Hone your understanding of your thermoforming material options! In this article, we’ll discuss composite plastics, including:

• What are composite plastics?
• Best composites for vacuum forming
• Thermoforming with composites
• When to use composite plastics for thermoforming
• Get the right material for your application

What are composite plastics?

Composites combine thermoplastics with other components. The thermoplastic functions as the matrix of the material, while fibers and fillers act as reinforcements within this matrix. 

Composite plastics, when made and formed correctly, can enhance the characteristics of the thermoplastic used. If you’re looking to make a component stronger or more durable, you might choose to use a composite plastic on your next model to augment these qualities.

Best composites for vacuum forming

Composite plastics used for vacuum forming must be capable of softening and stretching under heat. The reinforcement fibers and fillers used to create the composite must not disrupt the forming process or lose their own characteristics after vacuum forming. For example, if you want to increase durability, you need to ensure that the fibers in the composite you’re using can withstand heat without compromising their reinforcing properties.

Let’s discuss a few types of plastic composites you can use in vacuum forming:

Fiber-reinforced thermoplastics

Fiber-reinforced thermoplastics add glass, carbon, or aramid fibers throughout the base thermoplastic matrix.

• Benefits: Enhanced mechanical strength, stiffness, and impact resistance
• Use case examples: Automotive components and protective gear

Filled thermoplastics

Filled thermoplastics combine particulate materials like talc, calcium carbonate, and wood fibers with a common thermoplastic. 

• Benefits: Improved rigidity, thermal stability, and cost-effectiveness
• Use case examples: Applications where extra strength is needed without adding excess weight

Thermoplastic elastomer (TPE) composites

TPE composites mix multiple polymers (plastic and rubber, for example) to produce a material that retains both thermoplastic and elastomeric properties. Elastomers are materials that can return to their original shape after distortion. TPE composites add the ability to undergo heat and molding to these elastomer properties.

• Benefits: Flexibility, toughness, workability
• Use case examples: Seals and gaskets

Thermoplastic polyolefins (TPOs)

TPOs build on TPEs by adding polypropylene (PP) as well as other reinforcing agents to the composite.

• Benefits: Impact resistance, aesthetic appearance
• Use case examples: Bumpers and fenders

While less versatile than TPEs, TPOs can form more durable products.

Composite materials at SSI

While we most often see projects involving TPE and TPO, we can order any vacuum formable material needed for a job, whether that’s fiber/filler-reinforced thermoplastics or something else!

In addition to the materials listed above, we also frequently work with ABS laminated with TPE or TPO. This composite material is great for achieving structure along with a vinyl finish and removes the need to hermetically bond the two materials.

Thermoforming with composites

The presence of reinforcements or fillers in a composite can affect how the plastic behaves during thermoforming. This means plastic manufacturers must adapt the thermoforming process to account for the needs of different composites. 

The heat required for thermoforming can differ from material to material, and there can be a lot of variation in how each material responds to vacuum and pressure. This is due to differences in mechanical properties, including:

• Tensile strength 
• Elasticity
• Density
• Flexural stiffness
• Compressive strength and stiffness
• Thermal expansion

When forming prototypes for SSI customers, our engineers adjust controls and valves on our thermoforming equipment to evaluate how a material reacts to heat and pressure. The results of these tests help us determine how we need to adjust the factors listed above.

When to use composite plastics for thermoforming

Is a composite the right choice for you? We asked SSI Vice President of Operations Kyle Wirt for insight:

“We’ve noticed many vehicle manufacturers prefer using TPO and TPE for interiors. Door panels, consoles, gloveboxes, dashboards — these use a TPO/TPE-laminated or capped plastic to achieve a nice luxury look: leather, vinyl, woodgrain, stainless steel, et cetera. We also see a lot of TPO used for mast boots on sailboats.”

But composites aren’t always the right choice:

“The recreation industries — boat, auto, utv, anything off road — typically need to make parts economically and fast. We have found plastics to be a more attractive option for that than composites.

“Out of all the industries we work with, aerospace uses composites most often. While composites can be expensive, they also offer enhanced properties that aerospace manufacturers need to build aircraft that are safe and sustainable.”

Get the right material for your application

Like many decisions, whether or not a composite is the right choice for you depends on a variety of factors. But a good rule of thumb can be to weigh your needs: 

• Do you need extra strength for critical components? Or would the right base thermoplastic be enough for the job? 
• Do you have a budget that will allow you to benefit from the enhancements of composite materials? Or is economy and speed more important to you?
• Do you need to achieve a shiny, luxurious aesthetic? Or are your components more functional?

While you’ll be able to answer some of these questions on your own, there are some considerations — like whether you could achieve the right effect with a standard thermoplastic — that we can help you weigh. Our team is ready to help; request a quote to get in touch!