Components of Synthetic Binders

As mentioned previously, the difficulties in obtaining colourable blends from bitumen mixtures have forced the research and production of synthetic substances which are easily colourable, with mechanical properties similar to those of bitumen, allowing their use in most applications where coloured mixtures are advised. These products, known as binders or light synthetic binders, because of their light tones, are a mixture of substances that form a macroscopically compatible system. The colouring is easy and with 1-2% w/w pigment, colour shades are obtained which meet most of the desired colour range [5]. 

Synthetic binders have a similar behaviour to distillate bitumen oil, and have mechanical and rheological properties similar, or even better than, normal and modified bitumen. 

In general, a synthetic binder consists of 3 groups of components  

From a structural point of view, the above system involves the dispersion of polymer chains in an oil-resin medium, as will be discussed later. The mechanical properties of this system depend on their relative proportions, their chemical nature and the interactions and incompatibilities among the components. 

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Recycled materials, such as recycled polyolefin, have been widely employed as bitumen modifiers with exceptional results. In fact, recycled polymers will be one of the main components of synthetic binders in the near future, as discussed later in the chapter. From an environmental point of view, the addition of recycled polypropylene is an alternative option to other more destructive techniques which cause pollution, such as incineration, in order to reduce the waste disposal problem. So, the manufacturing of synthetic binders from recycled polymers, as well as other industrial processes that use waste as raw materials, is the way forward in order to decrease the use of the planet s finite resources. 

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