The pressure sensitive adhesive is a copolymer of ethylene and propylene that has a maximum load between 6.4 N and 11.2 N in a lap joint shear strength test. The copolymer is prepared by mixing ethylene and propylene in the presence of a diimine nickel catalyst and polymethylaluminoxane (MAO) co-catalyst. The molar ratio of the ethylene to propylene feed is between 60:40 and 40:60. The polymerization is carried out at 30° C. and 1.3 bar. The polypropylene molar percentage in the resulting copolymer is between 42% and 88%, and the weight average molecular weight is between 24,917 and 33, 314 Da. The copolymer is an amorphous polymer having a glass transition temperature (Tg) between −63° C. and −66° C.