Impact of high consistency enzymatic hydrolysis and defibration drying on cellulose fiber pore characteristics

The purpose of this study is to examine the hornification of enzymatically hydrolyzed high consistency softwood kraft pulp in an experimental defibration dryer. This device dries pulp under turbulent conditions which can prevent interfiber bonding and produce a separated fiber population. This is useful in certain applications, such as composites, which require dry, unbonded pulp fibers. In this study, we examine how fibrillated pulps behave in the dryer with respect to pore expansion in hydrolysis and collapse in drying (hornification). It was found that the endoglucanase cocktail increased the micro-, meso-, and macropore volumes as a function of hydrolysis time. Drying decreased the pore volumes of each size category, with the biggest changes in the macropore region. The pulp with the highest swelling after hydrolysis had the lowest swelling after drying. The mesopores that were formed in hydrolysis were somewhat preserved after drying. After drying, unfibrillated pulp had good fiber separation, while the highly fibrillated samples formed sub-millimeter, spherical particles.