PT Blog

Reactive Extrusion: Industry Icons Impart Their Insights

Reactive extrusion (REX) is viewed by many as a mysterious—if not scary—segment of the compounding industry. It is an area filled with tribal knowledge.  Yet it is also a value-added process segment that savvy compounders can tap into to distinguish themselves from the competition.

What are the challenges? What are the pitfalls? What kind of equipment do you need? To find the answers to these and other questions, Plastics Technology tapped into the expertise of three of the world’s foremost authorities on the subject: consultant Joseph Golba; retired machinery executive Bill Thiele; and Costas Gogos, a long-time author, professor and reseacher in the field.

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SABIC Steps-Up Specialty Thermoplastic Resins Fulfillment to Expedite Production of Critical COVID-19 Equipment

Over the last several months, we have reported on a number of companies across the plastics industry—from resin suppliers and compounders to processors and OEMs—who have geared up to meet the needs for a variety of critical equipment exacerbated by the coronavirus pandemic. SABIC recently unveiled how it has taken extraordinary steps to expedite order fulfillment for its specialty thermoplastics resins from global customers that manufacture lifesaving medical equipment, from ventilators and defibrillators to auto-chemistry analyzers.

For example, the company swiftly supplied significant quantities of thermoplastics to two Chinese medical device manufacturers—Mindray and DIRUI. Despite shutdowns and exponential increase in demand, SABIC has worked to ensure fast and steady supply of desperately needed medical equipment to hospitals on the front lines.

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Additive Manufacturing Media Announces New Educational Presentation Series

Additive Manufacturing Media is launching AM In-Depth, a series of discussions with those involved in production 3D printing exploring what is next for additive manufacturing (AM) technology. The series will be part the of IMTS spark platform and is scheduled to run Mondays, Wednesdays, and Fridays during the weeks of 9/21 and 9/28. There will be two speakers per day, one at 1:00 Eastern, one at 2:30 Eastern.

Sessions will focus on real-world applications of industrial AM, sharing the successes and speed bumps it took to get the applications up and running, with the sessions including Q&A with the presenters. Topics include design for additive manufacturing (DFAM), processes, materials, implementation strategies, serial production and more. Presenters are pulled from OEM manufacturers like Varroc Lighting Systems; research institutions like Penn State University; and contract manufacturers like Cumberland Additive, Knust-Godwin and Tangible Solutions.

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Materials Part 5: Annealing Tips for Crosslinked Polymers

Just as annealing is used in semi-crystalline thermoplastics to perfect the crystalline structure of the polymer, the same process can be used to obtain a level of crosslinking in thermosetting polymers that may not be achievable within the context of the molding cycle. The property changes that are associated with an increased level of crosslinking are in many ways very similar to those related to an increased degree of crystallinity.

But crystallization and crosslinking, while they respond to the same processing and post-processing influences, are fundamentally different processes. Thermoplastics have been built to a useful chain length before they arrive at the processing plant, and crystallization occurs spontaneously from the melt as temperature declines. At some point in the cooling process, we observe a sharp transition in the material structure that is a function of the chemistry of the material and the ambient or applied pressure.

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Tooling: Back to Basics on Die Springs Part 1

I counted more than 30 different types of springs in a well-known supply catalog, each with multiple variations. This month I will focus strictly on one type: compression die springs for injection molds. When you put a load on this type of spring it compresses, or gets shorter. The spring then pushes back against the load, trying to get back to its original uncompressed length. It is such a simple mechanism, and yet is often the cause of significant mold damage and downtime, usually due to improper selection or use.

The most common use of springs in an injection mold is to retract the ejector plates. We need to discuss this particular application because there are two contradictory beliefs. Theoretically, if the mold-closing sequence is adjusted correctly, there is no need to use springs, because the return pins will drive the ejector plates back to their proper position—flush against the stop buttons. If there is a concern about the noise, or potential damage to the return pins, Bellville washers can be installed under their heads to absorb the impact (see my November 2018 column). Alternatively and preferably, the ejector plates should be connected to the molding machine’s knockout system, which then controls the fore and aft position of the plates—also negating the need for springs.

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