Search results for "Cellulose"

Halloysite nanotubes filled with MgO for paper reinforcement and deacidification

2021

Abstract A novel material for the deacidification and protection of paper has been designed by using MgO filled halloysite nanotubes (Hal). The ability of MgO loaded nanotubes to control the acidic conditions was evaluated by pH measurements in aqueous solvent. Afterwards, paper was impregnated into hydroxypropyl cellulose dispersions containing the consolidating material. A simulation of strong acidic conditions allowed us to evaluate the deacidification effect of the composite material on the samples. In particular, the paper reaches a pH of 7.7 after 1 h exposition to HNO3 vapours when MgO-Hal nanoparticles are added to the impregnation mixture at a concentration of 10 wt% and it remains…

Membranes Directly Prepared from Solutions of Unsubstituted Cellulose

2005

Summary: Starting from 5 wt.-% solutions of a prehydrolysis kraft pulp ( = 135 kg · mol−1) in the mixed solvent (dimethylacetamide + 7 wt.-% LiCl) we have prepared cellulose membranes on different supports according to the phase inversion process using above all acetone (AC) and 2-propanol as precipitants. In this context we have studied the phase behavior of the quasiternary system (DMAc+LiCl)/AC/cellulose. The obtained membranes are mechanically stable and in their mechanical and separation properties on the whole comparable to membranes consisting of regenerated cellulose. With respect to gas separation the ideal selectivity of CO2 in combination with N2 and O2 turns out to be opposite f…

Investigation of the Interpolymer Complex between Hydroxypropyl Cellulose and Maleic Acid-Styrene Copolymer, 1

2004

The hydrogen bonding-interpolymer association of hydroxypropyl cellulose (HPC) with maleic acid-styrene (MAc-S) copolymer has been investigated in dilute aqueous solution by viscometry, turbidimetry and potentiometry. At a mixing ration between MAc-S and HPC of 10:90, the solution exhibits a phase separation upon heating, while for other mixing ration no phase separation could be detected. The stability of the interpolymer complex (IPC) increases as the temperatures rises. The stoichiometry of the IPC, in mole units, was estimated as being MAc-S:HPC=5:2. The thermodynamic functions (enthalpy and entropy) of the complexation process have been determined.

Fractional dissolution of “solid” unsubstituted cellulose

2000

Activated cellulose (Solucell, DP w = 1400) was extracted stepwise at room temperatures by means of mixed solvents consisting of N,N-dimethylacetamide (DMAc) and LiCl, starting with a salt concentration of 1 wt.-% and increasing it in increments of 1 wt.-% up to 7 wt.-%. Upon the regeneration of the thus obtained cellulose fractions by pouring the solutions dropwise into a large surplus of water, part of the mixed solvent is occluded in the polymer. For that reason the cellulose samples were purified by redissolving them in Ni-tren and by a second precipitation. This process, however, leads to pronounced polymer degradation. For that reason we have used a spinning nozzle to press the extrac…

Fractionation of unsubstituted cellulose from solutions in either Ni-tren or (N,N-dimethylacetamide + LiCl)

2000

Starting from solutions of unsubstituted cellulose (Avicel PH101, M w = 30.1 kg/mol and M w /M n = 3 or Solucell 500, M w = 230 kg/mol, M w /M n = 2.8) in either Nitren (0.8 M aqueous solution of the dihydroxotris(2-aminoethly)amine nickel(II) complex) or in a mixed solvent DMAc+LiCl (consisting of N,N-dimethylacetamide plus lithium chloride) it was investigated whether the segregation of a second phase caused by the addition of suitable precipitants leads to polymer fractionation. With Ni-tren the long chains accumulate in the precipitate formed upon the addition of sulfuric acid; as the pH falls below 9, the solution is free of cellulose. Nevertheless this route option for fractionation m…

Multi-objective optimization of building life cycle performance. A housing renovation case study in Northern Europe

2020

While the operational energy use of buildings is often regulated in current energy saving policies, their embodied greenhouse gas emissions still have a considerable mitigation potential. The study aims at developing a multi-objective optimization method for design and renovation of buildings incorporating the operational and embodied energy demands, global warming potential, and costs as objective functions. The optimization method was tested on the renovation of an apartment building in Denmark, mainly focusing envelope improvements as roof and exterior wall insulation and windows. Cellulose insulation has been the predominant result, together with fiber cement or aluminum-based cladding …

Midinfrared FT-IR as a Tool for Monitoring Herbaceous Biomass Composition and Its Conversion to Furfural

2015

A semiquantitative analysis by means of midinfrared FT-IR spectroscopy was tuned for the simultaneous determination of cellulose, hemicellulose, and lignin in industrial crops such as giant reed (Arundo donaxL.) and switchgrass (Panicum virgatumL.). Ternary mixtures of pure cellulose, hemicellulose, and lignin were prepared and a direct correlation area/concentration was achieved for cellulose and lignin, whereas indirect correlations were found for hemicellulose quantification. Good correspondences between the values derived from our model and those reported in the literature or obtained according to the official Van Soest method were ascertained. Average contents of 40–45% of cellulose, 2…

2019

Abstract. We present the laboratory results of immersion freezing efficiencies of cellulose particles at supercooled temperature ( T) conditions. Three types of chemically homogeneous cellulose samples are used as surrogates that represent supermicron and submicron ice-nucleating plant structural polymers. These samples include microcrystalline cellulose (MCC), fibrous cellulose (FC) and nanocrystalline cellulose (NCC). Our immersion freezing dataset includes data from various ice nucleation measurement techniques available at 17 different institutions, including nine dry dispersion and 11 aqueous suspension techniques. With a total of 20 methods, we performed systematic accuracy and precis…

Cellulose‑copper as bio-supported recyclable catalyst for the clickable azide-alkyne [3 + 2] cycloaddition reaction in water.

2018

Abstract Naturally-occurring cellulose has been employed as a bio-support macromolecule for the immobilization of either copper(I) or copper(II) ions in order to click azide and alkyne derivatives in water. Under such a click regime, 1,4-disubstitued-1,2,3-triazoles were obtained regioselectively in excellent yields at room temperature. The reaction work-up is simple and the bio-heterogeneous catalyst that has been fully characterized by AAS, SEM, EDX and FT-IR can be easily separated and reused at least five times without any significant decrease in its activity and selectivity, particularly in the case of the very stable CuI-Cellulose.

Generic Method for Modular Surface Modification of Cellulosic Materials in Aqueous Medium by Sequential Click-Reaction and Adsorption

2012

A generic approach for heterogeneous surface modification of cellulosic materials in aqueous medium, applicable for a wide range of functionalizations, is presented. In the first step, carboxymethyl cellulose (CMC) modified with azide or alkyne functionality, was adsorbed on a cellulosic substrate, thus, providing reactive sites for azide–alkyne cycloaddition click reactions. In the second step, functional units with complementary click units were reacted on the cellulose surface, coated by the click-modified CMC. Selected model functionalizations on diverse cellulosic substrates are shown to demonstrate the generality of the approach. The concept by sequentially combining the robust physic…