Flocking process

The flocking method covers applying short monofilament fibers, normally nylon, rayon or polyester right away on a substrate that has been formerly layered with an adhesive. So, by flock we mean short-cut textile fibers. For making flocking on textiles, generally we apply flock lengths of 0.5 or 1.0 mm of viscose or polyamide (Nylon). The most used sizes for polyamide are 3.3 dtex/0.5 mm and 6.7dtex/1.0 mm, and for viscose 3.3 dtex/0.5 mm and 5.6 dtx/1.0 mm. An enormously soft touch is achieved with 3.3 dtex/1.0 mm, but this flock is not effective as wear-resistant as the other sizes as described above. Furthermore, flocking with this flock occasionally makes troubles for the strength of the fiber in proportion to its length, is obviously low-grade and may decrease the flock's siftability. The value dtex points out the weight in grams of one individual fiber being 10 km long. So 3.3 dtex means that one fiber, 10 km long, has a weight of 3.3 g. Both types of fibers are presented with light-fast, washable and considered against bleeding. The washing capability of polyamide is superior to that of viscose, since polyamide absorbs a maximum of 6 percent humidity against 13 percent in viscose.

Because of the humidity, the fiber swells up faintly which of course decreases its tight embedding in the glue. For the flocking of door mats a longer and harder flock Nylon 22 dtex/2.0 mm is used. In the production of carpets the same type of flock is used. This thicker fiber has very hard-wearing and extremely abrasion resistant properties.

Adhesives

Adhesives create most favorable effect on the quality of flocking. They make the link between the flock and the substrate. They are preferred to be soft, flexible and wash-proof. Today acrylate based dispersions are significantly applied for special application, like waterproof jackets or other coated fabrics; solutions can be applied as well.
Dispersion glues are distinguished between low and high temperature curing glues. At room temperature curing within two to five days, the low temperature glue dries. This denotes, after this time has passed the garment can be washed. A fixing agent has to be applied for curing. It is critical to understand the producer's instructions concerning the mixing ratio and blend the fixing agent homogeneously into the glue.

With a temperature between 120 and 140 degree Celsius, high temperature curing glue needs 5 - 10 minutes fixing time. It has to be stressed that drying and curing is achieved in to two stages. In the first stage the glue has to get dry, i.e., the water included in the glue has to evaporate. During this time, by virtue of physical law, the temperature does not go over 100 degrees Celsius. Then only 120 or 140 degree Celsius is achieved.

The drying process is provided by concentrated air circulation with combination of fresh air. If a drying oven performs only with circulating air then the air humidity will be raised to its peak limit without any further drying outcome, here the air cannot absorb further humidity. Hence, healthy air circulation with an appropriate share of fresh air has to be obtainable. Dispersion glues are eco-friendly, the stencils and utensils are washed out with water. In case of water-resistant surfaces solutions should be applied, normally a polyurethane-based two-component system is used. Fastnesses are superior, just like those achieved with dispersions.

Printing Screens

The adhesive is used by screen printing. Normally, we apply a screen mesh prepared by polyester as it absorbs only less water and does not covered by the dispersion glue and in cleaning. Screen meshes of 24 T to 40 T are applied (standing for 24 to 40 threads per cm) as the adhesive layer is comparatively thick. In against ordinary screen printing these meshes are proved to be relatively rough, but the glues are paste like up to thixotropic, and an enough amount has to be used on the substrates. It is essential that the contours or lines are not extremely fine. The rough mesh would make saw tooth appearance, and, as not sufficient glue could be used, the flock would not restrain very well. Lines and dots in the design are kept at a minimum width of 1.5 mm. The needed quantity of adhesive is not only decided by the screen mesh, but also by the toughness and shape of the squeegees. Soft squeegees (60 to 70shore) with a rounded edge and a square edge have showed to be most excellent. The squeegee should extend beyond the design by at least 20 to 30 mm.