Chemistry Reference
In-Depth Information
5
Synthesis and Application of Rosin-Based
Surfactants
Xiaoping Rao
5.1 Introduction
Surfactants are amphipathic molecules with both hydrophilic and hydrophobic
moieties. The amphipathic structure makes them capable of reducing surface and
interfacial tension, forming microemulsion and exhibiting some superficial or
interfacial activity in solvents [1]. Since the advent of surfactants in the twentieth
century, the use of surfactants has matured and there are now thousands of different
kinds of surfactant products on the market for use in industry. The quality of our
lives is closely related to the safe use of surfactants [2]. Nowadays, surfactants play
an important role in almost every chemical industry, including detergents, emulsions,
paints, foaming agents, paper products, cosmetics, pharmaceuticals and insecticides
[3]. The worldwide production of surfactants was about 12 million tonnes in 2008
and the demand for them is expected to increase at a rate of 3% per year [4]. With
the increasing concern for the need to save energy and protect the environment,
renewable resources is a crucial area in the search for alternatives to fossil-based raw
materials. In the surfactants field, common synthetic products from petrochemicals
have often shown good functional properties, but they do not fulfill the requirements
for environmental protection and sustainable development. There are millions of
naturally occurring compounds which can be used as raw materials for the design
of surfactants. They can incorporate special structures in the final products that may
lead to surfactants with unexpected properties. The use of naturally occurring raw
materials in surfactant synthesis is expected to provide new types of surfactants with
better biodegradability. Further, in order to achieve long-term sustainable production,
it will become necessary to use renewable sources [5]. The interest in designing highly
specialised synthetic surfactants incorporating natural structural moieties has increased
remarkably during the last few years [6]. The varieties of naturally occurring structures
provide abundant selection for surfactant design. Some natural resources can provide
hydrophilic groups, and some can provide a hydrophobic moiety. Renewable sources
of hydrophilic groups include carbohydrates, proteins, amino acids and lactic acid,
and sources of the hydrophobic moiety are steroids, monoterpenes, rosin acids, fatty
