Лако-красочные материалы — производство

Single-part adhesives will usually offer benefits (from a dispensing viewpoint) over two-part adhesives as no mixing or dual application is necessary.

Most epoxies are supplied as two-part adhesives and typically these would be supplied in twin cartridges or syringes and then mixed in a helix nozzle (Figure 8.1).

In some industries, particularly where only small quantities are required, the epoxy adhesive can be pre-mixed in a small container and then decanted into a syringe where it can be dispensed via a syringe system (see Section 8.3). The risk here is that the viscosity of the epoxy will gradually increase as the adhesive begins to cure in the syringe thus making it more difficult to control the quantity dispensed.

Some two-part adhesives can be dispensed as a liquid activator (accelerator) and an adhesive. In this case, the activator is applied to one surface and the adhesive to the other and cure will commence when the joint is closed.

In other two-part acrylic applications, the adhesive is applied as ‘bead-on-bead’ and so a mixer nozzle is not necessary. This bead-on-bead method is not normally suitable for epoxies as the mix ratio of epoxies is quite critical and thorough mixing cannot always be guaranteed with a bead-on-bead process. Two-part acrylics, however, are far more tolerant of mix ratio and so bead-on-bead systems can work well in a high­speed production environment, although care is required to ensure that the nozzle tips do not become contaminated.

Single part adhesives will nearly always be the most convenient to dispense, especially for the bonding of small component parts.