Walk down any airport concourse and you will see the same thing: hundreds of hard-shell suitcases that look almost identical. Glossy, ribbed, four wheels, telescopic handle. 🧳 But under the paint they are built from very different plastics, and that difference decides whether your suitcase comes off the carousel with a scuff, a dent, or a crack running from corner to corner.
Most product pages will not tell you what really matters. They say "durable ABS" or "premium polycarbonate" and move on. In this guide we go through the 10 things that decide which suitcase material actually survives air travel: what ABS, polycarbonate and polypropylene really are, why "HPX" is not one material but two, how Peli builds its Protector, Air and ATX cases, and the checks that tell you more than any label. At the end you will find a comparison table, a checklist and the cases we recommend. 👇
🧪 Part 1: The Classic Suitcase Shell Materials
1. ABS: cheap, rigid and the first to crack
ABS stands for acrylonitrile butadiene styrene. It is the same family of plastic used for keyboard keys, car interior trim and plastic building bricks. It is easy to mould, takes colour and gloss beautifully and, above all, it is inexpensive. That is why most budget hard-shell suitcases in supermarkets and discount stores are made of ABS.
The problem is how ABS behaves under a hard, sudden load. It is stiff rather than elastic. A thin ABS shell resists everyday knocks well enough, but when a heavy bag lands on it from above, or it falls off the end of a baggage cart onto a sharp edge, it does not flex and spring back. It cracks. ABS also loses some of its toughness in freezing temperatures, which matters when a suitcase waits on the apron in winter or rides in an unheated hold.
- Strengths: low price, huge choice of colours and finishes, holds its shape well, fairly scratch-resistant for the money.
- Weaknesses: heavier than polypropylene for the same strength, brittle failure (cracks instead of dents), less tough in the cold.
- Best for: occasional trips, mostly as cabin baggage, where the case rarely goes through the full baggage-handling system.
An ABS suitcase is not a bad buy if you fly twice a year and keep it in the cabin. But if you check it in regularly, you are betting that nothing heavy ever lands on it at the wrong angle. Sooner or later that bet is lost.
2. Polycarbonate: flexible, glossy and often not 100% polycarbonate
Polycarbonate (PC) is a much tougher engineering plastic. It is used for safety glasses, riot shields and machine guards because it can absorb a lot of energy before it breaks. In a suitcase this shows up as elasticity: press on a good polycarbonate shell and it bends inwards, then pops back into shape. That flex is exactly what protects against cracking.
There are two catches. The first is scratches. Polycarbonate is relatively soft on the surface, so glossy PC suitcases pick up fine scratches and scuff marks quickly. Matte or textured finishes hide this much better than mirror-gloss ones. The second catch is the label. Many cheaper cases are sold as "polycarbonate" but are actually a PC/ABS blend, or a thin polycarbonate film laminated over an ABS core. They look the same in the shop and behave very differently on the carousel.
- Strengths: excellent impact toughness, flexes instead of cracking, keeps its toughness in cold weather, stylish finishes.
- Weaknesses: scratches easily, thin shells can crease or dent permanently at corners, quality varies enormously between "pure PC" and blends.
- Best for: frequent travellers who want a light, good-looking shell and accept cosmetic wear.
If a listing does not say 100% polycarbonate, assume it is a blend. We compare the two most popular shell plastics in detail in our guide to polypropylene vs polycarbonate carry-on suitcases.
3. Polypropylene: the lightest plastic and the toughest per gram
Polypropylene (PP) is the quiet champion of suitcase plastics. It is the lightest of the common engineering plastics: its density is about 0.9 g/cm³, compared with roughly 1.05 g/cm³ for ABS and 1.2 g/cm³ for polycarbonate. In practice that means a polypropylene shell can be made thicker, and therefore stronger, for the same weight.
Polypropylene is also naturally tough and slightly flexible, it does not absorb water, and it shrugs off most chemicals, oils and cleaning agents. Suitcases made from it are usually injection-moulded, which lets the manufacturer build in ribs, thicker corners and precise sealing surfaces. That is also why polypropylene is the material of choice for many serious protective cases.
There is also a practical reason polypropylene works so well on the baggage belt: it tends to fail gradually. Instead of a sudden crack, an overloaded PP shell usually deforms, scuffs or whitens at the point of impact. The case keeps working and keeps your things inside, even if it no longer looks new.
- Strengths: lowest weight for its strength, high impact resistance, water- and chemical-resistant, very long service life.
- Weaknesses: harder to print with bright colours and patterns, surface scuffs show on smooth finishes, basic homopolymer grades get brittle in deep cold (impact-modified copolymer grades solve this).
- Best for: checked baggage, frequent flyers and anyone who wants maximum protection per kilogram.
The catch with polypropylene is that the grade and the moulding process matter more than the word "PP" on the tag. A thin, cheap PP shell can still be flimsy. A thick, ribbed, impact-modified PP shell is among the toughest things you can put on a baggage belt.
4. Aluminium: the honourable mention
Aluminium suitcases are not plastic, but they belong in any material comparison because people often choose them "for strength". Aluminium does not crack. It dents, and every dent stays. It is also heavy: at about 2.7 g/cm³ it is three times denser than polypropylene, so aluminium suitcases eat a big part of your baggage allowance before you pack anything. Most aluminium luggage is also not waterproof, because the frame and hinge joints are not sealed.
For some travellers the dented, well-travelled look is part of the appeal. For protecting what is inside, it is not the best trade. We explain the differences in aluminium case vs Peli case.
🛡️ Part 2: Where Peli Cases Fit In
5. "HPX" is not one material: Storm HPX resin vs Air HPX²™
You will often see "HPX resin suitcases" mentioned as a fifth category, next to ABS and polycarbonate. That is misleading. HPX is not a generic plastic you can buy from any manufacturer. It is Peli's own name for proprietary high-performance polymers, and there are two different ones:
- HPX resin is used in Peli Storm cases, the heavy-duty line with push-button latches, developed from the Hardigg Storm range and widely used by military and industrial users.
- HPX²™ is the newer polymer used in Peli Air cases. It was developed to cut weight: Peli states that Air cases are up to 40% lighter than comparable polymer cases, while still being waterproof (IP67), crushproof and dustproof.
So when someone asks whether an "HPX suitcase" is better than a polycarbonate one, the honest answer is: it depends which HPX, and it only exists at Peli. What both have in common is that they are used for thick-walled, sealed protective shells, not thin decorative ones. That construction is the real reason they outperform ordinary luggage, more than the chemistry alone.
For travellers the practical difference is simple. Storm cases are built for crates, vehicles and equipment rooms, where weight matters less than brute strength. Air cases are built for people who fly: a carry-on such as the Air 1535 or a checked case such as the Air 1595 keeps the sealed, protective shell of a Peli case but leaves more of your baggage allowance for what you pack.
6. Peli Protector: impact-resistant copolymer polypropylene
The classic Peli Protector cases, including the famous Peli 1510 carry-on, are moulded from ultra high-impact copolymer polypropylene. That is exactly the "good" kind of polypropylene from point 3: an impact-modified grade that stays tough in cold weather, moulded thick, with a solid wall section and reinforced corners.
Add an O-ring seal in the lid, a pressure equalization valve that stops the case locking shut after a flight, stainless steel hardware and double-throw latches, and you get a case that is watertight to IP67 and built to be dropped, stacked and thrown. The 1510 measures 56.1 × 35.9 × 22.9 cm, which fits the cabin limits of most major airlines. It is heavier than a fabric carry-on, but it is one of the few suitcases you can sit on, stand on or leave in the rain without a second thought. More on why this design lasts decades in the strongest suitcases money can buy.
7. Peli ATX: a sealed polypropylene blend with Peli Armor™
The newest line, the Peli ATX travel cases (HC22 carry-on, HC25 medium and HC30 large check-in), takes the protective-case idea and packages it as a real travel suitcase. The shell is moulded from a proprietary polypropylene blend using Peli Armor™ construction. There is no zip at all: the two halves close on a sealed seam with integrated TSA locking latches made from zinc alloy.
That matters because on most hard-shell suitcases the weakest point is not the shell but the zip. A crushed or burst zip opens a suitcase that is otherwise intact. The ATX removes that weak point completely. It also rides on Hinomoto® spinner wheels and comes with a removable liner with compression, so it packs like a normal suitcase.
- ATX HC22 (carry-on): 55.9 × 35.6 × 23.1 cm, 30 litres, 4.8 kg empty (5.9 kg with liner).
- ATX HC25 (medium check-in): the sensible size for 20–23 kg fares.
- ATX HC30 (large check-in): 76.2 × 50.8 × 30.7 cm and 90 litres for long trips and higher allowances.
In short: Air is Peli's answer to "as light as possible", ATX is its answer to "a four-wheel suitcase that simply does not break", and Protector is the original that does both jobs for equipment.
✈️ Cabin cases built from better materials
🔍 Part 3: How to Judge Any Suitcase Material
8. Construction beats the label: thickness, ribs, corners and closure
Two suitcases made of "the same" plastic can differ in strength by a factor of several. The material sets the potential; the construction decides how much of it you get. Before you trust any material claim, check these points in the shop or in the product photos:
- Wall thickness. Press the middle of the shell with your thumb. If it gives way easily and stays dented for a moment, the wall is thin, whatever the plastic.
- How it is made. Injection-moulded shells (typical for polypropylene and protective cases) can have thicker corners and built-in ribs. Many cheap ABS and PC suitcases are thermoformed from a flat sheet, which stretches and thins the material exactly at the corners, where impacts hit hardest.
- Corners and edges. Look for reinforced corners, bumpers or a thicker rim around the opening. That is where most cracks start.
- Zip or latches. A zip is a fabric seam on a hard case. It can burst under pressure and it lets water in. A frame or latch closure with a gasket is a different class of protection.
- Wheels and handle mounts. A shell is only as strong as the points where the wheels and trolley bolt through it. Riveted mounts in thin plastic are a common failure point on budget cases.
This is also why a well-built case in a "cheaper" material can outlast a badly built one in a premium material. We go deeper into this in how to buy a travel suitcase that lasts for years.
One more myth is worth clearing up here: a hard shell is not automatically waterproof. Most hard-shell suitcases, whatever they are made of, close with a zip and have no gasket between the two halves. In heavy rain on the apron, or in a puddle on the loading ramp, water can get in along the zip line. Only cases with a continuous seal in the lid, such as IP67-rated protective cases, can honestly claim to keep water out.
9. Weight: why the lightest shell is not always the lightest suitcase
Material density is only half of the weight story. Here is how the common materials compare per cubic centimetre, from lightest to heaviest:
- Polypropylene: about 0.9 g/cm³, the lightest.
- ABS: about 1.05 g/cm³.
- Polycarbonate: about 1.2 g/cm³.
- Aluminium: about 2.7 g/cm³, the heaviest by far.
But a suitcase maker can use less of a stronger material, so a thin polycarbonate case can weigh less than a thick polypropylene one. The real question is not "which material is lightest" but "how much protection do I get per kilogram". A 3 kg bargain suitcase that cracks on its second trip protected nothing. On the other hand, on a 20 kg low-cost fare every kilogram of shell is a kilogram you cannot pack, which is exactly why Peli developed the Air line. If weight limits are your main concern, see how the empty weight of different cases eats into your allowance in our guide to the suitcase up to 20 kg.
10. Cold, sun, scratches, care and recycling
The last differences show up over years rather than on the first trip.
- Cold. Checked bags can sit on a frozen apron or in a cold hold. Polycarbonate and impact-modified polypropylene keep their toughness at low temperatures well; ABS and basic polypropylene grades become noticeably more brittle.
- Sun and UV. Long exposure to sunlight fades colours and can weaken many plastics over time. Dark, UV-stabilised shells cope best. Storing your suitcase in a dark cupboard rather than a sunny attic adds years to any material.
- Scratches. Glossy polycarbonate shows the most scratches; textured polypropylene and matte finishes hide them best. Scratches are cosmetic, cracks are not, so do not judge a suitcase by how new it still looks.
- Cleaning. All four materials clean with warm water and mild soap. Avoid solvents such as acetone on ABS and polycarbonate, which can cloud or weaken the surface. On sealed cases, wipe the lid gasket occasionally and keep it free of sand and grit.
- Repair and warranty. A good manufacturer sells spare wheels, handles and latches. Peli backs most of its cases with a lifetime guarantee and supplies spare parts, which keeps a case in service for decades.
- Recycling. Polypropylene carries recycling code 5 and is one of the more widely recycled plastics. ABS and polycarbonate fall under code 7 ("other") and are harder to recycle. In practice, the greenest suitcase is the one you do not have to replace every few years.
📊 Suitcase Materials Compared at a Glance
| Material | Weight | Impact | Scratches | Cold | Typical failure |
|---|---|---|---|---|---|
| ABS | Medium | Fair | Good | Weaker | Cracks |
| Polycarbonate | Low to medium | Very good | Poor | Good | Creases, scratches |
| Polypropylene | Lowest | Very good | Fair | Grade-dependent | Scuffs |
| Aluminium | High | Good | Fair | Good | Dents |
| Peli HPX²™ (Air) | Low | Excellent | Good | Good | Surface wear |
| Peli PP copolymer / Peli Armor™ | Medium | Excellent | Good | Good | Surface wear |
Ratings are general guidance for typical suitcase shells. Wall thickness and construction can move any material up or down this table.
For checked baggage the stakes are higher, because that is where shells meet conveyor belts, heavy bags and wet tarmac. These are the check-in cases we recommend: 👇
🧳 Checked suitcases that do not crack
🎯 Which Material for Which Traveller?
- Two holidays a year, cabin only: ABS or a PC/ABS blend is acceptable. You save money and the case rarely meets the baggage system.
- Frequent flyer who checks a bag: 100% polycarbonate at minimum, ideally thick injection-moulded polypropylene. For a suitcase that behaves like normal luggage but does not break, the Peli ATX HC25 or HC30.
- Every kilogram counts (low-cost fares): Peli Air. The Air 1535 in the cabin, the Air 1595 or 1615 in the hold.
- Cameras, drones, laptops or instruments: a sealed protective case with a fitted interior, such as the Peli 1510 or Air 1535 in the cabin. Never a thin shell with a zip.
- Harsh climates, boats, expeditions: sealed, IP67-rated Peli cases. Water resistance comes from the gasket and valve, not from the plastic alone.
If you want to see how different suitcases cope with real baggage handling, read what really happens to your suitcase after check-in and our overview of the toughest suitcases for air travel.
✅ Checklist: Before You Buy a Hard-Shell Suitcase
- ☐ The label names the exact material: "100% polycarbonate" or "polypropylene", not just "hard shell".
- ☐ Thumb test: the middle of the shell does not collapse under light pressure.
- ☐ Corners are thicker or reinforced, not stretched thin.
- ☐ Closure: latches with a seal beat a zip for protection and water resistance.
- ☐ Wheels and handle are solidly mounted, ideally replaceable.
- ☐ Empty weight checked against your usual baggage allowance.
- ☐ Finish suits your tolerance for scratches (matte or textured hides wear).
- ☐ Warranty and spare parts available from the manufacturer.
❓ Frequently Asked Questions
Is an ABS suitcase good?
For occasional travel and cabin use, yes. It is affordable and holds its shape. For regular checked baggage it is the weakest of the common materials, because ABS tends to crack under sharp impacts, especially in cold weather.
Which is stronger, ABS or polycarbonate?
Polycarbonate. It absorbs impacts by flexing and springing back, while ABS is stiffer and more likely to crack. Be careful with cheap "polycarbonate" cases, which are often PC/ABS blends.
Is polypropylene better than polycarbonate for a suitcase?
Polypropylene is lighter and usually tougher per gram, and it hides scratches better. Polycarbonate looks sleeker and comes in more colours. For protection, a thick, injection-moulded polypropylene shell is hard to beat.
What is HPX resin?
HPX is Peli's name for its own high-performance polymers. HPX resin is used in Peli Storm cases, and HPX²™ in the lighter Peli Air cases. It is not a generic material sold by other luggage brands.
What material are Peli cases made of?
Peli Protector cases use impact-resistant copolymer polypropylene, Peli Air cases use HPX²™, Peli Storm cases use HPX resin, and the Peli ATX travel cases use a proprietary polypropylene blend with Peli Armor™ construction.
What is the best suitcase material overall?
There is no single winner, but for travellers who check bags regularly, well-built polypropylene or Peli's HPX²™ offer the best mix of low weight and impact resistance. Construction quality matters as much as the material itself.
Are hard-shell suitcases waterproof?
Usually not. The shell itself does not let water through, but most hard-shell suitcases close with a zip and have no seal. Only cases with a gasket in the lid, such as IP67-rated Peli cases, are genuinely watertight.
Does a polycarbonate or ABS suitcase crack in the cold?
ABS becomes more brittle in freezing temperatures and is the most likely to crack. Good polycarbonate keeps its toughness in the cold much better. With polypropylene it depends on the grade: impact-modified copolymers, like the one used in Peli Protector cases, are designed to stay tough.
Why are protective cases heavier than some fashion suitcases?
Because their walls are much thicker and they carry seals, latches and reinforced corners. That extra material is what lets them survive drops, stacking and rain. Peli Air cases use HPX²™ precisely to bring that weight down.
🏁 The Bottom Line
ABS is the budget option that cracks, polycarbonate is the flexible option that scratches, and polypropylene is the light, tough option that professionals choose. Aluminium dents and weighs a lot, and "HPX" is Peli's own family of polymers rather than a fifth generic material. But the most important lesson is that the label is only the starting point: wall thickness, corners, closure and wheel mounts decide how much of the material's strength actually reaches your belongings.
If you travel often and check your bag, choose a sealed, thick-walled shell and ignore the gloss. It will look a little more used after a few years, and everything inside it will look exactly as you packed it. 🧳✈️
