Abstract: For polymer composite materials (PCM) with a reinforcing filler made of natural fibers, one of the problems is to
assess the quality of fiber preparation and determine the dynamics of the interaction of fibers and a poly-dimensional matrix. The
urgency of the problems is due to the expanding volume of research on PCM with plant fibers and various types and depth of
pretreatment of plant fibers. The subject of the study was a standard method for determining the wettability of cellulose materials.
The purpose of the experimental study is to propose a modified method for determining wettability, potentially suitable for assessing
the quality of preparation of reinforcing fillers of PCM from plant fibers. The standard GOST and modified method for determining
wettability were used. As a test material, wood cellulose, semi-green sulfite from coniferous wood in the form of a cellulose folder
was used. Cellulose samples were mechanically loosened to elementary fibers and tested for wettability. Three test schemes were
used – weighing a cup with a suspension immersed in water (scheme 1), weighing a vessel with water (scheme 2), standard
procedure according to GOST (scheme 3). According to schemes 1 and 2, measurements were carried out for up to 120 seconds,
according to scheme 3 – 30 seconds. The experiments were carried out in threefold repetition. The essence of the modified method
for determining the permeability is based on the constant control of the weight of the suspension as the sorption of water moisture.
The obtained laws of the kinetics of the process showed that the amount of water moisture absorbed by the samples varies nonlinearly over time. The wettability values determined according to various schemes, taking into account deviations, correspond to
each other. The determination of wettability by the modified method is proposed to be carried out within 120 seconds, periodically
monitoring the readings of the scales. The proposed modified method can be used for research purposes to study the dynamics of
water absorption and compare the behavior of various cellulose materials for PCM with a matrix based on hydrophilic polymers.