Compositions with Thermoplastic Additives

The ability of living polymers to resume growth with the addition of fresh monomer provides an excellent opportunity for the preparation of block copolymers. For example, if a living polymer with one active end from monomer A can initiate the polymerization of monomer B, then an A-AB-B type copolymer can be obtained (e.g., styrene-isoprene copolymer). If, however, both ends of polymer A are active, a copolymer of the type B-BA-AB-B results. Examples are the thermoplastic rubbers polysty-rene-polyisoprene-polystyrene and poly(ethylene oxide)-polystyrene-poly(ethylene oxide). In principle, for fixed amounts of two monomers that are capable of mutual formation of living polymers, a series of polymers with constant composition and molecular weight but of desired structural pattern can be produced by varying the fraction and order of addition of each monomer. 

Blends of EPDM rubbers with polypropylene in suitable ratios have been marketed as thermoplastic elastomers (TPE), also commercially known as thermoplastic polyolefin elastomers (TPO). These heterophasic polymers, characterized by thermoreversible interaction among the polymeric chains, belong to a broad family of olefinic alloys that can now be produced directly during the polymerization phase, unlike blended TPE and TPO, and various compositions (with various compounding additives) can be formulated which are primarily tailored to meet different requirements of most of car applications. The TPE-based synthetic leather and foam sheets are typical examples. 

Cellulose represents an important polymer, which is most abundant in nature, and serves as a renewable resource in many applications, e.g., fibers, films, paper, and as a composite with other polysaccharides and lignin in wood. Cellulose derivatives will also be used as films and fibers, food additives, thermoplastics, and construction materials, to name just a few. Cellulose and cellulose derivatives have played an important role in the development of the macromolecular concept. So far, little use has been made of the fact that cellulose represents a chiral material except, e.g., in a rare case as stationary material in liquid chromatography for the separation of chiral compounds. Nature ifself uses the chirality of cellulose occasionally, and twisted structures of cellulose molecules are found in cell walls. 

A combination of carbon fiber, glass fiber or polyester fiber with phenolics leads to fiber reinforced phenolics that are called phenolic composites. Phenolic composites are interesting materials for the aircraft and aerospace industry because, in case of fire, they produce very low smoke density and low toxicity gases. Thermoplastic or elastomeric additives improve mechanical properties, adhesion and toughness of these composites but these additives cause a decrease in flame resistance [1,6],... 

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