Glass fibre reinforced plastics (GFK) on an industrial scale are usually cured via a thermal process. UV-based consolidation of glass-fibre reinforced plastics as an inline production process is a quicker and more elegant solution.
Thanks to suitable resin formulations and the right radiant technology, panels, sleeves, or profiles can be cured and dried directly in the process in just a few minutes. IST Metz GmbH & Co. KG is receiving the ThinKing for March for this sustainable process option. UV curing is not only CO2-free, but is also a good choice in particular for series production thanks to faster lead times.
The Baden-Württemberg State Agency for Lightweight Technology will present the ThinKing for this innovation in March of 2022. Every month, Leichtbau BW GmbH promotes innovative lightweight technology products and services in Baden-Württemberg under this label.
At a glance:
“The chemical industry has made such great progress in formulating UV curing resins that we are now able to offer UV curing in series production of fibre-reinforced plastic parts as an inline process step as well” says Arnd Riekenbrauck, Senior Manager of New Markets at IST Metz GmbH & Co. KG.
To manufacture components or semi-finished products out of glass-fibre reinforced plastics, the (glass) fibres saturated with resin are first formed as desired – as a core for panels, wound for sleeves, or pultruded for profiles. Then the energy is activated to interlink, cure, and dry the impregnated fibre-resin system. In the past, long, heated process lines were required to do so for panels or profiles, or furnaces or drying chambers for wound parts. Previously, this process step in lightweight component manufacturing was plagued by large systems, high energy consumption and time requirements, as well as added transportation and handling tasks.
Quick and elegant inline curing
This could all change abruptly, thanks to the use of the UV process, as glass fibres are ideal for UV curing, thanks to their radiolucency. Consolidating the fibre-matrix systems with UV or UVVis radiation sources takes from a few seconds to a few minutes. The component is ready to handle loads directly after being interlinked and cooled, and can be processed further. “In one application, we were able to shorten a production line by over 80 percent” reports Arnd Riekenbrauck. In another case, all that was needed to consolidate a 50 cm long glass-fibre reinforced sleeve, manufactured using a filament winding process, was one minute of UV radiation. Due to these short throughput times, the UV curing process is idea for series and continuous processes. The process is also a good choice for very large components.
Because of this, ideal applications range across almost all industries, and include inline, continuous processes like pultrusion or manufacturing flat materials, as well as RTM processes or BMC/SMC processes.
Energy-saving, styrene and CO2-free
In contrast to a continuously heated furnace or heated line, the UV radiation sources only need energy when they are being used for consolidation. Therefore, energy costs can be translated directly to costs per piece. In addition, they can be operated with green electricity, producing no CO2 emissions. Across all applications, UV curing takes, on average, only around 30 percent of the energy required by thermal processes. In the example of the wound sleeve above, the required energy was only about 0.25 kW per workpiece.
The single-component, epoxy acrylate resin system suitable for UV curing theoretically has an unlimited pot life. Depending on the application, therefore, the cleaning required can be reduced, and mixing eliminated. Less waste is produced in production. In addition, the resins use no styrene or other solvents. Their mechanical parameters, in contrast, are at least comparable with past resin systems after consolidation.
Quality borne from process experience
Although UV consolidation seems simple, designing the inline process step requires experience, as it must be individually adapted to the specific product. Arnd Riekenbrauck explains: “Our application and process expertise covers not only the lights, but also the relevant cooling concept and any explosion protection measures required, due to the high temperatures. The system design of the lamp installation itself over the entire width of the process line strongly influences the reproducible quality of interlinking, curing, and drying”.
In addition to the temperature and homogeneous irradiation, the relevant wave lengths must be tailored to the fibre material, the component, and the process step: from long-wave UVVis radiation for thicker materials to short-wave UV-C radiation for simple surface curing of finishing layers on glass-fibre reinforced components. Simultaneous irradiation from the top and bottom may also be necessary, for example for sandwich materials or if the translucency of the fibres negatively impacts the penetration depth of the radiation.
About IST Metz GmbH & Co. KG:
IST Metz is an international, mid-sized mechanical engineering company headquartered in the southern German city of Nürtingen, with around 550 employees worldwide. The company has been producing systems for curing printings and coatings with UV light for over 40 years. The UV systems cure dyes, paints, silicones, adhesives, resins, and other materials in just fractions of a second. The IST Metz corporate group offers its customers the world’s largest portfolio of high-performing UV lights and UV LED systems. Their product range also includes hot air infrared drying systems and Excimer technology.