Reinforced Thermosets and Thermoplastics: A Process and Material Comparison in Composites Manufacturing

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The differences between reinforced thermosets and reinforced thermoplastics matter when it comes to selecting materials for composites manufacturing processes. In his role as a Technical Support Manager at Composites One, Neil Smith helps customers understand how to select the right process and material options for their end-use applications.

The most significant differentiation when deciding whether to use thermosets or thermoplastics in composites manufacturing are in the processing technique and production volume requirements.

Thermoset resins like epoxy, vinyl ester, and polyester are a great fit for a large array of applications while thermoplastics serve a higher-volume composites manufacturing market that can justify the capital expenditure that high-temperature tooling and equipment requires.

“Thermoplastics are processed at such high temperatures that even the lowest temperature processing requirements for a commodity type reinforced thermoplastic are typically quite a bit higher than those required for processing the highest temperatures capable by thermoset prepreg,” explains Neil Smith.

There are different grades of thermoplastics based on their processability, and there tends to be a  correlation between the temperature at which the materials are processed and the temperature at which they can perform in end-use applications.

Industrial/commodity thermoplastics, such as PVC, ABS, PP, and PE plastics, are processed at lower temperatures, typically temperatures as low as 350 degrees Fahrenheit, and commonly used for lower cost, less structural type applications.

Engineered thermoplastics, such as PA, PET, PPS, and PEI, have slightly higher processing temperature requirements, around the 400-600 degree Fahrenheit range, and have growing uses in sports and recreation applications requiring slightly higher level performance.

High-performance thermoplastics, such as the family of PEAK plastics, are processed in excess of 600 degrees Fahrenheit, making them ideal for use in demanding Aerospace applications.

To heat or not to heat? That is the question.

All reinforced thermoplastics require the addition of heat to process whereas thermosets chemically cross-link without the need for additional heat. Thermosets can never be reformed or recycled regardless of how much heat is applied.

Tooling requirements in composites manufacturing

The manufacturing implication of thermoplastics requiring the introduction of high heat is an increase in tooling costs and performance. Thermoplastics tooling must have the power to accommodate higher temperatures and repeated thermal cycling, including expanding and contracting with every single cycle.

“It’s the general rule of thumb that you’re not going to consider processing reinforced thermoplastics without a metallic tool because of the temperature requirements, and compared to a room temperature processing composite tool, a metallic tool is going to be quite a bit more expensive,” says Neil.

The overarching characteristic of reinforcement thermoplastics from a performance standpoint is fatigue resistance and damage tolerance. What tends to differentiate thermoplastic materials used among industries is the end-use temperature capability. For instance, commodity thermoplastics are used for rock guards on tractor-trailers where there’s no real temperature requirements based on the application.

For applications with higher temperature requirements, it is important to specify high-performance reinforced thermoplastics where regulations specify much lower mechanical property drop-off at elevated temperatures. While there is a high-volume potential, these high-temperature conditions can present technical challenges when it’s necessary to introduce that level of heat into the tool and also to extract the heat out of the tool when releasing the part.

Neil explains, “We understand the more formal requirements of the Aerospace industry from a material approvals and specifications standpoint,” which makes Composites One a valuable partner to Aerospace manufacturers.

Thermoplastic formats

There are several formats of reinforced thermoplastic materials that composites manufacturing customers should consider.

Fully impregnated – This format refers to reinforcements that are fully impregnated similar to thermoset prepreg. They can include unidirectional fiber or ‘tape’ and a variation of laminates with both continuous and short fiber reinforcements. They are not drapeable at room temperature.

Partially impregnated – With partially impregnated thermoplastics, filaments are woven or ‘comingled’ within the dry reinforcement. This format of material is much more conformable than a fully impregnated tape or laminate and drapeable at room temperature, similar to a dry fabric reinforcement.

Braided – By braiding a fully impregnated unidirectional tape, A&P Technology, a world leader in braiding technology, offers a unique material format category of conformable thermoplastics with some distinct processing advantages.

Neil explains, “A&P utilizes slit tape at various thin widths down to roughly 1/8-inch, depending on application and processing requirements, and braids it together using the same braiding technology as its braided reinforcement. This creates a thin, fully impregnated braided tape that can form better at room temperature and can form into some intricate mold geometries.”

Watch this video demonstration from CAMX 2021 where Composites One and A&P demonstrate using a conformable braided commingled nylon carbon sleeve to produce a bladder molded reinforced thermoplastic part. The video demonstration utilizes the nylon carbon braided slit tape to produce a diaphragm molded, higher volume composite part.

The benefit of your technical support manager at Composites One

Technical Support Managers at Composites One serve as objective advisors for customers, with the goal of improving composites processing efficiency, regardless of which materials – thermosets or thermoplastics – and processing methods are used. Technical Support Managers bring a toolkit of processing options to customers and together determine the best approach based on the application, production volumes, and end-use requirements for the products.

“Composites One has a material agnostic, diversified product portfolio and we’re able to apply our knowledge and resources across industry applications and capabilities to benefit our customers,” says Neil.

At Composites One, we strive to be innovative and dependable and to deliver results for our customers. Our Advanced Composites Team offers expert knowledge of composites materials as the leaders in providing materials management and logistics solutions for demanding markets. In Aerospace, Marine, Wind Energy, and beyond, our industry-leading distribution model and Technical Team are ready to support manufacturers that are using composites to design the innovations of tomorrow.