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Melt Flow Rate Testing—Part 5
There are two points in the manufacturing supply chain where a determination of average molecular weight (MW) is important. The first is when the material is first received by the molder. The second is after molding.
Columns Published: 11/26/2013
Melt Flow Rate Testing—Part 4
Few molders perform the test in-house. Of those that do, most don't understand why they are doing it or what they are measuring.
Columns Published: 10/24/2013
Melt Flow Rate Testing—Part 3
There is a well-established relationship between something called the weight-average molecular weight of a polymer and a parameter known as the zero-shear viscosity.
Columns Published: 9/23/2013
Melt Flow Rate Testing – Part 2
To fully appreciate the strengths and weaknesses of the melt-flow-rate (MFR) test it is important to know something about the way the test is performed.
Columns Published: 8/26/2013
Melt Flow Rate Testing–Part 1
Though often criticized, MFR is a very good gauge of the relative average molecular weight of the polymer. Since molecular weight (MW) is the driving force behind performance in polymers, it turns out to be a very useful number.
Columns Published: 6/24/2013
Dimensional Stability after Molding—Part 5
All materials possess a property called the coefficient of thermal expansion (CTE). The vast majority of materials increase in size as their temperature increases and decrease in size as their temperature declines.
Columns Published: 4/29/2013
Dimensional Stability After Molding: Part 4
In the first three parts of this series we focused on those influences that cause molded parts to get smaller. But there are environmental factors that also cause parts to increase in size over time.
Columns Published: 3/25/2013