing production process and its requirements for the bonding step, including whether the bonding needs to be completed within a specific time frame, if there are subsequent processing steps, and any limitations on curing and open times. Different hot melt adhesive products have varying curing speeds and open times, so it is crucial to select a product that matches the process requirements to ensure smooth production.

4. Determine End-Use Requirements: Clearly define the final application and environmental requirements of the hot melt adhesive. Consider whether the usage environment is indoors or outdoors, and if the product needs to withstand harsh conditions such as high and low temperatures, humidity, or chemical corrosion. Additionally, check for any special performance requirements, such as aging resistance, weather resistance, or flame retardancy. Only by fully understanding the end-use requirements can you select the most suitable hot melt adhesive product to ensure the performance and lifespan of the product.

Future Trends in the Hot Melt Adhesive Industry

With increasing policy support from the government, the hot melt adhesive industry is experiencing a favorable development environment and significant opportunities, driving rapid and healthy growth. Against the backdrop of industrial upgrading and growing environmental awareness, the development of hot melt adhesives suitable for high-speed automated production and safe, environmentally friendly applications has become a priority. Meanwhile, as technology continues to advance and market demand diversifies, the application scope of hot melt adhesives will further expand, and the demand for personalized and customized products will increase. In fields such as new infrastructure (5G), green packaging, electronics, construction and interior decoration, automotive, and new energy, hot melt adhesives will show a broader market prospect and become an important force in driving continuous innovation and development in the industry.

In this wave of industry development filled with opportunities and challenges, Jia Yuan, as a national high-tech enterprise specializing in the research and development and sales of hot melt adhesive coating equipment, is increasingly demonstrating its advantages. Jia Yuan's products have passed international certifications such as CE and SGS, which not only attest to the quality and technology of the products but also lay a solid foundation for entering the international market. Currently, Jia Yuan's products are exported to more than 80 countries and regions, including Europe, the Middle East, Southeast Asia, and Africa. With rich experience in hot melt adhesive applications, Jia Yuan can accurately grasp the diverse needs of different customers and provide comprehensive high-quality solutions, earning high praise from domestic and international customers.