Long Fiber Injection of Polyurethanes 970147

Due to their excellent mechanical properties, glass fiber reinforced plastics are currently used in many applications. In polyurethanes, these fiber reinforced parts have been traditionally manufactured by RRIM, glass fiber mixed into the polyol, and by SRIM, glass mat placed in the tool and polyurethane is then poured or injected onto the mat. These processes are plagued with several manufacturing steps that are undesirable; such as handling glass fiber, trimming glass mat prior to molding, punching and trimming large holes in the finished part which wastes materials and time, manual handling of the mats or mold parts several times in the process, etc.
Prompted by industry's wish to produce these articles more efficiently and cost-effectively, and to be able to employ long fibers Krauss-Maffei developed the Long Fiber Injection Process, named LFI. This revolutionary process introduces long fibers directly at the mixhead.
This paper has been prepared to present the state of development and testing of the process since it's introduction in 1995. The paper will provide a detail of the typical pieces of equipment required for the LFI-PUR plant as envisioned by Krauss-Maffei. It will describe the LFI process unit and it's flexibility in production of molded parts with varied levels of reinforcement. It will compare the processing advantages of LFI over traditional RRIM and SRIM. The paper will also offer suggested areas of application for the process.


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