The Removal of Flourides from Water by Ionic Exchange

Mottled enamel is the term originated by McKay to describe the disfigurement of teeth which Smith and others discovered was caused by the presence of fluorides in drinking water. Since then considerable time, energy and money have been spent in an effort to find an economical method of removing fluorides from drinking water. At first the use of activated carbon and activated alumina were rather promising; but more recently the use of tricalcium phosphate to remove fluorides from water has been developed (2). A patent by Adams and Holmes (1), wherein it was claimed that the sulphate ion concentration could be reduced nearly to zero, suggested that the fluoride content of water might be reduced to a permissible value by anionic exchange. Such a method of fluoride removal was investigated as a part of the research program concerning water treatment which has been in progress for many years at Iowa State College

Development of high shrinkage Polyethylene Terephthalate (PET) shape memory polymer tendons for concrete crack closure

YesThe shrinkage force exerted by restrained shape memory polymers can potentially be used to close cracks in structural concrete. This paper describes the physical processing and experimental work undertaken to develop high shrinkage die-drawn Polyethylene Terephthalate (PET) shape memory polymer tendons for use within a crack closure system. The extrusion and die-drawing procedure used to manufacture a series of PET tendon samples is described. The results from a set of restrained shrinkage tests, undertaken at differing activation temperatures, are also presented along with the mechanical properties of the most promising samples. The stress developed within the tendons is found to be related to the activation temperature, the cross-sectional area and to the draw rate used during manufacture. Comparisons with commercially-available PET strip samples used in previous research are made, demonstrating an increase in restrained shrinkage stress by a factor of two for manufactured PET filament samples.Thanks must go to the EPSRC for their funding of the Materials for Life (M4L) project (EP/K026631/1) and to Costain Group PLC. for their industrial sponsorship of the project and author