Melt flow index on high molecular weight polyethylene: …

The OP5 measurement of Melt Index is performed in a batch process, termed a cycle. The MI result is based on a tiny part of the sample, which gives the OP5 a pin point accuracy. The result shows every small variation in the polymer product and which can be used to steer polymer reactions in a way not possible by long term averaging or less than adequate sample preparation. The MI result can of course be used for Quality Control but the finely resolved and accurate measurements will bring a better precision and thus maximise the added value of the production.

Melt Flow Rate (MFR, MVR) - Instron

Melt Flow Enhanced Model 7027.000 The Model 7027.000 is an evolution in Melt Flow Testing
Photo provided by
Flickr

Process for determining and evaluating melt flow index values

Melt flow rate is a quick tool to compare batches of the same material or to estimate flow properties of different materials (typically for extrusion processes), when a deep understanding of material properties is not required. A true rheological characterization can be carried out by means of rheometers. Melt flow rate is inversely proportional to (shear) viscosity, but is not used to determine the latter (can give just a rough estimation).

Synonyms of Melt Flow Index are Melt Flow Rate and Melt Index

MFR and MVR are typically used in Quality Control labs and Production Control labs. The basic procedure foresees a manual timing, cutting and weighing of the extruded material, giving directly a value of MFR. Semi-automatic procedures allowed by modern instruments are based on direct measurements of piston displacement, hence they give directly a value of MVR. Melt density can be typed in or measured, and therefore MFR results are also obtained. Semi-automatic procedures can achieve a much higher accuracy and guarantee a wider range of measurable flow rates. More advanced methods foresee the application of several loads during the same test, each one giving a MFR (MVR) result. This is called a multiweight test and gives additional information on the sample, with some insight on the shear dependence of viscosity. A single-weight MFR test can be correlated with average molecular mass, while the shear dependence depends on the molecular mass distribution.

Melt Flow Index Tester
Photo provided by
Flickr

SOTC: Ice Sheets | National Snow and Ice Data Center

Typical Melt Flow instruments are compact and easy to use. The basic principle is that a thermoplastic sample (originally in the shape of granules, powder or flakes) is made fluid by heating and forced to flow out of a cylinder through a capillary die. The extruding piston is loaded with dead weights, normally up to 21.6 kg. MFR (and MVR) are obtained under standard conditions of temperature and applied load, defined for each type of material, and normally using a fixed type of die (inner diameter 2.095 mm, length 8 mm). The result must always specify the test conditions because it’s strongly dependent on those.

Since 1993, Greenland’s Ice Sheet Melt Has Added Just …

The Melt Flow Rate is a measure of the ease of flow of melted plastic and represents a typical index for Quality Control of thermoplastics. Originally called Melt Flow Index or Melt Index (typically for polyethylene, but applied to a variety of materials), the standard designation today is Melt Mass-Flow Rate or MFR, which is a mass flow expressed (SI units) in g/10min. An alternative quantity is the volume flow expressed (SI units) in cm3/10min, called Melt Volume-Flow Rate or MVR. MVR multiplied by the melt density (i.e. density of the material in the melted state) gives MFR.

The criteria weight determination of factors impacting …

Recent studies have found, however, that there is a limit to the effect of surface meltwater penetration. The relative speedup of outlet glaciers is small in most years, less than 15 percent (). Satellite observations of southwestern Greenland in the 1990s documented ice flow development, showing how it changed in years of differing melt rates. In the first half of the summer, the flow rates were similar in all years, but flow rates differed in the second half. Surprisingly, the flow rate was 62 ± 16 percent, lower in warmer years, and the period of fast ice flow lasted only a third as long. The data suggested that, like mountain glaciers, melt-induced glacier acceleration actually stops in years of intense melting once subglacial water erodes through the sediments and creates channels for water flow ().