Melt flow indexes

This property is measured by a melt flow index extrusion plastomer, which measures the weight of polymer extruded through a standard orifice in 10 minutes (see Table 16.1). Alternatively, a multi-functional extrusion plastomer that measures melt flow rate resistance to thermal degradation is available. 

Melt flow studies have been reported on PP [30], isotactic butadiene [31], glass fibre-filled PP [32], and LDPE [33]. 

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Modification of BPA-PC for adaptation to the conditions of production of CD and CD-ROM disks, and of substrate disks for WORM and EOD was necessary. BPA-PC standard quaHties for extmsion and injection mol ding have, depending on molecular weight, melt flow indexes (MEI), (according to ISO 1130/ASTM 1238 in g/10 min at 300°C/1.2 kg, between less than 3 g/10 min (viscous types) up to 17 g/10 min. For CDs and optical data storage disks, however, MEI values exceeding 30 g/10 min, and for exceptionally short cycle times (5—7 s) even >60 g/lOmin are demanded at an injection mass temperature of 300°C (see Table 5). 

Fig. 23. Correlation between properties (general characteristics), melt flow index (MFI), and mol wt for standard BPA polycarbonate and CD-modified...

Ionomer resins are produced in multiple grades to meet market needs, and prospective customers are provided with information on key processing parameters such as melt-flow index. Nominal values for many other properties are Hsted in product brochures. The ASTM test methods developed for general-purpose thermoplastic resins are appHcable to ionomers. No special methods have been introduced specifically for the ionomers. 

MFI = melt flow index IV = intrinsic viscosity in CH2CI2 at 25°C From gel-permeation chromatography using polystyrene standards. 

Fig. 9. Melt flow index as a function of temperature for varying molecular weights of poly(ethylene oxide). WSR = Polyox water-soluble resins.

HVA 6 Automated CapiUary/Sht Viscometer MFM Melt Flow Rheometer Automatic Melt Flow Indexer AK Continuous Capillary Rheometer Han Slit Rheometer... 

Polymers ranging in melt flow index (an inverse measure of molecular weight) from less than 0.1 to greater than 600 can be obtained by this process but commercial products have a melt flow index of only 0.2-5 and have the highest density of any commercial polyethylenes ( 0.96 g/cm ). 

With the availability of the higher density polymers the value of the melt flow index as a measure of molecular weight diminishes. For example, it has been found that with two polymers of the same weight average molecular weight (4.2 X 10 ), the branched polymer (density = 0.92 g/cm ) had only 1/50 the viscosity of the more or less unbranched polymer (density = 0.96 g/cm ). This is due to long chain branches as explained above. 

Figure 10.7. Effect of density and melt flow index on elongation at break. (Separation rate 45 em/min on specimen of 1 in gauge length.) A, constant density (0.92 g/cm ). B, constant MFI (0.7). C, constant density (0.94 g/cm ). (Reproduced by permission of ICI)...

Figure 10.8. Effects of melt flow index and density on the room temperature tough-brittle transition of polyethylene. (Reproduced by permission of ICI)...

Figure 11.3. Variation of tensile yield stress with melt flow index (10 kg load at 190 C) and isotactic index. (After Crespi and Ranalli )...

Figure II.5. Variation of Vicat softening point (5 kg load) with isotactic index and melt flow index.

Figure 11.6. Variation of ASTM D746 brittle point with melt flow index and isotactic index (After...

The standard melt flow index machine is often used for characterising the flow properties of polypropylene and to provide a rough measure of molecular weight. Under the conditions normally employed for polyethylene (2.16 kg load at 190°C) the flow rate is too low for accurate measurement and in practice higher loads, e.g. 10 kg, and/or higher temperatures are used. It has been found that a considerable pressure drop exists in the barrel so that the flow towards the end of a test run is higher than at the beginning. 

The commercial grades available in the 1970s used either zinc or sodium as the cross-linking ion and ranged in melt flow index from 0.4 to 14. The main application of the ionomer resins has been for packaging film. The polymer is particularly useful in composite structures to provide an outer layer with good heat sealability. The puncture resistance of film based on ionomer film has the puncture resistance of a LDPE film of twice the gauge. 

Melt flow index (g/10 min) 150°C, 2160 g Thermal properties ASTM D1238 3 3 3... 

Melt Flow Rate (also known as Melt Flow Index)... 

Table 2 Melt Stabilizing Efficiency of Antioxidants in PP (processed in an internal mixer at 190°C). Melt flow index (MFI) Measured at 230 C and 2.16 Kg...

Important physical properties include the density, melt flow index, crystallinity, and average molecular weight. Mechanical properties of a polymer, such as modulus (the ratio of stress to strain), elasticity, and breaking strength, essentially follow from the physical properties. 

The melt flow index describes the viscosity of a solid plastic. It is the weight in grams of a polymer extruded through a defined orifice at a specified time. The melt viscosity and the melt flow index can measure the extent of polymerization. A polymer with a high melt flow index has a low melt viscosity, a lower molecular weight, and usually a lower impact tensile strength. 

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