Bread Tray Materials Compared: HDPE vs. Polypropylene vs. Aluminum vs. Fiberglass

For a bread distribution tray the real choice is HDPE or polypropylene. In resin reference data, HDPE keeps its toughness to far lower temperatures and polypropylene keeps its shape to higher heat; that is the direction, not a tray rating. Aluminum is an oven material and fiberglass is a display material, so neither belongs in a delivery stack. A molded tray also depends on its grade, additives, recycled content, wall and rib design and how it was molded, so the rating the maker puts in writing for your exact tray model is the number that decides.

Which material should a distribution tray be made of?

Start from the two temperature extremes your trays actually see: the coldest room they enter and the hottest water or steam they are washed in.

• If trays go into a freezer, start from the model’s written low-temperature rating. The resin data point in one direction: standard polypropylene’s listed brittleness temperature is the freezing point of water, and HDPE’s is far lower. So a polypropylene tray with no written cold rating is the one to question first, and a polypropylene tray the maker rates for your freezer temperature can do the job.
• If trays run through a hot tunnel washer or steam cycle, polypropylene has more heat margin than HDPE. The washer temperature still has to sit inside the tray’s written rating.
• If trays never leave ambient temperature, either plastic works, and the decision moves to design, fit with your dollies and racks, and price.

You will meet both resins when you buy, and sometimes a blend of the two in one tray; the maker statements further down show one example.

How do HDPE and polypropylene differ in cold and heat?

One published table that lists both resins side by side comes from laboratory plastics. Thermo Fisher’s physical properties table for its Nalgene resins gives these reference values:

Sources for the table: Thermo Fisher, Nalgene labware physical properties. These are resin reference values for labware grades, not ratings for any bread tray.

Cold is where the two resins split hardest in this data. HDPE’s listed brittleness temperature is 180°F below standard polypropylene’s. Treat that as direction, not as a prediction for a tray: a molded tray’s behavior when dropped cold also depends on the exact grade, any impact modifier, recycled content, wall thickness and ribs, molding conditions, and the test method behind any rating. Only the maker’s rating and testing speak for the finished tray.

Copolymer changes the cold answer. Polypropylene copolymer is listed at -40°F; if your coldest room stays warmer than that, the base resin does not rule the tray out, and the tray’s rating decides. Copolymer is one way a polypropylene tray can be rated for the cold, so ask any maker which polypropylene it uses. The word “polypropylene” on a spec sheet does not tell you which kind you are buying.

Heat favors polypropylene. Its heat deflection temperature, the point at which a test bar bends under a set load, is about 76°F higher than HDPE’s in this table, and it survives an autoclave cycle that HDPE does not. The footnote to the same table adds that “Materials may be used above Heat Deflection Temperatures in non-stress applications” and points to the maximum use temperature. A tray in a washer is under little load; a tray at the bottom of a hot, loaded stack is not.

The weight difference between the resins is small. Polypropylene’s specific gravity is 0.90 against HDPE’s 0.95, so the same volume of plastic weighs about 5 percent less. The tray weights in the maker statements below run from 2.90 to 5.40 lb within one maker’s HDPE line, which suggests design moves weight far more than resin does.

What does the tray rating tell you that resin data does not?

The resin table describes the plastic. A tray rating should describe the finished product, which adds what the resin table cannot: the grade and any impact modifier, the colorant, recycled content, the wall thickness and ribbing, and how the tray was molded. When the two disagree, the tray rating is the one to plan around.

Ratings are not always stated precisely. The ORBIS statement below gives temperatures without a unit, and a limit of 120°F and a limit of 120°C lead to very different washer settings.

Before you commit a fleet to freezer or hot-wash service, get four answers in writing for the exact model number:

1. The lowest and highest rated temperatures, with the unit.
2. Whether the high limit applies to wash water, steam, or loaded storage.
3. The resin, including whether a polypropylene tray is a homopolymer or a copolymer.
4. How the cold rating was set: the impact or drop test, the method and the temperature it was run at.

Then compare them with two measurements from your own plant: the coldest reading in the room the trays enter, and the hottest reading at the washer. If either sits outside the rating, the tray is the wrong tray for that step, whatever the resin family. The cold side of this decision has its own page on deciding whether trays can go into your freezer, including when to run a separate freezer fleet; on the hot side, check the wash temperatures and sanitizer strengths your trays will face.

What makers state (checked September 25, 2026). Product lines and wording change; recheck these before relying on them.

• Rehrig Pacific’s bakery tray sheet lists HDPE for every model but one, the HBT-23, which is an “HDPE/PP Blend”; its HDPE models weigh 2.90 to 5.40 lb (<a href="https://www.rehrigpacific.com/application/files/6517/2919/0456/RPCBakeryTraysOneSheet_8.5×11.pdf”>Rehrig Pacific).
• Flexcon lists its 28 x 22 x 7 inch stack/nest bakery tray at 4.6 lb (Flexcon).
• ORBIS says its bread trays are “freezer-safe down to -20 degrees and heat-safe up to 120 degrees,” with no unit on the page (ORBIS).
• Cambro describes its market trays as “made from high-impact resistant fiberglass with aluminum-reinforced rims” (Cambro).

Does either plastic have an advantage with the FDA?

No. Both are olefin polymers, covered by the same federal regulation, 21 CFR 177.1520. What decides compliance is the specific resin grade and additives in your tray, not whether it is HDPE or polypropylene. Before you buy, ask for the compliance paperwork a tray supplier should give you; the same page explains where NSF certification fits. If a tray contains recycled resin, a separate set of questions applies, covered in what to ask before buying trays with recycled resin.

Where do aluminum and fiberglass fit?

Neither is a distribution tray material, and each does a job the plastics cannot.

Aluminum belongs in the oven. Sheet pans and baking trays go through the oven because metal tolerates baking heat and moves it into the dough. A plastic distribution tray never goes into an oven: the highest maximum use temperature in the table above, 275°F, is below the lowest bakery oven set point BAKERpedia gives, 300°F (BAKERpedia, oven temperature). The two are sequential tools: bread baked on pans comes off them and goes into plastic trays for cooling, staging and delivery.

Fiberglass belongs at the display counter. Fiberglass market trays, such as the Cambro line in the maker statements above, are presentation trays for a case or counter, not stack-and-nest trays built to ride a dolly on a delivery route. If you are choosing trays for an in-store bakery’s display, the trade-offs are different; see choosing trays for display and back of house in an in-store bakery.

How do the four materials compare head to head?

Sources for the table: resin rows from Thermo Fisher; fiberglass role from Cambro. The resin rows give direction only; the written rating for a specific tray model overrides them.

When is switching materials not worth it?

A fleet already running one resin without cracking in the cold or warping in the washer has no material problem to solve. Switching resin means buying new trays, checking that they fit your existing dollies and racks, and living with a mixed fleet during the changeover, where trays from different molds may not lock together.

A switch is worth pricing when one of your two temperature extremes sits outside the current tray’s written rating, or when you add a step, such as a blast freezer or a hotter washer, that the current trays were never rated for. In every other case, the material question is settled and your next decision is the tray design itself, and working through a tray purchase in order starts there.