The shear viscosity of carbon fibre suspension and its application for fibre length measurement

The viscosity of short carbon fibre suspensions in glycerol aqueous solution was measured using a bespoke vane-in-cup viscometer, where the carbon fibre has an aspect ratio from 450 to 2209. In the semi-concentrated regime, nL3 ranging from 20 to 4400, the suspensions demonstrated strong shear-thinning characteristics particularly at higher concentrations. The shear-thinning characteristic is strongly related to the crowding factor proposed by Kerekes, indicating that non-hydrodynamic interactions occur in the suspensions. The influence of fibre bending on viscosity emerges when the bending ratio is lower than 0.0028. An empirical model based on transient network formation and rupture was proposed and used to correlate the relative viscosity with fibre concentration nL3 and shear rate. Based on the model, a viscosity method is established to analyse the fibre length by measuring the viscosity of the fibre suspension using a bespoke vane-in-cup viscometer

DETERMINATION OF TOTAL BETA-GLUCAN IN MALT

An enzymic method for the estimation of total β‐glucan in barley has been modified to make it suitable for determination of the small amounts of β‐glucan present in malt. Interference from the high levels of reducing sugars in malt has been eliminated by reducing the free sugars in the sample with sodium borohydride rather than extracting them using 80% (v/v) ethanol. The reduction procedure also inactivates endogenous carbohydrate hydrolases in the sample. Because it is no longer necessary to extract the samples with ethanol and centrifuge repeatedly, the modified method is also advantageous in the analysis of barley β‐glucan. Errors associated with extraction are eliminated and the speed of analysis of large batches is greatly increased. 1986 The Institute of Brewing & Distillin