Selecting the Appropriate Resin Grade for Your Application

 

Resins are categorized by family and type that fall into three different grades; commodity, engineering, and specialty/high-performance. When selecting a plastic to use, you should begin by choosing the appropriate grade of material that has the performance requirements your finished product must meet. The correct resin grade can make or break an application.

Commodity Resin Grade

Commodity resins not only offer a variety of uses when it comes to plastic injection molding, but they serve as a budget-friendly option to customers during processing. They are typically produced at high-volume and low-cost for common disposable items and durable goods where mechanical properties are not critical. The essential features of these types of thermoplastics are separability, mobility, and easy processing.

3 examples of this type of resin include:

1. Polypropylene (PP)—Easily processed and moldable. However, it is susceptible to UV degradation and oxidation.
2. Polyethylene (PE)—Corrosion resistant, high flexibility, and low weight. However, it has high thermal expansion and poor weatherability.
3. Polystyrene (PS)—Flame retardant, fast cycle time and expandable. However, it is a poor solvent and chemically resistant.

Engineering Resin Grade

Engineering resins are commonly used for durable goods, classified (military) products, and industrial applications because they are a potential substitute for metal parts. They offer better thermal, chemical, and mechanical properties than commodity resins. However, they are more expensive and require the proper skill to processing. Essential features of these types of thermoplastics are cost and weight reduction without sacrificing strength, thermal, and chemical resistance.

3 examples of this type of resin include:

1. Acrylonitrile Butadiene Styrene (ABS)—Chemically resistant, excellent ductility, and has high impact strength. However, it has poor solvent resistance and poor weatherability.
2. Polyethylene terephthalate (PET)—High resistance to water, high strength and is shatterproof. However, it is susceptible to oxidation and is not biodegradable.
3. Polycarbonate (PC)—High impact resistance, lightweight, and it is incredibly useful in applications requiring transparency. However, it is extremely susceptible to scratching and discoloration if in contact with a flame (depending on flame rating).

Specialty/High-Performance Resin Grade

High-performance resins are specialized thermoplastics used in extremely demanding applications. Compared to large-volume engineering polymers, they have superior short-and-long term thermal stability, chemical and radiation resistance, and improved mechanical properties.

3 examples of this type of resin include:

1. Polyamide-imide (PAI)—Extremely strong, stiff, and dimensionally stable material used in elevated temperature environments.
2. Polyetherimide (PEI)—High dielectric strength, biocompatible, and exceptional strength. However, it is notch sensitive and can be difficult to process because it requires high melt temperatures.
3. Polyphenylene Sulfide (PPS)—Outstanding chemical resistance, thermal and dimensional stability, and an exceptional corrosion-resistant coating. However, fillers are required to get great impact strength. It can be subject to warpage, and it can be difficult to process because it requires high melt temperatures.

Choosing the appropriate resin material for your project is one of the most crucial factors in creating the perfect plastic product. We have developed long-lasting and trusting relationships with the best resin suppliers nationwide. If you still are unsure of what type of resin should be used in your application, it’s time to consult the experts at Midstate Mold. Contact us today!