Vacuum Forming Adhesive And Curing Agent Mixing Ratio Requirements

The adhesive used for vacuum forming film is vacuum forming adhesive, which is mainly water-based polyurethane glue mixed with other resins. Hot melt adhesives and solvent-based adhesives can also be used in principle, but water-based adhesives are non-toxic, odorless, moderately priced, and suitable for mechanized operations. The biggest advantage of this process is that it eliminates the need for painting or coating, making it a paint-free process. Furthermore, it can cover grooves, curved edges, and hollowed-out engravings, which is unmatched by other processes.

Vacuum forming uses spray coating, therefore the adhesive must have moderate viscosity, be adaptable to changes in weather (winter and summer), and be able to achieve atomization. In addition, the vacuum forming adhesive must have the following characteristics:

(1) Good flowability, resulting in a clean, pitted surface after vacuum forming.

(2) High solids content and fast drying.

(3) Good initial tack, especially important in grooves and edges.

(4) Good heat aging resistance; at least at 60℃, after 24 hours of baking, the film should not curl, shrink, or bubble.

(5) Low activation temperature; water-based polyurethane adhesives require an activation temperature within the range of 55-65℃. Too high a temperature can cause PVC film to perforate.

Vacuum forming adhesives are typically environmentally friendly water-based polyurethane (PU) adhesives, mainly used in conjunction with isocyanate-based curing agents to firmly bond PVC decorative films to substrates such as MDF or particleboard.

Core Characteristics and Formulation

• Composition: The main component is a water-based polyurethane emulsion; the curing agent is used as a crosslinking agent.

• Mixing ratio: Generally, the weight ratio of the main agent to the curing agent is about 20:1 (that is, the amount of curing agent accounts for 3% to 5%).

• Applicable scenarios: When the heat resistance requirement of the finished product exceeds 70℃, or when the temperature and humidity in the production workshop are too high, a curing agent must be added to improve the heat resistance and water resistance.

Precautions for use

• Accurate weighing: The main agent and curing agent must be weighed accurately using an electronic scale in strict proportion.

• Stir thoroughly: While stirring the main agent, slowly add the curing agent and stir continuously for more than 3 minutes to ensure complete dispersion.

• Shelf life limitation: The mixed adhesive should generally be used within 4 hours. After that time, the cross-linking will fail and it cannot be used anymore.