Chemical Compatibility of a Helix Trapezoidal Screw Assembly with Plastic Nuts

Christopher Nook by Christopher Nook

As you know, the performance of trapezoidal screw assemblies doesn't just rely on the type of screw used, but in matching the given screw with the proper nut.

As you know, the performance of trapezoidal screw assemblies doesn't just rely on the type of screw used, but in matching the given screw with the proper nut. At Helix, we offer standard nuts that are manufactured  from various materials as well as those that are custom engineered from less conventional materials. Generally speaking, however, our plastic nuts are said to be more efficient than nuts made from most other materials. Such plastic nuts - available in varieties including PEEK, polyester, acetal, Torlon, Vespel, PVDF, UHMW and Ertalyte, among others - are designed to provide self-lubrication, which thereby makes the trapezoidal lead screw assembly work more smoothly, operate more quietly and work with greater reliability.

Plastic nuts have become one of the top choices among design engineers due to their various pressure velocity and thermoplastic characteristics. Pressure velocity, or PV, is a measure of a material's ability to be dynamically loaded. As you know, certain plastic compositions perform differently under certain loads based on their characteristics - a consideration that one must keep in mind when selecting the right type of nut for the screw assembly.

This brings us to another important consideration when it comes to nut selection - chemical compatibility. Chemical compatibility refers to whether or not certain materials are impacted by the environment in which the trapezoidal screw assembly is operating. For instance, will the assembly be negatively affected based on the environment? Is the assembly corrosion resistant? These are important factors to keep in mind not only when selecting the particular trapezoidal screw to be used, but the nut as well. Failure to recognize and consider the chemical compatibility could wind up costing you and your application further down the road.

So just how do you know whether or not plastic nuts are chemically compatible with the intended application? At Helix, we've made it easy for you. Not only are our experienced professionals on hand to discuss your application in detail with you and pair you with the precise nut for your particular application, but we also offer a reference guide concerning our acetal-blended lead screw nuts to help you get an idea of whether or not this plastic variety will be chemically compatible with your application.

The information in the reference guide has been compiled from a variety of literary references and sources to help you determine the performance of the plastic nut. However, it's worth noting that while this reference guide is intended to be a considering factor when it comes to plastic nut chemical resistance, it's not necessarily a guide that guarantees performance. Hence, it's recommended that you test products in their actual conditions to get a better feel for their performance as well as consult with our trained staff.


Chemical Compatibility Reference Guide


In this guide, you'll see that the chemical effect ratings are broken down into seven different ratings based on hundreds of different chemicals, all listed from A to Z. These chemical effect ratings consist of:

A: Excellent - There is little to no effect and continuous use is recommended.

B: Good - There's minor effect, with little corrosion and/or discoloration.

C: Fair -  Moderate effect, including softening, loss of strength and/or swelling. Continuous exposure is not recommended.

D: Severe - Not recommended for any use.

NA: Information is unavailable.

1: Applicable up to 72 degrees Fahrenheit.

2: Applicable up to 120 degrees Fahrenheit.

Is a plastic nut right for you? Simply download and refer to the reference guide below to get a better understanding. It includes chemicals from acetaldehyde all the way to zinc sulfate and many more in between to better help you make that determination.




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Additional Reading          

Chemical Compatibility of a Helix Lead Screw Assembly with Plastic Nuts                         

How to Compare Acme Nuts and Acme Nut Material