Modifying the flocculation of microfibrillated cellulose suspensions by soluble polysaccharides under conditions unfavorable to adsorption.
Carboxymethylcellulose (CMC) and xanthan gum were studied as dispersants for microfibrillated cellulose (MFC) suspension using a rotational rheometer and imaging methods. The imaging was a combination of photography and optical coherence tomography (OCT). Both polymers dispersed MFC fibers, although CMC was more effective than xanthan gum. The negatively charged polymer chains increased the viscosity of the suspending medium and acted as buffers in between the negatively charged fibers. This behavior decreased the number and strength of contacts between the fibers and subsequently dispersed the flocs. The stronger separation of the fibers was reflected in the frequency sweep where the MFC/polymer suspensions had lower gel strength than pure MFC suspension. Dispersing effect was also observed in the flow measurements, where the floc size was more uniform with polymers in the decelerating flow and after long, slow constant shear, which normally induces a heterogeneous structure with large flocs into the MFC suspension.
Polymer Technology, Department of Biotechnology and Chemical Technology, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland. Electronic address: anni.sorvari@aalto.fi.
Anni
A
Sorvari
Polymer Technology, Department of Biotechnology and Chemical Technology, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland. Electronic address: tapio.saarinen@aalto.fi.
Tapio
T
Saarinen
VTT Technical Research Centre of Finland, P.O. Box 1603, 40101 Jyväskylä, Finland. Electronic address: sanna.haavisto@vtt.fi.
Sanna
S
Haavisto
VTT Technical Research Centre of Finland, P.O. Box 1603, 40101 Jyväskylä, Finland. Electronic address: juha.salmela@aalto.fi.
Juha
J
Salmela
Forest Products Surface Chemistry, Department of Forest Product Technology, Aalto University, P.O. Box 16300, 00076 Aalto, Finland. Electronic address: maija.vuoriluoto@aalto.fi.
Maija
M
Vuoriluoto
Polymer Technology, Department of Biotechnology and Chemical Technology, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland. Electronic address: jukka.seppala@aalto.fi.
Jukka
J
Seppälä
D000327:Adsorption; D002482:Cellulose / Q000737:chemistry*; D005427:Flocculation; D005782:Gels; D010781:Photography / Q000379:methods; D011108:Polymers / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry*; D011135:Polysaccharides, Bacterial / Q000737:chemistry; D012212:Rheology; D033081:Shear Strength; D012995:Solubility; D012996:Solutions; D013499:Surface Properties; D013535:Suspensions; D041623:Tomography, Optical Coherence; D014783:Viscosity; D014934:Wood
D005782:Gels; D011108:Polymers; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; D012996:Solutions; D013535:Suspensions; D002482:Cellulose; C002563:xanthan gum
Carboxymethyl cellulose; Dispersant; Microfibrillated cellulose; Optical coherence tomography; Rotational rheometry; Xanthan gum