Plug Assist Materials for Improved Forming of Transparent Polypropylene

The performance of a new class of copolymer syntactic foam (HYTAC-FLX and HYTAC-FLXT) was evaluated and compared to an engineered solid polymer (PEEK) and the industry’s leading thermoplastic syntactic foam (HYTAC-B1X) for use as a plug assist when forming transparent polypropylene (PP).  These new copolymer syntactic foams have been designed to minimize scratching and improve clarity when forming transparent materials and offer additional benefits in machining/polishing of plug materials.    The results, including the effect of plug geometry and surface finish quality, for gloss, scratch, haze, clarity, plug mark and material distribution are detailed in the study.

Syntactic foam as a mold material?

Though syntactic foam is most widely recognized for top performance as a plug assist or pusher inside a mold, a recent study found high performance when used as a mold.  Andrew Sneeringer, a recent graduate of Pennsylvania College of Technology in Williamsport, PA, compared the performance of MDF board to HYTAC-C, a unique syntactic foam resin system that may be cast to shape at a customer facility.  Performance was compared for mold cost, mold integrity/usable life and part quality produced.  The results, as published in Thermoforming Quarterly Magazine (second quarter 2012), provide beneficial details for all.  Full articles become available over time for download at or contact CMT to discuss your immediate application needs.

The World’s Toughest Syntactic Foam – HYTAC® XTL

HYTAC®-XTL is the first material to combine the machined surface quality of an epoxy syntactic with the durability and dust free machining of a thermoplastic syntactic foam. Thermoformers and toolmakers report excellent performance when using XTL for plug assist.

HYTAC®-XTL was developed to offer an improved surface quality after machining when compared to our popular HYTAC-B1X.  This is particularly important when working with sticky or transparent plastics due to the challenge of polishing any thermoplastic syntactic material.

In addition to enhanced surface quality, HYTAC®-XTL has these outstanding attributes:

  • The highest toughness ratings for any syntactic foam
  • Superb machinability with no dust
  • Excellent where edge definition and detail are required
  • Low thermal conductivity
  • Low coefficient of thermal expansion
  • Excellent material distribution

CMT Materials will be promoting its new line of XTL thermoplastic syntactic foam at several major tradeshows this year including Chinaplas in May, SPE Thermoforming Conference in September and K in October.

CMT Field Notes: 2013 SPE Thermoforming Conference – Part 2

This is the second in our 2-part summary of the 2013 SPE Thermoforming Conference in Atlanta, GA. As we hinted at the end of our last post, CMT had many engaging conversations with heavy gauge thermoformers. The rapidly growing interest for syntactic foam plug assists in the heavy gauge world seems to stem from the following factors:

  • a steady increase in the price of plastics
  • an increase in quality demands from the market
  • an industry-wide focus on reducing scrap, i.e. eliminating waste
  • many, many companies looking to implement “Lean” or Continuous Improvement projects

Our work with Penn College and a number of processors has shown that HYTAC® can be used with great success in thick-sheet, deep-draw applications.

Because many heavy gauge projects have short runs (from a few dozen to several thousand parts) compared to thin-gauge or roll-fed applications, processors tend to be very cost-conscious when it comes to plug materials. Given that syntactic foam can range from $500-1000/ft3, this is not unreasonable. In many cases, a simple wooden plug can be slapped together and short runs can be achieved with minimal problems.  When one stops to consider the total cost of ownership, however, the calculus changes. While wood offers low costs and easy manufacturability, it has limited temperature resistance which becomes problematic for longer dwell times associated with many heavy gauge projects. Wood also has a tendency to mark-off on the plastic which, if texturing and surface finish are important, can result in rejected parts. When used as a plug material, aluminum offers benefits beyond what you get with wood, but aluminum plugs must be heated and precisely controlled in order to achieve optimally formed parts. This adds a level of cost and complexity to the process.

As a result, syntactic foam is gaining acceptance as an option for large part plug assists. Low heat transfer, durability and minimal mark-off are three key reasons why some heavy gauge thermoformers will use syntactic foam. During the show in Atlanta, we had numerous conversations with processors about their positive results with HYTAC® materials. In some instances, they are using HYTAC® in limited fashion as pushers to eliminate webbing while improving material distribution. In other scenarios, syntactic foam can also be used on the clamp frame to minimize chilling of the sheet.

In July 2012, our senior materials engineer, Kathleen Boivin, published a paper that appeared in Plastics Technology. The following excerpt is taken from that piece as it neatly encapsulates much of what we talk about in heavy gauge thermoforming:

“Production volume is the main consideration when deciding whether to go with a full-size plug or localized pusher. For a 24/7 manufacturing operation, the cost of a full-size syntactic plug can be easily justified by the 15% to 20% cost savings per part. The bulk of this savings is achieved through better material distribution, allowing for down-gauging, which also leads to reduced cycle time and lower energy costs.”

If you weren’t at the show and want to learn more about how syntactic foam can work for you, give us a call at 508.226.3901 or fill out our application form.

How to Improve Material Distribution in Thermoformed Parts

Here at CMT Materials, we like to work with partners and end-users to develop practical information that can help you get more from your plugs. We recently received a summary of tooling and plug trials done by a large thermoforming company and we wanted to share it with you.

This mini case-study is only 1 page, but it clearly illustrates why our new XTL syntactic foam is quickly becoming the plug material of choice.


We hope you enjoy it. As always, send us your comments, thoughts or application notes.

Have it Your Way: HYTAC Custom Cast

We’ve seen a lot of new, custom cast requirements in recent weeks. These tend to be large or oversized parts where a standard, stock-sized piece of syntactic foam will not do the job.  In most cases, these projects are the result of multiple discussions with customers on specific application requirements. While we have always offered this service, it has sometimes been unclear what options are available and what the limitations are. Now we are releasing new product data sheets (PDS) on custom cast work as well as new HTYAC LPX.

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Plug Assisted Thermoforming of Multilayer Sheet

SPECIAL GUEST POST: Sven Engelmann, Dipl. -Ing. Director of Research & Development, EBB Microparts, Crailsheim, Germany

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Spotlight on HYTAC C1R: High-Performance Copolymer Syntactic

It’s not often that we will single out a material for special consideration, but given some recent thermoforming test results, we think HYTAC C1R deserves some love.

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New HYTAC Thermoforming Case Studies

This week we have posted 2 new case studies to our website. If you haven’t already received copies from us, be sure to take a look and let us know what you think:

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Understanding the True Cause of Failure in Plugs

This week we received a package with a damaged plug and its mounting system. After reviewing the plug material and the failure modes, we suspect the cracking was due to a mismatch of thermal conductivity rates in a tightly confined area.   The plug design was efficient and neatly put together – at room temperature.   The chosen plug material, HYTAC-WF, is a thermoset epoxy-based material formulated for low thermal conductivity and minimal thermal expansion to provide consistent performance when contacting a heated sheet.  In this particular plug design, those same properties provide a challenge for the mounting system and result in significant stress on the most brittle element – the syntactic foam.


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