الفهرس | Only 14 pages are availabe for public view |
Abstract Surfactants are a diverse group of chemicals that are designed to have cleaning or solubilisation properties. They generally consists of a polar head group (either charged or uncharged), which is well solvated in water, and a nonpolar hydrocarbon tail, which is not easily dissolved in water. Hence, surfactants combine hydrophobic and hydrophilic properties in one molecule. Synthetic surfactants are economically important chemicals. They are widely used in household cleaning detergents, personal care products, textiles, paints, polymers, pesticide formulations, pharmaceuticals, mining, oil recovery and pulp and paper industries. The world production of synthetic surfactants amounts to 7.2 million tons annually (1). Surfactants are used together with polymers in a wide range of applications, formulations usually contain a combination of a low molecular weight surfactant and a polymer which mayor may not be highly surface active. Together, the surfactant and polymer provide the stability, archeology, etc., needed for specific application. The solution behavior of each component is important, but the performance of the formulated product depends to a large extent on the interplay between the surfactant and polymer. Hence knowledge about physicochemical properties of both surfactants and polymers and not least about surfactant-polymer interactions, is essential in order to make formulation work more of a science than an art. Until recent years soap and water the only cleaning agents available. Soap served society well for many years, until shortage in animal and vegetable fats and oils, the basic ingredients necessary to make soap, during the World Wars I and Il, prompted research into potential alternatives. The studies led to the commercial discovery of surfactants which could be made synthetically from petrochemicals, which readily available. This development proved to be a further stroke of luck for the cleaning industry and society. Unlike the traditional soap, the surfactants were more resistant to hard water and therefore improve the efficiency of the cleaning process. Surfactants consisted mainly of three types: anionic, nonionic, and cationic (Table 1). Linear alkylbenzene sulphonates (LAS), alkyl ethoxy sulphates (AES), alkyl sulphates (AS), alkylphenol ethoxylates (APE), alkyl ethoxylates (AE), and quaternary ammonium compounds (QAC) are the commonly used commercial surfactants. Especially, LAS, APE, and QAC are the most extensively studied surfactants. Linear alkylbenzene sulphonates (LAS) was first commercialized in the early 1960s as a replacement for the poorly biodegradable DDBS (Dodecyl benzene sulphonate - Branched alkylbenzene sulphonate), which caused persistent foam in sewage treatment plants, streams and rivers. Linear alkylbenzene sulphonates (LAS) may be considered as the first ”green” cleaning agent, because it was the first surfactant introduced to solve an environmental problem. Such replacement was the result of a vast research effort followed by investments to provide the world surfactant and detergent industry with one of the most cost-effective and environmentally safe surfactants. These investments activities have continued during the last 40 years and have yielded continuous improvements in quality and safety as well as new developments in both LAB (Linear alkylbenzene, the raw material for LAS) and sulphonation processes. In parallel with the technological developments, substantial research is also continuing, and still continuous today, in order to provide all the stakeholders with the most detailed and comprehensive knowledge about the environmental and human safety of LAS. Today LAS is probably the most researched chemical available. LAS, after soap, the most widely used surfactants in all detergents and cleaning products. It is the surfactant of choice by detergent manufactures, not only. |