Cyanoethylation of several fiber materials and their utilization as adhesive in wood-based panels
This study examines the cyanoethylation and thermoplasticity of several cyanoethylated fiber materials. Cyanoethylated pulps with a degree of substitution of 1.43 have the lowest Vicat softening point. Cyanoethylated poplar with a weight gain of 18.2 % has the lowest melting temperature. Instead of traditional adhesives, cyanoethylated materials can be used to produce wood-based panels because of their good thermoplasticity. Plywood bonded with cyanoethylated pulp has a bonding strength of 2.06 MPa and an average wood failure of 62.7 %. Wheat straw particle board containing 40 % cyanoethylated pulp has an internal bonding strength of 0.49 MPa, a modulus of rupture (MOR) of 33 MPa, and a density between 0.5 and 0.6 g cm−3. Fiberboard containing 40 % cyanoethylated pulp has an internal bonding strength of 0.53 MPa, MOR of 38 MPa, modulus of elasticity of 4,200 MPa, and a density between 0.7 and 0.8 g cm−3. Its swelling in thickness is 41 %.
Manipulating the colloidal properties of (non-)sulfated cellulose nanocrystals via stepwise surface cyanoethylation/carboxylation
Abstract When creating new materials, surface modification is an effective means of controlling the characteristics and the colloidal properties of cellulose nanocrystals (CNC), thereby increasing its compatibility with composite matrices. In this paper, the CNC surface is modified in aqueous media by cyanoethyl groups, followed by the hydrolysis of grafted nitrile groups. Particles having a surface composition close to that of native cellulose (N-CNC) and particles with sulfated surfaces (S-CNC) are used. The influence of the functional composition of CNC, as well as that of temperature and the ratio of reagents on the modified particles is investigated. It is shown that under identical synthesis conditions, a higher degree of cyanoethylation can be achieved for N-CNC. Particles modified with only nitrile groups and those with a polyfunctional composition modified with amide and carboxyl groups are obtained. Atomic force microscopy (AFM) and X-Ray diffraction (XRD) data indicate the preservation of both the morphology and structure of CNC post modification. The modified CNC particles are characterized by elemental analysis, synchronous thermal analysis (STA) and Fourier-transform infrared (FTIR) spectroscopy. The thermal stability of the resulting particles is close to that of the starting materials but higher for N-CNC and its derivatives. The acid-base properties of the CNC surface are established using a combination of methods (photometric measurements), namely potentiometric titration, dynamic light scattering, and microelectrophoresis. It is shown that the aggregative stability of modified particles along with the activity and number of acid-base centers on their surface increases sharply after the hydrolysis of nitrile groups.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.