ABS vs. HIPS for Vacuum Forming: Which Plastic Should You Choose?

When choosing a plastic sheet for vacuum forming, ABS and HIPS are two of the most commonly considered materials. Both are widely used in thermoforming, but they have different properties that make each one better suited to particular applications.

ABS vs. HIPS for Vacuum Forming: Properties, Advantages, Disadvantages, and Applications

When choosing a plastic sheet for vacuum forming, ABS and HIPS are two of the most commonly considered materials. Both are thermoplastics that can be heated, softened, formed over a mould, and cooled into a permanent shape.

However, they are not interchangeable in every application.

ABS generally offers better impact resistance, toughness, heat resistance, and durability, while HIPS is often chosen because it is economical, easy to thermoform, lightweight, and well suited to packaging, displays, liners, prototypes, and other applications where extreme mechanical performance is not required.

Understanding the differences between these two materials can help you choose the right sheet before starting a vacuum-forming project.

What Is ABS?

ABS stands for Acrylonitrile Butadiene Styrene. It is an amorphous thermoplastic composed of three main components:

Acrylonitrile, which contributes chemical resistance and heat resistance Butadiene, which contributes toughness and impact resistance * Styrene, which contributes rigidity, surface appearance, and ease of processing

ABS is widely used for thermoformed housings, covers, panels, machine guards, automotive components, electronic enclosures, and other products that need a combination of strength, appearance, and formability.

For vacuum forming, one of the important characteristics of ABS is its combination of relatively good mechanical properties and good thermoformability.

What Is HIPS?

HIPS stands for High Impact Polystyrene. It is polystyrene modified with rubber to improve its impact resistance compared with standard polystyrene.

HIPS is widely used in thermoforming because it is economical, easy to form, and available in many colours and surface finishes. Common applications include packaging trays, point-of-sale displays, signage, refrigerator liners, prototypes, model parts, and various lightweight formed components.

Despite the name "High Impact Polystyrene", HIPS should not be assumed to have the same toughness as ABS. In general, ABS provides better resistance to impact, cracking, and mechanical abuse.

ABS vs. HIPS: The Main Differences

The exact properties depend heavily on the particular grade, sheet thickness, additives, extrusion process, and manufacturer. Therefore, the manufacturer's technical data sheet should always take precedence over generic material comparisons.

Thermoforming ABS

ABS is an amorphous thermoplastic, meaning that it softens progressively over a temperature range rather than having a single sharp melting point. This characteristic is useful in thermoforming because the material can be heated until it becomes sufficiently flexible for forming.

Typical sheet-forming temperatures reported for ABS are approximately 150–180°C, although the appropriate temperature depends on the specific grade, sheet thickness, heating equipment, and forming process.

The sheet should be heated as uniformly as possible. If one area becomes significantly hotter than another, the hotter section can stretch more readily during forming, potentially producing uneven wall thickness.

Advantages of ABS for vacuum forming

1. High impact resistance

One of the major reasons to choose ABS is its toughness. It is generally more resistant to impact than HIPS, making it appropriate for parts that will be handled, knocked, or subjected to mechanical abuse.

2. Good rigidity

ABS provides a useful combination of stiffness and toughness. This makes it suitable for equipment covers, housings, guards, panels, and similar components.

3. Good surface appearance

ABS sheets are available in different colours, textures, and finishes. Thermoformed ABS can reproduce mould textures effectively, which is useful for visible components.

4. Good machinability

After forming, ABS can generally be cut, drilled, routed, and otherwise machined relatively easily. This is useful when a vacuum-formed part requires trimming or additional holes and openings.

5. Better resistance to heat than HIPS

ABS generally has better heat resistance than HIPS. This can be important when the finished component will operate in a relatively warm environment.

6. Suitable for durable products

ABS is often a better choice when the formed part is intended to have a relatively long service life and needs to tolerate mechanical abuse.

Disadvantages of ABS

ABS is not automatically the best material for every vacuum-forming project.

Higher cost is one of its main disadvantages compared with HIPS.

ABS also has limited UV resistance in its standard form. For prolonged outdoor exposure, a UV-resistant grade or a suitable protective layer may be necessary.

Another consideration is that ABS normally requires a higher forming temperature than HIPS, which means the heating system must be capable of reaching and controlling the appropriate temperature range.

For applications where the mechanical performance of ABS is unnecessary, HIPS may provide a more economical solution.

Thermoforming HIPS

HIPS is particularly popular in vacuum forming because it is relatively easy to heat and form.

Typical forming temperatures reported for HIPS are approximately 130–160°C, although, as with ABS, the correct temperature depends on the particular sheet grade and the manufacturer's specifications.

Its predictable forming behaviour makes HIPS attractive for both industrial production and small-scale vacuum-forming projects.

Advantages of HIPS for vacuum forming

1. Lower material cost

HIPS is generally less expensive than ABS. This becomes particularly important when producing large quantities of parts or when material cost is a major part of the product's total cost.

2. Easy thermoforming

HIPS is widely regarded as an easy material to thermoform. It can be formed at lower temperatures than ABS and is commonly used for deep-drawn thermoformed products.

3. Good surface for printing and decoration

HIPS is commonly used for point-of-sale displays, signage, and other products that require printing or graphics.

4. Lightweight

HIPS has a density of approximately 1.04–1.06 g/cm³ in typical sheet formulations, making it a relatively lightweight material.

5. Wide range of colours and finishes

HIPS sheets are available in many colours, including common white and black grades, as well as textured surfaces.

6. Good choice for prototypes

For prototypes, models, packaging, displays, and other applications where low material cost and easy forming are more important than maximum toughness, HIPS can be an excellent choice.

Disadvantages of HIPS

The biggest disadvantage compared with ABS is lower mechanical performance.

HIPS is generally more susceptible to cracking and breaking than ABS when subjected to severe mechanical abuse.

It also has lower heat resistance than ABS and standard HIPS has relatively poor resistance to prolonged UV exposure. Weather-resistant grades are available when required.

Consequently, HIPS is usually a better choice for indoor products, packaging, displays, liners, and other applications where extreme durability is not required.

Which Material Is Easier to Vacuum Form?

Both ABS and HIPS are very suitable for vacuum forming, but HIPS is often considered particularly forgiving for basic vacuum-forming work.

HIPS generally forms at a lower temperature and has predictable forming characteristics. This can be advantageous when using a relatively simple oven or a small DIY vacuum-forming machine.

ABS is also very suitable for vacuum forming, but its higher forming temperature means that the heating system must be capable of delivering sufficient and reasonably uniform heat.

For a home-built machine, however, the quality of the heating system, temperature control, sheet support, vacuum system, mould design, and forming technique can be just as important as the choice between ABS and HIPS.

A poorly heated sheet can produce bad results regardless of which of these materials is being used.

Applications: When Is ABS the Better Choice?

ABS is generally a better candidate when the finished component needs to withstand significant mechanical use.

Typical applications include:

Machine housings Protective covers Equipment enclosures Electronic housings Automotive interior components Machine guards Protective cases Durable panels Long-life prototypes Industrial components

These applications benefit from ABS's combination of impact resistance, rigidity, surface quality, and heat resistance.

For example, if you are making a protective enclosure for electronic equipment that will be repeatedly handled, ABS is usually a more logical starting point than HIPS.

Applications: When Is HIPS the Better Choice?

HIPS is particularly attractive when cost, easy forming, and appearance are more important than maximum toughness.

Typical applications include:

Packaging trays Food packaging made from appropriate food-contact grades Point-of-sale displays Retail signage Refrigerator liners Product inserts Prototypes Models Lightweight covers Retail fixtures * Display components

HIPS is also widely used for refrigerator liners, where specially formulated grades can provide properties required for that application.

It is important to note that food-contact suitability is grade-specific. The fact that a material is HIPS does not automatically mean that every HIPS sheet is suitable for contact with food. The particular sheet must have the appropriate regulatory compliance and formulation.

ABS or HIPS for a DIY Vacuum Forming Machine?

For someone building a vacuum-forming machine at home, both materials are useful.

HIPS can be attractive for experimentation because it is relatively inexpensive and forms at lower temperatures. This makes it a practical material for learning the basics of heating, mould preparation, vacuum application, and trimming.

ABS becomes more attractive when the objective is to produce a stronger and more durable finished component.

A practical approach is therefore:

Choose HIPS when:

Cost is important The part is mainly for indoor use The part does not need exceptional impact resistance Easy forming is a priority * You are making prototypes, models, packaging, or displays

Choose ABS when:

The part needs higher impact resistance Durability is important The component will be handled frequently Better heat resistance is required * You are making housings, guards, covers, or other durable components

Heating: An Important Difference

One of the most important practical differences for vacuum forming is the temperature range.

HIPS generally forms at a lower temperature than ABS. Representative ranges from published thermoforming sources are approximately:

HIPS: 130–160°C ABS: 150–180°C

These numbers should be regarded as starting points rather than universal settings. The correct sheet temperature depends on the exact material grade, thickness, heating method, mould geometry, and machine.

For this reason, it is better to use the manufacturer's recommended forming temperature whenever a technical data sheet is available.

The temperature of the plastic sheet itself is also more important than simply knowing the oven's air temperature. Different heating systems can produce very different results even when the oven is set to the same temperature.

Sheet Thickness and Material Selection

The thickness of the original sheet has a major influence on the final part.

During vacuum forming, the sheet stretches over the mould, so the finished wall is normally thinner than the original sheet. The amount of thinning is not uniform: areas subjected to greater stretching, particularly around deep draws and corners, can become significantly thinner.

This means that choosing the material alone is not enough. The following factors should also be considered:

Original sheet thickness Depth of draw Shape of the mould Draw ratio Presence of sharp corners Use of plug assistance Heating uniformity Required final wall thickness * Mechanical requirements of the finished part

For deep parts, mould design and forming technique can have a major influence on the final wall thickness.

Mould Design Still Matters

Neither ABS nor HIPS can compensate for a poorly designed mould.

Vacuum-formed parts generally require appropriate draft angles so that the cooled part can be removed from the mould. Deep draws and sharp transitions can also cause excessive stretching and uneven wall thickness.

If a component has a particularly deep cavity, a plug-assist technique can be used to mechanically pre-stretch the heated sheet before vacuum is applied. This can help improve material distribution in deep-drawn parts.

The mould surface is also important because the plastic can reproduce its texture and surface imperfections.

What About Outdoor Applications?

Neither standard ABS nor standard HIPS should automatically be considered an ideal material for prolonged outdoor exposure.

Both materials can be affected by ultraviolet radiation, with standard HIPS being particularly unsuitable for many outdoor applications. ABS also has UV limitations, although UV-resistant grades and protective cap layers are available.

If a vacuum-formed component will remain outdoors for long periods, it is better to select a grade specifically designed for weather exposure rather than assuming that ordinary ABS or HIPS will provide adequate long-term UV resistance.

ABS vs. HIPS: The Bottom Line

There is no universally "better" material between ABS and HIPS.

The better choice depends on what the finished part needs to do.

ABS is usually the better choice when durability, impact resistance, rigidity, and heat resistance are important.

HIPS is usually the better choice when low cost, easy thermoforming, lightweight construction, printing, packaging, displays, or prototypes are the priority.

For a DIY vacuum-forming machine, HIPS is an excellent material for learning and producing economical parts, while ABS is worth choosing when the finished product needs to be tougher and more durable.

The most important point is to select the specific sheet grade for the intended application. "ABS" and "HIPS" describe broad material families, and their actual properties can vary considerably between grades.

Before forming a new sheet, always check the manufacturer's technical data sheet for the recommended forming temperature, thickness limitations, mechanical properties, and any special processing requirements.

Quick Comparison

Ultimately, the choice between ABS and HIPS should be based not simply on which material is easier to form, but on the requirements of the finished part. A material that is inexpensive and easy to form is not necessarily the most economical choice if the finished component later cracks, deforms, or fails in service.