PT Blog

By: Michael Sepe 2/5/2020

Polyethylene Fundamentals: Part 6 of 6

Polyethylene Fundamentals: Part 6 of 6

Before we leave the topic of polyethylene grade selection, it may be productive to look at one more practical example of how the performance of PE is influenced by the dual considerations of molecular weight and density. This case study involves a relatively large molded part that was being produced in a variety of colors in an HDPE with a melt-flow rate of 7.0 g/10 min and a density of 0.952 g/cm3. Periodically the supplier of these parts would receive complaints from the field about cracking. It was assumed that these cracks occurred due to relatively high mechanical stresses that were part of the application.

However, when this problem became significant enough to start tracing it back from the field through the manufacturing process, a review of parts in inventory showed that cracking was occurring spontaneously in parts that had never been in service. It was further determined that parts that had been recently molded were free of the defect, but parts that were older did show evidence of cracking, and the older the parts were the more extensive the cracks appeared to be.

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Make Your Mark in Plastics Technology’s 'Top Shops' Survey

If you’re an injection molder, you’re going to be hearing a lot from us in the coming weeks about our annual Top Shops survey. You’ll receive gentle nudges in our e-newsletters and blog postings—and through social media—about the study. You’ll also be receiving reminders from us in the mail. Remember the mail?

We published the results of our Top Shops 2019 survey in our October issue, in an article written by Senior Editor Tony Deligio, who heads up this project. In the months since that article was published, I have received numerous emails and phone calls from molders who wished they had participated in that study, but somehow missed it. We want to make sure that doesn’t happen again.

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K 2019 Report: More Control, Faster Ordering for Molds, Hot Runners

During October’s K 2019 show in Düsseldorf, several suppliers in the mold technology space rolled out online systems allowing users to spec out a tool package online and order it from the web. Among the items they can order? More and more sophisticated valve-gate system for precise control of melt flow. (For a full picture of hot-runner and tooling news at K, see the September show preview and Keeping Up sections in September to December.)
 

Less downtime and more processing capability is the promise of Mold-Masters Melt-Cube EVO side-gating hot-runner system. At K, Mold-Masters offered attendees the chance to try out the new in-line design themselves. With this system, tips are secured by a single bolt, reportedly making mold service 85% faster. On a 64-cavity system, Mold-Masters says up to 5 hr of downtime could be saved. Offering simultaneous horizontal direct side gating for up to eight cavities, Mold-Masters says the Melt-Cube EVO is perfect for high-cavitation molds producing deep-draw medical parts.

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Adidas Increasing Usage of Recycled Plastics in its Products

 

Adidas says that 2020 will mark the first time more than half of the polyester used in its products will come from recycled plastic waste. From 2024 onwards, the company is committed to using only recycled polyester.

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Procrastinate No More: Key Molding 2020 Deadlines Are Here

For the kind of procrastinators that require only hours to be left before a deadline before they feel the need to act, the time to move Molding 2020 to the top of your to-do list is right now. Friday Jan. 31 marks the last chance to secure Early Bird registration deals on either the full conference or single-day passes—it’s also the last chance to enter a part into the inaugural Hot Shots part competition.

Early Bird registration saves you a full $200 off the price of a full conference ticket and $100 off a single-day pass. If cost is an element in convincing your manager that you need to attend Molding 2020, that argument will become more difficult after Jan. 31.

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