Cross-linking of thermoplastics can improve their thermal,physical and mechanical properties.Polymers like polyethylene or natural rubber can be easily cross-linked by peroxide or radiation curing.Unfortunately,network synthesis of polymers that contain tertiary C-atoms is more complicated.The main problem consists in the nature of radical reactions since the majority of macro radicals decays by β-scission resulting in a decrease of molecular weight and branching instead of cross-linking.Here we report on the improved properties of cross-linked polypropylenes.