Populus alba L., an Autochthonous Species of Spain: A Source for Cellulose Nanofibers by Chemical Pretreatment

In order to identify new sustainable sources for producing cellulose nanofibers (CNFs), fast-growing poplar (Populus alba L.) wood was evaluated herein. For that purpose, bleached poplar kraft pulp was produced and submitted to TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) mediated oxidation (TEMPO-ox) chemical pretreatment followed by microfluidization. The resulting CNFs were thoroughly characterized, including a rheological study at different pH values. Poplar CNFs showed properties comparable to eucalypt CNFs (reference material for CNFs production), showing high carboxylate content (1048 ± 128 µmol g−1), fibrillation yield (87.3% ± 8.1%), optical transmittance (83% at 700 nm) and thermal stability (up to more than 200 °C). Regarding the rheological study, whereas pH from 4 to 10 did not produce significant changes in rheological behavior, a reduction of pH down to 1 led to an order-of-magnitude increase on the viscoelastic functions. Therefore, poplar CNF shows potential in the pH-sensitive hydrogels application field. Finally, the possible ecotoxicity of poplar CNF was assessed. The decrease in cell viability was very low so that only concentrations causing a 10% cytotoxicity could be calculated for the assay detecting alterations in cell metabolism (10 µg mL−1) and plasma membrane integrity (60 µg mL−1).

A Rheological Study of Fibre Reinforced Composites and The Factors That Affect Rheological Behaviour During Impregnation Process: A Review

Rheological behaviour is an important factor affecting the flow behaviour of a fluid and many aspects related to this, mainly in the manufacturing process of fiber reinforced composites, either for Newtonian fluids or non-Newtonian fluids. During impregnation process, the viscosity changes with temperatures and their strain rate, has influenced the resin flow behaviour during curing process. In this paper, a review on the rheological studies of fiber reinforced composites for both, synthetic and natural based fibers, respectively, are presented. In addition to that, this review paper highlighting a few research studies conducted in literature on the main factors that affecting the rheological quality and performance of the composites. The aims of this review, mainly to capture the trend ranging from the recent five years back and summarize the various studies via experimental, theoretical or modelling works. Furthermore, also aiming to provide an ideal baseline information in the selection of the methods regarding rheological study to ensure better quality of pre-preg product and fibre reinforced composites can be produced in the author’s future work.

Rheological study of orange honey with influence on concentration

The rheological behavior of orange honey was studied in the temperature range 25-45 degrees Celsius with Haake VT 550 viscometer when the HV1 viscosity sensor at high shear rates 3.3 and 1312s-1. The assortment of orange honey has a dilating behavior being influenced by concentration and humidity. Honey was studied with a humidity of 16%, 17%, 19% and 21%. The rheological behavior is influenced by both humidity and its composition.