An Adhesive That Grows on Trees

SpecialChem | Edward M. Petrie - Apr 23, 2008


Can an adhesive grow on trees? Today's editorial looks at one that does. And it is a very effective pressure sensitive adhesive that even comes pre-packaged.

Well, I just returned home from my yearly holiday. My family spent two great weeks on a lovely French/Swedish Caribbean island that many of you may know - St. Bartholomew. I returned with a rather good tan, some scratches where the surf and sand was a bit rough to my body, a larger belt size, and significantly reduced wallet contents. Although I have visited St. Barth several times, this is the first time that I was introduced to their "home-grown" adhesive.

Outside where we were staying on the island, there grows a large tree with copious amounts of berries (see Figure below). This tree grows wild and appears all over the island. On questioning of the local inhabitants of the island, I found that the berries have been used for decades (if not centuries) in the local schools by the students as a pressure sensitive adhesive.

Almost everyone on St. Barth refers to the tree as a Glue Tree or in French they say Pied de Colle. I checked in a local plant store for a botanical reference, but they could not identify it more than "Pied de Colle".

It is truly amazing that on this tree "grows" a rather aggressive pressure sensitive waterborne adhesive that is of natural origins, environmentally most kind, and biodegradable. It obviously requires no manufacturing or formulation compounding. And even more amazing is that it comes in its own packaging. The berries' skin is rather tough and resistant to abuse, but once punctured either by finger pressure or with a needle, the adhesive dispenses out in a straightforward and well-controlled manner.

I wanted to take several berries home to examine the properties a bit more closely but US customs got in the way of that. However, I was able to determine that the "adhesive" had excellent green strength and tack, rather good adhesion to paper, and significant open time. Shelf-life must have been good as well because the berries that I picked up off the ground had been laying there for awhile.

Once arriving home and at my computer, I tried to "google" the glue tree, and I think that I found it. It is called the clammy cherry or red manjack tree. It is said to be a native of India but grows in South America, Mexico, and the Caribbean. The small red fruit of this tree grows in clusters and look like miniature sized cherry tomatoes. They have a sticky consistency and are edible, but on St. Barth these berries are used as a substitute for common white paste or school glue.

The clammy cherry will never be relished as one of the world's most useful trees (the mango), or one noted for flavorful fruit (the banana tree), or its virtues have not merited it being called the "tree of life" (baobab tree) or even the "village pharmacy" (neem tree). However, to someone that spent his career in (literally) adhesives and sealants, I feel that the clammy cherry ranks as one of the more amazing trees.

I spent several hours relishing the possibility of growing my own glue factory of clammy cherry trees. I would not need energy, raw materials, or waste disposal  only sun and water. I thought that the only problem was that I would have to toil in the fields at times to plant and cultivate a continuing forest of glue trees. To my surprise Mother Nature even has a solution to this. The clammy cherry seeds are spread by bats and apparently germination occurs in any exposed, isolated region. The seeds sprout quickly and send up strong seedlings that will soon provide perches for birds. Those birds will defecate and disperse seeds that can then flourish in the clammy cherry's shady protection. So no work is even required to plant and keep-up my glue forest. But bats and bird defecationI guess even paradise must have some drawbacks.

Should you have any comments or feedback, please contact me.

Edward M. Petrie

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