Extrudable compositions were prepared comprising poly(propylene) and a liquid additive comprising a lactam group. The compositions can comprise other optional additives that include a polyhemiaminal, antioxidants, UV light absorbers, and surfactants. The extruded compositions have higher percent elongation at break and lower Young's modulus compared to extruded poly(propylene) lacking the liquid additive. These and other property improvements make the extruded compositions attractive for forming field joint coatings for undersea pipeline applications.