Dangale Robinson, Ph.D. (2009) 

Dissertation Topic: 
Optimization of Sonication Parameters, Manufacturing Processes and Characterization of Nanophased Low Density Polyurethane Foam Sandwich Composites

Major Professor: Dr. Mahesh Hosur, Professor of Materials Science & Engineering

B.S.:  Materials Science Engineering, University of Alabama-Birmingham

Employment:  Xavier University, New Orleans, LA

Dissertation Abstract:

In the present investigation, an innovative process to develop optimum manufacturing parameters using the sonication route and characterization of thermal, microstructural, and quasi-static mechanical properties of liquid polyurethane foams are established.  Low density liquid polyurethane foam composed of Dimethyl Diisocyanate (Part A) and Polyol (Part B) is processed using various sonication amplitudes at 40%, 50%, and 60% and various sonication times of 15, 30, 45, and 60 minutes.  Subsequently, the foams were evaluated for thermal, microstructural, compressive, and flexural behavior.  The diverse sample groups were extensively compared with respect to the specified sonication amplitude and/or time. The as-prepared foams were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), density calculations, static compression, and flexural analysis.  Fabrication processes for the liquid polyurethane foam were optimized using sonic irradiation.  Results of the study have shown that foam cells are well structured and uniform in size and shape. The thermal, morphological, and mechanical analyses have been used to corroborate material properties and performance of the as-cast polyurethane foams. 

The continued research effort established the as prepared foam and sandwich structures via testing to identify the effect of adding the nanoclay on the thermal and mechanical properties. Microstructural analysis and morphology of the samples were studied also. The increase or decrease in thermal and mechanical properties was examined by comparing the neat and nanophased systems. Generally, the highest improvement on thermal and mechanical properties was obtained with 0.5 wt% loading of nanoclay.  In rare occasions, there was no improvement with the addition of the nanoparticle; however, in such cases, the lower wt% of nanoclay usually preformed better among the addition amounts.  It can be concluded that adding nanoparticles such as nanoclay dispersion and interfacial interactions with the base polymer matrix, which in turn enhances the overall morphological, thermal, and mechanical properties of nanocomposites.