Studies on the ultrasonic degradation of cellulose macromolecular properties

Abstract

The ultrasonic degradation of cellulose was investigated using a Bandelin-Sonopuls-HD 60 equipment with a frequency of 20 kHz and an output power of 22 W. As cellulose samples five polymeranalogous nitrates with an initial degree of polymerization DP,,,, between 400 and 7500 dissolved in ethyl acetate were used. The resulting macromolecular properties were determined viscosimetrically as well as by SEC (DP, DP,, DP,, and distributions).The results show the following characteristics, some of them have already been known for the ultrasonic degradation of synthetic polymers:The rate of degradation is the more rapid the higher is DPo. At longer degradation times a limiting DP (DP,) is observed. Materials with a DP,(,, < 700 do not degrade further. During degradation a very rapid narrowing of the distribution of DP takes place which is the more rapid the higher is DP,. Correspondingly the polydispersity U decreases. The distributions show one maximum only during the whole degradation. The behaviour of polydispersity and distribution gives indications about the mechanism of scission of the molecules.The possibility to use ultrasonication to produce cellulose samples with narrow distributions is discussed. ZUSAMMENFASSUNG:Der Ultraschallabbau von Cellulose rnit einem Bandelin-Sonopuls-HD-60-Gerat mit einer Frequenz von 20 kHz und einer Leistungsabgabe von 22 W wurder untersucht. Es wurden funf Celluloseproben polymeranaloger Nitrate mit Ausgangspolymerisationsgraden DP,(,, zwischen 400 und 7 500 untersucht, gelost in Ethylacetat.Die resultierenden makromolekularen Eigenschaften wurden viskosimetrisch bzw. mit SEC (DP, DP,, DP, und Verteilungen) bestimmt. Die Resultate zeigen folgende charakteristische Merkmale, von denen die meisten von synthetischen Polymeren her bekannt sind:Die Abbaugeschwindigkeit ist vom Polymerisationsgrad (DP) abhangig. Der Abbau ist urn so stiirker, je hoher der Ausgangspolymerisationsgrad (DP,) ist. Bei Ian-Hiithig & Wepf Verlag, Zug CCC 0003-3146/97/$07.00 85 M. Marx-Figini geren Abbauzeiten wird ein sich nicht mehr andernder DP (DP,) beobachtet. Cellulosen mit DP,(,, < 700 werden nicht mehr abgebaut. Wahrend des Abbaus tritt eine sehr rasche Verengung der Verteilung des DP ein, die um so schneller stattfindet, je hoher DP, ist. Entsprechend nimmt die Uneinheitlichkeit (U) der Proben ab. Die Verteilungen sind wahrend des gesamten Abbaus monomodal. Die angefiihrten Charakteristika geben Hinweise auf einen Spaltungsmechanismus der Molekiile. Die Moglichkeit, die Ultraschallbehandlung fur die Herstellung einheitlicher Cellulosematerialien zu benutzen, wird diskutiert.

Characterization of Poly(ε-caprolactone)/Polyfumarate Blends as Scaffolds for Bone Tissue Engineering

“…1a it can be seen that the blend and PDIPF* were degraded faster than PCL, and that in all cases a decrease of the degradation rate was observed after 10 min. This result is in agreement with other sonication studies, which have reported that chain scission attains a limiting molecular weight below which no further degradation occurs [22,23]. The formation of postsonication inter-polymer coupling products was verified by SEC of a blend that included an azo-labeled PDIPF (Fig.…”

Novel process for isolating fibrils from cellulose fibers by high‐intensity ultrasonication. II. Fibril characterization

“…15 The crystallinity of the treated Lyocell fibers increased as the treatment time exceeded that estimated by WAXD. All four cellulose samples had a narrow peak at a 2y of about 20 and a lower peak at a 2y of about 12 ( Fig.…”

Pretreatment of garden biomass by alkali-assisted ultrasonication: effects on enzymatic hydrolysis and ultrastructural changes

“…The measurement of crystallinity index is important because ultrasonic treatment of cellulose generally cause a strong decrease in the degree of polymerization [38]. A perusal of results showed an increase (0.828) in CrI of alkali-ultrasonicated GB over the control (0.729).…”