Through the development of its new polyurethane (PUR) matrix resin, Loctite MAX 3, Henkel (Dusseldorf, Germany) says it has taken a further important step toward fully automated series production of composite components for the automotive industry. In collaboration with KraussMaffei, the company has developed a process for the manufacture of components based on glass or carbon fiber and using high-pressure resin transfer molding (HP-RTM) technology that creates a surface quality good enough for automobile exteriors. Using a model of the light, high-strength carbon fiber roof segment of the Roding Roadster R1, the production process was presented at K 2013
While composite materials based on carbon or glass fibers combine lightness in weight with high strength, thus offering outstanding properties in relation to safety and crash behavior, until now there have been certain limitations in the use of lightweight components. They are restricted in the degree to which they can meet the requirements of the automotive industry with respect to cycle times and level of automation. In particular, composites have been very rarely used for the external components of production vehicles, as the requisite post-treatment of the surface for subsequent painting has been too time-consuming and had to be performed manually.
The roof segment of the Roding Roadster R1 is manufactured using an RTM process and a polyurethane-based carbon fiber composite.
With the support of Henkel, KraussMaffei has now succeeded in producing composite components in a fully automated process, that reportedly exhibit a surface quality suitable for immediate painting. This has become possible thanks to the development of Loctite MAX 3, a three-component polyurethane-based matrix resin system from Henkel that contains not only the resin and hardener but also a high-performance release agent. Henkel is - together with the companies Dieffenbacher, Zoltek, Chomarat, Rühl Puromer, Alpex, Mühlmeier and Roding Automotive - part of KraussMaffei's network to create mature production chain extending from the fibers and matrix materials through to the finished component.
This polyurethane-based matrix resin technology from Henkel is characterized by significantly faster curing compared to the epoxy resins usually used for the RTM process. Due to its low viscosity, the resin penetrates the fiber material more easily and with less disruption, giving rise to shorter injection times and thus short cycle times in series production.
The high toughness of Loctite MAX 3 also reportedly facilitates achievement of an optimized component structure. Henkel has likewise improved the temperature resistance of the PUR resin, taking Loctite MAX 3 to a level comparable with that of epoxy resins. This high temperature resistance means that the fiber-reinforced composites can be demolded more quickly.
Further, with the internal release agent ensuring easy detachment of the component from its mold, the resultant surface is of sufficiently high quality to allow immediate painting and bonding. This accelerates the production process and enables manufacture of external and visible components of outstanding surface quality.
"With Loctite MAX 3, we now have a matrix resin system that further increases the feasibility and attractiveness of manufacturing automotive parts from composite materials," says Frank Deutschländer, Global Market Manager Automotive at Henkel. "Working closely with KraussMaffei, we have optimized the properties of our resin so that both painted coatings and adhesives can be applied to the resultant composite surface without the need for any pretreatment." With the adhesives portfolio from Henkel, this gives rise to a complete system solution enabling the manufacture and integration of composite components in automobiles.