Cellulose experimental procedures

Chaudhuri, D. K. R., and J. J. Hermans Grafting onto cellulosic macromolecules through chain transfer to mercaptoethyl side chains. I. Experimental procedure and results. J. Polymer Sci. 48, 159 (1960). 

Results from the initial resin studied are also being employed in the development of additional experimental procedures. Plans are currently being drafted to prepare three-ply test specimens that are similar to the specimens used in the initial study, with the middle ply consisting of solid polystyrene. Comparing specimens with and without the graft polymers introduced to the ply interfaces should provide additional information on the ability of the cellulosic graft polymers to facilitate bonding between wood and plastic materials. If this approach proves successful, additional procedures will then be developed for the production of simple composite specimens. 

The results confirm that TGA experiments are not significantly affected by heat transport phenomena if low initial sample masses as well as the described TGA configuration and experimental procedures are applied. The temperature gradients inside the samples are sufficiently small to allow the fitting of formal kinetic models to the experimental mass loss curves assuming a homogeneous sample temperature. Cellulose samples with initial sample masses of around 5 mg and higher can only be submitted to kinetic analyses under consideration of the enthalpy balance. 

Interestingly, the identical experimental procedure was Independently developed, under the name of "solute exclusion" (SE) technique, in the studies of water swollen cellulosic materials (ref. 15-18) (See Fig. 2). Though this technique proved to be effective in elucidating the porous structure of swollen pulps and related materials, it suffered from a lengthy experimental procedure for obtaining a solute exclusion curve through a series of accurate concentration measurements of polymer solutions. 

The experimental procedure is similar to that used for dye adsorption [79], Since PNP does not adsorb on cellulose it can also be used for the measurement of speciflc surface of colorants in cellulose [80]. 

The competitive adsorption isotherms were determined experimentally for the separation of chiral epoxide enantiomers at 25 °C by the adsorption-desorption method [37]. A mass balance allows the knowledge of the concentration of each component retained in the particle, q, in equilibrium with the feed concentration, < In fact includes both the adsorbed phase concentration and the concentration in the fluid inside pores. This overall retained concentration is used to be consistent with the models presented for the SMB simulations based on homogeneous particles. The bed porosity was taken as = 0.4 since the total porosity was measured as Ej = 0.67 and the particle porosity of microcrystalline cellulose triacetate is p = 0.45 [38]. This procedure provides one point of the adsorption isotherm for each component (Cp q. The determination of the complete isotherm will require a set of experiments using different feed concentrations. To support the measured isotherms, a dynamic method of frontal chromatography is implemented based on the analysis of the response curves to a step change in feed concentration (adsorption) followed by the desorption of the column with pure eluent. It is well known that often the selectivity factor decreases with the increase of the concentration of chiral species and therefore the linear -i- Langmuir competitive isotherm was used ... 

The more stable carbohydrate constituent of wood is assumed to be almost pure alpha cellulose. This is shown by the fact that 94-96% of the reducing materials, obtained in the later stages of hydrolysis, is fermentable. High temperatures and longer periods of time are required for the hydrolysis of the stable cellulose when dilute acid is used. If strong acid (72% sulfuric, 45% hydrochloric, 85% phosphoric) is used, the cellulose dissolves and then is converted into smaller units. Both of these procedures have been studied by many experimenters. 

Eq. (5) in conjunction with Eqs. (8) and (9) have, so far, provided adequate representation of experimental isotherms6 32, which are characterized by an initial con vex-upward portion but tend to become linear at high pressures. Values of K, K2 and s0 have been deduced by appropriate curve-fitting procedures for a wide variety of polymer-gas systems. Among the polymers involved in recent studies of this kind, one may cite polyethylene terephthalate (PET) l2 I4), polycarbonate (PC) 19 22,27), a polyimide l6,17), polymethyl and polyethyl methacrylates (PMMA and PEMA)l8), polyacrylonitrile (PAN)15), a copolyester 26), a polysulphone 23), polyphenylene oxide (PPO)25), polystyrene (PS) 27 28), polyvinyl acetate 29) and chloride 32) (PVAc and PVC), ethyl cellulose 24) (EC) and cellulose acetate (CA) 30,3I>. A considerable number of gases have been used as penetrants, notably He, Ar, N2, C02, S02 and light hydrocarbons. 

Experimental error entered the data, of course, through the manual measurement of the viscosities of the four very dilute fractions. Another error in the viscosities was introduced by contamination of each fraction by some of the fraction preceding it. Not all of the liquid in the measuring syphon could be removed as the syphon emptied thus a small portion of the fraction was retained and added to the incoming fraction. Furthermore, the previous procedure required exact weights in each fraction, whereas now only relative weights are necessary. The relationship developed here can be extended to polymers other than cellulose. To do this, the values of K and a have to be determined for the particular polymer, dissolved in the desired GPC solvent which was used to establish the calibration curve. 

Collection of metal complexes of the analytes on suitable adsorbing materials is often employed as an enrichment step in combination with flame methods. In a procedure proposed by Solyak et al. [20], five metals [Co(II), Cu(II), Cr(III), Fe(III), and Pb(II)] were complexed with calmagite 3-hydroxy-4-[(6-hydroxy-m-tolyl)azo]-naphthalenesulfonic acid and subsequently collected on a soluble cellulose nitrate membrane filter. In this way an effective separation from alkaline and alkaline earth metals was achieved, based on the differences in their complex formation constants and those of the transition elements. The experimental parameters were optimized for the quantitative recovery of the elements. After hot dissolution of the filter with HNO3, the analytes were determined by FAAS. Minimum detectable concentrations ranged from 0.06 pg l-1 for Cu to 2.5 pg l-1 for Cr. 

Fig. 6. Investigation of kinetic properties of immobilized invertase by flow microcalorimetry in the circulation mode. Initial sucrose concentration 51 mM, invertase immobilization by biospecific binding on concanavalin A-bead cellulose was prepared by binding on concana-valin A linked to chlorotriazine-activated cellulose, a Raw experimental thermometric data b data after conversion by the procedure indicated in Fig. 4. Concentrations were determined spectrophotometrically (open symbols) and by transformation of thermometric data explained in Section 5 (closed symbols) [32]...

In the preceding methods, the enzyme is confined to small droplets, capsules, or inert carrier. Enlargement of a capsule to the size of a fermenter is theoretically possible, and this principle has been applied with practical modifications. The enzyme is free in solution as in the batch procedures, but an ultrafilter serves to separate the reaction products from the enzyme and substrate. Substrate is continuously pumped into the system, and product is removed by ultrafiltration to provide a continuous system. This method is applicable only to systems where the substrate is a large or an insoluble substance, so that it - with the enzyme - are retained inside the membrane. Successful demonstration of experimental runs on cellulose saccharification (Chose and Kostick, 1969) and on starch hydrolysis (Butterworth et al., 1969) have been made. Success depends upon the availability of suitable membranes and practical application on their cost. 

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