Control of polymer properties by melt vibration technology: A review

This paper reviews the technology of melt vibration (more specifically at low frequency) to reduce viscosity during processing of plastics and to enhance mechanical performance of the solidified parts. The effect of vibration frequency and amplitude on melt viscosity is explained in terms of shear-thinning criteria. The effect of pressure and temperature on shear thinning is also reviewed to predict how these variables interfere with melt vibration. Practical applications of the principles of melt vibration are provided in injection molding, extrusion and compression molding/thermoforming, from reduction of viscosity to lowering processing temperature and pressure to the elimination of melt defects and weld lines, to the enhancement of mechanical properties, stiffness and strength, by modification of the amorphous and semicrystalline texture and orientational state. Commercially available equipments are reviewed. Results showing the effect of melt vibration during processing for two classical polymers, polystyrene and polypropylene, are discussed. The paper concludes on the remaining challenges to bring the benefits of the new technology to full commercialization.

[1]  L. Utracki.  Temperature and pressure dependence of liquid viscosity , 1983 .

[2]  D. G. Legrand,et al.  Crazing, yielding, and fracture of polymers. I. Ductile brittle transition in polycarbonate , 1969 .

[3]  D. Bogue,et al.  Pressure effects in polymer melt rheology , 1990 .

[4]  L. Piché,et al.  Ultrasonic characterization of polymer viscoelasticity. Application to polystyrene , 1989 .

[5]  W. Cox,et al.  Correlation of dynamic and steady flow viscosities , 1958 .

[6]  L. Utracki.  Correlation Between PVT Behavior and the Zero‐Shear Viscosity of Liquid Mixtures , 1986 .

[7]  A. J. Giacomin,et al.  The Transition to Quasi-Periodicity for Molten Plastics in Large Amplitude Oscillatory Shear , 1994 .

[8]  J. Clermont,et al.  The oscillating die: A useful concept in polymer extrusion , 1990 .

[9]  D. Binding,et al.  Complex flow of viscoelastic fluids through oscillating pipes. Interesting effects and applications , 1979 .

[10]  J. Ibar.  Rheomolding: A New Process to Mold Polymeric Materials , 1981 .

[11]  L. Utracki.  A method of computation of the pressure effect on melt viscosity , 1985 .

[12]  C. H. Chen,et al.  Flow of thermoplastics in an annular die under parallel oscillations , 1990 .

[13]  A. Faghri,et al.  Experimental and Numerical Study of Microwave Thawing Heat Transfer for Food Materials , 1994 .

[14]  K. Pae,et al.  The Effects of Hydrostatic Pressure on the Compressibility, Crystallization, and Melting of Polymers , 1975 .

[15]  O. Manero,et al.  Further developments on non-Newtonian flow in oscillating pipes , 1978 .

[16]  S. Onogi,et al.  Rheological properties of polymethyl methacrylate and polyvinyl acetate in the molten state , 1968 .

[17]  H. H. Chiang,et al.  Shear‐rate‐dependence modeling of polymer melt viscosity , 1992 .

[18]  C. A. Hieber,et al.  A unified simulation of the filling and postfilling stages in injection molding. Part I: Formulation , 1991 .

[19]  B. Mena,et al.  Heat transfer in non-Newtonian flow through pipes , 1978 .

[20]  L. Utracki.  Pressure dependence of newtonian viscosity , 1983 .

[21]  O. Manero,et al.  An interesting effect in non-newtonian flow in oscillating pipes , 1977 .

[22]  B. Brulé,et al.  ON THE PRESSURE DEPENDENCY OF THE VISCOSITY OF MOLTEN POLYMERS , 1994 .

[23]  J. Economy,et al.  Super strong polymers in planar directions , 1983 .