Лако-красочные материалы — производство

When it necessary to create a safe and removable assembly, reclosable fasteners (dual­lock fasteners or ‘hook-and-loop’ fasteners) offer outstanding advantages and an almost unlimited variety of applications. In the wall and roof panels of trains, trams and buses, reclosable high-performance fasteners replace screws, thereby avoiding corrosion owing to a lack of holes, and allowing access for maintenance purposes in a matter of seconds.

The interlocking of the stems of dual-lock fasteners is signaled by a distinct noise. The tensile strength of these fasteners is sufficiently high so as to replace nonesthetic mechanical fasteners in many applications. In terms of reliability, dual-lock fasteners can easily be opened and closed many thousands of times (Figure 8.53). These systems are not only reclosable, but also have excellent tensile strength, damping characteristics with regard to noise and vibrations, and resistance to both solvents and temperatures ranging from —30 °C to +95 °C.

Hook-and-loop fasteners are ideal for products that require thousands of easy openings and closings; often, they are used to hold in place the cushions of motorcycle, bicycle or safety helmets. In operation, the tiny, stiff hooks mesh with the soft, pliable loops following the application of slight pressure to provide a quick fastening. Moreover, their production is both quick and cheap.

8.6.1.9 Screen-Printable Adhesives

Screen-printable adhesives can be positioned, but only where they are needed. The new systems rapidly cure with UV light, without harming the surfaces involved. As these products can be applied locally and with high precision, they will in time replace the fastening systems that use double liner tapes (that used pre-cut films) in the production of switches, instruments or light-emitting diodes.

New systems are exclusively derived from liquid acrylates, with up to 40% higher yield and greater flexibility than conventional, dispersion-based, screen-printed adhesives. As they contain neither solvents nor water, the printing results are excellent, providing for sharp edges. In addition, even during breaks in production the screen does not suffer clogging, and there is no need for intermediate cleaning or replacement. Consequently, material savings of up to 30% can be achieved simply by using up the adhesive after breaks. However, although the very rapid UV curing saves production time, the precutting offilms leads to the production oflarge quantities of waste compared to die-cut production (up to 80% more).

Screen-printable adhesives are available which have thicknesses after printing and curing that range from 0.025 to 0.075 mm, and a resistance to temperatures between -40 °C and +80 °C.

8.6.2