There are two separate things being described when someone says their crates have gone brittle in the cold room, and they need different responses. One is impact failure at low temperature, which happens immediately and is a specification issue. The other is genuine material degradation over years, which is slower and usually about additives rather than cold.
The immediate one: impact at temperature
PP becomes less able to absorb a knock as it gets colder, and the change is significant by the time you are at freezer temperatures. A crate that handles fine at ambient will crack when dropped in a cold room. Nothing has degraded; the material is behaving as it does.
This is why crates crack in cold storage and the fix is grade selection, not thicker walls. The mechanism is set out in why PP crates crack in cold storage.
The slow one: additive depletion
Over years, the stabilisers and impact modifiers in the resin do get consumed. UV exposure accelerates this a lot; cold alone does very little. A crate that has spent five years in a dark cold room has aged much less than one that spent two years outside.
So “long-term cold storage” is, on its own, comparatively gentle. What ages a crate is sunlight, washing at high temperature with aggressive detergent, and repeated impact – not cold.
What washing does
Hot washing is harder on crates than cold storage, and it is worth knowing if your crates go through a wash tunnel. Temperature, detergent chemistry and drying all contribute. The practical constraints are covered in can PP crates go through a wash tunnel.
The visible sign is a crate that is still intact but has lost its surface sheen and feels dry rather than slightly waxy.
How to tell which you have
Look at the failure. Clean fractures at corners and handle roots, on crates that have not been out in the sun, means impact at temperature – specify a better grade. Crazing or surface powdering across the whole crate, on crates that have been outdoors, means UV degradation – keep them out of the sun.
A crate showing both is common, and in that case the UV damage came first and made the impact failure more likely.
How long a crate should last
In a closed cold-store loop with reasonable handling, years. Trip counts and what ends them are discussed in how many trips a PP crate survives – and the honest answer depends far more on handling than on temperature.
What to do about it
First, stop dropping them – most cold-room crate loss is handling. Second, if the crates are genuinely failing at temperature rather than from knocks, move to an impact-modified grade. Third, if they are stored outside between seasons, cover them, because that is doing more damage than the cold room.
What to record
Count your losses. A crate fleet with no failure record is a fleet where nobody knows whether the specification is wrong, and the argument about grade versus handling cannot be settled without a number.
Record the date, where the crate failed and what it was doing. Three months of that tells you whether it is a material problem, a handling problem or a specific operation – and it is usually the last one.
What we can do
We make PP crates for fruit and vegetables in grades specified for cold storage, and we will tell you which is needed rather than the most expensive one. Tell us your temperature, whether the crates go outside, and how they get handled – that is enough for us to say whether you have a grade problem at all.