Materials Know How
A Processor’s Most Important Job, Part 4: Mold Temperature
Engineering polymers require higher mold temperatures to achieve their ideal structure. The temptation to turn down the mold temperatures can hurt part performance.
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A Processor’s Most Important Job, Part 3: Unintended Consequences
Processors are often expected to compensate for ill-advised decisions made earlier in the product-development process. In the case of shrinkage, one of the most common ‘fixes’ is to simply reduce the mold temperature.
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A Processor’s Most Important Job, Part 2: Crystallinity
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.
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A Processor’s Most Important Job, Part 1: Molecular Weight
Many processors don’t realize that preserving material characteristics is crucial to product success and failure. The focus here is on molecular weight.
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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 processing.
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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.
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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.
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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.
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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.
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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.
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