Effect of Synthesis Conditions on the Molecular Weight and Activation Energy of Urea-formaldehyde Prepolymer and Their Relationship

Atqiya  Anjum; Gazi Md. Arifuzzaman Khan

doi:10.38032/jea.2020.04.003

Authors

Atqiya Anjum Department of Applied Chemistry and Chemical Engineering, Islamic University, Kushtia-7003, Bangladesh
Gazi Md. Arifuzzaman Khan Department of Applied Chemistry and Chemical Engineering, Islamic University, Kushtia-7003, Bangladesh

DOI:

https://doi.org/10.38032/jea.2020.04.003

Keywords:

Urea-formaldehyde Prepolymer, F/U Molar Ratio, pH, Viscosity, Molecular Weight, Activation Energy

Abstract

The aim of this study is to find out the viscosity change of urea-formaldehyde (UF) resin with the synthesis parameters namely formaldehyde/urea (F/U) mole ratios, pH and temperature. The viscosity of UF resins, related to molecular weight and activation energy is very important factor of their usability. Urea-formaldehyde (UF) prepolymer was synthesized through polycondensation reaction with F/U ratio 0.8, 1.0, 1.2, 1.4, 1.6. The synthesis was carried out by two steps: alkali catalysis at reaction pH 8.3, 90°C for 60 min and thereafter acid catalysis at pH 4.3, 83°C for 15 min. Viscosity of prepolymer was determined at acid catalysis step by simple glass viscometer. Weight average molecular weight (Mw) was calculated from the viscosity data of UF prepolymer using Mark-Houwink equation. Highest Mw (2020.9) of prepolymer was obtained at F/U molar ratio 1.0 and pH 4.3. In addition, it was found that pH 4.0 yielded greater Mw (2049) UF prepolymer among the four reactions which were performed at pH 4.0, 4.3, 4.7, and 5.0. The energy of activation (E_a) of UF prepolymer was also calculated from the measured viscosity at temperature 70, 75, 80 and 85°C. The highest values of E_awere also found at F/U molar ratio 1.0 and pH 4.0 & lowest values was obtained at F/U molar ratio 1.6 and pH 5.0. From the experimental data, it was shown that the values of E_a and Mw were varied comparably with the change of reaction parameters.

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