Abstract: Product in subdivided form comprising: a) at least one additive for crosslinkable elastomeric compositions; and b) a thermoplastic binder comprising at least (i) one copolymer ethylene with at least one aliphatic or aromatic &agr;-olefin, and optionally a polyene, said copolymer being characterized by a molecular weight distribution (MWD) index of less than 5 and a melting enthalpy (&Dgr;Hm) of at least 30 J/g. Said product in subdivided form is particularly useful for preparing crosslinkable elastomeric compositions.

Abstract: Catalyst components for the polymerization of olefins are disclosed. Said components comprise the solid product of the reaction of a halogenated Ti compound and of an electron-donor compound not containing active H atoms with the solid product of the reaction between an electron-donor compound containing active H atoms and a Mg dihalide obtained by decomposition, with halogenating agents other than the above halogenated Ti compound, of product (d) obtained from the reaction between an organometallic Mg compound of formula R.sub.m MgX.sub.n is which R is a hydrocarbon or --OR group, X is halogen or a group R, OR, or COX' (X' being halogen), 0<m=2, 0<n<2 and m+n is 2; and a Si compound selected from polysiloxanes, hydropolysiloxanes, silanols and polysilanols.