When No Standard Adhesive Fits: Starting a Development Project

Most adhesive enquiries are a selection problem: the structure is known, the fill is known, and the work is to pick the grade that already exists. A smaller number are not selection problems at all. No grade in any catalogue fits, and the job becomes a development project — a different kind of work, with a different sequence of steps and a different set of risks.

The distinction matters early, because a development project run as if it were a selection exercise produces a predictable result: samples that work on the draw-down bench, a trial that fails on the line, and no shared record of what was actually being asked for. What follows is how to start the work properly, written for converters, printers and brand owners who are about to brief a formulator.

Four triggers that mean development, not selection

A development project is usually opened by one of four things, and it is worth naming which one applies before anything else is discussed.

• A substrate the chemistry does not like. Untreated or lightly treated PE and PP, some bio-based and mono-material films, heavily printed or coated surfaces, foil carrying a lacquer the adhesive cannot wet out. Standard grades are tested against common substrates; a new one is not common.
• A fill that attacks the bond. High-acid products, high-fat fills, essential oils, alcohol-containing liquids, and anything that migrates into the adhesive layer during storage. The bond that holds on day one may not hold at month six.
• A process window the line cannot widen. A short drying tunnel, limited capacity, a sealing or retort cycle with little margin, or a line speed the adhesive cannot tolerate. When the line cannot be changed, the adhesive has to be.
• A combination requirement. Heat resistance and low activation temperature together, or adhesion to a difficult film plus food-contact compliance plus a pot life long enough for a shift. Each requirement is served by an existing grade; the combination is not.

Naming the trigger is not administration. It decides which experiments are worth running, and it tells the formulator which property has the least room to move.

What a development brief has to contain

The brief is the whole basis of custom adhesive development, and it is where most projects go wrong. It is usually written as a sentence — “we need something that sticks to our film” — and a sentence cannot be tested against.

A usable brief answers five questions in writing:

• What is being bonded, and how is each surface prepared? Film type and thickness, treatment level if known, whether the surface is printed, lacquered or metallised, and which side of which web the adhesive goes on.
• What does the bond have to survive? Temperature and duration through the process, then the storage and service conditions: retort or pasteurisation, hot fill, freezing, flexing, chemical contact. Include the time dimension — a week, a season, a shelf life.
• How is it applied? Machine type, coating method, target coat weight, line speed, and the drying or curing condition the plant actually has. Adhesives are formulated to a process, and a grade that needs a tunnel the plant does not own is not a candidate.
• What are the limits? Pot life, working viscosity, colour, odour, cure temperature, food-contact status, and anything the customer's own specification fixes in advance.
• What has already been tried, and how did it fail? The most useful section, and the one most often left out. “Grade X delaminated after the retort cycle, at the seal area only” is worth more than a page of general description.

Where a number is not known, say so. An assumed treatment level or an estimated coat weight becomes a false constraint in the formulation, and the trial then tests the assumption instead of the application.

How the work is staged

Development runs in three stages, each with a different purpose. Collapsing them — going straight to a drum because the first sample looked right — is the most common way a project loses months.

Stage one: a formulation proposal. The brief is read against the chemistry and a proposal comes back: which polymer system, what the trade-offs are, which part is expected to be difficult. A proposal claiming no trade-offs at all is not a proposal.

Stage two: a lab sample for screening. Small quantities, tested against the brief rather than against a generic data sheet. Screening should eliminate, not confirm; the useful outcome of this stage is knowing which of two directions is dead.

Stage three: a trial batch sized for the production line. The candidate is run on the customer's equipment, at the customer's speed, through the customer's fill. Only this stage proves an adhesive, and only after full cure — a laminating adhesive that measures well on the reel and separates in the pouch has been run, not proven.

The grade is specified when stage three passes. Not before.

What to measure on the trial

A trial produces a reel and a set of opinions. The measurements that decide the outcome are usually four:

• Coat weight across the web width, not only at the centre. An adhesive that applies unevenly fails first where it is thinnest, and the failure gets blamed on the chemistry.
• Bond strength after full cure, at the interval stated for the grade rather than the day after lamination. Early readings flatter any two-component system.
• Performance after the fill and the storage condition the brief named. This is the test the application actually cares about.
• Appearance and handling — haze, bubbles, blocking in the reel, residual solvent or odour where relevant. A bond that passes mechanically and hazes the laminate has still failed a printed pack.

Record the conditions alongside the results: line speed, tunnel temperatures, mix ratio, ambient humidity. A result without its conditions cannot be reproduced, and the next trial starts from zero.

When development is the wrong answer

Some briefs should not become projects. If an existing grade already meets the requirement once the structure or the process is adjusted, the cheaper answer is to change the structure or the process. If the requirement conflicts with itself — a very low activation temperature and a high retort resistance, at the same coat weight and the same chemistry — no amount of development reconciles it, and the honest response is to say so before samples are made.

A supplier who guarantees a novel adhesive before seeing the substrate is selling optimism. What can be offered at the start is a documented proposal, a defined trial, and a straight answer when the requirement falls outside what the chemistry can do.

OEM and private-label programmes

Development work is often tied to an OEM or private-label programme, where the formulation is agreed against the customer's specification and supply continues against that specification with batch documentation. Confidentiality is agreed before the brief is shared, not after. The specification that comes out of the trial becomes the reference for every later batch, which is why it should be written down and signed rather than left in an email thread.

Starting the conversation

The fastest way to start is with the brief, not with a request for a sample. Substrates, fill, process, limits and past failures are enough to say whether the requirement is a standard grade, a modification of one, or a development project — and to say which within a short exchange rather than after a drum has been shipped.

Our novel specialty adhesive development page sets out how the work is staged, from proposal to trial batch. If the brief is ready, send it to us and it will be answered against the five questions above.