Application of environmental scanning electron microscopy in the development of detergents and personal products
Environmental scanning electron microscopy enables the observation of samples in their natural state with no preparation. Unilever Research employs this technology in the research and development of detergents and personal products with much success. The results presented are from various studies which demonstrate the versatility and utility of the technique. Vacuum sensitive samples such as microcapsules were successfully characterized, the efficacy of dental products was shown by monitoring an enamel surface before and after treatment, and the performance of an adhesive was assessed by dynamic experimentation. © 1993 Wiley‐Liss, Inc.
Environmental scanning electron microscopy of personal and household products.
The ability to forego sample preparation and to make observation directly in the environmental scanning electron microscope has benefited both household and personal product research at Unilever Research. Product efficacy on biological materials such as microcomedones was easily ascertained. Skin biopsies were examined in a moist state with no sample preparation. Effects of relative humidity on detergents were visually determined by recreating the necessary conditions in the microscope. Effects of cooling rates on the morphology of softener sheet actives that remained on polyester fabric were characterized via dynamic experimentation.
Surface adsorption of fluoride and ionic exchange reactions on hydroxyapatite.
The experiments showed that a part of the fluoride which was taken up by hydroxyapatite or teeth at low concentrations of fluoride at neutral pH was soluble in alkali (IN KOH, 24 h) and was thus not fluoroapatite. Calcium fluoride could not form under the present conditions because the solubility of this compound was not exceeded. It is suggested that the alkali soluble fluoride is adsorbed to calcium ions bound as counterions in the hydration layer of the hydroxyapatite or the enamel. This is consistent with previous findings in this laboratory, showing that fluoride displaced acidic proteins adsorbed to calcium receptors on the hydroxyapatite surface in the same way as other anions displace proteins. It could also be shown that polyanions and polycations adsorbed to hydroxyapatite surfaces by ionic exchange, displacing phosphate or phosphate and calcium respectively in the process. A model is suggested which differs slightly from that proposed by Bernardi.