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Polypropylene (PP) is one of the most abundantly produced polymers worldwide due to its low cost, good mechanical properties and easy processability. However, the lack of polarity in PP makes it difficult to use it in applications that require strong adhesion between polymer chains such as 3D-printing and composites. A polar functionalization of PP is necessary to overcome this property gap and improve its affinity with other polar materials. Industrial functionalized PP is already produced. However, the functionalization is often energy intense, costly and makes use of reactive peroxides, which also cause chain scissions. These extreme conditions result in products that are still lacking in properties such as molecular weight, strength and viscosity. In order to broaden the applicability of PP, it is necessary to develop mild functionalization protocols using reusable and recyclable ingredients. This research focuses on the functionalization of PP with maleic anhydride (MAh) via post-polymerization modification, using a mild and photocatalytic approach. Given the novelty of this method, all major contributing factors of the functionalization and their influence on the grafting of MAh were inspected. The four major contributing factors that are investigated are the concentration of MAh and N-hydroxyphthalimide (NHPI), the photocatalysis duration and the dichlorobenzene (DCB) volume. To perform photocatalysis, the PP is first dissolved in DCB with MAh and NHPI. Reusable iron (III) oxide-coated glass beads, which operate as a photocatalyst, are added then to the mixture. Thereafter, 455 nm LEDs are used to irradiate the solution. To analyze the produced PP-MAh, different analysis methods such as FTIR, acid-base titration, and contact angle analysis are used. A commercial grade of PP-MAh, ExxelorTM PO 1020, is used as a reference polymer. The results showed significant influences of the MAh concentration, photocatalysis duration, and NHPI concentration on the absorbance peaks, whereas changing the DCB volume did not. The optimal recipe has a concentration of 20 wt% MAh, a photocatalysis duration of 16-24 h, an NHPI concentration of 37,5 wt%, and 100 ml of DCB. Using this recipe, the absorbance peaks in the carbonyl region are higher compared to the reference ExxelorTM PO 1020. These results are confirmed by using acid-base titrations. The grafting percentage [Pg (wt%)] of the PP-MAh amounted up to a Pg up to 2,35 wt%. This is significantly higher compared to a Pg of 1,34 wt% with the reference material. One of the main problems during photocatalysis is a significant decrease in viscosity from 650 Pa s to 100 Pa s. The antioxidant butylhydroxytoluene (BHT) is added in different concentrations (0-5 wt%) to analyze the effect of it on polymer degradation and functionalization. When using a concentration of 5 wt% BHT, the viscosity doubled to 200 Pa s. This is significantly higher than the viscosity of ExxelorTM PO 1020, which amounts to 35 Pa s. Although photocatalysis still has a minor drawback, namely longer catalysis times, the functionalization of PP with MAh, using this newly developed protocol, shows promising results. The grafting percentages of the produced PP-MAh outdo the grafting percentages of the ExxelorTM PO 1020 without using highly reactive peroxides or heating. Furthermore, an optimal recipe is formulated and surface functionalization, which maintains the bulk properties of polymers, showed promising results.