Sudhin Datta

Synchrotron X-Ray Studies of Vulcanized Rubbers and Thermoplastic Elastomers

Synchrotron X-ray diffraction technique has revealed strain-induced crystallization and molecular orientation in vulcanized rubbers and thermoplastic elastomers (TPE) during deformation in real time. The stress-strain curves and wide angle X-ray diffraction (WAXD) patterns in vulcanized rubbers and TPE were measured simultaneously. In-situ WAXD patterns were taken not only at different strains during uniaxial deformation but also at different temperatures at a constant strain. Results lead to several new insights. (i) Strain-induced crystallization is a common phenomenon in vulcanized rubbers, except SBR (styrene-butadiene rubber), and in TPE (with crystalline hard segments). (ii) Strain-induced crystallization decreases the stress and increases the elongation in the strained rubber. (iii) The hybrid structure of chemical networks and strain-induced crystallites is responsible to the tensile strength and elongation at break for both systems. (iiii) Some original crystal fraction (hard segment domain) in TPE is destroyed. During deformation, strain-induced crystallization increases with strain. Upon retraction even to stress zero, the majority of oriented strain-induced crystallites remains in tack with preferred orientation.

Filler distribution and domain size of elastomer compounds by solid-state NMR and AFM

Abstract Solid-state NMR methods were used to characterize the filler distribution in rubber blends and domain size of thermoplastic vulcanizates (TPV). Correlation between filler content and magic...

Specialty Elastomer Modifiers with Isotactic Propylene Crystallinity for Polypropylene Modification

Abstract Specialty elastomers possessing isotactic propylene crystallinity are a novel class of polyolefins made possible by advances in metallocene polymerization. These polymers contain a propylene rich component endowed with isotactic crystallinity, and the balance of the composition is ethylene with other alpha olefins. Typical molecular weight of these elastomers is greater than 100,000. These polymers, when used as modifiers for toughening polypropylene (PP) homopolymers demonstrate improved impact strength to stiffness balance, enhanced low temperature toughness and improved impact to flow balance over conventional ethylene alpha-olefin modifiers. Morphological features of the blends were determined using Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The detailed morphological characterization indicates that the isotactic propylene crystallinity species of the elastomers function by localizing themselves at the interface of the polypropylene matrix and the ethylene-alpha...

12 – Elastomer Blends

Publisher Summary Blends of elastomers allow the user to access properties of the final blended and vulcanized elastomer that are not accessible from a single, commercially available elastomer alone, and thus, are of technological and commercial importance. These potentially improved properties include chemical, physical, and processing benefits. This chapter shows some of the instances of the uses of elastomer blends. Blends provide an acceptable technological process for accessing properties not available in a single elastomer. Intermolecular changes in blends are not limited by such systemic or synthetic limitations. Blends of elastomers can attain a wide variation in properties. Combinations of elastomers can lead to changes in properties because of either intrinsic differences in the constituents or differences in the reinforcement and vulcanization of the constituents. Miscible blends of elastomers that consist of a single elastomeric phase with microscopically uniform cross-linking and distribution of reinforcing agents reflect a compositionally weighted average of the intrinsic properties of the constituents. Miscible blends are commonly used though they have been very rarely recognized.

Chapter 12 – Elastomer Blends

This chapter reviews the formulation and use of elastomer blends: miscible blends, which are widely used but usually not recognized because analytical separation of the vulcanized elastomer is experimentally difficult; and immiscible blends, which require excellent phase dispersion and interfacial adhesion typical of all polymer blends.