Thermal Stability of Polyurethane Coating Prepared by Using Diphenylolpropane

Thermal stability on air of polyurethane varnish coating prepared from diphenylolpropane, polyetherpolyol and polyisocyanate was assessed. The presence of urethane groups, formed by phenolic hydroxyl of diphenylolpropane, in the polymer structure was shown to decrease its thermooxidative degradation onset temperature. At the same time, deceleration of thermooxidative processes due to stabilizing effect of diphenylolpropane released at the beginning of thermal decay of polyurethane is observed in the higher temperature region.

EPOXYACRYLATE-BASED PHOTOPOLYMERIZABLE COMPOSITIONS FOR THERMOOXIDATIVE RESISTANT MATERIALS

The characteristics of thermooxidative degradation of the samples of cured epoxy acrylates based on epoxy resins ED-20 and UP-637, as well as their compositions with oligoether acrylate TGM-3, were investigated by the method of simultaneous thermal analysis. It has been found that the photopolymers have a sufficiently high resistance to thermal oxidation, the start temperature of active thermal destruction exceeds 325 ° C. Differences in the chemical structure of the aromatic fragment determine the features of thermal resistance. The addition of an active diluent to the composition is capable to reduce the internal stresses of the polymer structure and to promote a shift in the onset of thermal oxidation to higher temperatures.

Nanofragmentation of Expanded Polystyrene Under Simulated Environmental Weathering (Thermooxidative Degradation and Hydrodynamic Turbulence)

Fragmentation of macroplastics into microplastics in the marine environment is probably one of the processes that have generated most drive for developing the microplastics research field. Thus, it is surprising that the level of scientific knowledge on the combinative effect of oxidative degradation and mechanical stressors on fragmentation is relatively limited. Furthermore, it has been hypothesized that plastic fragmentation continues into the nanoplastic size domains, but environmentally realistic studies are lacking. Here the effects of thermooxidative aging and hydrodynamic conditions relevant for the shoreline environment on the fragmentation of expanded polystyrene (EPS) were tested in laboratory simulations. The pre-degraded EPS was cut into pieces and subjected to mechanical, hydrodynamic simulations during four-day stirring experiments. Subsamples were filtered and subsequently analyzed with light microscopy with automated image analysis particle size distribution determinations, polymer identification with Raman spectroscopy, Scanning Electron Microscopy (SEM) with automated image analysis particle size distribution. The nanoplastic size fraction was measured using nanoparticle tracking analysis. In addition, the degree of polymer oxidation was spectroscopically characterized with Fourier transform infrared (FTIR) spectroscopy. The results illustrate that fragmentation of the mesoplastic objects is observed already after 2 days, but that is more distinct after 4 days, with higher abundances for the smaller size fractions, which imply more release of smaller sizes or fragmentation in several steps. For the nanoplastic fraction, day four shows a higher abundance of released or fragmented particles than day two. The conclusions are that nanofragmentation is an important and understudied process and that standardized test protocols for both thermooxidative degradation and mechanical treatments mimicking realistic environmental conditions are needed. Further testing of the most common macro- and mesoplastic materials to assess the rates and fluxes of fragmenting particles to micro- and nanoplastic fractions should be conducted.

Thermooxidative Degradation of Composites Based on Epoxy Resin and Metal Nanopowders

The thermooxidative degradation behavior of the epoxy composites filled with metal nanopowders has been investigated by thermogravimetric analysis under nonisothermal conditions in air atmosphere. The mechanical characteristics of epoxy composites were also studied by three-point bending method. The comparison of two different types of metal nanopowder was made. Aluminum and copper nanopowders prepared by electrical explosion of wires were used as fillers separately as well as in combination with conventional fame-retardant boric acid. It was shown that aluminum nanopowder increased slightly thermal stability of the epoxy composites. On the contrary, the introduction of copper nanopowder in epoxy resin led to rapid degradation of the epoxy composite. The combination of metal nanopowders and boric acid improved thermal stability of the epoxy composites. The highest flexural properties showed the epoxy composite filled with copper nanopowder.