Polymer Film Micro Fracture Mechanisms under High Strain Shear in Folding Boxboard Creases
High strain shear during boxboard creasing causes polymer film micro fractures when local elongation exceeds film yield capacity along the outer bend radius.
Optical Microtomy
Sectioning Precision
Precision sectioning instruments slice embedded paperboard and laminate samples into ultra-thin cross sections for microscopic structural analysis. Application of optical microtomy enables quality laboratories to inspect individual coating layers and interface boundaries at high magnification. Glass or diamond blades cut sections ranging from two to ten micrometers in thickness without distorting delicate substrate structures.
Embedded resin matrix supports preserve original pore geometry and multi-layer boundaries during cutting.
Layer Inspection
Sample preparation begins by embedding paperboard specimens in synthetic epoxy or acrylic resin blocks that cure under heat or ultraviolet light. Using optical microtomy, technicians cut cross-sectional ribbons that are mounted onto glass microscope slides for transmission light microscopy. Transmitted light and fluorescence microscopy reveal coating thickness uniformity and barrier layer continuity across complex laminates.
Polarized light illumination differentiates synthetic polymer films from natural cellulose fibers based on refractive index variations. Starch distribution and surface sizing applications show distinct contrast within the fiber network under chemical staining. Measurements taken from calibrated digital images yield precise thickness values for individual plies and barrier coatings.
Insufficient resin curing or dull sectioning blades create deformation artifacts that distort structural layer measurements.
Defect Analysis
Investigation of delamination defects and pinholes relies on undamaged cross-sectional sample views. Employing optical microtomy isolates structural anomalies responsible for poor ink holdout or barrier breakdown on commercial packaging lines. Microscopic inspection verifies that barrier layers maintain consistent thickness over underlying paperboard surface roughness.
High-resolution cross-sectional profiles validate multi-layer packaging construction against manufacturing specifications.