The impact resistance is one of the most critical characteristics of the thermosetting resins. Its enhancement by the use of elastomers or other soft polymers is an efficient way.
We are going to investigate four examples:
* Toughening of unsaturated polyesters with virgin rubbers and TPE
* Toughening of epoxy resins by polyurethane wastes
* Comparison of the properties of pure and toughened phenolic resins
* Toughening of a hi-tech polymer matrix as polycyanate by a hi-tech elastomer as silicone.
It must be noticed that the improvement of the impact resistance has a secondary effect, generally undesirable: the softening of the polymer that reduces the modulus, the hardness and, often the ultimate properties.
For example, the Young's modulus and the impact resistance of an unsaturated polyester (UP), a rubber and their blends are plotted.
Nevertheless, in any case, the study of the impact resistance alone is not sufficient and it is essential to examine simultaneously the modulus and the ultimate stresses.