Materials Know How
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.
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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.
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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.
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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.
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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.
Read MoreDimensional 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.
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Dimensional Stability after Molding—Part 3
Any process that involves melting and re-solidifying a polymer involves a compromise between achieving the perfect structure and producing a part that can be sold at a price that the market is willing to pay.
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Dimensional Stability After Molding—Part 2
After molding, acetal parts can continue to shrink at room temperature and even in the cold.
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Dimensional Stability After Molding: Part 1
The degree to which molded parts shrink as they cool is largely dependent upon the composition of the material being processed.
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