Rotational Molding Of Automobile Structures

Financial, technological and legislative factors are compelling automobile manufacturers to adopt light-weight design practices. Rotational molding can aid them in this endeavor by offering a cost effective alternative to the traditional manufacturing of composite automobile structures.As a process rotational molding is characterized by lower residual stresses in parts, simpler machinery and molds, and the ability to produce single or double walled components with complex geometries and varied sizes. The process, however, is limited by a number of factors that include: difficulties in process control, a narrow range of applicable polymers, long cycle times, poor surface finish and low mechanical properties of its moldings. The application of reactive liquid polymers can offset some of these concerns due to the fact that these systems require shorter heating durations with little cooling and possess a wider selection of applicable materials. They also possess low initial viscosities which improve mold surface reproducibility and allow the use of reinforcements. In this work a novel molding scheme that adds pre-determined volumes of material at various intervals without interrupting mold rotation was developed. The scheme, appropriately named Continuously Multi-shot, was used to investigate the noldability of two reactive liquid polymer resins: Polycaprolactam and Unsaturated Polyester Resin. Surface quality on both the inner and outer surfaces of the moldings was analyzed and the processing parameters that resulted in suitable surfaces were determined.Further, composites were prepared using these two systems and the mechanical properties obtained were applied in the simulation of a specially designed composite automobile tub. The results from this research, both theoretical and experimental, show the potential of rotational molding in the production of automobile structural components. Also, the Continuously Multi-shot scheme developed in this study possesses far reaching applications in the rotational molding field in general. Its efficacy in the production of superior quality moldings is displayed in the results of this study.