The basic morphological unit of a closed cell rigid foam is the gas-filled cavity surrounded by cell walls and struts. Typically, these cavities (cells) are pentagonal dodecahedral or tetrakaidecahedral. Their average dimensions and dispersity are known to influence foam physical properties and foam performance.We have devised a reliable method for the measurement of cell-size and cell-size distribution which exploits both geometry and statistics, and which has allowed the realization of useful correlations and trends in our development of rigid foam formulations and additives. A thin slice of foam (100-300 microns) is subjected to optical microscopy and image analysis. Measurements of the areas of cell windows and of the average ferets of these windows are made independently. Windows are usually pentagonal, hexagonal or square and are variously distorted. Cells are assumed to be dodecahedral and cell diameter (d) is calculated by the formulae: Thereby, two independent determinations of cell diameter are obtained from each window viewed. Values are typically within 2% of each other. Cell-size distribution is quantified by measuring a large number ( -500-1000) of windows and calculating the simple and weighted averages. This paper will present the mathematical basis for the method, illustrate the excellent agreement between the window area and the feret cell-size determinations and demonstrate the utility of cell-size and cell-size distribution data in physical property correlations, for example for k-factor. POLYURETHANES HAVING HIGH REFRACTIVE INDEX AND HIGH ABBE'S NUMBER T. Ohkubo and R. OkadaHOYA Corporation For optical uses such as lens, filter, prism and so forth, polymethylmethacrylate, polystyrene and polycarbonates have been commonly used. Recently polymer materials having high refractive index have been developed for the above uses.Generally speaking, for many inorganic or organic materials refractive index and Abbe's number relate to each other, that is, the higher the refractive index, the lower the Abbe's number. Consequently, it is very difficult to obtain a material having higher refractive index and sufficiently high Abbe's number at the same time.Recently we succeeded in synthesizing a novel thiol namely 2,5-dimercaptomethyl-1,4-dithiane, the refractive index (nD) and the Abbe's number (UD) of which are 1.646 and 35.2, respectively. Both of these values are considerably large compared with those of common organic compounds.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.