Molecular Weight Of Cellulose Acetate Research Articles

Electrospinning of cellulose nanocrystals; procedure and optimization

Cellulose nanocrystals (CNCs) and cellulose microfibrils (CMFs) are promising materials with the potential to significantly enhance the mechanical properties of electrospun nanofibers. However, the crucial aspect of optimizing their integration into these nanofibers remains a challenge. In this work, we present a method to prepare and electrospin a cellulosic solution, aiming to overcome the existing challenges and realize the optimized incorporation of CNCs into nanofibers. The solution parameters of electrospinning were explored using a combined experimental and simulation (molecular dynamics) approach. Experimental results emphasize the impact of polymer solution concentration on fiber morphology, reinforcing the need for further optimization. Simulations highlight the intricate factors, including the molecular weight of cellulose acetate (CA) polymer chains, electrostatic fields, and humidity, that impact the alignment of CNCs and CMFs. Furthermore, efforts were made to study CNCs/CMFs alignment rate and quality optimization. It is predicted that pure CNCs benefit more from electrostatic alignment, while lower molecular weight CA enables better CNC/CMF alignment.

Effect of organoclay content and molecular weight on cellulose acetate nanocomposites properties

Nanocomposites based on cellulose acetate (CA), a commercial organoclay (Cloisite30B) and triethyl citrate (TEC) were obtained using a solution casting method. Different nanocomposites were prepared according to different organoclay contents (2.5, 5.0, 7.5 and 10.0 wt.%) and molecular weight of cellulose acetate (Mn 30,000 and 50,000). The properties of the nanocomposites were evaluated by means of opacity index, X-ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical (modulus of elasticity, tensile strength and elongation at break), scanning electron microscopy (SEM) and oxygen transmission rate (OTR) measurements. All obtained nanocomposites showed the intercalation of polymer inside the clay structure which was slightly favored for nanocomposites with CA 30,000. Important changes on the opacity index, mechanical properties, glass transition and melting temperatures, crystalline fraction, oxygen permeability and fracture morphology of nanocomposite films were observed according to the increase of organoclay content. On the other hand, intercalation level and oxygen permeability showed some differences with the molecular weight of cellulose acetate.

Effects of electron beam irradiation of cellulose acetate cigarette filters

A method to reduce the molecular weight of cellulose acetate used in cigarette filters by using electron beam irradiation is demonstrated. Radiation levels easily obtained with commercially available electron accelerators result in a decrease in average molecular weight of about six-times with no embrittlement, or significant change in the elastic behavior of the filter. Since a first step in the biodegradation of cigarette filters is reduction in the filter material's molecular weight this invention has the potential to allow the production of significantly faster degrading filters.

Permeability performance of different molecular weight cellulose acetate hemodialysis membrane

Dialysis membranes were casted from solutions containing 20 wt.% cellulose acetate (CA), various concentrations of monosodium glutamate (MSG) and formic acid. Effect of MSG and different molecular weights of cellulose acetate on membrane permeability was investigated. As the MSG concentration increased from 2 wt.% to 6 wt.%, the uremic toxins permeability was enhanced, but further increase beyond this point did not improve the permeability performance. Similar separation trend was observed regardless of the CA molecular weight used, but membranes produced form high molecular weight CA membrane exhibit better uremic toxic permeability. SEM images illustrated that MSG influences the membrane thickness and macrovoids formation, while high molecular weight CA tends to suppress the size of the macrovoids. MSG also tends to reduce the membrane resistance promoting the formation of porous structure and thus explained for high ultrafiltration rate (UFR). In order to gain more insight on the influence of both MSG and molecular weight of CA on membrane properties, the membrane surfaces were analysed using Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), contact angle measurement (CAM), atomic force measurement (AFM). In addition, mechanical test and thermal stability studies were performed in this study to evaluate the strength of the membranes. In short, MSG and high molecular weight CA played crucial roles in enhancing the separation performance.

Enhanced degradation of cellulose acetate films in the copresence of triphenylsulfonium salt and benzophenone

AbstractTo investigate whether benzophenone (BP) enhances triphenylsulfonium salt (TPS) degradation of cellulose acetate (CA) during photoirradiation, CA (degree of substitution = 2.45) films containing TPS and BP were prepared, and their degradative behavior was examined under simulated solar exposure. The irradiation‐evoked generation of acetic acid from the films was greater in the copresence of TPS and BP than in the sole presence of TPS. This result indicates that the TPS was activated by BP to produce Brønsted acid, which induced the deacetylation of CA effectively. As a possible mechanism for this activation of TPS, we postulated that the TPS oxidized free‐radical species induced by the photoreaction of BP, which was followed by the generation of Brønsted acid. The activation of TPS by BP did not appear to significantly accelerate the main‐chain cleavage of CA because size exclusion chromatography data did not reveal any decrease in the molecular weight of CA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Enhanced degradation of cellulose acetate film containing diphenyliodonium salt–benzophenone

Cellulose acetate (degree of substitution 2.45) films containing diphenyliodonium salt and benzophenone were prepared and their degradative behavior was examined under simulated solar exposure. Acetic acid generation from the films under irradiation was greater in the co-presence of diphenyliodonium salt and benzophenone than in the sole presence of diphenyliodonium salt. Photosensitization and free-radical oxidization, which are followed by Bronsted acid generation, were postulated as the mechanism for the observed increase of deacetylation. The patterns of decreased molecular weight were different between the films with the diphenyliodonium salt and those with benzophenone; while the films with the diphenyliodonium salt kept a relatively constant molecular-weight distribution, the polydispersity increased in the films with benzophenone during the degradation. Since the synthesized characteristics of those two different patterns of change in molecular-weight distribution were observed in the co-presence of the diphenyliodonium salt and benzophenone, each additive appeared to act independently to lead to main-chain cleavage of cellulose acetate. Therefore, decrease in the molecular weight of cellulose acetate by diphenyliodonium salt did not seem to be enhanced in the co-presence with benzophenone.

The mechanical properties of gels in dimethyl phthalate of cellulose acetate of different degrees of substitution

The dependence of the temperature of transition to the high elastic and viscous flow state, on the degree of substitution and molecular weight of cellulose acetate has been found, using thermomechanical and dynamic mechanical methods. The molecular weight of the mechanical segment of the polymer was found from the temperature range of the high elastic state. The relaxational transitions in cellulose acetate gels in dimethyl phthalate are classified as segmental or local types, in accordance with the calculated apparent energies of activation and the lengths of the segments between branch points. Increase in the degree of substitution and in the concentration of the polymer raises the transition temperatures and increases the dynamic modulus and the apparent energy of activation for the relaxational processes in these systems.

A polarographic method of determining the molecular weight of cellulose acetate

A polarographic method of determining the molecular weight of cellulose acetate

Determination of average molecular weight of cellulose acetate by dielectric dispersion in solution

AbstractThe capacity of cells containing solutions of 5% cellulose acetate in dioxane was measured from 50 cycles to as high as 5 megacycles by a bridge method. A dispersion region was found between zero and approximately 40 kc. The frequency where the dielectric dispersion was 0.50 was taken as the critical frequency which was found to be related to the viscosity determined degree of polymerization. An empirical correlation enabled the calculation of degrees of polymerization from dielectric dispersion which could be readily duplicated and which agreed reasonably well with those found by the viscosity method. It is suggested that this procedure may develop into a very convenient and rapid method for molecular weights pending the accumulation of further experimental evidence.