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Gas-assisted compression moulding of glass reinforced polypropylene

By Ian Brzeski


A new process of combining gas injection with compression moulding was developed\ud and studied in this research work. The process is called Gas Assisted Compression\ud Moulding (or GasComp). The principle is based on the injection of nitrogen gas\ud during a conventional compression moulding cycle. The flow of the material due to\ud the compressive force of the press is assisted by the injection of gas into the centre\ud of the molten material. The gas assists in the flow by coring out the material,\ud reducing the weight by up to 45 percent and increasing the dimensional stability of\ud the component.\ud Novel glass matt thermoplastic mould tools were designed and developed during the\ud course of the research program for use with the process. These designs were of a\ud flash compression mould tool design with a horizontal clamping face, rather than the\ud conventional positive plug compression mould tool with a vertical shear edge. This\ud created a fixed volume mould tool, which when used in conjunction with a short shot\ud of material, would allow the gas to flow the material to fill the remaining volume.\ud Several materials were investigated for their suitability with the process. Their\ud characterisation showed that they contained different glass fibre contents and\ud architectures. A material with a short, dispersed glass fibre content of 11 percent\ud proved to consistently contain a significant gas cavity. The glass architecture proved\ud to be the most significant contributing factor in the creation of a successful gas cavity.\ud The most significant processing parameter in the creation of a large volume cavity\ud proved to be the gas injection delay time. The gas pressure and gas ramp time\ud affected the cavity shape, length and extent of gas fingering.\ud The shrinkage was reduced in the presence of a gas cavity, along with the visible\ud reduction of sink marks. The presence of other moulding features, such as hesitation\ud marks, gas packing and the change in fibre orientation were also discussed

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  7. Compression Molding Tooling for Thermoplastic Composites, doi
  8. (2003). Compression Molding. doi
  9. (1999). Compression moulding of glass and polypropylene composites for optimised macro- and micro-mechanical properties II. Glassmat-reinforced thermoplastics. doi
  10. (2002). Correction of the measurement of fiber length of short fiber reinforced thermoplastics. Composites Part A: Applied Science and Manufacturing, doi
  11. (2002). Cryogenic gas-assisted injection moulding, in School Of Engineering. doi
  12. (2000). Determination of the rheological properties of thermoplastic composites for compression flow molding. Polymer Composites, doi
  13. (1995). Development of moldability diagrams for gasassisted injection molding. doi
  14. (2000). Directive 2000/53/EC of the European Parliament and of the doi
  15. (2006). Effect of filler treatments on rheological behavior of calcium carbonate and talc-filled polypropylene hybrid composites. doi
  16. (1991). Effect of processing and particulate fillers on the rheology of a nematic polymer melt. Rheologica Acta, doi
  17. Effects of residual fiber length on the mechanical properties of long fiber reinforced polypropylene from various processes.
  18. (2007). Eigenfunction expansions with continuous spectrum, hydrogen atom, and Van der Waals
  19. (1990). Elementary fluid dynamics. Oxford applied mathematics and computing science series. doi
  20. (1984). Elongational behavior of short glass fiber reinforced polypropylene melts. Polymer Composites, doi
  21. (1996). Energy Recovery from Plastic Wastes in Waste Incineration Plants. Recycling and recovery of plastics,
  22. (2008). Essentials of polymer science and engineering
  23. (1995). Experimental evaluation and numerical simulation of fibre orientation during compression moulding of GMT.
  24. (2002). Experimental study of gas penetration in gasassisted injection molding.
  25. (2000). Extensional processing behavior of thermoplastics reinforced with a melt processable glass. Polymer Composites, doi
  26. (2002). Feature Article: Water Injection Molding Makes Hollow Parts Faster,
  27. (2008). Fiber-reinforced composites : materials, manufacturing, and design doi
  28. (1989). Fibre degradation during processing of short fibre reinforced thermoplastics. Composites, doi
  29. (2005). Filler use to grow. Plastics, Additives and Compounding, doi
  30. (2003). Filling simulation and gas penetration modeling for gasassisted injection molding. Applied Mathematical Modelling, doi
  31. (1986). Finite element simulation of fountain flow in injection molding. doi
  32. (2000). Flow induced fiber orientation in compression molded glass mat thermoplastics. Polymer Composites, doi
  33. (2001). Forming and Shaping Plastics and Composite Materials,
  34. (2006). Free Surface Instability and Gas Entrainment during Blast Furnace Drainage. doi
  35. (1997). Gas-Assisted Injection Molding of Glass Fiber Reinforced Thermoplastics,
  36. (2002). Gas-assisted injection molding: The effects of process variables and gas channel geometry. doi
  37. (1995). Glass mat reinforced polypropylene, in Polypropylene: Structure, doi
  38. (1994). Handbook of polymer-fibre composites. Polymer science and technology series. doi
  39. (1984). III, Orientation Behavior of Fibers in Concentrated Suspensions. doi
  40. (2008). Improved aerodynamics and weight-saving for BMW M3 with SymaLITE® underbody shields from Quadrant Plastics Composites.
  41. (1991). Injection molding of long fiber-reinforced thermoplastics: A comparison of extruded and pultruded materials with direct addition of roving strands. doi
  42. (1986). Injection molding: The effect of fill time on properties. doi
  43. (1996). Innovation in polymer processing : molding.
  44. (2001). Interfacial instabilities : implications for multi-material
  45. (1966). Introduction to polymer crystallization. doi
  46. (2008). LFT - development status and perspectives. Reinforced Plastics, doi
  47. (1995). Manufacturing methods for long fibre reinforced polypropylene sheets and laminates, in Polypropylene: Structure, doi
  48. (2008). Market Study: Polypropylene doi
  49. Mechanical properties of short -and long-glass-fibrereinforced polypropylene compounds,
  50. (2008). MEPS - World carbon steel prices - with individual product forecasts ($US/tonne).
  51. (1978). Method for injection molding of hollow shaped bodies from thermoplastic resins,
  52. Multilayer plug flow modeling of the fast stamping process for a polypropylene/glass fiber composite. Polymer Composites, doi
  53. New developments in co-rotating twin-screw extrusion for production of long glass fiber composites,
  54. (1997). Novel composites by hot compaction of fibers. doi
  55. (1995). Particulate filled polypropylene: structure and properties, doi
  56. (1989). Plastics moulding containing reinforced fillings,
  57. (1994). Plastics processing technology /
  58. (2006). Plastics Recycling. doi
  59. Plastics technology handbook, in Plastics engineering 72. 2006, Taylor & Francis Group: Boca doi
  60. (2001). Polymers: Structure, General Properties, and Applications,
  61. (1996). Preparation of Feedstock for Petrochemical Recycling -Requirements Imposed on Plastic Waste, in Recycling and recovery of plastics
  62. (2008). Primary Aluminium
  63. (1989). Process and apparatus for manufacturing a component moulded from reinforced plastic,
  64. (2003). Process for gas assisted and water assisted injection molding. doi
  65. (1995). Processing and properties of reinforced polypropylenes, doi
  66. (2008). Processing, in Essentials of polymer science and engineering.
  67. (1996). Pyrolytic Processes for Recycling Plastics, in Recycling and recovery of plastics doi
  68. (1992). Random glass mat reinforced thermoplastic composites. Part V: Statistical characterization of the tensile modulus. Polymer Composites, doi
  69. (2007). Rapid Temperature Cycling, in Plastic Engineering.
  70. (1996). Recycling and recovery of plastics doi
  71. (2007). Reinforced Thermoplastics: LFRT/GMT Roundup. Composite Technologies,
  72. (2005). Rheological properties of long glass fiber filled polypropylene. doi
  73. (1999). Rheology of polypropylene, in Polypropylene : an A-Z reference, doi
  74. (1995). Rheology of short fiber filled thermoplastics. Polymer Composites, doi
  75. (1980). Rheology of short glass fiber-reinforced thermoplastics and its application to injection molding. II. The effect of material parameters. doi
  76. (1980). Rheology of short glass fiberreinforced thermoplastics and its application to injection molding I. Fiber motion and viscosity measurement. doi
  77. (1981). Rheology of short glass fiberreinforced thermoplastics and its application to injection molding. III. Use of a high shear rate capillary rheometer in the injection molding shear rate range. doi
  78. (1985). Rheology of Suspensions in Polymeric Liquids. doi
  79. (1989). Short fiber reinforced thermoplastics. I. Rheological properties of glass fiber reinforced Noryl. Polymer Composites, doi
  80. (1989). Short fiber reinforced thermoplastics. II. Interrelation between fiber orientation and rheological properties of glass fiber-reinforced Noryl. Polymer Composites, doi
  81. Short-fiber-reinforced thermoplastics. Part III: Effect of fiber length on rheological properties and fiber orientation. Polymer Composites, doi
  82. (2007). Smart pioneers first full polypropylene body panels.
  83. (2009). Solidworks : 3D CAD Design Software. doi
  84. (1996). Squeeze flow testing of glass mat thermoplastic material. doi
  85. (1990). Stamping rheology of glass mat reinforced thermoplastic composites. Polymer Composites, doi
  86. Statistical Experiment Study of Gas-Assisted Injection Molding Process, doi
  87. (1991). Structures and properties of injection moldings of crystallization nucleator-added polypropylenes. I. Structure-property relationships. doi
  88. (1999). Study of `gas fingering' behavior in gas-assisted injection molding. Polymer Engineering and Science, doi
  89. (1996). The calculation of cooling time in injection moulding. doi
  90. (2001). The characterization of low cost fiber reinforced thermoplastic composites produced by the DRIFT(TM) process. Composites Part A: Applied Science and Manufacturing, doi
  91. (1991). The effects of injection molding on the mechanical behavior of long-fiber reinforced PBT/PET blends. doi
  92. The influence of fibre length and concentration on the properties of glass fibre reinforced polypropylene: 2. Thermal properties. Composites - Part A: Applied Science and Manufacturing, doi
  93. The influence of fibre length and concentration on the properties of glass fibre reinforced polypropylene: 5. Injection moulded long and short fibre PP. Composites Part A: Applied Science and Manufacturing, doi
  94. (1997). The influence of fibre length and concentration on the properties of glass fibre-reinforced polypropylene: 4. Impact properties. Composites - Part A: Applied Science and Manufacturing, doi
  95. (1996). The influence of fibre length and concentration on the properties of glass fibre-reinforced polypropylene: Part 3. Strength and strain at failure. Composites - Part A: Applied Science and Manufacturing, doi
  96. The Structure of Turbulent Shear Flow. 2nd ed. 1980, Cambridge:
  97. (1982). The time, temperature and shear dependence of the viscosity of polypropylene and its influence upon the extrusion process. Rheologica Acta, doi
  98. (1981). The viscosity of fiber suspensions at low fiber volume fractions. doi
  99. (1999). Thermoelastic properties of short-fibre-reinforced thermoplastics. doi
  100. (2008). Trends in polypropylene production and uses.
  101. United States: Society of Plastics Engineers,

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