PolySkin: the first meltable package

What it replaced

Pavement maintenance products have been packaged in cardboard boxes with plastic bags or liners since the late 1970s. Both parts of that cause work.

The plastic goes into the melter with the material and does not reliably melt. It wraps agitators, settles onto intake valves, and leaves remnants stuck to the inside of the kettle that somebody has to get out later. The cardboard never goes in, which means it has to come off and then be collected, hauled and disposed of. On a plain carton that starts with a knife, on a job site, in gloves, which is the problem ZipBox solves for the products that still ship in cardboard. It does not solve the other half: the box still has to go somewhere.

Neither of those is the job anybody is being paid to do. They are both time spent on the packaging instead of on the pavement.

It started with lunch

The idea was not new. Ted Maxwell, who founded the company and was its first chemist, had wanted a meltable package for years and had tried at it more than once.

A meltable plastic wrapper would melt, but it would not hold a pallet up. Plastic buckets held their shape, but melted slowly and put too much incompatible plastic into the material. The requirement was awkward: something rigid enough to stack and ship, and compatible enough to dissolve into a sealant without changing it.

The answer turned up in the lab entryway, in somebody's lunch.

From a takeout box to a pallet

What followed was several years of prototyping, because a foam box that survives one night of hot sealant is a long way from a package that ships.

It had to melt quickly and completely, and it had to be made of polymers compatible with the material it was going into, so that it mixes in rather than sitting in the kettle as clumps. It had to survive the filling line, which turned out to shape the design as much as anything. And it had to build a pallet that stood up.

That last requirement is where the shape came from. The early prototypes shifted in transit, so the containers were molded to interlock, the bosses on the top of one block seating into the base of the next, the way the pallet above shows. A wrapped pallet of PolySkin does not need the wrap to stay standing, and it does not sag, slump or topple when it comes off. It stores outside.

Everyone makes one now

Maxwell got there first. Ted had wanted a meltable package for years, Mike found the shape of the answer in a takeout container, and Ken had to go and sell a foam box to an industry that had always used cardboard.

Meltable packaging is normal now, and that is the part worth being pleased about. It stopped being our idea and became how the industry works.

Does it clog the melter?

This is the question we get asked, and it is worth answering plainly rather than dismissing, because it is a reasonable thing to worry about. Anyone who has run plastic liners through a kettle has good reason to distrust the idea of putting packaging into it deliberately.

The answer is in the material. PolySkin is expanded bead foam, which floats. While it is melting it stays at the top of the melter, and the material intake is at the bottom, so the packaging and the intake are never in the same place at the same time. It is not that the foam clears the intake quickly. It is that it does not get there.

The rest follows from the polymers being chosen for compatibility with the sealant: it melts in rather than staying as clumps, and it does not wrap the agitator the way a sheet of liner does.