This series of products is a thermoplastic adhesive formulated with a variety of imported high - quality ingredients. It is widely applied in the packaging and box - sealing of food, beverages, instant noodles, cigarettes, beer, pharmaceuticals, and other industries. Sichuan UNISN provides detailed explanations of the parameters of our carton - sealing adhesive products. This aims to assist you in saving time when selecting the most suitable solutions.

•   Exterior color:

Resin is the main component of hot melt adhesive. Different types of resin will affect the basic color of hot melt adhesive. For example, ethylene-vinyl acetate copolymer (EVA) resin is usually white or slightly yellow, and hot melt adhesive with EVA resin as the main component will generally appear white or light yellow. Polyamide resin is relatively dark in color, often brown or brown, and the hot melt adhesive made from it will also be darker in color.

  Smell:

Resin composition: The resin in hot melt adhesive is the main component, and different types of resins have different odors. For example, some synthetic resins release a slight pungent odor when heated and molten, which is due to physical or chemical changes in certain chemical groups in the resin molecular structure when heated.

•   Softening point (°C) (Ring and ball method):

The softening point of hot melt adhesive refers to the temperature at which the hot melt adhesive changes from a solid state to a semi-solid state with a certain fluidity under specified conditions. It is an important performance indicator of hot melt adhesive and has a significant impact on the use and performance of hot melt adhesive.

Significance in practical applications

Choose the appropriate use temperature: The softening point determines at what temperature the hot melt adhesive can be used. In practical applications, it is necessary to select appropriate heating equipment and heating temperature according to the softening point of the hot melt adhesive to ensure that the hot melt adhesive can achieve good fluidity and facilitate coating and bonding. If the use temperature is lower than the softening point, the hot melt adhesive may not be fully melted, resulting in poor bonding effect; if the use temperature is too high and exceeds the softening point too much, the hot melt adhesive may flow excessively, affecting the accuracy and quality of bonding, and may also cause the performance of the hot melt adhesive to deteriorate, such as accelerated aging and reduced viscosity.

Evaluate the heat resistance of hot melt adhesive: The softening point is an important indicator for measuring the heat resistance of hot melt adhesive. For some hot melt adhesives that need to be used in a higher temperature environment, such as hot melt adhesives used in automotive parts bonding, electronic equipment packaging and other fields, a higher softening point is required to ensure that they will not soften and deform due to heat during use, affecting the bonding effect and product quality. Generally speaking, the higher the softening point, the better the heat resistance of the hot melt adhesive, but other performance indicators, such as viscosity and flexibility, also need to be considered to comprehensively evaluate whether the hot melt adhesive is suitable for specific application scenarios.

•   Density (g/cm3):

The density of hot melt adhesive refers to the mass of hot melt adhesive per unit volume, usually in grams per cubic centimeter (g/cm³).

Different types of hot melt adhesives have different densities. Generally speaking, the density of EVA (ethylene-vinyl acetate copolymer) hot melt adhesive is around 0.92-0.96g/cm³; the density of polyamide hot melt adhesive is about 1.0-1.15g/cm³; the density of polyester hot melt adhesive is usually around 1.2-1.3g/cm³.

The significance of density in practical applications

Product design and quality control: In the product design stage, understanding the density of hot melt adhesive helps to calculate the required amount of hot melt adhesive, thereby accurately controlling costs. During the production process, the stability of product quality can be monitored by testing the density of hot melt adhesive. If the density is abnormal, it may mean that the quality of the raw materials has changed or there is a problem with the production process, which needs to be adjusted in time.

Performance evaluation: Density is also related to other properties of hot melt adhesive to a certain extent. For example, hot melt adhesive with higher density may perform better in hardness, strength, etc., but may have relatively poor flexibility; while hot melt adhesive with lower density may have better flexibility and elasticity, but may have slightly lower hardness and strength. Therefore, the density can be used to preliminarily evaluate some performance characteristics of hot melt adhesive and provide a reference for selecting suitable hot melt adhesive.

•   Opening hours:

The open time of hot melt adhesive refers to the time interval from the application of hot melt adhesive on the adherend to the loss of the ability to wet the adhered object due to solidification or crystallization.

Importance: The open time directly affects the bonding effect and application speed of hot melt adhesive. Only by completing the bonding operation within the open time can the hot melt adhesive have good bonding strength and achieve the ideal bonding effect.

Construction temperature: Increasing the melt temperature of the equipment can extend the open time, because the hot melt adhesive has better fluidity at high temperature and can maintain its bonding performance for a longer time, but the maximum temperature cannot exceed the construction temperature of the hot melt adhesive, otherwise it will cause adhesive damage.

Glue coating amount: The larger the glue output, the lower the specific surface area of the hot melt adhesive, the slower the cooling, and the longer the open time.

Environment and material temperature: The lower the ambient temperature and substrate temperature, the faster the hot melt adhesive cools, and the open time will be shortened accordingly.

When using hot melt adhesive in practice, it is necessary to select hot melt adhesive with appropriate opening time according to specific bonding requirements, working environment and construction process, pay close attention to changes in opening time, and complete the bonding operation within the specified time.

Significance in practical applications

Provide operation time: The open time provides operators with time to accurately align and position the parts to be bonded. For example, in book binding, workers need to neatly arrange the pages and fit them to the spine within the open time of the hot melt adhesive to ensure the quality of the binding. If the open time is too short, the workers will not have time to operate, which will affect the accuracy and firmness of the binding; if the open time is appropriate, the workers can complete the operation calmly, improving production efficiency and product quality.

Adapt to different production rhythms: Different production scenarios have different rhythms and speed requirements. Hot melt adhesives with longer open times are suitable for situations where the production process is more complicated and more time is required for component combination, such as the assembly of large furniture, where workers need time to adjust the position of each component. Hot melt adhesives with short open times are suitable for high-speed automated production lines. For example, in some food packaging production lines, the product flow speed is fast, and the hot melt adhesive needs to be quickly positioned. The short open time can meet the needs of fast bonding and ensure the continuity of production.

Influence on bonding effect: The open time has an important influence on the full contact and wetting of the hot melt adhesive with the surface of the adherend. During the open time, the hot melt adhesive can better spread on the surface of the adherend to form a good bonding interface. If the open time is too short, the hot melt adhesive cannot fully wet the surface of the adherend, resulting in a decrease in bonding strength; if the open time is too long, the hot melt adhesive may be oxidized or contaminated due to excessive exposure to the air, which will also affect the bonding effect. For example, in the bonding of automotive interior parts, the appropriate open time can ensure that the hot melt adhesive is in full contact with the surface of materials such as plastics and fabrics to form a strong bond.

•   Curing speed:

The curing speed refers to the rate at which the hot melt adhesive changes from liquid to solid after coating, thereby achieving bonding. 

The curing speed directly affects production efficiency and process flow in practical applications. Hot melt adhesives with fast curing speed can shorten the bonding cycle, and parts can be assembled quickly, thereby improving overall production efficiency. On the contrary, if the curing speed is too slow, it will lead to longer production time and increased costs, and problems such as glue overflow or component displacement may occur during the waiting process.

Significance in practical applications

The curing speed of hot melt adhesives has many important significances in practical applications, which are mainly reflected in the following aspects:

Improve production efficiency: Fast-curing hot melt adhesives can enable products on the production line to quickly enter the next process, reduce waiting time, and thus improve production efficiency. For example, in mobile phone assembly, using hot melt adhesives with fast curing speed to bond mobile phone shells and internal components can achieve rapid assembly and increase output per unit time.

Reducing production costs: Fast curing speed means shorter production cycles, higher equipment utilization, and reduced labor costs. Taking carton packaging as an example, fast-curing hot melt adhesive can quickly shape the carton after packaging, without waiting for a long time for the glue to dry, thereby reducing the manpower and material costs in the production process.

Ensure product quality: The appropriate curing speed can ensure that the hot melt adhesive can fully wet the surface of the substrate during the bonding process to form a good bonding effect. If the curing speed is too fast, the glue may not be fully spread, affecting the bonding strength; if the curing speed is too slow, the glue layer may flow and shift during the bonding process, which also affects the product quality. For example, in furniture manufacturing, choosing a hot melt adhesive with a moderate curing speed to bond wood can ensure that the glue layer is uniform and firm, and improve the quality and stability of the furniture.

Adapt to different production processes: Different production processes have different requirements for the curing speed of hot melt adhesive. For example, on an automated production line, hot melt adhesive is required to have a faster curing speed to meet the rhythm of high-speed production; in some manual operations, the curing speed can be relatively slow so that the operator has enough time to perform the bonding operation. Therefore, selecting a hot melt adhesive with an appropriate curing speed according to the characteristics of the production process can better adapt to production needs and improve production flexibility and controllability.