button: text-only site map
New Metallocene Polythenes
Metallocenes have well-understood structures and only one kind of active site, producing very uniform polythene. Since Kaminsky's discovery an estimated $3bilion worth of research has focused on modifying and improving this family of catalysts.

Catalyst composition and geometry can be varied systematically to produce extremely uniform homo- or co-polymers designed to have the desired properties. Not just the length of branches is controlled but also their distribution.

One poly(ethene) is even better than Kevlar for making bullet-proof vests. It can stop bullets because it has a molecular mass of between 6,000,000 and 7,000,000, much higher than Ziegler catalysts can give. Other polymers can be made with long chain branches, distributed as desired by the manufacturer, either uniformly branched or completely amorphous.

What limits their application is the cost, many times the cost of traditional Ziegler catalysts. But they are more productive giving 10 to 100 times more polymer per kg of catalyst. As development continues costs are expected to decrease.