In the packaging industry, cushioning products are usually made of plastic materials, such as polystyrene. The insulation and lightweight character make it more popular and convenient to use. However, the extensive use of it creates more waste leading to an environmental problem. Usually the cushioning foams are discarded after being used for inbox protection as packaging material; eventually they end up in a landfill. Most plastic foams are not biodegradable, which cannot be composted and will create more and more waste that affects the ecological system. In the mean time, foams made up of bio-degradable materials are considered. In general, biodegradable plastics are starch-based or cellulose-based, and the biodegradable components can be found in corn (e.g. corn starch, and corn cob). Instead of extracting the corn component, here popped corn kernel will be investigated for its suitability in packaging applications.

The production of highly aerated foods remains a challenge that requires skill to obtain desired appearance and texture. Since foams are fragile and inherently unstable, evaluation of structure changes with time requires a delicate approach. Non-invasive but informative evaluation of changes in aerated food properties is a desired goal to be achieved in this thesis. I studied the aging of egg white foams of different void fraction using two noninvasive techniques - ultrasonic spectroscopy and electrical resistivity - with a view to understanding aging mechanisms that would affect the quality of the final product. To help in interpretation of the results, a commercial high void fraction foam, Gillette (Sensitive), was also analyzed. As a support technique for ultrasound results I used image analysis in order quantitatively evaluate the size of bubbles in the foams. Large increases in attenuation were observed with increasing aging time and frequency. Results were modeled using an effective medium theory originated by Foldy (1945) in order to understand the factors governing foam lifetime and texture. From electrical resistance measurements, liquid fraction changes in an egg white foam column were evaluated quantitatively and qualitatively by using a generalized free drainage model. Although egg-white foams were more prone to changes due to drainage, I observed that for all foams the ultrasonic scaling parameter alfa*lambda/freq was proportional to the square of average bubble size (indicative of a diffusively driven aging process due to disproportionation of bubbles). Slopes of alfa*lambda/freq versus aging time were 6*10-8 and 11*10-8 for egg white foams of void fraction 0.65 and 0.78, respectively, indicating that disproportionation progressed approximately twice as fast in the high void fraction foam. The slopes of alfa*lambda/freq versus aging time were similar for both Gillette foam void fractions (0.93 and 0.91) at a value of 1.5*10–8 s-1, attributable to a lower solubility of isobutane compared to air. By combining ultrasound and electrical resistivity, this thesis has provided novel insights into understanding instability processes occurring in foams. Potentially, ultrasound techniques could be used instead of imaging for foam aging studies, since non-invasive and non-destructive measurements of attenuation and phase velocity permit interrogation of opaque foam structures.

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No description available.

The production of highly aerated foods remains a challenge that requires skill to obtain desired appearance and texture. Since foams are fragile and inherently unstable, evaluation of structure changes with time requires a delicate approach. Non-invasive but informative evaluation of changes in aerated food properties is a desired goal to be achieved in this thesis. I studied the aging of egg white foams of different void fraction using two noninvasive techniques - ultrasonic spectroscopy and electrical resistivity - with a view to understanding aging mechanisms that would affect the quality of the final product. To help in interpretation of the results, a commercial high void fraction foam, Gillette (Sensitive), was also analyzed. As a support technique for ultrasound results I used image analysis in order quantitatively evaluate the size of bubbles in the foams. Large increases in attenuation were observed with increasing aging time and frequency. Results were modeled using an effective medium theory originated by Foldy (1945) in order to understand the factors governing foam lifetime and texture. From electrical resistance measurements, liquid fraction changes in an egg white foam column were evaluated quantitatively and qualitatively by using a generalized free drainage model. Although egg-white foams were more prone to changes due to drainage, I observed that for all foams the ultrasonic scaling parameter alfa*lambda/freq was proportional to the square of average bubble size (indicative of a diffusively driven aging process due to disproportionation of bubbles). Slopes of alfa*lambda/freq versus aging time were 6*10-8 and 11*10-8 for egg white foams of void fraction 0.65 and 0.78, respectively, indicating that disproportionation progressed approximately twice as fast in the high void fraction foam. The slopes of alfa*lambda/freq versus aging time were similar for both Gillette foam void fractions (0.93 and 0.91) at a value of 1.5*10–8 s-1, attributable to a lower solubility of isobutane compared to air. By combining ultrasound and electrical resistivity, this thesis has provided novel insights into understanding instability processes occurring in foams. Potentially, ultrasound techniques could be used instead of imaging for foam aging studies, since non-invasive and non-destructive measurements of attenuation and phase velocity permit interrogation of opaque foam structures.

This thesis is about "nano-cellular" polymer foams, i.e., to understand nano-bubble nucleation and growth mechanisms, we used Self-Consistent Field Theory(SCFT) for the research.\\ Classical Nucleation Theory (CNT) is often used to calculate nucleation rates, but CNT has assumptions which break down for a nano-sized bubble: it assumes planar sharp interfaces and bulk phases inside bubbles. Therefore, since the size of a nano-sized bubble is comparable to the size of the polymer molecule, we assumed that a bubble surface is a curved surface, and we ivestigated effects of curvature on the nucleation barrier. SCFT results show that sharper curvatures of smaller s cause a higher polymer configurational entropy and lower internal energy, and also the collapse of the bulk phase for smaller bubbles causes low internal energy. Consequently, the homogenous bubble nucleation barrier for curved surfaces is much smaller than flat surface (CNT prediction).\\ We calculated direct predictions for maximum possible cell densities as a function of bubble radius without calculation of nucleation barrier or nucleation rates in CNT. Our results show higher cell densities at higher solvent densities and lower temperatures. Moreover, our cell density prediction reveals that rather than surface tension, the volume free energy, often labelled as a pressure difference in CNT, is the dominant factor for both cell densities and cell sizes. This is not predicted by CNT.\\ We also calculated direct predictions for the maximum possible cell densities as a function of system volume in compressible systems. With an assumption that system pressure has an optimal pressure which gives the maximal density of good quality foams (bulk phase inside bubble), we calculated the inhomogeneous system pressure, the homogeneous system, and cell density as a function of system volume.\\ Maximal cell prediction in compressible system shows the incompressible system prediction is the upperbound maximal cell density, and qualitatively consistent with the compressible system results - higher cell densities at low temperatures and high solvent densities.\\ In addition, our results show a bigger expansion as well as a high cell density at low temperature and high solvent density, but temperature is a more dominant factor than the solvent density. From our results, we assume that a quick pressure dropping is required to get a better quality foam of a higher cell density.

Thesis (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references (ℓ. 134-138)

Thesis (Master)--İzmir Institute of Technology, İzmir, 2005. / Keywords:crushing, aluminum foam, foam filling, energy absorber, composite tubes. Includes bibliographical references (leaves. 93-96).

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 96-100). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 96-100). Also available on the Internet.