A roll cover and a roll in particular for use in a machine line for the production or processing of a fibrous web is provided, wherein the roll cover includes a radial outer functional layer which provides the surface of the roll cover in contact with the web, and wherein the functional layer has structural elements, in particular in the form of grooves and/or bores, wherein the functional layer is constructed of an elastomer material with a Poisson number greater than 0.4, between 0.45 and 0.5.

Calender for treating web materials, comprising a structure for supporting two heated rollers forming a nip, wherein each roller has surface reliefs (RR) and in an operational setting of the calender the reliefs of one roller are radially opposed to those of the other roller, each roller rotates with a predetermined angular speed around its axis, the rollers are heated by heating means, and each roller undergoes an axial elongation as a consequence of its heating. The calender comprises detection means (E1, E2; IS) adapted to detect the axial elongation of each roller and a programmable control unit (UCP) connected to the detection means and to the heating means. The control unit is programmed to determine the difference between the axial elongations of the rollers and emitting an alarm signal if the absolute value of this difference is greater than a limit value.

Calender for treating web materials, comprising a structure for supporting two heated rollers forming a nip, wherein each roller has surface reliefs (RR) and in an operational setting of the calender the reliefs of one roller are radially opposed to those of the other roller, each roller rotates with a predetermined angular speed around its axis, the rollers are heated by heating means, and each roller undergoes an axial elongation as a consequence of its heating. The calender comprises detection means (E1, E2; IS) adapted to detect the axial elongation of each roller and a programmable control unit (UCP) connected to the detection means and to the heating means. The control unit is programmed to determine the difference between the axial elongations of the rollers and emitting an alarm signal if the absolute value of this difference is greater than a limit value.