Enhanced Thermo-Mechanical Stiffness, Thermal Stability, and Fire Retardant Performance of Surface-Modified 2D MoS2 Nanosheet-Reinforced Polyurethane Composites

  • Kuruma Malkappa, Suprakas Sinha Ray, Neeraj Kumar
  • Macromolecular Materials and Engineering, November 2018, Wiley
  • DOI: 10.1002/mame.201800562

Fire Retardant Performance of MoS2

Photo by Ricardo Gomez Angel on Unsplash

Photo by Ricardo Gomez Angel on Unsplash

What is it about?

This article reports new‐generation 2D‐MoS2 nanosheet‐containing polyurethane (PU) composite materials with improved thermo‐mechanical stiffness, thermal stability, and fire retardation properties. The surface of 2D‐MoS2 nanosheets is modified with melamine (M‐MoS2), and then PU composites with varying M‐MoS2 loadings are synthesized using an in situ polymerization method. During polymerization, 3‐amino‐propyl‐trimethoxy silane is introduced to create silicate functionality on the PU chains, which further improves the compatibility between PU and M‐MoS2. Microscopy studies confirm the distribution of highly intercalated and agglomerated M‐MoS2 nanosheets in the PU matrix. The PU composite containing 5 wt% M‐MoS2 shows a 65% higher storage modulus (at 30 °C) than that of pure PU. The thermal stability of pure PU is significantly improved (62 °C) after composite formation. Thermogravimetric analysis in combination with FTIR spectroscopy shows that the PU/M‐MoS2 composites release less toxic gases during thermal degradation compared to pure PU. Moreover, the composite containing 5 wt% M‐MoS2 shows improved fire retardation properties, with 45% and 67.5% decrease in the peak heat and total heat release rates, respectively, as compared with those of pure PU. In summary, 2D‐MoS2 is shown to have potential as an advanced nano‐filler to obtain stiffer PU composite with improved fire retardant property for structural application.

Why is it important?

In this work, we synthesized 2D MoS2 nanosheets by hydrothermal method and further modified the product with melamine (M‐MoS2), for use in development of flame‐retarding PU composites with improved thermo‐mechanical stiffness and thermal stability. FTIR analysis indicates that M‐MoS2 nanosheets in the PU composites improve the compatibility between filler and polymer due to the formation of hydrogen bonds between NH2 groups of melamine and the urethane urea and silicate functionalities of PU chains. For this reason, the PU/M‐MoS2 composites exhibited excellent FR activity with decreased toxic gas evolution during combustion. Increasing the content of organic‐modified M‐MoS2 in the PU matrix increased the organic/inorganic phase mixing, which further improved the mechanical stiffness and thermal stability of PU. The residual char analysis showed that in the presence of MoS2, the developed char was not compact, while that developed on M‐MoS2 composites was more compact and stronger, which further improved the FR activity with decreased toxic gas evolution.

Perspectives

Dr Neeraj Kumar
Council for Scientific and Industrial Research

In summary, the PU/M‐MoS2 system reported in this work may be a cheap and simple formulation for PU materials with excellent thermo‐mechanical stiffness and FR property, which further widens the use of PU as an advanced fire-retardant composite material for structural applications.

Read Publication

http://dx.doi.org/10.1002/mame.201800562

The following have contributed to this page: Dr Neeraj Kumar