# Windscreen adhesive shelf life and storage

> Why a cartridge skins over in the nozzle, what heat does to a moisture-curing adhesive, and how to store it so the last cartridge behaves like the first.

Updated: 2026-11-10 · Source: https://karmindadhesive.com/resources/windscreen-adhesive-shelf-life/

A moisture-curing adhesive starts curing the moment it meets water — including the humidity in the air inside the cartridge. Storage is therefore part of the product specification, not an afterthought.

## What shortens shelf life

- **Heat.** Every 10 °C above 25 °C roughly doubles the reaction rate of the residual moisture in the cartridge.
- **Humidity at the nozzle.** A part-used cartridge with a crusted nozzle draws moisture down the barrel.
- **Physical damage.** A dented cartridge allows air ingress at the seam.
- **Age.** Even perfect storage has a limit; the batch date is the reference.

## The nozzle test

Before loading a cartridge, look at the nozzle and the first 10 mm of product. A thin skin is normal on a part-used cartridge and can be purged. A crust that extends into the barrel means the cartridge has taken moisture and should not be used for a structural bond.

## Storage rules that actually get followed

1. Store below 25 °C, out of direct sun, off a cold concrete floor.
2. Keep cartridges in the original carton; the box is a moisture buffer.
3. Use oldest stock first — write the batch date on the carton when it arrives.
4. Seal part-used cartridges with the nozzle cap, and use them within the working day.

## What the date code is telling you

A shelf life figure — typically 9–12 months for a one-component PU — is quoted for a storage temperature, usually 25 °C. It is not a guarantee that the cartridge is good on the last day and bad the next; it is the point at which the probability of a skinning or cure problem becomes material.

The useful translation is the same doubling rule used for cure:

```
stored at 25 °C    shelf life as stated (say 12 months)
stored at 35 °C    roughly 6 months
stored at 15 °C    longer — but not indefinitely, and not a reason to over-order
```

A container that crossed an ocean in August and sat on a quay has spent part of its life at 40 °C. Ask for the production date, not just the month of shipment, and subtract the hot weeks from the shelf life you were quoted.

## Part-used cartridges

A cartridge opened on Monday and used again on Friday is the most common source of a bad bead in a small bay. The failure is at the nozzle and the first 10 mm of product; the rest of the barrel is usually fine.

- **Cap it immediately**, nozzle down, and store it upright.
- **Purge 20–30 mm** before the next use, and inspect what comes out.
- **Do not use a part-used cartridge for a structural bond** if the crust extends beyond the nozzle — the moisture has travelled further than it looks.
- **Discard at the end of the week.** The cost of a cartridge is small against the cost of a comeback.

## Stock rotation that survives a busy week

The rule is first-in-first-out, and it fails when cartons are opened and mixed. Two habits fix it: write the production date on the outside of every carton on arrival, and issue from one shelf at a time. A bay that cannot tell which cartridge is oldest will always use the newest, because it is at the front.

## Storage temperature and usable life

| Storage | Approximate usable life | Note |
|---|---|---|
| 15 °C | Longer than rated | Do not use this to over-order |
| 25 °C | Rated life (typically 9–12 months) | The reference condition |
| 35 °C | About half the rated life | A hot warehouse in summer |
| 45 °C | About a quarter | A container on a quay |

The arithmetic is the same doubling rule that governs cure: every 10 °C roughly doubles the rate of the residual reaction inside the cartridge. A pallet that spent six weeks at 40 °C has spent more of its life than the calendar suggests, and the carton does not record it.

## What this means for buyers

1. Ask for the production date, not just the shelf life.
2. Do not buy a year's stock to get a price break on a moisture-curing product.
3. Store centrally and issue by batch; a hot van is not a warehouse.
4. Train the nozzle test — it catches a bad cartridge before it reaches a windscreen.