Starting from the application needs, the quality of kraft paper and kraft paper can be roughly summarized into the following six aspects:
(1) Appearance quality
Appearance quality refers to the defects that can be observed by the naked eye, such as dust, holes, needle eyes, transparent spots, translucent spots, wrinkles, folds, tendons, screen marks, wool cloth marks, spots, pulp bumps, fish scale spots, cracks, curls, and inconsistent color. For all kinds of kraft paper and kraft paper, certain appearance quality requirements should be proposed.
(2) Physical properties
Physical properties mainly include quantitative, thickness, tightness, mechanical strength (also known as physical strength, including tensile strength, crack length, burst resistance, bending resistance, elongation, ring compressive strength, crushing elasticity, puncture strength, bending performance, etc.), elasticity, compressibility, stiffness, air permeability (or porosity), softness and so on. The physical properties are determined by special instruments.
(3) Absorption performance
The absorption performance includes sizing degree, water absorption performance, ink absorption performance, oil absorption performance, etc. Most of the paper is sizing to achieve some liquid-repellent properties. Paper that requires liquid absorption or oil absorption (such as filter paper, parchment base paper, impregnated base paper, etc.) cannot be sized. Absorption can be determined by chemical or physical methods.
(4) Optical properties
Optical performance refers to the items that can be verified by optical instruments such as brightness, whiteness, color, gloss, transparency, opacity, etc.
(5) Surface properties
Surface properties include smoothness, anti-wear performance, linting performance, rubbing resistance, adhesive performance, powder shedding performance, corrugated performance, roughness, etc. These items require the use of specialized instruments for measurement.
(6) Printability
Printability is an important quality requirement for printing paper. The printability of kraft paper and kraft paper mainly depends on its smoothness, sizing sheet, compressibility, opacity, dimensional stability, mechanical strength, lint shedding performance, powder shedding performance, etc.
Some packaging kraft paper and kraft paper can be tested by certain test methods to determine their performance in final use, such as the bag drop test of multi-layer paper bag paper, the drop test of fiberboard boxes and the drum test. The results measured in these tests are dynamic intensities.