What is a high-strength plastic?
A high-strength plastic is one that possesses excellent mechanical qualities and doesn’t break or deform easily. Sometimes, a plastic with high strength may be generally high performance, and will have good resistance to heat or chemicals as well as being strong and durable.
Many high-strength plastics fall into a group known as engineering plastics. These include the polycarbonates used in motorcycle helmets and polyphenylsulfone (PPSU) used to create aircraft parts.
For a material to be ‘strong’, we generally mean that it takes a lot of force to break it. A strong plastic is one with strong bonds and the ability to absorb and withstand a large amount of energy, like from impacts.
However, a strong plastic can be weakened by temperature, so even the strongest of plastics might only be strong in the right contexts. Strong, durable plastics with poor thermal management properties aren’t any good if they’re put in situations where they might heat up and fail.
One example of a high-strength plastic is nylon, which may seem unusual given how much of a commonly used material nylon now is.
Nylon plastics can possess a tensile strength of well over 12,000 psi, coupled with a relatively high melting point of around 232 degrees Celsius. Despite its common usage in things like clothing and fishing nets, its high strength makes it useful for machine parts as well as safety critical objects like parachutes, seatbelts, and ropes.
High-strength plastics as a loose group commonly include polymers that have been bolstered by something else included in their makeup such as carbon fiber. In that sense, ‘pure’ plastics will often be lacking compared to these mixed materials.
What is the hardest plastic on Earth?
When considering the toughest, strongest, and hardest plastics for various uses, it can be easy to equate one property with another. However, an exceptionally hard plastic isn’t necessarily a super strong plastic.
High hardness means that a plastic won’t dent or scratch easily – plastic won’t scratch something like glass, because the latter is harder than the former.
One of the hardest plastics in use is acrylonitrile butadiene styrene, or ABS as it’s more commonly known. ABS is found everywhere from children’s toys to automotive parts, and it has fantastic impact resistance. It also possesses great abrasion resistance, meaning it won’t easily scratch and scuff.
Another very hard plastic perhaps more common that ABS is polycarbonate. Polycarbonate is transparent, making it a widespread replacement for glass that boasts even better impact strength. Polycarbonate doesn’t just replace ordinary glass, as it’s also used for bulletproof glass and protective gear like riot shields.
Like ABS, it’s also resistant to abrasion, furthering its usefulness as a hard see-through plastic.
Another plastic well-loved for its toughness is polydicyclopentadiene (PDCPD), which has uses including body panels for tractors and military and construction equipment. Being a thermoset plastic, PDCPD is also highly resistant to temperature changes.
It’s hard to label any plastic as the definitive hardest or toughest, but between these three, some of the most high-demand roles for plastic are covered between machine guards, tool housings, car bumpers, and more.
Hard plastics can be brittle, so whilst a hard plastic is good for resisting dents and dings in hazardous environments, they may not be the greatest option if put under a lot of strain. The mechanical properties of plastics need to be considered as a whole rather than focusing on one area, for that reason.
What plastic is as strong as steel?
Some plastics are stronger than steel, but not necessary therefore better than steel.
For instance, Kevlar—the synthetic fibre commonly used in bulletproof vests—has more tensile strength than steel. The material has been used to replace steel in certain tyres and wheels, making it a stronger alternative with less weight.
However, steel is harder than Kevlar, and so a steel knife could easily cut through it. When talking about plastic strength, it’s important to remember that having just one mechanical property better than a metal alternative doesn’t mean the plastic is better in all regards and makes for a good replacement.
It’s also important to remember that spider silk is many times stronger than steel, but it’s not about to replace steel in our industries. Due to the size difference, the pound-for-pound strength is irrelevant and spiders silk is easily broken.
Therefore, when talking about a plastic being stronger than steel, the realistic applications need to be considered. A thin piece of plastic might be mechanically stronger than steel, but it’s no match for a thick steel beam.
A good example of this lies in a recent development by MIT. Their research into plastics has produced a new material that boasts higher strength than steel. The plastic has been dubbed 2DPA-1, and its potential uses are numerous.
However, the strong plastic comes only the form of thin sheets, drawing a similarity again between spider silk and steel. While one might be stronger, it can’t be used in the necessary densities and volumes needed.
Still, strong plastics don’t need to outright replace steel to be stronger in useful ways. Plastics stronger than steel can be used for small component and part replacements, or for applications that enhance existing practices.
For example, 2DPA-1 has been theorised as being a useful coating for paint or metal to protect them from the elements.
Is there a plastic as strong as aluminium?
Aluminium is the most abundant metal in the Earth’s crust, and it’s commonly used in quite thin forms.
Combined with its natural malleability, this makes it quite easy to bend, but its strength-to-weight ratio is very good. Aluminium can be used to make many alloys, which can technically add to its strength quite significantly.
In certain weights and forms, there are plastics that would be stronger than aluminium, just as there are plastics that would be stronger than steel. However, applications like architecture and aerospace engineering, which use high-strength aluminium, can’t currently be done with plastic replacements.
Aluminium is stronger than many ‘pure’ plastics, but some plastic composites that involve materials like carbon fibre may rival the strength of aluminium.
Glass-mat-reinforced thermoplastics (GMT) are made to replace metals such as steel and aluminium. The material is more complex than pure plastics, but finds a home commonly in sectors like the automotive industry for being a strong plastic whilst being lighter than aluminium.
What is the most unbreakable plastic?
The aforementioned 2DPA-1 plastic developed by MIT has been dubbed as a genuinely unbreakable plastic when built up in layers, but with the material still being in its infancy, this claim is likely still theoretical.
Arguably the most unbreakable plastic currently in use is polycarbonate, with shatter-proof strength that is sometimes claimed as nearly unbreakable.
Polycarbonate can take incredible impacts without cracking and breaking, and a good example of this is its use in police shields. These shields are designed to take punishment from all kinds of sources like blunt objects such as bats and pipes, thrown projectiles like rocks and bottles, and even ballistics like rubber bullets.
Given that rubber bullets can hit with enough force to break bones, the toughness of polycarbonate is easier to understand.
However, there is no plastic which is truly unbreakable regardless of how it’s marketed. Polycarbonate, like many plastics, can be affected by certain chemicals which cause cracking and weakening. While this might not ‘break’ the plastic in and of itself, it may degrade the plastic’s ability to stand up to impacts that it would otherwise withstand.
Be wary of any plastic touted as ‘unbreakable’—this is likely nothing more than an exaggerated claim.
What plastic has the highest compressive strength?
The compressive strength of a plastic describes its ability to take force in a specific unit area in the form of compression.
Compressive strength can be seen as the opposite of tensile strength, which is more commonly used to describe material qualities.
Tensile strength describes a material’s ability to take pulling force without increasing greatly in size. Compressive strength is the material’s ability to take a pushing force in the same way.
Polyimide plastic shows a high compressive yield strength on its own, but when reinforced with glass fiber it outstrips other plastics by a healthy margin. Making a composite with glass fiber increases the compressive strength of polyimide by almost 50%.
However, polybenzimidazole (PBI)—commonly marketed under the name Celazole—is a ‘pure’ plastic that boasts even greater compressive strength at around 400 MPa, nearly double that of polyimide + glass fiber which sits around 220 MPa.
Due to this high compressive strength, PBI is used in the creation of astronauts’ space suits and aircraft walls. The extremes of pressure that both of these applications involve mean that a high compressive strength is essential.
Some uses of PBI involve blending it with other synthetic fibres like Kevlar to boost its properties even further.
Which strong plastic do I need?
Not every application needs a high-performance plastic. While some plastics are relatively ‘strong’ in the right purpose, the cost of manufacturing parts needs to be taken into account. A strong plastic can make products longer lasting and higher quality, but it may be an unnecessary overinvestment and could ultimately end up costing more.
It may be that the design of your part lends itself to structural strength that doesn’t require as tough a plastic as initially thought, and so you could select something a little less heavy duty. If in doubt, ask!
Being experts in plastic fabrication and machining, ask our expert team at GA Profiplast if you’re unsure what sort of plastic you need and how it can be professionally machined to create the parts required.
We can simplify the process of a selecting a plastic and give you the facts in clear terms, making the choice an easy one with minimal stress.
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