A cord, thread or filament is treated by applying to it a dilute solution of a polysiloxane prepolymer which is then cured, such that either (a) the outer envelope of the cord, thread or filament is enrobed, or (b) in the case of a cord or thread, the filaments thereof are substantially individually encapsulated by, a coating of cured polysiloxane polymer. The treated cords, threads and filaments have inter alia improved abrasion and fray resistance, water repellance and slip qualities.