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Michael Sepe Independent Consultant
A Processor's Most Important Job, Part 9: Avoid Molded-In Stress
How to establish molding conditions that minimize internal stress in a part.
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A Processor’s Most Important Job, Part 8: Molded-In Stress
How processing adjustments can control molded-in stress.
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A Processor's Most Important Job, Part 7: Reviewing Crystallinity
There are several process-related issues that influence crystallinity besides cooling rate. Let’s examine a few.
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A Processor's Most Important Job, Part 6: Long-Term Effects
The importance of mold temperature to the development of the desired polymer crystalline structure becomes absolutely crucial in the case of high-performance materials.
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A Processor's Most Important Job, Part 5: POM Polymers
Using a mold temperature above a polymer’s Tg ensures a degree of crystallinity high enough to provide for dimensional stability, even if the part must be used at elevated temperatures. But POM is an exception. Why?
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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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