Thermoplastic dynamic vulcanizates

Abstract

Thermoplastic dynamic vulcanizates (TDV) belong to a novel family of thermoplastic rubbers. They are blends composed of thermoplastic resins and elastomers in which the fully or partially cured elastomer component is finely dispersed (mean particle size: 1–2 μm) in the thermoplastic matrix. If both the matrix and dispersion-giving polymer are of polyolefin nature, they are called thermoplastic olefin elastomers (TPO). The matrix is mostly polypropylene (PP), whereas the elastomer component is either a saturated (EPM) or nonsaturated (EPDM) ethylene/propylene (E/P) rubber (in the abbreviations M and D stay for monomer and diene, respectively). Among the TPO grades, a further distinction is made depending whether the elastomeric phase is crosslinked (vulcanized, cured; TPO-V) or not (blend or elastomeric alloy; TPO-O). TDVs are produced via dynamic vulcanization, credited to Gessler, that was later intensively studied, explored and brought for commercialization by Fischer (Uniroyal) and Coran and coworkers (Monsanto, later Advanced Elastomer Systems) [1, 2]. Dynamic crosslinking means an intensive kneading, mixing operation of a blend composed of a crosslinkable elastomer and a noncrosslinkable thermoplastic resin, performed above the melting temperature of the latter. The vulcanizing agents and related additives should result in a selective crosslinking of the rubber (i.e. not affecting the molecular characteristics of the matrix polymer during melt blending). As usual rubber vulcanizing systems (such as sulfur,