Thermal and rheological properties of unsaturated polyester resins-based composites

Unsaturated polyester resins (UPR) are among the most commercially important thermosetting matrix materials for composites. This chapter summarizes the importance of the thermal and rheological properties of UPR. The kinetics and mechanisms of thermal degradation (for both inert and reactive atmospheres) are presented. A little information about the toxicity of the major thermal degradation products is given. The main parameters affecting thermal stability (prepolymer structure, styrene content, cure regime, fillers, and reinforcements) are summarized. A comprehensive study of the methods of improving thermal stability and flame retardancy with a special emphasis on nonhalogenated flame retardants is presented. Bearing in mind that the rheological characteristics of UPR govern and limit their usage potential, a comprehensive study of the parameters affecting the viscosity of UPR composites (thickening and thixotropic agents, low profile additives, fillers, and reinforcements) is presented. Also, briefly introduced and described are the main processing techniques with special emphasis on the rheological requirements for each technique. Finally, some rheological concerns and challenges for the development of fully bio-based UPRs are described