Choosing the Best Plastics for your Vacuum Forming Project

When I first got into vacuum forming, I had no idea what kind of plastics you could use for it. If you’re just getting started with your vacuum forming machine, it may take some trial and error before you start getting reliable pulls and using the best plastic for the job is an important first step in getting professional results faster.

After building my own vacuum forming machine I couldn’t wait to use it and I’m sure you’re just as excited to make custom props, housings for electronics, and costume elements so here’s a run-down of some of the most popular thermoplastics to use in your vacuum form machine. Each has its own specific properties that make it a good choice for certain applications. Ideally the material should be easy to form with a low forming temperature, good flow characteristics and thermal strength, high impact strength and low shrinkage on cooling.

First-time Vacuum FormERS

If you’re new to vacuum forming and want to make parts for your DIY projects, HIPS (polystyrene) and PETG are by far among the most popular choices so we’ll cover those first.

HIPS (High Impact Polystyrene)

Like the name suggests, HIPS is a tough, rigid plastic with high impact strength. Its low cost makes it a popular choice for vacuum forming a variety of parts from manufacturing to protective packaging. HIPS thermoplastics have a relatively high melting point and a formula that includes a small amount of rubber making it a pliable material, meaning it’s easy to shape and form. Once this smooth, glass-like plastic is shaped and cooled, it’s durable to impact. HIPS thermoplastics are available in a number of different colors and finishes (including matte and gloss) and as it’s FDA compliant it’s used in a number of food and medical applications. It doesn’t have the greatest UV protection so you may want to go with another plastic if your project is for long-term outdoor use.

Try HIPS for your next vacuum form project!

Formability: Very Good – Forms to a high definition

Strength: Medium to Good impact strength

Shrinkage Rates: 0.3% – 0.5%

Finishing/Machining: Needs a special etch primer before spraying. Great machining with all methods. Parts can be assembled easily, using mechanical fasteners, adhesives, or solvents.

Colors: Available in a variety of colors and finishes. Also available in a flocked finish, ideal for presentation trays and inserts.

Clear: Yes – but not as clear as PETG/PC/PMMA.

Price: Low – Medium

Recommended Application(s): Low cost and disposable items, toys and models, packaging and presentation, as well as displays.

Co-Polyester (PETG / VIVAK)

PETG is a transparent plastic available in a variety of different thicknesses. It’s easy to vacuum form especially for applications that require deep draws, complex die cuts and more precisely molded details. Since PETG is FDA approved and can be sterilized it’s commonly used for food packaging and medical products as well as in the retail industry for product packaging, trays and displays. Despite being extremely lightweight, it can withstand high impact and is resistant to a range of acids, oils and alcohols. Like HIPS thermoplastics though, PETG is also less UV-resistant.

Try PETG for your next vacuum form project!

Formability: Very Good – forming range 80 – 120-degrees C / 176 – 248-degrees F

Strength: Good impact strength

Finishing/Machining: Paints and inks for polyester can be used for printing on PETG. Can be guillotined, saw cut or routered. Die cutting and punching also possible up to 3mm.

Colors: Limited colors available.

Clear: Yes – this is a popular choice for DIYers when a clear finish is needed.

Price: High (but competitive with other clear material options)

Recommended Application(s): Food packaging, point of sale, displays and medical applications.

Other Great Thermoplastics

Once you get comfortable fabricating parts using your vacuum form machine, you may find you need thermoplastics with more specific characteristics for your project. Here’s a rundown of other popular choices.

ABS (Acrylonitrile butadiene styrene)

ABS is a very rigid, sturdy plastic that offers toughness without heaviness. It can tolerate impacts, chemical and UV exposure. But despite its strength ABS thermoplastics are still flexible and easy to work with. These features, combined with its relatively low cost and ease of fabrication make it a commonly used thermoplastic.

Formability: Good – Forms to a high definition

Strength: Good- high impact

Shrinkage Rates: 0.3% – 0.8%

Finishing/Machining: Machines well with circular saws, routers and band saws. For prep and paint, it accepts all sprays.

Colors: Black, white and grey as well as other limited colors. Also available in a flocked finish, ideal for presentation trays and inserts.

Clear: No – not available in a clear finish.

Price: Medium

Recommended Application(s): Toys, luggage, caravan parts, vehicular parts, sanitary parts, electrical enclosures, machine housings, retail store fixtures, and point-of-purchase displays. Popular in the building, automotive and engineering industries.

Try ABS for your next vacuum form project!

Polycarbonate (PC)

PC thermoplastics are one of the most expensive in the bunch, and for good reason. They’re incredibly tough and self extinguishing. Depending on the grade PC thermoplastics can be rated from slow burning to passing some of the strictest fire tests known. It’s no wonder they’re used for the most demanding applications like riot shields, crash helmets, visors, machine guards and the aerospace industry. You may have also heard fabricators refer to these thermoplastics using their more common trademarked names like Lexan or arcoPlus – similar to how many of use say “Kleenex” instead of tissue.

Formability: Good

Strength: Very Good impact strength

Shrinkage Rates: 0.6% – 0.8%

Finishing/Machining: Good for screen and digital printing. Good machining qualities. Can be ultrasonically welded, drilled and tapped. Takes spray paint easily.

Colors: Available in translucent and solid colors, opal and diffuser patterns as well as in a variety of embossed textures.

Clear: Yes – excellent clarity.

Price: High

Recommended Application(s): Light diffusers, signs, machine guards, aircraft trim, skylights, riot shields, guards and visors, electronic components and data storage devices.

Polyethlene (PE, HDPE, LDPE, PE FOAM)

PE plastics are a group of thermoplastics that vary in density – giving you a wide range of uses. They’re low cost, are moisture- and chemical-resistant and have a high strength-to-density ratio, making PE thermoplastics a popular choice across many industries. While they are bit more difficult to form and have higher shrinkage rates than other thermoplastics, they do have good impact strength while maintaining flexibility.

High density polyethylene (HDPE) has more strength than standard polyethlene materials and is also resistant to oils, alcohol and acids. It can withstand extreme temperature ranges too. You’ll see it used in products ranging from water storage and liquid containers, outdoor furniture, medical radiation shields and outdoor equipment to ballistic armor, hydraulic seals and bearings, and marine infrastructure components that utilize HMWPE (High-Molecular Weight Polyethylene) thermoformed materials. Other varieties include lower density materials such as MDPE (Medium-density Polyethylene) and LDPE (Low-density Polyethylene).

Formability: PE – Difficult, PE Foam – Good but form it at lower temperatures to prevent surface scorching

Strength: Very Good impact strength

Shrinkage Rates: LDPE 1.6% – 3.0%, HDPE 3.0% – 3.5%

Finishing/Machining: Does not take spray. Takes some specialty inks.

Colors: Black, white and colors available.

Clear: Translucent – goes clear when in its plastic state which happens within temperature band of about 10-degrees C and provides excellent indicator to forming temperature.

Price: Low

Recommended Application(s): Caravan parts, vehicular parts, enclosures and housings.

Acrylic – PMMA (Perspex, Oroglas, Plexiglas)

Acrylic is a transparent and flexible material that can be thermoformed with relative ease. Although it softens at high temperatures, it won’t melt into a liquid state until it reaches about 320 degrees. This makes acrylic a great candidate for heat shaping using a heat gun. It’s a bit more expensive than other clear options but still less expensive than polycarbonate and is also available in many colors. With strong UV resistance and the ability to be polished, you’ll commonly see acrylic thermoplastics used for point of sale and retail, LCD screens, windshields, helmet visors, aircraft windows, and more.

Formability: Tends to be brittle and is temperature sensitive

Strength: Medium to High impact strength

Shrinkage Rates: 0.3 – 0.8%

Finishing/Machining: Prone to shatter, takes cellulose and enamel spray and good for hand working

Colors: Available in solid colors

Clear: Yes

Price: High

Recommended Application(s): Signs, roof lights and domes, baths and sanitary ware, light diffusers

Polypropylene (PP)

Polypropylene is a recyclable plastic (number 5) and a popular choice for reusable food containers that can be used in microwaves and dishwashers. It’s low cost, flexible and has high impact strength but is rather difficult to form. PP’s chemical resistance also works well for laboratory parts, medical applications, acid tanks, piping systems and more. However, it’s not as UV-resistant as some other thermoplastics.

Formability: Difficult – translucent material goes clear when in its plastic state. This happens within temperature band of approx. 10-degrees C/50-degrees F and provides excellent indicator to forming temperature. Good temperature control required in conjunction with a sheet level facility.

Strength: Very Good impact strength

Shrinkage Rates: 1.5 – 2.2%

Finishing/Machining: Doesn’t take spray

Colors: Black, white and colors available

Clear: Translucent

Price: Low

Recommended Application(s): Luggage, food containers, toys, enclosures, medical applications, chemical tanks

Polyvinylchloride (PVC)

PVC is a versatile thermoplastic that’s easy to fabricate, weld and machine. It’s also low cost with medium to high strength impact. PVC is a natural fire retardant and highly resistant to chemicals and stains. It can be very thin and highly flexible to make shower curtains and plastic wrap and it can also be used to make durable, rigid pipes. While it’s pure state is a white, opaque, brittle material, plasticizers and pthalates can make it much softer, while blending it with cotton can create canvas material.

PVC is used in a variety of applications in the building and construction, health care, electronics, automobile and other sectors, in products ranging from piping and siding, blood bags and tubing, to wire and cable insulation, windshield system components and more.

Formability: Forms well but has a tendency to web

Strength: Good impact strength

Finishing/Machining: Doesn’t take spray but takes some specialty inks

Colors: Black, white and colors available

Clear: Yes – different web widths available with thickness from 150 – 750 microns

Price: Low

Recommended Application(s): Packaging, machine guards and car trim

Every project is unique so it’s difficult for me to tell you which thermoplastic is the best one for you. But now that you have a starting point with HIPS (Polystyrene or Styrene) and PETG (copolyester), and are familiar with the other plastic options you’ll be able to narrow down to the right choice as you advance with your robotics, animatronics or other creative electronics projects.

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