β Scribed by Frederick H. Silver; Joseph J. LiBrizzi; Dominick Benedetto
No coin nor oath required. For personal study only.
Previous observations on polysaccharides used as viscoelastic agents in ophthalmic surgery suggest that the pseudoplasticity of solutions of hyaluronan (HA) and the low surface tension of hydroxypropylmethylcellulose (HPMC) solutions are physical properties that make these solutions useful clinically. Our laboratories are interested in correlating the physical properties of macromolecular solutions with the ability of these molecules to protect ocular structures during eye surgery. The purpose of this study is to compare the physical properties of model viscoelastics with the properties of HA and HPMC. The results of these studies suggest that polysaccharides that form extended structures in solution at low shear rates and that are characterized by large decreases in the axial ratio at high shear rates, exhibit pseudoplastic behavior. In this study pseudoplasticity is exhibited by polysaccharides with molecular weights in excess of 450 000, and is insensitive to the backbone chemistry for linear macromolecules. In addition, low surface tension is associated with charged macromolecules that have a high positive second virial coefficient. Β© 1994 John Wiley & Sons, Inc.
π SIMILAR VOLUMES
The viscoelastic properties of three classes of soft relining materials (acrylic resins, silicones, and EVA copolymers) were studied comparatively. Their behaviors were investigated by in vitro tests at a frequency o = 1 Hz, which simulates the masticatory cycle. The experimental parameter was the t