Unbleached Sulfate Pulp (UKP, Unbleached Kraft Pulp) is kraft pulp without bleaching, brown in color, with maximum fiber strength. It does not undergo the bleaching stage — the fibers retain residual lignin, which strengthens interfiber bonds. Breaking length ≥9000–11,000 m — higher than bleached pulp. Applications: high-strength kraft paper (sack, wrapping), kraft liner (outer layer of corrugated cardboard), electrical insulating paper. Grades according to GOST 9571-89: NS-1 (highest strength, for sacks), NS-2 (standard, for liner). Softwood pulp from spruce and pine. More environmentally friendly than bleached pulp: no bleaching effluents. Brown color is in demand in the eco-packaging trend (kraft bags, boxes, wrapping). Form: bales of 200–250 kg. Shipment: rail wagons, containers. UKP is the basis of the corrugated industry: kraft liner (testliner) made from unbleached pulp + fluting (corrugated medium) = corrugated cardboard. Liner weight 125–225 g/m². High tensile and puncture strength — key to the quality of corrugated cardboard and transport packaging. Electrical insulating kraft paper: for power transformer windings. Specialized market. Documentation: CoA, phytosanitary certificate, strength test report. Export: China, Europe, Turkey. Documentation: quality certificate, TR CU, certificate of conformity. Bulk supplies within Russia and for export. Technical consultation.