Лако-красочные материалы — производство

One-part and two-part structural adhesives are solvent-free and cured under the effect of heat (one-part adhesives) or at room temperature (two-part adhesives). The curing process oftwo-part adhesives can be accelerated by heat (e. g. a temperature of 65 ° C for 120 min). Structural bond strength can be achieved with versatile high-performance epoxy resin, polyurethane and acrylate adhesives that have been designed for the bonding of metals (e. g. steel, aluminum, copper, brass) and plastics (e. g. polycarbo­nates, PVC, acryl-butadiene-styrene (ABS), polymethyl methacrylate), as well as glass, ceramics and wood. The manufacturer tailors the flexibility of the adhesives to the desired application, ranging from hard to rubber-like and flexible.

In the world of plastics, PE and PP are versatile materials. However, a major challenge is encountered when attempts are made to bond them to each other, or to other materials. In both industry and handicraft trades, PE and PP are used on a large scale (as commodity plastics), although until recently structural adhesive bonding was only possible following elaborate surface preparation.

Whilst these thermoplastics can indeed be welded to each other, due to their low — surface energies the structural bonding requires previous chemical or physical surface preparation, such as corona or plasma pretreatment. Thus, mechanical solutions were always the first choice in industry when a simple method was sought to join these materials.

Recently new rubber-like, two-part structural acrylic adhesives have made it possible to create an easy, quick — and, above all, high-strength — bonding between materials such as PE or PP, without the need for any surface preparation. This new generation of adhesives is also suitable for bondings that involve thermoplastic elastomers (TPE).

As soon as both parts of the adhesive are mixed, a chemical reaction starts on the wetted surface that provides for an adhesion-friendly surface condition with a higher energetic state. The newly created surfaces can also easily be bonded to other materials, as the pot-life is approximately 2.5-3 min and the joined materials can be processed further at only 30-60 min after adhesive application. These new

adhesive systems are solvent-free and cure at room temperature, with the final adhesive strength taking place within 8 to 24 h at room temperature, or within 30 min when heated to 70-75 ° C. The structural bond strength of the joint is comparable to the inherent strength of the low-energy materials (PE and PP).

Structural adhesives are either manually or automatically applied by means of knife coating, extrusion or injection. Special equipment allows the two-part adhesives to be processed in an economical, rapid, clean and accurate manner (Figure 8.48), for example with hand-held applicators and air-spray guns with double-chamber car­tridges and static mixer nozzles. The adhesive is applied as dots or beads, with its metering, mixing and application being performed in a single step.