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How to Configure Your Twin-Screw Extruder for Mixing: Part 5
Understand the differences between distributive and dispersive mixing, and how you can promote one or the other in your screw design.
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The Role Barrel Temperatures Play in Melting
You need to understand the basics of how plastic melts in an extruder to properly set your process and troubleshoot any issues. Hint: it’s not about the barrel temperature settings.
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Fundamentals of Polyethylene – Part 6: PE Performance
Don’t assume you know everything there is to know about PE because it’s been around so long. Here is yet another example of how the performance of PE is influenced by molecular weight and density.
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Screw Design Tips to Boost Productivity
In this collection of articles, two of the industry’s foremost authorities on screw design — Jim Frankland and Mark Spalding — offer their sage advice on screw design...what works, what doesn’t, and what to look for when things start going wrong.
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Fundamentals of Polyethylene – Part 5: Metallocenes
How the development of new catalysts—notably metallocenes—paved the way for the development of material grades never before possible.
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Polyethylene Fundamentals – Part 4: Failed HDPE Case Study
Injection molders of small fuel tanks learned the hard way that a very small difference in density — 0.6% — could make a large difference in PE stress-crack resistance.
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Solving Issues with Gloss
Your problem may be related to tooling, material, processing, or combinations thereof. Here’s how to find the root cause.
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EXTRUSION: Melting 101
Learn the basics on how polymer melts in a single screw. Barrel temperature plays less of a role than you might think.
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Featured Posts
How To Design Three-Plate Molds – Part 4
There are many things to consider, and paying attention to the details can help avoid machine downtime and higher maintenance costs — and keep the customer happy.
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What You Need to Know About the Design and Operation of Maddock Mixers
Designed properly, all entering solid polymer fragments and certain types of PE gels entering the Maddock mixer can be trapped and dispersed into the matrix resin. But many are not properly designed. Here’s what to look out for.
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Unraveling the Science and Myth Associated With Moisture Analysis — Part 2
Once you’ve selected the right moisture analyzer, the task of method development begins. Don’t skip this step or you’ll run into problems. Here’s what happened in my lab decades ago.
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Fundamentals of Polyethylene – Part 3: Field Failures
Polyethylene parts can fail when an inappropriate density is selected. Let’s look at some examples and examine what happened and why.
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The Fundamentals of Polyethylene – Part 2: Density and Molecular Weight
PE properties can be adjusted either by changing the molecular weight or by altering the density. While this increases the possible combinations of properties, it also requires that the specification for the material be precise.
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Understanding the Effect of Pressure Losses on Injection Molded Parts
The compressibility of plastics as a class of materials means the pressure punched into the machine control and the pressure the melt experiences at the end of fill within the mold will be very different. What does this difference mean for process consistency and part quality?
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