Is My Dryer’s Desiccant Still Working?

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Let’s understand why materials need to be dried in the first place.  For thermoplastics, there are hygroscopic and non-hygroscopic resins.  Hygroscopic resins have an affinity for moisture, and it gets absorbed into the polymer chains of the material.  For hygroscopic resins (polymers that naturally absorb moisture such as Nylon, PBT, PET, ABS, and PC products), it is critical to ensure proper drying of the material prior to processing it.  In doing so, you will help prevent part failure due to hydrolysis and cosmetic defects such as splay or silver streaking.  Hydrolysis is the chemical breakdown of a compound due to the reaction caused by the presence of moisture in elevated temperatures.  This means that when a hygroscopic resin is processed with moisture, it causes the polymer chains to break, resulting in a significant decrease in mechanical properties.

Below is an example of the resin moisture capacity of 3 polymers; polyethylene (non-hygroscopic), polycarbonate (hygroscopic), and nylon (hygroscopic). Every polymer has its own capacity to absorb water, meaning some will absorb water more readily than others.

When molding hygroscopic materials, it’s recommended to use a desiccant dehumidifying style dryer to properly remove moisture from the material.  Let’s understand how a desiccant dehumidifying style dryer works:

  • It dries the air to the required dew point level
  • Heats the air to a specified temperature
  • Circulates the heated airflow within its own closed-loop system
  • Moisture migrates out of the polymer and is removed from the circulating air via desiccant bed

The desiccant bed is a cartridge type “filter” made up of moisture-absorbing desiccant beads.  An example of this would be the silica gel desiccant beads found in everyday consumer items/packaging (i.e., dry goods, shoe boxes, vitamin containers, clothing, and packaging).  The silica gel desiccant beads act as a dryer and capture unwanted moisture, preserving the product.

Now let’s review dryer maintenance and how you can tell if your desiccant beads are bad.  This is important to understand, so you aren’t molding material that still has moisture in it when processing.  As mentioned previously, processing hygroscopic materials with moisture leads to cosmetic defects and hydrolysis, which breaks the polymer chains affecting the overall mechanical properties of the material/ part.

There are three ways to tell a desiccant is bad in your dryer:

  • You cannot hold the desired set dew point on your dryer for the material. If it never reaches the desired dew point or doesn’t hold it for long, then it’s probably time to change the desiccant.
  • Pull the desiccant beads out and squish them between your fingers. If they are very brittle and crumble upon doing so, they’re bad and need to be replaced.
  • Take a styrofoam cup, fill it with about 1 inch of desiccant beads, and pour water on them, just enough to cover them or leave a few above the water. It’s good to know what the water temperature is before filling the cup.  If the cup and water get hot, then they’re still good.  However, if it remains cold, then it’s time to change the desiccants.  When desiccants absorb moisture, they give off heat.  You can then use a thermometer to measure the water temperature difference after the water reacts with the desiccant beads to see the change in temperature.

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The Chase Plastics team of engineers is ready to assist with any drying and process related questions you may have. Give us a call at 844-411-2427 or send an email at engineering@chaseplastics.com to get support on any of your technical needs today!

If you have questions on the topic above or have another issue to tackle, please submit your inquiry in the questions/contact form. Someone from our technical team will be in touch once it has been submitted.

Hunt for resin continues, even as supplies improve

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Frank Esposito
Plastics News
April 9, 2021

North American resin availability is improving in the wake of recent outages, but many companies throughout the supply chain still can’t get all the material they need.

In the wake of Winter Storm Uri, which hit Texas and the Gulf Coast in mid-February, many material suppliers put customers on force majeure sales limits or other types of allocation.

LyondellBasell Industries of Houston operates multiples sites making polyethylene, polypropylene and related resins and compounds in Texas. In an email to Plastics News, spokeswoman Chevalier Gray said that “nearly all of our assets, except for Corpus Christi, are back to normal operations.”

A spokesman for Wilmington, Del.-based DuPont Co. said that the firm still has force majeure limits in place for nylon, polybutylene terephthalate and several other materials. DuPont “is taking commercially reasonable steps to mitigate the effects of these shortages on its customers, but many of the upstream supply constraints persist,” he said.

“We take this matter very seriously and recognize the importance of supply reliability to meet the needs of our customers,” he added.

At Midland, Mich.-based Dow Inc., the firm “has continued to restart units and ramp rates through March and into April, as we manage a few raw material constraints and freeze damage repairs,” a spokesman said.

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Visit our new 3D Printing page

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Let our experts help you simplify and guide you through the most complex 3D printing material selection processes.

3D printing helps manufacturers reduce time and costs while increasing efficiency. Chase Plastics will help you navigate the process of additive manufacturing with the tools, resources and suppliers to help you thrive. As a stocking distributor with several options, our trusted experts simplify and guide you through the most complex 3D printing material selection processes to provide more design freedom and efficiency at your target cost.

 

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Recovery underway for resin distribution in 2020

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Frank Esposito
Plastics News
August 19, 2020

North American resin distributors have overcome many obstacles to keep their customers supplied with material during the global COVID-19 pandemic — and their work isn’t over.

“We almost have a moral obligation to provide key raw materials to our customers at a time like this,” said Vishal Goradia, senior vice president at Vinmar International of Houston. “Early on, we saw the global effect of rolling shutdowns. It was affecting a different region every month, but we kept our focus on being reliable to our customers and suppliers.”

Plastics News recently spoke with several resin distribution executives to see how they were navigating the uncharted waters of 2020. Here’s what they had to say:

The year begins…

Many executives said the year was off to a good start. Then the pandemic caused global shutdowns across almost every industry in March.

“A lot of places shut down and there were some stranded rail cars of resin,” said Ed Holland, President and CEO of M. Holland Co. in Northbrook, Ill. “The trough in May wasn’t as deep as we expected, and June and July bounced back.”

“In mid-March, everything fell off,” added Kevin Chase, president of Chase Plastic Services Inc. in Clarkston, Mich. “In automotive, all tiers were shut down until most places made automotive an essential business. We’re slowly recovering now.”

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Visit our new Automotive page!

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In the automotive market, meeting your future goals starts with the decisions you make today. Look to Chase Plastics as your trusted partner for insight on factors that heavily impact performance and efficiency. Our technical service support team includes dedicated on-staff experts to serve automotive customers like you.

Even as industry standards evolve, our methodical approach extends to every step of the process. From material selection, design assistance and testing to production and compliance—we’re committed to doing more than helping you meet mandates and standards—we aim to exceed your goals.

 

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