Characteristics of polyurethane rigid foam nanocomposites, utilizing silica based nano-complex

M.M. Alavi Nikje^1,2[*],  A. Bagheri Garmarudi^1,2, Z. Mazaheri¹, M. Haghshenas²

1-      Chemistry Department, Faculty of Science, IKIU, Qazvin, Iran

2-      Department of Chemistry & Polymer Laboratories, Engineering Research Institute, Tehran, Iran

Email: alavim2006@yahoo.com

Nowadays polyurethane foams have found wide application in the industry as wide ranging physical characteristics after polymerization. New styling trends, surface design, safety functions and comfort are made possible by these materials. Rigid polyurethane foam is widely applied in construction and home appliance industry as a heat insulation system. Improving the physical and thermal properties of this kind of polymers has been interesting for researchers during last decade. In this research, it was tried to improve the mechanical and thermal properties of rigid polyurethane foams by synthesis and doping of a nanocomplex which was based on nano silica. The complex formation reaction was conducted using n-(2-aminoethyl)-3-aminopropyl trimethoxy silane. Interaction of organic coupling agent and surface of silica nanoparticles was monitored by FT-IR spectra. The signal at 3442 cm^-1 in Aerosil A200 was attributed to silanol group on the surface of nanoparticles and thr peak at 1107cm^-1 was assigned due to Si-O-Si bond. The IR spectrum of nano-complex demonstrated a band at 2900-3000 cm^-1 spectral region which was related to C-H stretching and indicated the formation of covalent bond between silanol groups on the nano-silica surface and coupling agent. Synthesized nanocomplex was added to the polyurethane foam formulation in different ratios (0-2.4 %w). Prepared nanocomposites were analyzed by tensile test, TGA, TMA, DMA and SEM. Dramatically improvement was observed in the characteristics of rigid polyurethane foam nanocomposites which allow a wider application range to be defined for these materials. The increasing effect of nano particulate fillers on the stress–strain behavior of foam samples was desired according to increment in the stiffness of composite. As the complexation of nano silica provides a treatment on surface of nano particles, it prevents the particle from accumulating, which results in the increase of the tensile strength of the nano composite. Investigating the DMA thermogram of prepared nanocomposites, it was observed that storage modulus is increasing in accordance with amount of nano-complex, while the loss modulus is vise versa. In the other hand glass transition temperature is also increased. The presence of coupling agent would cause surface modification for silica nanoparticles, providing chemical bond at the interface of the nano-complex and urethane structures. Thus relaxation mobility would be retarded at the interface of nano complex and urethane structure's chain end. This nanocomposite would be high interest for industrial and constructional applications e.g. for heat and sonic insulations.

Keywords: polyurethane, rigid foam, nano silica, coupling agent