PP board is used in cleanrooms and controlled environments, and the reason it works is not that the material is inherently clean. It is that it can be made and finished in a way that does not shed particles, does not trap contamination, and survives the cleaning regime the area requires.
What the environment demands
- Low particle generation. The material must not shed. This rules out anything with an exposed cut edge that can break down, and anything with a coating that can flake.
- Cleanability. Surfaces have to be wipeable and, where required, compatible with the area’s cleaning agents – which are often aggressive, and often include alcohol or oxidising agents.
- No harbourage. Crevices, open flutes, unsealed joints and recessed fasteners all hold contamination that no wipe can reach.
- Chemical compatibility. The cleaning agent, at the temperature used, for the frequency required.
- Outgassing. Some cleanroom classifications limit volatile release, which is a material selection question rather than a design one.
- Low static generation in areas handling sensitive components.
Where standard board falls short
A standard corrugated board box has open flutes at every cut edge, a folded or stapled construction with crevices, and possibly a printed label. In a cleanroom that is three sources of contamination and a cleaning problem.
The failure is not that the material is unsuitable – PP itself is commonly used in controlled environments. The failure is the construction.
What a cleanroom construction looks like
- Sealed or welded edges, so no flute is exposed and no particle can be released from inside.
- Welded joints rather than folded and stapled ones, removing crevices and metal parts.
- Smooth, non-porous surfaces with no recesses that hold residue.
- Identification that is moulded or welded in, not a label that can peel.
- A grade compatible with the area’s cleaning agents, verified by immersion testing rather than assumed from a general chemical-resistance chart.
Cleaning agents are the usual surprise
Cleanrooms commonly use isopropyl alcohol, and some use oxidising agents such as hydrogen peroxide or peracetic acid. These are considerably more aggressive than a general-purpose detergent, and they are used frequently.
PP handles alcohols well. Strong oxidisers attack it progressively, and the attack accelerates with temperature. If your area uses an oxidising agent, that is the condition to specify against, and it is worth immersion testing a sample before committing to a fleet.
Abrasion matters more than people expect
Repeated wiping with a wipe or a cloth abrades a plastic surface over time, and an abraded surface is harder to clean because it holds residue. Surface hardness and finish therefore affect the practical life of the item, not just its appearance.
Where an item is wiped frequently, it is worth asking what surface finish is available and whether a harder grade exists. The difference in service life can be substantial.
Validation
Where the environment is validated, the packaging may be part of the validation. That usually means establishing that the item can be cleaned to the required standard, and documenting the procedure and the frequency.
It is easier to do that with a construction designed for it – a welded, sealed, smooth item with no labels – than to try to validate an ordinary box.
What we can do
We supply PP board and can build boxes and trays with welded construction, sealed edges and moulded identification for controlled environments. Tell us the classification, the cleaning agents and the frequency, and we will tell you what construction and grade suits – and where a sample should be tested before you commit.