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.

Phenol oxidation in supercritical water was carried out in a tubular

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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Abstract. The curing of bisphenol A-aniline based benzoxazine was studied applying different accelerators (4,4"-thiodiphenol, o-dianisidine, 2-mercaptobenzimidazole and 4-mercaptophenol) to initiate the catalytic ring-opening of benzoxazine. Possible pathways of benzoxazine ring-opening, polymerization and cross-linking without and with the addition of different accelerators are presented. The curing kinetics was investigated by model-free kinetic analysis of experimental data obtained by differential scanning calorimetry (DSC). The addition of different accelerators significantly reduced the onset temperature of curing in dynamic experiments. The effects of accelerators on the results of isothermal conversion prediction were studied and discussed in detail. Among the used accelerators, thiodiphenol showed the best accelerating efficiency and was consequently used in further studies, where its amount was varied. By low heating rate DSC analysis the catalytic ring-opening, thermally accelerated ring-opening and the diffusion-controlled steps were identified. The amount of added accelerator affected particularly the ring-opening and diffusion-controlled steps.

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Abstract. The Diels-Alder reaction between N-phenylmaleimide and benzoxazine bearing furan group was investigated for the purpose of successful appliance of self-healing in benzoxazine polymer networks. The reaction as a function of temperature/time was performed in molten state and in a solution, where also the kinetic study was performed. The Diels-Alder reaction leads to a mixture of two diastereomers: endo presented at lower cyclo-reversion temperature and exo at higher. Therefore, the conversion rates and exo/endo ratio were studied in detail for both systems. For instance, in molten state the Diels-Alder reaction was triggered by the temperature of the melting point at 60°C with exo/endo ratio preferable to the endo adduct. The study of the kinetics in a solution revealed that the Diels-Alder reaction followed typical bimolecular reversible second-order reaction. The activation energies were close to the previous literature data; 48.4 and 51.9 kJ·mol -1 for Diels-Alder reaction, and 91.0 and 102.3 kJ·mol -1 for retro-Diels-Alder reaction, in acetonitrile and chloroform, respectively. The reaction equilibrium in a solution is much more affected by the retro-Diels-Alder reaction than in a molten state. This study shows detailed investigation of DA reaction and provides beneficial knowledge for further use in self-healing polymer networks.