Phenol-urea-formaldehyde (PUF) resins were synthesized by a two-step polymerization process. The first step was the synthesis of 2,4,6-trimethylolphenol (TMeP) from phenol and formaldehyde, under alkaline conditions. In the second step PUF resins were synthesized by the reaction of TMeP with urea, under acidic and alkaline conditions. The influence of temperature on the synthesis of TMeP was investigated. The molar ratio between TMeP and urea was varied to study the composition effect on the second step of the PUF synthesis and final product properties. Synthesis of TMeP and PUF resins were monitored by inline FTIR-ATR system. Analytical methods, such as differential scanning calorimetry, nuclear magnetic resonance, thermogravimetric analysis, and infrared spectroscopy were used for characterization of TMeP and PUF resins. Obtained PUF resins were cured and tested on flexural strength.
Aqueous acrylic-polyurethane hybrid emulsions were prepared by semibatch emulsion polymerization of a mixture of acrylic monomers (butyl acrylate, methyl methacrylate, and acrylic acid) in the presence of polyurethane dispersion. Equivalent physical blends were prepared by mixing acrylic emulsion and polyurethane dispersion. The weight ratio between acrylic and polyurethane components varied to obtain different emulsion properties, microphase structure, and mechanical film properties of hybrid emulsions and physical blends. Particle size and molecular mass measurements, scanning electron microscopy, glass transition temperature, and rheological measurements performed characterization of the latex system. The mechanical properties were investigated by measuring tensile strength and Koenig hardness of dried films. The experimental results indicate better acrylic-polyurethane compatibility in hybrid emulsions than in physical blends, resulting in improved chemical and mechanical properties.
The oxidation kinetics of phenol in supercritical water
was examined in the presence of a solid
catalyst consisting of supported copper, zinc, and cobalt oxides in an
integrally operated fixed-bed reactor. For the conditions studied the rate of phenol
disappearance was found to be well
described by the Langmuir−Hinshelwood kinetic formulation, which
accounts for the equilibrium
adsorption of phenol and for dissociative oxygen adsorption processes
to the different types of
active sites and a bimolecular surface reaction between adsorbed
species on adjacent active
catalyst sites to be the controlling step. The apparent activation
energy and the heat of phenol
adsorption in the temperature range 400−440 °C were found to be 109
and 24 kJ/mol,
respectively. The products identified in the effluent include
dimers, single-ring compounds,
organic acids, and gaseous end products. The involvement of a
homogeneous−heterogeneous
free-radical mechanism is indicated by the intermediates formed.
The product distribution
suggests that the catalyst is much more selective on the para isomer of
phenoxy radical.
Comparing the wide spectrum of organic acids formed during the
noncatalytic phenol oxidation
in supercritical water with only formic and acetic acid found in the
effluent of catalytic process,
it may be concluded that the intermediates adsorbed on the catalyst
surface are probably rapidly
oxidized to the low molecular weight acids.
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