A series of alkyl ammonium/montmorillonite (MMT) organoclays were selected and melt blended with polyoxymethylene (POM) to explore the effect of MMT on the thermostability and mechanical properties of POM. The effects of the nature of the surfactants used in MMT modification on the intercalation of POM chains within the silicate galleries, the interfacial compatibility of POM/MMT and the thermostability of the composites were studied. The POM/MMT composites were prepared via melt, solution, solid state pan milling and in situ intercalative polymerisation blending method respectively, and the effects of preparation methods on the dispersion and exfoliation of MMT in POM matrix were measured by the wide angle X-ray scattering analysis. The thermal stabilisation effect of MMT on POM was studied by the isothermal weight loss analysis, thermogravimetric analysis (TGA) and formaldehyde emission amount measurement (FEA), which showed that a proper type and content of surfactant modified MMT may endow POM with improved thermostability. The crystallisation behaviour of POM/MMT composite was studied by the methods of polarised light microscopy (PLM), isothermal and non-isothermal crystallisation, which showed that a proper type and content of MMT had remarkable nucleation effect on POM and can improve the mechanical properties of POM efficiently.
A new type of highly efficient formaldehyde (FA) absorbent of polyoxymethylene (POM), hexamethylenediamine–formaldehyde polycondensates (HF) was prepared by the condensation reaction of hexamethylenediamine (HA) and FA. The effects of the synthetic technique including FA/HA molar ratio, reaction temperature and dispersant dosage on the thermal stability of POM/HF were studied, and finely divided, slightly branched HF polycondensates with high molecular weight and relatively high processing thermal stability were obtained. The thermal stabilization effect of HF on POM was studied through the isothermal weight loss analysis, FA emission amount (FEA) measurement, and balance torque analysis, which showed that HF had better thermal stabilization effect on POM than the commonly used FA‐absorbent melamine (MA). In order to improve the crystallization performance and mechanical properties of POM, the nucleation effect of HF on POM was studied by means of polarized light microscopy (PLM), isothermal and nonisothermal differential scanning calorimetry (DSC), indicating that HF had remarkable nucleation effect on POM. The investigation of mechanical properties showed that the addition of HF could improve the impact toughness of POM to a certain degree. Copyright © 2008 John Wiley & Sons, Ltd.
The thermostabilization of polyoxymethylene (POM) through amine treatment was studied by the measurements of isothermal weight loss, formaldehyde emission amount, balance torque, multiple processing and long-term aging analysis. The results showed that due to its chemical property, triethanolamine played the role of deactivator for residual initiator of POM, the absorbent for formaldehyde and formic acid produced by POM degradation, and it also helped to remove the unstable end groups of POM. Melting treatment with triethanolamine was a simple and effective processing method, and the thermostability of POM can be improved efficiently.
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