The properties of polymers can not only be controlled by starting from suitable monomers, but also by modification of preformed commercial polymers. This relatively simple, though scientificallly highly challenging approach has gained increasing interest during the last decades. It is economically very attractive to start from relatively cheap commodity plastics and to alter and transform in a controlled manner the properties of e.g. polyolefines into new/speciality materials with tailor-made properties and custom-designed performance for target applications by bulk modification. In addition very often polymers have excellent bulk properties, but lack surface properties such as hydrophilicity, conductivity or biocompatibility needed for a lot of applications. By surface modification the chemical and physical properties of polymer surfaces can be altered without affecting bulk properties. Essential ingredients of almost all commercially important polymers are additives and demands of service requirements, environmental concerns and regulatory constraints as well as increased consumer demands have led to the development of new, safer and more efficient additives. Our work in the field of polymer modification also includes the chemical modification of biopolymers, silicone rubber and silicone dioxide.