Characterization of packaging grade papers from recycled raw materials through the study of fibre morphology and composition

The restrictions in availability of forest-based raw materials along with favourable
environmental policies towards alternative sources of raw materials have forced corrugated
packaging industry to shift towards recycled paper and other fibre sources such as non-wood
and agro-residues. The variability in raw pulp materials with increasing percentages of
recycled fibres is a very common technical problem for the corrugated packaging industry
worldwide. Corrugating packaging production is facing the challenge to ensure a satisfactory
strength of packages despite the increase of recycled paper as the main fibrous component.
Sustainable manufacturing of papers of consistent and acceptable quality requests
comprehensive characterization of the fibrous components, which are becoming more
heterogeneous. Understanding the influence that heterogeneous recycled raw materials have
on packaging grade paper properties offers great potential value to the corrugated board and
packaging industry.
57 linerboards and corrugating medium were selected to represent all the variety of paper
grades available on the market at the moment for the production of corrugated board in
Spain. The papers were analyzed for their fibre morphology (fibre length, fibre width, lumen
diameter, cell wall width and flexibility) and fibre composition (softwood to hardwood and nonwood
fibre count and weight) and their strength (compression, bursting and crushing
resistance) was evaluated. All the determinations were in accordance with the relevant TAPPI
Test Methods. The significant differences found in most of the anatomical characteristics,
fibre composition and strength properties among the paper grades reflected the diverse raw
materials used for their production as well as their qualitative differences. By means of simple
correlation the influence of fibre characteristics and composition on the strength of the papers
was determined under two different conditions, at 23 oC and 50% RH and at 20 oC and 90%
RH.
The results demonstrate that besides the physical-mechanical characterization of packaging
grade papers, fibre anatomy and composition can be used successfully as a complementary
practical test to predict the performance of papers. The application of the predicting
correlations is proposed for the evaluation of the fibre supplies for the packaging industry. An
enormous potential for cost reduction can be created by the selection of the most appropriate
and inexpensive combination of grade papers for a specific packaging use.