Laser-imageable flexographic printing precursors and methods of relief imaging

A method for preparing a flexographic printing precursor, comprising:

• forming a laser-engravable composition into a laser-engravable layer, the laser-engravable composition comprising one or more EPDM elastomeric rubbers in an amount of at least 30 weight % and up to and including 80 weight %, based on the total laser-engravable composition dry weight, the one or more EPDM elastomeric rubbers comprising a first EPDM elastomeric rubber comprising at least 8 weight % and up to and including 15 weight % of polyene recurring units, the first EPDM elastomeric rubber comprising at least 50 weight % and up to and including 100 weight % of the total elastomeric rubber weight,
• the laser-engravable composition further comprising:
• a) at least 2 phr and up to and including 60 phr of a near-infrared radiation absorber, and
• b) at least 3 phr and up to and including 20 phr of a sulfur vulcanizing composition comprising a sulfur-containing vulcanizing compound,
• wherein the laser-engravable composition is essentially free of peroxides, the weight ratio of the near-infrared radiation absorber to the vulcanizing composition is from 1:10 to and including 20:1, and the weight ratio of total first EPDM elastomeric rubbers to total second EPDM elastomeric rubbers is from 0.67:1 to 4:1.