Written by Barbara Gerard, • CEO
Craftech Industries, Inc.
Although most of the world’s fasteners are produced from metal, that choice is gradually changing for some engineers and designers. Depending on the application, a switch to plastic offers several material advantages.
Plastic fasteners are typically lightweight and flexible, yet also strong, reliable, and cost-effective. What’s more: they fail to rust, which is a benefit because this means less maintenance and replacements.
As one example, PEEK (or polyetheretherketone) is a type of plastic that offers high-performance engineering and versatility. This material has an extremely stable chemical structure that’s rare to find in other plastics, making it ideal for use in fasteners in demanding applications and industries. PEEK is often used in components for the auto, aerospace, marine, nuclear, oil and gas, and electronics sectors.
If you’re considering plastic fasteners, however, there are several questions you’ll want to ask first to ensure you make the ideal choice for your project.
1. What exactly are you looking for?
First, you’ll need to know what type of fastener that’s required for your application…an anchor, bolt, pins, or screws? Also, what dimensions do you need or can they range? Fully understanding your application requirements is the first step. Often, a diagram or drawing can help an expert fastener manufacturer or distributor suggest the ideal options.
2. Will your application be exposed to elements and, if so, which ones?
Whether it’s extreme temperatures, vibration, or chemicals, it’s important to consider the elements fasteners will be exposed to before choosing the type and material. This means noting the environment (indoor or outdoor), potential exposure levels (such as from UV rays or electrical conductivity), and the likelihood of moisture or chemicals, which may lead to rust or degradation of the components.
Here are a few examples where the properties of plastic components may offer the best durability:
• For chemical resistance: There are plastics available that can hold up to almost any chemical exposure, which is one area where this material offers far greater benefits than metal. Swimming pool parts that are exposed to chlorine is one example.
• For extreme temperatures: In general, plastics can withstand maximum service temperatures up to 300° C or 572° F.
• For low-outgassing: Outgassing is a release of gasses or impurities, which is a major concern in the semiconductor and aerospace industries, where there are high-vacuum environments. There are strict requirements for the purity of plastics for outgassing but certain types of this material are capable of measuring up.
• For non-conductivity: Plastic materials with low conductivity are available and commonly used as thermal insulators.
• For non-flammability: This is critical for parts potentially exposed to extreme temperatures, gas, or flames. Flammability tests measure a material’s combustibility, smoke-generation, and ignition temperatures. Additives can ensure plastics are non-flammable.
• For UV-ray exposure: Certain plastics hold up extremely well to UV rays. For others, a UV inhibitor can often be added to help lessen the detrimental effects.
• For water-absorption: If the application is likely to be exposed to water, this could affect the weight of the components. Mechanical, electrical, and dimensional properties can also be affected.
• For wear and tear: This is a common concern for equipment that’s subject to harsh conditions, such as continuous vibrations — such as the bearings used in automobiles, generators, or wind turbines. Some plastics offer excellent wear-resistance for such conditions.
3. What are your quality requirements?
Do you need parts that fit the ANSI (American National Standards Institute) or DIN (Deutsches Institut für Normung) standards, which ensure the safety and reliability of certain products? Do you require an ISO-certified supplier? ISO (the International Organization for Standardization) is a global, independent organization that develops standards and certifications to ensure the quality, safety, and efficiency of products.
What testing is required and will you require certification of the material used? Does the fastener require particularly tight tolerances?
Knowing the quality requirements for your application from the start can save unexpected material changes for the fasteners and downtime due to ineffective choices later on.
4. What plastic material is the ideal choice?
You’ve decided that plastic is the best material for your application. However, the type selected is critical because it will affect the function, longevity, appearance, and cost of the project.
These are important considerations. For example, some materials can be machined, but not molded. The opposite is also true. There are plastics as strong as stainless steel, yet the addition of glass or carbon fibers can make such materials even stronger, depending on the measure of strength required (such as tensile, compressive, or impact).
If weight is a concern, different plastics vary appreciably but most are less than metal. There’s also a wide cost variance between plastics and recycled materials can sometimes offer considerable savings. Plastic components can also be molded in almost any color and certain types can be made transparent. The choice is yours and it will depend on the application.
5. How many parts are needed?
As with many components, higher quantities can translate to a lower cost per part. Quantity can also dictate the most appropriate manufacturing process. For small and moderate volumes, machining is often the right approach. For higher volumes, molding parts are typically more cost-effective — and consistent. Just keep in mind that if a mold needs to be built for your part, there are associated costs and a time commitment.
As with any important purchase, choosing a knowledgeable supplier for plastic components is key. Look for one with insight into the different materials available for fasteners that can offer strong technical support.