Mechanical Greaseproof Paper Grade Selection for Bakeries and Fast Food Packaging
Optimize mechanical greaseproof paper selection by specifying 80-88 SR refining and 15000+ s Gurley porosity to secure non-PFAS grease resistance.
Specific Edge Load Refining
Energy Intensity
Mechanical energy transfer calculations quantify the intensity of bar-to-bar impacts on papermaking fibers inside disk or conical refiners during stock preparation. Controlling specific edge load refining allows papermakers to select between internal fibrillation for fiber bonding and direct cutting for sheet formation control. The calculation divides net refining power by the cutting edge length per second generated by rotating refiner plates.
Values expressed in watt-seconds per meter define the severity of individual bar impacts on cellulose fibers.
Fiber Cutting
Operating refiners at high edge load values transfers intense energy over a small contact area, causing transverse fiber cutting and short average fiber length. Low edge load levels distribute energy broadly across fiber surfaces, promoting internal fibrillation and cell wall swelling without shortening fiber length. Hardwood kraft pulps require low edge load intensity around 0.5 to 0.8 watt-seconds per meter to prevent excessive fiber shortening and fines generation.
Softwood pulps with thicker cell walls withstand higher energy intensities up to 2.0 to 3.0 watt-seconds per meter, promoting internal delamination that enhances sheet density and tensile strength. Refiner plate pattern design, bar width, groove depth, and rotational speed control the cutting edge length parameter. Papermakers adjust net motor load in real time to compensate for changes in pulp throughput or furnish consistency.
Selecting inappropriate edge loading damages fiber strength potential, leading to lower web wet-tensile strength and higher draw breakdown rates on high-speed paper machines.
Fibrillation Limit
Exceeding upper energy thresholds causes severe fiber shortening and excessive fines creation, which reduces drainage rates on the paper machine wire. Insufficient energy loading leaves fibers stiff and unrefined, yielding poor sheet formation and weak inter-fiber bonding strength. Process control limits maintain edge intensity within specific pulp supplier recommendations.