What kinds of thermoplastics can you thermoform?

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.

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

The Core Thermoforming Processes

Vacuum Forming — The Industrial Workhorse

The most widely used thermoforming process, especially in heavy-gauge industrial applications. The heated 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. It’s simple, reliable and scalable.

Why manufacturers use it: lower tooling cost than injection molding, faster development cycles, ideal for large surface-area parts, works well for medium production volumes. Commonly used for automotive interior panels, EV battery covers, generator housings, machine covers, industrial enclosures, retail displays and medical equipment housings. For large-format parts above 500 mm, vacuum forming is often the most practical solution.

Pressure Forming — When Detail Matters

Builds on vacuum forming by adding compressed air on the opposite side of the sheet, forcing it deeper into fine features. The result is sharper definition, better texture reproduction and improved surface finish — often described as “injection molding appearance without injection molding cost.” Used for electrical enclosures, medical device housings, office equipment panels, user-facing covers, and panels with cutouts for gauges or controls.

Plug Assist Forming — For Deep Parts

When parts have deep-draw requirements, the sheet can thin excessively in stretched areas. A mechanical plug pre-stretches the sheet into the cavity before vacuum or pressure is applied, improving wall-thickness distribution and structural consistency. Used for deep battery enclosures, industrial trays, structural covers and parts with high depth-to-width ratios.

Twin Sheet Forming — Hollow and Structural

Two sheets are heated at the same time, formed separately, and fused together while hot — creating a hollow, double-wall structure. The result is increased rigidity, lightweight structural components, and internal reinforcement without extra assembly. Used in pallets, tanks, ducting systems and large structural panels.

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.

ABS (Acrylonitrile Butadiene Styrene) — The Industrial Standard

Good rigidity, high impact strength, flame-retardant grades available, available in textures and colours, cost-effective. Common in automotive interior panels, EV battery covers, machine housings, equipment shrouds and electrical enclosures. Forms well in both vacuum and pressure forming, with one of the best cost-to-performance balances in industrial manufacturing.

HDPE (High-Density Polyethylene) — Chemical and Moisture Resistant

Moisture resistant, FDA-compliant grades available, good outdoor performance, impact resistant. Used for industrial tanks, food containers, protective liners and outdoor equipment covers. Excels in functional applications.

Polypropylene (PP) — Chemical Resistant and Flexible

Good impact resistance, chemical resistance, higher temperature tolerance than many commodity plastics, and living-hinge capability. Common in automotive components, industrial containers, packaging and hinged parts.

Polycarbonate (PC) — Transparent and Impact Resistant

High impact resistance, heat resistant, glass-like transparency. Used for machine guards, safety covers, lighting components and protective shields. More expensive than ABS but chosen where performance justifies cost.

HIPS (High Impact Polystyrene) — Easy to Form

Forms easily and is cost-effective. Used in trays, packaging inserts, medical trays and consumer components.

PETG — Clear and Detail-Friendly

Easy to thermoform, good detail reproduction, recyclable, food-safe grades available. Used in medical packaging, food packaging, transparent enclosures and signage.

PVC — Versatile and Widely Used

Used across medical components, electrical panels and industrial parts. Forms well but requires careful temperature control.

TPO — Automotive Focused

High impact resistance, good weather resistance, automotive-grade performance. Used for bumpers, dashboards and exterior panels.

When Does Thermoforming Make Sense?

When the part is large, the tooling budget needs to stay controlled, annual volumes are moderate, the product may still evolve, weight reduction is important, or 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 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 method and material combination is critical — based on geometry, performance requirements, environment and production volume, not just cost alone.