Fiber Morphology Characterization in Recycled Packaging Substrates
Automated optical morphology testing under ISO 16065-2 quantifies fiber shortening and hornification to control secondary substrate strength and yield.
Coarseness
Fibre Weight
Linear density of pulp fibres determines the structural properties and surface texture of a finished sheet of paper. Measured in milligrams per hundred metres, coarseness describes the mass of dry cell wall material per unit length of fibre. This characteristic governs the flexibility of the fibres and dictates how they conform to one another during sheet formation.
Sheet Structure
Fibre flexibility decreases as the cell wall thickness increases relative to the fibre diameter. Rigid fibres with high coarseness resist collapse during the drying process, creating a bulkier sheet with higher porosity but lower tensile strength. Conversely, low values for this property yield highly collapsed, ribbon-like fibres that bond tightly, producing a dense paper with a smooth surface.
Refining Response
Mechanical action during refining alters the fibre structure to compensate for high cell wall thickness, yet the inherent density limit of the raw material remains. Papermakers select softwood species with lower cell wall mass for fine printing papers where opacity and smoothness are paramount. When heavy packaging grades are manufactured, coarser fibres are preferred because they provide high tear resistance and bulk.
Measurement occurs via automated optical analysers that evaluate thousands of wet fibres in a diluted suspension to ensure consistency across different batches of pulp.