Results 81 to 90 of about 436,213 (129)

Urea–formaldehyde resin prepared with concentrated formaldehyde

Journal of Adhesion Science and Technology, 2016
AbstractThe characteristics of UF resin prepared with concentrated formaldehyde were studied in this paper. With the molar ratio F/U = 1.1, the UF resin prepared with concentrated formaldehyde showed better mechanical properties than that with formalin. The 13C-NMR and FTIR results indicated that there were more methylene groups, ether groups and urons
Zhigang Wu, Hong Lei, Guanben Du, Ming Cao, Xuedong Xi, Jiankun Liang   +5 more
openaire   +1 more source

Colloidal aggregation of aminoplastic polycondensation resins: Urea–formaldehyde versus melamine–formaldehyde and melamine–urea–formaldehyde resins

Journal of Applied Polymer Science, 2006
AbstractColloidal particles formation followed by their clustering have been shown to be the normal way of ageing of aminoplastic resins, namely urea–formaldehyde (UF) resins, melamine–formaldehyde (MF) resins, and melamine–urea–formaldehyde (MUF) resins. Ageing or further advancement of the resin by other means such as longer condensation times causes
A. Despres, A. Pizzi
openaire   +1 more source

Physical gelation of water‐borne thermosetting resins by percolation theory—Urea‐formaldehyde, melamine‐urea‐formaldehyde, and melamine‐formaldehyde resins

Journal of Polymer Science Part B: Polymer Physics, 2008
AbstractPercolation and effective‐medium theories are applied for calculating the connectivity threshold of colloid particles of given shapes, observed during the physical gelation, distinguished from chemical gelation, of aminoplastic resins. The rigidity threshold, being the critical solid fraction at which a rigid network is first formed, was also ...
Celzard, A., Pizzi, Antonio, Fierro, V.
openaire   +2 more sources

The structure of urea—formaldehyde resins

Journal of Applied Polymer Science, 1988
Fourier transform infrared (FTIR) spectroscopy has been used as a modern analytical tool to elucidate the structure of urea—formaldehyde (UF) resins. Several low molecular weight condensation products of urea and formaldehyde were synthesized and characterized.
openaire   +1 more source

Decreasing the Content of Free Formaldehyde in Urea-Formaldehyde Resins

Russian Journal of Applied Chemistry, 2005
The possibility of decreasing the content of free formaldehyde in urea-formaldehyde resins by varying the pH and urea-formaldehyde ratio in various synthesis steps was examined. Urea-formaldehyde resins containing no free formaldehyde were prepared.
V. Z. Maslosh, V. V. Kotova, O. V. Maslosh   +2 more
openaire   +1 more source

Fibers from urea–formaldehyde resins

Journal of Applied Polymer Science, 2000
The preparation of fibers from aqueous urea–formaldehyde resins has been investigated; a dry spinning process has been developed based on the extrusion of catalyzed resin into a drying chamber at 180–220°C, producing a multifilament yarn at spinning speeds of up to 600 m/min.
V. Rogers‐Gentile, G. C. East, J. E. Mcintyre, P. Snowden   +3 more
openaire   +2 more sources

Formaldehyde Liberation and Cure Behavior of Urea-Formaldehyde Resins

Holzforschung, 1990
On a etudie par calorimetrie differentielle a balayage le comportement au durcissement de plusieurs adhesifs uree-formaldehyde pour bois qui contenaient differents systemes de catalyseurs et agents ...
George E. Myers, James A. Koutsky
openaire   +1 more source

Rheokinetics of urea-formaldehyde resins gelation

Rheologica Acta, 1996
Rheokinetics of gelation of aqueous suspensions of urea-formaldehyde oligomers was studied. Experiments were carried out with a rotational viscometry method using two regimes of deformation: constant stress or constant shear rate. It was shown that a maximum on a viscosity vs.
Sergei G. Kulichikhin, Veronika B. Voit, Alexandre Ya. Malkin   +2 more
openaire   +1 more source

Hantzsch reaction in urea-formaldehyde resins

Russian Journal of Applied Chemistry, 2008
The effect of acetylacetone and ammonia in urea-formaldehyde resins on the reactions occurring in their presence was examined. The formation of 2,6-dimethyl-3,5-diacetyl-l,4-dihydropyridine in urea-formaldehyde resins was confirmed by 1H NMR spectroscopy.
V. V. Kotova, V. Z. Maslosh, T. M. Pekhtereva, A. Yu. Chervinskii   +3 more
openaire   +1 more source

Uron and uron-urea-formaldehyde resins

Journal of Applied Polymer Science, 1999
The favored pH ranges for the formation of urons in urea-formaldehyde (UF) resins preparation were determined, these being at pH's higher than 6 and lower than 4 at which the equilibrium urons N,N′-dimethylol ureas are shifted in favor of the cyclic uron species. Shifting the pH slowly during the preparation from one favorable range to the other causes
C. Soulard, C. Kamoun, A. Pizzi
openaire   +1 more source