Synthesis of melamine-formaldehyde polycondensates as the thermal stabilizer of polyoxymethylene through ultrasonic irradiation

Melamine (MA), as the formaldehyde (FA) absorbent of polyoxymethylene (POM), was polymerically modified by a condensation reaction with FA to form the melamine-formaldehyde (MF) polycondensates with high molecular weight and comparatively high processing thermal stability. Ultrasonic irradiation was used for the synthesis, and ultrafine, crosslinked, and thermally stable MF polycondensates were obtained. The synthetic technique was discussed, and the thermal stabilization and nucleation effects of MF on POM were studied by the measurements of isothermal weight loss, balance torque, analysis of the formaldehyde emission amounts (FEAs), multiple extrusions, polarized light microscopy (PLM), isothermal and non-isothermal differential scanning calorimetry (DSC), and scanning electron microscopy (SEM), which indicated that the thermal stability and the crystallization performance of POM was greatly enhanced by using MF as a thermal stabilizer and nucleation agent. The MF prepared using ultrasonic irradiation can improve the mechanical properties of POM more effectively compared with that prepared with normal mechanical stirring. Copyright (c) 2008 John Wiley & Sons, Ltd.