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| Author | Topic: PA66 |
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kubko99 Member Posts: 1 |
posted August 12, 2004 03:17 AM
   
Hallo, Could you anybody help me, what is the mainly diferent between PA66 for injection moulding and extrusion ??? It is in density, and MFR, or in processing temperatures too??? Thank for advice.. best regards IP: Logged |
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Tom C Moderator Posts: 357 |
posted August 12, 2004 07:52 AM
Nylon 66 for injection molding is a very low viscosity fluid as a melt. This allows for rapid mold filling and the filling of narrow channels quickly. In order for a successul extrusion to be made with Nylon 66 the viscosity must be much higher than that of injection molding grades. The high viscosity helps the extrudate hold it's shape between exiting the die and cooling. It is possible to use extrusion grade Nylon 66 for injection. Generaly the extrusion grade Nylon 66 will cost more and perform less well in injection molding. Nylon 66 has a sharp melting point at around 500F. Typical processing temperatures are 520F to 560F. Higher temperatures lower the viscosity of the extrusion grade and ease processing in some cases. Tom C IP: Logged |
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TomBlack Moderator Posts: 47 |
posted August 13, 2004 07:45 AM
Typically, as is the case for mose injection molding grade materials, the molecular weight distribution is far more narrow than it would be for extrusion grade compounds. The narrow MWD also assures that all of the polymer melts at approximately the same temperature, but possibly more importantly for injection molding , that all of the material freezes at the same temperature. This helps to assure faster cycles. In addition to their narrow MWD, IM grades are typically lower in molecular weight (and thereby higher in melt flow rate) than extrusion grades as they do not require the melt strength contributed by long chain ends (the higher MW fraction). The result is a much lower viscosity compound (overall) than typical extrusin grades. As for nylon 66 (injection molding grade), indeed it has a well defined, sharp melting point resulting from its' narrow MWD, relatively high degree of crystallinity and significant amount of hydrogen bonding. In other words, once enough "work" has been put into the compound to "unwind" the crystal structure and "dissociate" the hydrogen bonding, "look out" as the material will transition from a hard solid to a low viscosity melt in no time... ------------------ www.ppsincorp.com IP: Logged |
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