Copyright
IIT Kharagpur
xi
ABSTRACT
The main objective of the work presented in the thesis is to develop special type of rigid polyurethane foam (PUF) of different density which will have good mechanical properties, and specialty fire−retardant properties like generation of low smoke, high limiting oxygen index (LOI), intumescent char forming property, etc. In this investigation rigid PUFs with wide range of density (30−450 kg/m3) were prepared by using both free−rise as well as molding technique. The effects of different raw materials such as polyols, catalyst, chain extender, surfactant, blowing agent, etc.
on the properties have been studied systematically. Effect of fillers (both micro and nano-sized) like precipitated silica, precipitated calcium carbonate, glass powder, nanosilica and nanoclays on the properties of water blown PUF have also been investigated.
Effects of different types of non−halogenated fire resistant additives on fire resistance characteristics of PUF were studied. Development of intumescent char during fire prevents fire spread. Effects of expandable graphite to modify these characteristics have also been studied. Various properties like density, compressive strength and modulus, thermal conductivity and thermal stability of these foam composites were measured. Different characterization techniques like Fourier Transform Infrared Spectroscopy (FT−IR), Scanning Electron Microcopy (SEM), Wide Angle X−ray Diffraction (WAXD), Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and cone calorimeter analysis, etc. were used in this investigation. Detailed studies on thermal and fire resistance behavior like LOI, flame spread rate, heat release rate, char yield, smoke density and toxicity gas generation in the event of fire were also investigated.
Finally it may be concluded that the judicious selection of different fire retardant ingredients in appropriate proportions can provide rigid PUF with good fire retardant properties. The proper monitoring of preparation process is important to develop foam having good mechanical, thermal and fire retardant property.
Keywords: Rigid PUF, flame retardant, intumescent, nanoclay, LOI, phosphorus, melamine, expandable graphite, smoke density.
