Poly-V belts are disclosed that have a body in an elastomeric material, preferably EPDM, a plurality of durable filiform inserts longitudinally embedded in the body, and a coupling portion integrally connected to the body and comprising a plurality of V-shaped ribs in side by side arrangement alternating with V-shaped grooves. A layer of a thermoplastic material at least partially covers the ribs, and a knitted fabric is arranged over the thermoplastic material. Preferably, the thermoplastic material includes a polyolefin irradiated with a dose amount of radiation between 60 and 140 kGy.