Recycleable Elastomers: Properties of Stereoblock Polypropylene

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9528636 Waymouth This research investigates an innovative new strategy for the synthesis of elastomeric polypropylene. The objective of the proposed studies is to investigate the structure and properties of thermoplastic elastomers based upon propylene homopolymers. These materials offer an environmentally attractive alternative to conventional vulcanized elastomers, but little is known about their properties. Specific aims are: (i) to establish the relationship between molecular structure, solid-state organization, and physical and mechanical properties, (ii) to prepare a series of elastomeric polypropylenes with systematic variations in polymer microstructure, and (iii) to investigate how changes in the microstructure of elastomeric polypropylenes influence solid-state structure and organization. The experimental approach includes characterization of elastomeric polypropylene to probe the structure of these materials over a range of length scales, from the atomic length scale (microstructure) to length scales appropriate for characterizing isotactic helix lengths, crystallite dimensions and large scale morphological features. A complementary set of experiments will investigate how changes in microstructure influence the solid state organization, structure and properties of these materials. %%% Thermoplastic elastomeric polypropylene has the properties of a vulcanized rubber, but the production and processing advantages of polyolefin thermoplastics. The development of this new material should enable the substitution of less environmentally attractive vulcanized rubbers. The environmental benefit of elastomeric polypropylene derives from the high efficiency in manufacturing, processing, and recyclability. The ability to flow upon heating and solidify on cooling allows manufacturers to produce rubber- like materials using melt-extruders, blow molders and other energy-efficient thermoplastic processing equipment. Expensive, wasteful, and energy-inte nsive compounding and vulcanizing steps can be avoided and scrap from molded articles can be re-used. These materials can be manufactured with minimal waste to give materials that have elastomeric properties yet the recycling characteristics of polyolefins. Elastomeric polypropylene should be readily incorporated into normal polypropylene recycling streams. An important feature of the program is the training of graduate and undergraduate students in a fundamentally and technologically significant area. ***