What in-mould labelling is
In-Mould Labelling (IML) is a decoration process for plastic containers — bottles, tubs, pails, and cups — in which a pre-printed plastic label is placed inside the injection mould or blow mould before the plastic container is formed. The molten plastic bonds directly with the label during moulding, creating a container where the label is fused into the wall of the container rather than being a separate adhesive-applied element. The result looks like the graphics are printed directly on the container.
IML is used extensively in India for: ice cream tubs (Amul, Kwality Wall's), margarine containers, paint pails, yoghurt cups, and increasingly for premium FMCG food packaging where a no-label look is desired. The Indian IML market has grown significantly since 2015 as injection moulding technology costs have come down and brand owners have sought alternatives to sleeve labels and pressure-sensitive labels.
How IML works — the three processes
Injection moulding IML
The most common IML process for rigid containers (tubs, pails, cups with straight or tapered sides). A pre-printed polypropylene (PP) or BOPP label is placed against the interior wall of the injection mould by a robotic arm. Molten polypropylene is injected into the mould at high pressure. The heat and pressure of the molten plastic bond the label to the container wall — the label and container become a single unit. After ejection, the container has graphics integrated into its wall with no edges, no bubble risk, and no peeling.
Blow moulding IML
For round bottles and containers where the label needs to wrap around a curved surface. The label is placed inside the blow mould, and the container is formed by blowing air into a heated plastic preform that expands to fill the mould. The label bonds to the exterior (or interior in some configurations) of the blow-moulded container. Used for: detergent bottles, edible oil bottles, pharmaceutical HDPE bottles.
Thermoforming IML
For thin-wall containers formed by thermoforming — yoghurt cups, food trays. The IML label is applied to the thermoforming mould base, and the container is formed over it. Less common than injection or blow moulding IML.
IML label specifications — what the printer needs to produce
IML labels are not the same as pressure-sensitive labels. The substrate, print process, and converting requirements are different:
- Substrate: Typically 60–80 micron biaxially oriented polypropylene (BOPP) or 50–70 micron PP film. The substrate must be compatible with the container material and withstand the temperatures of the moulding process. The label must have the same coefficient of thermal expansion as the container to prevent post-mould warping.
- Print process: Offset lithography is the dominant process for IML labels in India — the combination of high print quality, good register, and the ability to print on thin BOPP film makes sheetfed offset the preferred choice. The ink must be UV-cured (UV offset) for adhesion and resistance to the heat of the moulding cycle.
- Varnish/lacquer: A specific heat-activatable lacquer on the back face of the label creates the bond between label and container in the mould. This lacquer must be compatible with both the label substrate and the container resin.
- Static charge: Static charge is deliberately applied to the label to hold it against the mould wall electrostatically before the molten plastic arrives. The film must have appropriate surface energy for static cling.
- Cutting: IML labels are die-cut to exact shape — no tolerance for dimensional variation as they must fit precisely in the mould cavity.
Advantages of IML over labels and sleeves
| Factor | IML | Pressure-Sensitive Label | Shrink Sleeve |
|---|---|---|---|
| Recyclability | ✓ Monomaterial — label and container same resin | ✗ Different materials — delamination needed | ✗ Different resin — sleeve must be removed |
| Label adhesion risk | None — fused to container | Edge lifting, bubbling in humidity | Sleeve may loosen if heat tunnel calibration wrong |
| Moisture resistance | Complete — no paper, no adhesive | Paper labels deteriorate; film labels better | Good if sleeve fits correctly |
| Print quality achievable | High — offset printing on flat label before moulding | High — printed on flat substrate | Good — flexo or gravure on film in round form |
| No-label look | ✓ Complete — graphics appear printed directly on container | Limited — label edges visible | Good with full-body sleeve |
| Minimum run length | Higher — mould setup cost | Low — short run digital possible | Medium — gravure/flexo minimum runs |
IML in India — market context
India's IML market is growing at approximately 12–15% annually (2023–2026 estimate). Key drivers: premium FMCG packaging demands, dairy sector expansion (Amul, Mother Dairy, regional dairies), and the EPR recyclability advantage. The Ice cream category was the early adopter — virtually all premium Indian ice cream tubs (500ml and above) use IML. Paint manufacturers (Asian Paints, Berger) have adopted IML for 1-litre containers where the label quality directly impacts retail shelf presence.
IML printers in India are concentrated in Gujarat (Ahmedabad, Rajkot) and Maharashtra (Pune, Mumbai suburbs). The injection moulding + IML combination is increasingly being offered as an integrated service — some moulders have print operations, and some print specialists have invested in moulding.