RESUMO
The self-plasticization, i.e., the increase in the polymer chains' mobility by including its monomer, has a major impact on a polymer's structural, thermal, and mechanical properties. In this study, differential scanning calorimetry (DSC), optical and Raman microscopies, thermo-mechanical analysis (TMA), size exclusion chromatography equipped with a multi-angle light scattering detector (SEC-MALS), and X-ray diffraction analysis (XRD) are used to investigate the effect of thermally induced self-plasticization of poly-(p-dioxanone), PDX, on the crystal growths from the amorphous and molten states. Significant changes in the crystallization behavior and mechanical properties of PDX are found only for samples self-plasticized at the depolymerization temperature (Td) above 150 °C. The intense self-plasticization leads to the decrease of the crystallization temperature, increase of the crystal growth rapidity, disappearance of the distinct αâα' polymorphic transition, reduction of the overall melting temperature, and segregation of the redundant monomer. Although the morphology of the crystalline phase has a major impact on the mechanical properties of PDX, the self-plasticization itself does not seem to result in any major changes in the magnitude, localization, or morphology of formed crystallites (these are primarily driven by the temperature of crystal growth). The manifestation of the variable activation energy concept is discussed for the present crystallization data.
RESUMO
Epoxy resins are characterized by excellent properties such as chemical resistance, shape stability, hardness and heat resistance, but they present low flame resistance. In this work, the synthesized derivatives, namely hexacyclohexylamino-cyclotriphosphazene (HCACTP) and novel diaminotetracyclohexylamino-cyclotriphosphazene (DTCATP), were applied as curing agents for halogen-free flame retarding epoxy materials. The thermal properties and combustion behavior of the cured epoxy resins were investigated. The obtained results revealed that the application of both derivatives significantly increased flame resistance. The epoxy resins cured with HCACTP and DTCATP exhibited lower total heat release together with lower total smoke production compared to the epoxy materials based on conventional curing agents (dipropylenetriamine and ethylenediamine). Comparing both derivatives, the HCACTP-cured epoxy resin was found to provide a higher flame resistance. The designed novel class of epoxy materials may be used for the preparation of materials with improved flame resistance properties in terms of flame spreading and smoke inhibition.
