The mechanical behaviour of paper depends on both fibres and the properties of the fibre-fibre joints.The fibre surfaces will constitute the contact zone between the fibres and will hence be very important for paper strength. The links between the mechanical behaviour of single fibre joints and paper properties were studied by introducing negative charges to the surface and the bulk of regenerated cellulose fibres selectively. This will affect the properties of fibres and fibre surfaces differently. Both the chemical and mechanical properties were investigated.