A polar group-containing polypropylene having: • MFI less than 10 (g/10min), determined according ISO1133 at 230 °C and 2.16 kg weight. • grafted polar group content between 0.3 and 5 wt% wherein the polar group is a maleic acid derivative and wherein the polar group-containing polypropylene comprises at least a constituent unit represented by the following formula, a constituent unit represented by the following formula and Optionally a constituent unit represented by the following formula In which X is selected in the group comprising CH 2, O, S, NH, When X is CH 2, R is selected in the group comprising a saturated aliphatic group with C 1 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines, amides or R is selected in the group comprising an aromatic moiety with C 5 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines and amides. When X is O, S or NH, R is selected in the group comprising hydrogen or a saturated aliphatic group with C 1 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines, amides or R is selected in the group comprising an aromatic moiety with C 5 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines and amides. R' is selected in the group comprising hydrogen or a saturated aliphatic group with C 1 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines, amides or an aromatic moiety with C 5 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines and amides. Y is selected in the group comprising O, S and NR" when R" selected in the group comprising hydrogen, a saturated aliphatic group with C 1 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines, amides or R" is selected in the group comprising hydrogen, an aromatic moiety with C 5 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines and amides. • MFI less than 10 (g/10min), determined according ISO1133 at 230 °C and 2.16 kg weight. • grafted polar group content between 0.3 and 5 wt% wherein the polar group is a maleic acid derivative and wherein the polar group-containing polypropylene comprises at least a constituent unit represented by the following formula, a constituent unit represented by the following formula and Optionally a constituent unit represented by the following formula In which X is selected in the group comprising CH 2, O, S, NH, When X is CH 2, R is selected in the group comprising a saturated aliphatic group with C 1 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines, amides or R is selected in the group comprising an aromatic moiety with C 5 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines and amides. When X is O, S or NH, R is selected in the group comprising hydrogen or a saturated aliphatic group with C 1 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines, amides or R is selected in the group comprising an aromatic moiety with C 5 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines and amides. R' is selected in the group comprising hydrogen or a saturated aliphatic group with C 1 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines, amides or an aromatic moiety with C 5 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines and amides. Y is selected in the group comprising O, S and NR" when R" selected in the group comprising hydrogen, a saturated aliphatic group with C 1 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines, amides or R" is selected in the group comprising hydrogen, an aromatic moiety with C 5 to C 15 which may include functional groups selected from the list including alcohols, thiols, ketones, aldehydes, ethers, carboxylic acids, carboxylic acid anhydrides, esters, amines and amides.