Ground Tyre Rubber (GTR) particles have been treated with glycidyl methacrylate (GMA) and methacrylic acid (MAA) using a proprietary photoinitiated surface grafting process. The grafted GTR (GMA-g-GTR and MAA-g-GTR, respectively) was incorporated in various polar thermoplastics (PA-6, PBT) and elastomers (PUR) in order to assess the effectiveness of the grafting process. It was concluded that the most promising way is to use the grafted GTR in PUR compounds. PUR blends with 10 wt.% MAA-g-GTR showed the best mechanical performance.