The Melt Flow Rate of Different Polymeric Materials

2472 Words10 Pages
E3: The Melt Flow Rate of Different Polymeric Materials
Objectives:
1) To learn the operating procedure of TWELVindex
2) To determine the melt flow rate of different polymeric materials
Introduction:
Melt flow index is given by the weight of the extrudate in gram per 10 min [1]. Referring to Figure 1.1, the melt flow index measured according to Condition-E (190°C, 2160g) which is the normal condition for polyethylene is called “Melt Index (MI)”. Polypropylene requires Condition-L (230°C, 2160g) because of its high melting point, and the melt flow index at Condition-L is called “Melt Flow (MF)’.

Figure 1.1: Conditions that found satisfactory for the material listed

Melt index is a common measurement used to characterize thermoplastic polymers [2]. Different polymer types often report melt index at differing conditions. Melt index values are not always directly comparable between polymer types since polyethylene typically report melt index at 190°C whereas polypropylenes are typically reported at 230°C due to their different melting points.
There are standardized methods for melt index under ASTM and ISO, for example, ASTM D1238. Such standard methods specify the geometry and other constraints on the device used as well as the combinations of conditions. The device is essentially an upright, narrow cylindrical barrel fitted with a plunger and a removable (for cleaning) orifice at the bottom as in Figure 1.2.

Figure 1.2: Schematic drawing of the Melt Flow Indexer.
The barrel is temperature controlled and a defined weight is placed on the plunger to provide the prescribed force and thus pressure on the plunger, which drives the polymer melt through the orifice. Typically, polymer pellets are loaded into the barrel and allowed...

... middle of paper ...

...s due to their molecular weight distribution and chain branch as well as their crystallinity.

References:
[1] Chan I. Chung. 2000. ‘Extrusion of Polymers: Theory and Practice’. Germany: Hanser Verlag.
[2] Ken. 2012. What is Melt Index? Viewed on 20 October 2013. Available from: < http://www.vitaldose.com/blog/what-is-melt-index/>.
[3] A. B. Mathur, I. S. Bhardwaj, A. B. Mathur. 2003. ‘Testing and Evaluation of Plastics’. New Delhi: Allied Publishers.
[4] Muralisrinivasan Natamai Subramanian. 2013. ‘Plastics Additives and Testing’. Canada: John Wiley & Sons.
[5] Clive Maier, Theresa Calafut. 1998. ‘Polypropylene: The Definitive User's Guide and Databook’. USA: William Andrew Inc.
[6] T. Hatakeyama, Hyoe Hatakeyama. 2006. ‘Thermal Properties of Green Polymers and Biocomposites’. USA: Springer.
[7] Barbara H. Stuart. 2008. ‘Polymer Analysis’. USA: John Wiley & Sons.

More about The Melt Flow Rate of Different Polymeric Materials

Open Document