New Additive Compatibilizes PE/PP Alloys

Researchers believe they have found a solution to meld PE and PP to create new polymer alloys. Geoffrey Coates, professor of chemistry and chemical biology at Cornell University, and his team have collaborated with a group from the Univ. of Minnesota to develop a multiblock polymer that, when added in small amounts to a mix of the two otherwise incompatible polyolefins, creates a mechanically tough blend. The two groups’ work is detailed in a paper, “Combining polyethylene and polypropylene: Enhanced performance with PE/PP multi-block polymers,” published online Feb. 23 in Science.

By adding a miniscule amount of their tetrablock (four-block) polymer—which contains alternating polyethylene and polypropylene segments—the resultant blend reportedly has strength superior to diblock (two-block) polymers the authors tested.

“People have done things like this before,” Coates says, “but they’ll typically put in 10% of a soft material, so you don’t get the nice plastic properties, you get something that’s not quite as good as the original material. What’s exciting about this is we can go to as low as 1% of our additive, and you get a plastic alloy that really has super-great properties.”

James Eagan, a postdoctoral researcher in Coates’ group and lead author of the paper, believes this tetrablock polymer shows promise for improving recycling and could also spawn a whole new class of tough polymer blends.