What kinds of thermoplastics can you thermoform?

Processes, Materials, and Where It Actually Makes Sense

Before talking about which plastics can be thermoformed, it helps to understand what thermoforming really is — and more importantly, where it fits in modern manufacturing.

Thermoforming is not a “cheap alternative” to injection molding.

It is a different engineering decision.

Instead of melting plastic pellets and injecting them into a high-pressure steel mold, thermoforming starts with a flat plastic sheet. That sheet is heated until it becomes soft and flexible. Once it reaches forming temperature, it is shaped over or into a mold using vacuum, air pressure, or mechanical force. The plastic cools, hardens, and is then CNC trimmed to final dimensions.

That’s the core process.

But the variation in how the sheet is shaped defines the type of thermoforming.

The Core Thermoforming Processes

Vacuum Forming

The Industrial Workhorse

Vacuum forming is the most widely used thermoforming process, especially in heavy-gauge industrial applications.

The heated plastic sheet is placed over a mold. Air is removed through small vent holes, creating a vacuum that pulls the sheet tightly against the mold surface. Atmospheric pressure forces the material into shape.

It’s simple. Reliable. Scalable.

Why manufacturers use it:

• Lower tooling cost compared to injection molding

• Faster development cycles

• Ideal for large surface area parts

• Works well for medium production volumes

Where it’s commonly used:

• Automotive interior panels

• EV battery covers

• Generator housings

• Machine covers

• Industrial enclosures

• Retail displays

• Medical equipment housings

For large-format parts above 500 mm, vacuum forming is often the most practical manufacturing solution.

Pressure Forming

When Detail Matters

Pressure forming builds on vacuum forming by adding compressed air on the opposite side of the sheet. After vacuum pulls the plastic toward the mold, positive air pressure forces it deeper into fine features.

The result is sharper definition, better texture reproduction, and improved surface finish.

Pressure forming is often described as “injection molding appearance without injection molding cost.”

It’s used for:

• Electrical enclosures

• Medical device housings

• Office equipment panels

• User-facing covers and doors

• Panels with cutouts for gauges or controls

Tooling cost remains significantly lower than injection molding, which makes pressure forming ideal for medium volumes or when design flexibility is important.

Plug Assist Forming

For Deep Parts

When parts have deep draw requirements, the plastic sheet can thin excessively in stretched areas. Plug assist forming solves this problem.

A mechanical plug pre-stretches the sheet into the cavity before vacuum or pressure is applied. This improves wall thickness distribution and structural consistency.

It’s often used for:

• Deep battery enclosures

• Industrial trays

• Structural covers

• Parts with high depth-to-width ratios

For heavy-gauge components, wall thickness control is not cosmetic — it’s structural.

Twin Sheet Forming

Hollow and Structural

Twin sheet forming involves heating two sheets at the same time. Each sheet is formed separately, and while still hot, the two halves are fused together at designed contact points.

The result is a hollow, double-wall structure.

Why it matters:

• Increased rigidity

• Lightweight structural components

• Internal reinforcement without extra assembly

Used in:

• Pallets

• Tanks

• Ducting systems

• Large structural panels

Twin sheet forming sits between traditional thermoforming and rotational molding in terms of structural capability.

So What Plastics Can Be Thermoformed?

Most thermoplastics can be thermoformed. The difference lies in how well they form, how they perform structurally, and what environment they’re used in.

Below are the most common materials used in heavy-gauge thermoforming.

ABS (Acrylonitrile Butadiene Styrene)

The Industrial Standard

ABS is one of the most widely used heavy-gauge thermoforming materials.

Why it’s popular:

• Good rigidity

• High impact strength

• Flame-retardant grades available

• Available in textures and colors

• Cost-effective

Common applications:

• Automotive interior panels

• EV battery covers

• Machine housings

• Equipment shrouds

• Electrical enclosures

ABS forms well in both vacuum and pressure forming processes and offers one of the best cost-to-performance balances in industrial manufacturing.

HDPE (High-Density Polyethylene)

Chemical and Moisture Resistant

HDPE is known for durability and chemical resistance.

Key characteristics:

• Moisture resistant

• FDA compliant grades available

• Good outdoor performance

• Impact resistant

Used for:

• Industrial tanks

• Food containers

• Protective liners

• Outdoor equipment covers

HDPE is not chosen for high cosmetic detailing but excels in functional applications.

Polypropylene (PP)

Chemical Resistant and Flexible

PP offers:

• Good impact resistance

• Chemical resistance

• Higher temperature tolerance than many commodity plastics

• Living hinge capability

Common uses:

• Automotive components

• Industrial containers

• Packaging

• Hinged parts

It is widely thermoformed in both thin and thick gauges.

Polycarbonate (PC)

Transparent and Impact Resistant

Polycarbonate is used when clarity and strength are required.

Properties:

• High impact resistance

• Heat resistant

• Glass-like transparency

Applications:

• Machine guards

• Safety covers

• Lighting components

• Protective shields

It is more expensive than ABS but chosen where performance justifies cost.

HIPS (High Impact Polystyrene)

Easy to Form

HIPS is widely used in both thin and thick-gauge applications.

It forms easily and is cost-effective.

Used in:

• Trays

• Packaging inserts

• Medical trays

• Consumer components

PETG

Clear and Detail-Friendly

PETG combines clarity with good impact resistance.

Benefits:

• Easy to thermoform

• Good detail reproduction

• Recyclable

• Food-safe grades available

Used in:

• Medical packaging

• Food packaging

• Transparent enclosures

• Signage

PVC

Versatile and Widely Used

PVC is used across industries for:

• Medical components

• Electrical panels

• Industrial parts

It forms well but requires careful temperature control.

TPO

Automotive Focused

TPO is primarily used in automotive exterior components.

It offers:

• High impact resistance

• Good weather resistance

• Automotive-grade performance

Used for bumpers, dashboards, and exterior panels.

When Does Thermoforming Make Sense?

Thermoforming is the right decision when:

• The part is large

• Tooling budget needs to stay controlled

• Annual volumes are moderate

• The product may still evolve

• Weight reduction is important

• Development time needs to be short

It is especially effective for heavy-gauge industrial components where injection molding tooling would be excessively expensive.

Final Thought

Thermoforming is not a “secondary” process. It is a strategic manufacturing choice.

Understanding the differences between forming processes and material options allows engineers and procurement teams to make better decisions — not just cheaper ones.

If you’re developing industrial covers, EV battery enclosures, machine housings, or large-format plastic parts, choosing the correct thermoforming method and material combination is critical.

And that decision should be based on geometry, performance requirements, environment, and production volume — not just cost alone.

If you want next, I can:

• Add comparison tables for quick scan

• Add a material selection guide section

• Create a downloadable PDF version

• Or write the next deep blog in the same magazine style

Your call.