Premium
Principles of rotational molding
Author(s) -
Rao M. Anandha,
Throne James L.
Publication year - 1972
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760120402
Subject(s) - materials science , mold , composite material , molding (decorative) , wetting , sintering , polystyrene , polymer , flow (mathematics) , melting point , thermal , compression molding , rotational speed , capillary action , mechanical engineering , mechanics , thermodynamics , physics , engineering
Rotational molding is a process by which powdered or liquid plastics are converted into hollow articles. This paper is devoted to the theoretical understanding of the process of rotational molding. There are seven sections: The Art , wherein we describe the process, discuss previous attempts at understanding the process, and mention processes that are similar in principle to rotational molding. Transient Heating of Mold Surface , wherein we show that the criterion for selection of mold materials is the ratio of the thermal diffusivity to the thermal conductivity, and present the heating curve for a mold in a rotational mold machine. Melting of Plastic Powder in a Rotating System , wherein we discuss in detail those physical powder characteristics that are necessary for good flow within the mold cavity. Fluid Flow During Rotational Molding , wherein we discuss the velocity profiles within the melt film, point out that there is very little bulk polymer flow possible within the mold cavity under normal processing conditions, and consider capillary flow forces and surface wetting. Sinter ‐ Melting , wherein we compare the Kuczynski‐Neuville empirical sintering model with the Lontz viscoelastic model, conclude that the latter is correct for the sintering of materials such as ABS, and apply the Frenkel glass densification theory to the prediction of void disappearance in sinter‐melt polymers. Degradation , wherein we compare our experimental tensile strengths of polystyrene, obtained at varying oven cycle times and oven set point temperatures, with values obtained from degradation models given in the literature. Laboratory Simulation of Rotational Molding , wherein we propose two series of experiments, the first series being carried out without using rotational molding equipment, and the second using rotational molding equipment with molds having relatively simple geometries.