Toughening with rubber can effectively improve the toughness of PPS, and its mechanism is the same as that of common rubber toughened polymers. The early theories of rubber toughened plastics include direct energy absorption theory, yield expansion theory and crack core theory. Among them, the crack core theory on stress concentration and induced small cracks has a great role in promoting and enlightening the development of toughening theory. After that, people developed many theories about rubber toughened plastics, but now there are two widely accepted theories, one is the craze branching theory and the other is the craze shear band theory.

The research of craze branching toughening mechanism focuses on the control of craze formation, propagation and termination process, so as to achieve energy dissipation without causing craze to develop into cracks and finally leading to the damage of polymer materials. According to this theory, the material first has craze core at the local stress strain concentration point, and then the length of craze microfiber increases and craze thickens continuously under the effect of stress. Finally, the crazing was terminated by the interaction of craze and craze, the encounter of craze and shear band, cavity and dispersed rubber particles. A quantitative explanation for the effect of rubber particles on preventing crazing is that rubber particles can branch the crazing that develops rapidly.

However, the coexistence theory of shear band and craze holds that when two shear bands intersect, the molecular chain will be cut off at their intersection to form microvoids, and then the microvoids will expand to form elliptical craze cavities. This theory is an organic combination of the multiple craze theory and the shear yield theory. Its basic view is that craze and shear band are two ways of energy consumption that exist simultaneously in the impact process of materials. When the micro strip area interacting with craze and shear band expands in the whole volume, the material toughness will be greatly improved.

At present, the coexistence theory of shear band and craze has been widely accepted, but there are still some detailed problems, such as the sequence of shear band and craze, the microscopic mechanism of interaction between shear band and craze, and how to make shear band stop craze more effectively. Moreover, some existing results are only for a specific rubber toughening system.

The factors that affect the toughening effect of rubber include compatibility between components, rubber particle size, distance between rubber particles, rubber content, glass transition temperature of rubber phase, and rubber particle structure. Recent studies believe that the distance between adjacent particles of rubber phase is the key to produce the toughening effect. This theory points out that when the distance between two adjacent rubber particles is less than a certain critical value, the polymer will show a ductile fracture. When it is roughened, it will show a brittle fracture. There is a sudden change in the impact toughness of the material, that is, the brittle ductile fracture transition point. Among them, it is determined by the properties of the substrate, independent of the volume fraction of rubber.