Which Resin Dryer Is Right For You?
By Mark Haynie and Joshua Belisle · Edited by Dana Gardner
Published August 31, 2024 · Reviewed by Mark Haynie · July 10, 2026
Summary
Which type of resin dryer should I use?
The right resin dryer depends on the material. Hot-air dryers suit non-hygroscopic resins that pick up only surface moisture, but not hygroscopic resins like nylon and polycarbonate. Vacuum dryers dry heat-sensitive resins at lower temperatures, infrared dryers crystallize and dry PET in one step, and membrane dryers deliver -40°F dew point air year-round, unlike plain compressed air dryers that lower dew point only 10 to 20 degrees.
Selecting the right resin dryer can be a challenging task, considering the multitude of options available. For many years, the choice was simply between hot-air and dehumidifying desiccant dryers. However, in recent years, new dryer types have emerged on the market, and processors now have at least five different types of dryers to choose from, each with its own benefits and limitations. In this article, we’ll explore the different types of resin dryers available and discuss problems with the traditional ‘time-based’ drying process, which is typically inaccurate and can lead to over-dried or under-dried parts as well as wasted production time.
Types of Resin Dryers:
Hot Air Dryers
Hot-air dryers are a good choice for resins that have no affinity to moisture. Non-hygroscopic resins such as polyolefins, polystyrene, and PVC pick up only surface moisture from condensation when exposed to humid air. Hot-air dryers use heated ambient air to dry the resin pellets. They are simple, reliable, and relatively inexpensive compared to other types of dryers. However, hot-air dryers are not suitable for drying hygroscopic resins like nylon and polycarbonate.
Vacuum Dryers
Vacuum dryers use a vacuum to lower the boiling point of water, allowing moisture to evaporate from the resin pellets at lower temperatures. By subjecting the resin to a vacuum environment, the boiling point of water decreases, allowing moisture to evaporate at lower temperatures. This reduces the risk of resin degradation or thermal damage, especially for heat-sensitive materials making vacuum dryers ideal for drying heat-sensitive resins that cannot be dried at high temperatures. Vacuum dryers have also come into the mainstream recently because of their speed in drying and low cost of operation. The 30 lb./hr. models are very well positioned for lab applications.
Infrared Dryers
Infrared dryers use infrared radiation to heat the resin pellets, allowing moisture to evaporate. Infrared dryers are generally used in drying PET for sheet and some fiber applications. They tend to have a higher cost than a typical desiccant dryer but can be very competitive when doing both crystallizing and primary drying. The infrared heat penetrates well to the inside of the resin flake or pellet and drives the moisture out while crystallizing the resin at the same time. These dryers can shorten the drying crystallizing process start up from 6-10 hours to one hour.
Membrane Dryers & Compressed Air Dryers
A compressed air resin dryer is a type of dryer used to remove moisture from plastic resin using compressed air. The dryer uses a combination of heat and compressed air to dry the resin. A membrane dryer is a type of compressed air dryer that uses a membrane to remove moisture and other contaminants from the air; however, it is easy to get confused about the differences between membrane dryers and compressed air dryers but when it comes to resin drying it is critical to understand the differences. Firstly, compressed air dryers typically reduce the dew point of the incoming air by only 10 to 20 degrees F. That means if the incoming air is at a 40-degree dew point, your plastic pellets will only see “drying air” with a 20 or 30-degree dew point, despite the fact that resin manufacturers specify that most resins be dried by -40 degree dew point air. So in some geographic areas where it is typically humid, these compressed air dryers will not work very well at all. In climates that are typically dry in the winter but often humid during summer months, the compressed air dryer may work alright during the winter but have to be shut down during humid days in the Spring, Summer, and Fall.
Conversely, Membrane dryers, much like desiccant dryers, produce -40° low dew point air for drying – year-round, regardless of humidity. The low dew point is achieved by drying high dew point compressed air with a hollow fiber membrane that separates the moisture from the airstream. These systems can provide similar economies to a desiccant dryer if equipped with the necessary flow. The membrane has an extremely long life and they have no moving parts making them very well-fitted for smaller injection molding applications.
The other big difference is the comparison of operating costs. Plain compressed air dryers use about 3 times as much compressed air as membrane dryers with a built-in membrane. Even compressed air dryers with add-on membranes use about 2.5 times as much compressed air as membrane dryers with built-in membranes. You may save some money on the initial purchase of a compressed air dryer or one with an add-on membrane BUT your operating costs will be so much lower with the built-in membrane dryer that over a 10-year period, you will save tens of thousands of dollars to dry your plastic resins.
Frequently Asked Questions
Can I use a hot air dryer for nylon?
No. Hot-air dryers use heated ambient air and remove only surface moisture from condensation, which is enough for non-hygroscopic resins such as polyolefins, polystyrene and PVC. They are not suitable for hygroscopic resins like nylon and polycarbonate. Hot-air units are simple, reliable and relatively inexpensive compared with other dryer types, which is why they remain a good choice for materials with no affinity for moisture.
What is the difference between a membrane dryer and a compressed air dryer?
A plain compressed air dryer lowers the incoming air’s dew point by only 10 to 20 degrees F, so 40°F dew point plant air gives 20 to 30°F dew point drying air, well short of the -40°F most resin makers specify. A membrane dryer uses a hollow fiber membrane to strip moisture and produces -40°F dew point air year-round with no moving parts.
When should I use a vacuum dryer or an infrared dryer?
Vacuum dryers lower the boiling point of water so moisture leaves the pellets at lower temperatures, which suits heat-sensitive resins; they dry quickly, cost little to run, and 30 lb./hr. models fit lab work. Infrared dryers are mainly used for PET sheet and some fiber applications, where the infrared heat crystallizes and dries at once and can cut start-up from 6–10 hours to about one hour.
About the Authors
Vice President of Moisture & Drying Technologies, Novatec
Mark Haynie has designed and installed resin drying systems for more than 40 years, working in thousands of plastics plants across the industry. As Novatec’s Vice President of Moisture & Drying Technologies, he leads the company’s drying technology group, including its work on moisture measurement and predictive drying. He also serves as a technical reviewer for Novatec’s Drying Knowledge Center and has authored numerous technical articles and whitepapers on resin drying and moisture.
Mark earned a Bachelor of Science in Chemical Engineering from Virginia Tech.
Through Novatec’s Ask the Expert program, Mark regularly helps processors troubleshoot drying performance and resin-moisture challenges.
Technology Manager, Novatec
Joshua Belisle is Technology Manager at Novatec, where his work focuses on simulation and technology development for resin drying. He earned a B.S. in Mechanical Engineering with a minor in Engineering Business from the University of Virginia in 2023 and joined Novatec that same year. Joshua uses simulation tools to investigate previously difficult-to-measure aspects of the drying process, helping Novatec better understand airflow, heat transfer and other variables that influence resin-drying performance.
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Author Profile:
Mark Haynie has designed and installed resin drying systems for more than 40 years, working in thousands of plastics plants across the industry. As Novatec’s Vice President of Moisture & Drying Technologies, he leads the company’s drying technology group, including its work on moisture measurement and predictive drying. He also serves as a technical reviewer for Novatec’s Drying Knowledge Center and has authored numerous technical articles and whitepapers on resin drying and moisture.
Mark earned a Bachelor of Science in Chemical Engineering from Virginia Tech.
Through Novatec’s Ask the Expert program, Mark regularly helps processors troubleshoot drying performance and resin-moisture challenges.