Design, Characterization, and Evaluation of Elastomeric Materials

点击翻译按钮获取中文摘要

9422223 Mark End linking of functionally-terminated polymer chains will be used to obtain elastomers of known and controlled structures. Some will contain dangling-chain irregularities, and others unimodal and multimodal distributions of network chain-lengths. Included will be trimodal networks and unusually broad pseudo-unimodal networks obtained by combining separately-prepared batches of polysiloxanes of widely varying molecular weights. Additional elastomers will be produced under conditions giviing structures that are unusual in other respects, for example by cross linking in solution or in a state of strain. Experiments will be performed for identifying strain-induced crystallization, in elongation, biaxial extension, shear, and torsion. Simulations will also be carried out to characterize the crystallization occurring in some new polysiloxane chains of unusually high stereoregularity. Elastomeric gels will also be studied, including some involved in processing techniques giving liquid-crystalline polymers of enhanced orientation. Gelation kinetics will be studied, as will diffusion coefficients of solvents into and out of swollen networks. Novel reinforcing fillers will be prepared by the hydrolysis, photolysis, or thermolysis of organometallic materials such as silicates, titanates, zirconates, aluminates, and simple metal salts such as ferric chloride. Of particular importance will be identifying the particle size that maximizes reinforcement, and characterizing the effects of particle shape. The resulting filler-reinforced elastomers will be characterized primarily by mechanical property measurements, electron microsocpy, and by X-ray and neutron scattering. Simulations will also be carried to elucidate reinforcing mechanisms in filler-reinforced elastomers in general. Finally, experiments will be carried out to exploit the ability of elastomeric domains to improve the impact resistance of polymer-ceramic hybrid composites in which the cer amic is the continuous phase. %%% The primary significance of these projects is the achievement of a better molecular understanding of rubberlike elasticity and the ways in which fillers reinforce elastomers. The results should provide importance guidance for producing elastomeric materials and elastomeric- modified ceramics having unusaully attractive mechanical properties.