Materials

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Published: 1/23/2018

Materials: A Processor’s Most Important Job, Part 2
Process conditions help determine the difference between the maximum degree of crystallinity that can be achieved in a polymer and the degree that is present in a molded part.

Published: 1/2/2018

Materials: A Processor’s Most Important Job, Part 1
Many processors don’t realize that preserving material characteristics is crucial to product success and failure. The focus here is on molecular weight.

Published: 12/1/2017

Materials: Cycle Time—Science vs. Rules of Thumb, Part 6
This installment—on elastomers—completes a series, whose theme is to bring more science to the discipline of molding. The overall message: Ask a lot of questions whenever someone posits this or that ‘rule of thumb’ about proc...

Published: 10/27/2017

Materials: Cycle Time: Science vs. Rules of Thumb—Part 5
Let’s examine the behavior of semi-crystalline materials that never reach their glass-transition temperature as they cool.

Published: 9/25/2017

Cycle Time: Science vs. Rules of Thumb—Part 4
While laboratory tests are helpful in determining how polymers behave, you must remember the fundamental differences between laboratory measurements and the real world of plastic processing. Let’s examine semi-crystalline polymers here.

Published: 8/30/2017

Materials—Cycle Time: Science vs. Rules of Thumb—Part 3
To properly calculate cycle time, you need to understand how the modulus of a polymer increases as it cools in the mold.

Published: 7/25/2017

Materials: Cycle Time: Science vs. Rules of Thumb—Part 2
Understanding cooling—how a given material develops modulus as it solidifies—requires access to data that provides some insight into the relationship between modulus and temperature. Dynamic mechanical analysis is a helpful tool.

Published: 5/30/2017

Cycle Time: Science vs. Rules of Thumb, Part 1
What temperature must the polymer reach so the part can be ejected from the mold? Here, more than for any other variable, ‘rules of thumb’ unfortunately prevail.

Published: 4/25/2017

The Need for Generalists: Part 4
Solving problems generally requires distinguishing good samples from bad ones. But that can become clumsy when one person runs the test while another analyzes the data.

Published: 3/24/2017

The Need for Generalists: Part 3
In failure analysis, there is a tendency to gravitate to a few common test protocols. But this approach can result in a mismatch of techniques to the problem.