Isotactic polypropylene is a thermoplastic polymer whose standout features are:
Its discovery was the result of a brilliant collaboration between the Politecnico di Milano Institute of Industrial Chemistry and a private company named Montecatini. The joint venture also involved the training of graduates in Chemistry and Chemical Engineering in order for them to join the company’s team.
It all started back in 1952, when Professor Giulio Natta learned that the German chemist Karl Ziegler had prepared linear and highly crystalline polyethylene using new catalytic systems based on triethylaluminium and transition metal salts as co-catalysts.
Realising that Ziegler’s discovery could be applied to the polymerisation of propylene, Natta set up a research group with highly skilled young chemists and technologists, who worked on an innovative process to obtain linear and highly crystalline polypropylene. Their work paid off – so much so that they developed processes capable of synthesising an entire family of polymers suitable for crystallisation, such as polystyrene, polybutene, polybutadiene, polypentene, polymethylpentene, and more.
The research carried out by Prof. Natta and his collaborators was extremely important, because it clarified not only the kinetic mechanisms that regulated the polymerisation processes, but also the molecular factors that made these polymers intrinsically capable of crystallising.
A vinyl polymer crystallised if each repeat unit contained a tertiary carbon atom which, in a macromolecule of finite length, represented an asymmetric centre.
The discovery of ‘stereoregular’ and therefore crystallisable polyolefin polymers earned Giulio Natta the Nobel Prize in 1963 in collaboration with Karl Ziegler as the discoverer of organometallic catalysis and low-pressure polyethylene synthesis.
Meanwhile, Montecatini, which had opened the first major European petrochemical plant in Ferrara in 1952, began producing isotactic polypropylene there, enjoying great success.
In recognition of the scientific, technological and industrial significance of this discovery, the Swedish and Italian post offices even printed commemorative stamps in 1988 and 1994, while Prof. Natta was awarded one of the world’s most important prizes.
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