Open Time

Open time refers to the maximum duration that the mixed resin and curing agent, after being applied to a substrate, can be left before the substrates are bonded together. Generally, if the final tensile strength after bonding after a certain period of glue application still retains 80% of the strength obtained by bonding immediately after glue application, this period can be deduced as the open time.

• (1) After the resin and curing agent are mixed, the viscosity changes and continuously increases, which affects the glue application operation and the bonding effect.
• (2) The open time is also affected by temperature.

The biggest difference between the two lies in that pot life considers the time before the adhesive is applied to the substrate, while open time considers the time after it is applied to the substrate.

Skin-over Time

Skin-over time usually refers to the time required for a single-component moisture-curing adhesive when a small PE sheet (approximately 2cm x 5cm) is placed on the surface of the adhesive and removed without residual adhesive on the surface. The adhesive itself remains sticky but does not leave a trace on the PE sheet. It is also called "skin formation time" or "tack-free time".

• (1) The skin-over time is affected by temperature and humidity.
• (2) For single-component moisture-curing adhesives, the skin-over time is usually the pot life.