Syrene Research Paper

At room temperature is a colorless gas with an odor similar to gasoline. It is an alkene used to manufacture rubber by addition polymerization. It has two C-C double bonds in its structure which allows the compound to form a wide variety of polymers including ABS. This compound is a toxic gas listed as a human carcinogen. Figure 2. Representation of 1.3-butadiene (mw: 54.09 g/mol)

Styrene:

A colorless to yellowish liquid that produce polystyrene by homopolymerization. Styrene is a derivative of benzene and could be found in small quantities in plants and foods. It is slightly soluble in water and very soluble in ethanol, acetone and carbon disulfide. Its rate of polymerization is low at room temperature but increases at higher temperatures.

There are different process that can be used to synthesize ABS but all of them involve the polymerization of styrene and acrylonitrile in the presence of an elastomer (butadiene). The product of this polymerization is SAN that later will be graft polymerized to the rubber component and produce ABS.

The rubber component is synthesized by free radical polymerization of 1,3 butadiene to produce 1,4 polybutadiene. The cross linking process happens with the abstraction of the reactive allylic sites or by copolymerization through the double bonds.

The grafting of SAN to a rubber component is the most essential part of the synthesis of ABS because it combines a styrene-acrylonitrile copolymer with a rubber substrate. The features of the ABS synthesized will depend on the composition of the reagents involved in the grafting process. This process starts with the abstraction of allylic hydrogens of the rubber substrate or by copolymerization of the double bonds in rubber. The grafting process always leaves a certain amount of ungrafted SAN. The proportion of ungrafted SAN in the final product depends on the conditions used of the manufacture of ABS. There are many factors that can be modified to change the amount of grafted and ungrafted SAN. This factors include temperature, chain-transfer agent and content of rubber. The graft SAN involves a process of free radical polymerization

Graft initiation mechanism

This is the initiation step of polymerization in which an active site will be created. This active site will be the responsible of the generation of the polymer chain. There are two compunds that are used in the initiation process and are the polybutadiene and 1,4-polybutadiene. Both compounds have a carbon-carbon double bond where the radical initiation will start. The next step in the formation of SAN is the graft propagation. Figure 5. Graft propagation mechanism

This is the final step of the graft process in which the acrylonitrile and styrene form a copolymer with a butadiene radical. Both final compounds are in form of radicals and can be copolymerized to form a random copolymer. As said before graft process is the base of the synthesis of ABS and it is important to follow the steps in order to obtain the desired product. Rubber and monomers like acrylonitrile and styrene are the only reagents that can produce this thermoplastics whose properties will depend on the proportion of the reagents used. All the grafting process could be summarized by the following reaction that has ABS as the final product: Figure 6. General reaction of the synthesis of