Relationships between material properties and microstructure-mechanical attributes of extruded biopolymeric foams

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Show simple item record Agbisit, Roderick Nazario Malcaba 2007-05-21T13:54:04Z 2007-05-21T13:54:04Z 2007-05-21T13:54:04Z
dc.description.abstract Material formulation and extrusion process parameters affect the foaming process in terms of expansion, cell nucleation, and resultant foam microstructure, which, in turn, control mechanical properties. This study utilizes non-invasive x-ray microtomography (XMT), in combination with mechanical testing and novel phase transition analysis techniques, to understand these complex relationships. The first part of this study provided significant insight into the deformation mechanism of extruded cornstarch foams. Microstructure features, including average cell diameter (2.07-6.32 mm), wall thickness (0.13-0.25 mm) and number density (18-146 cm-3), were measured. Microstructure had moderate to high correlations (|r| = 0.48 - 0.81) with mechanical properties, including compression modulus (2.2-7.8 MPa), crushing stress (42-240 kPa), number of spatial ruptures (2.6-3.6 mm-1), average crushing force (22-67 N) and crispness work (6.4-22 N-mm). The second part of this study investigated the effects of formulation, using model systems comprising of cornstarch, whey protein isolate (WPI) and sucrose, on phase transition behavior, and physical, microstructure and mechanical properties of extrudates. Increase in WPI led to greater specific mechanical energy (SME) and higher extrudate expansion. WPI had a foaming effect, which increased the cell number density accompanied by decrease in average cell diameter. Increase in sucrose led to lesser SME and lower expansion of extrudates. Contrary to expectations, phase transition properties (softening temperature, Ts, and flow temperature, Tf) were not good indicators of SME. The concluding part of this study investigated glass transition and rheological properties of cornstarch at different moisture contents (18-30% wet basis) using differential scanning calorimetry (DSC), phase transition analysis (PTA) and on-line slit-die rheometry. Glass transition temperature (Tg) (31.20 - 57.55 C) of extrudates decreased as moisture content increased. Ts (42.5 - 85.6C) and Tf (109 - 136C) also followed the same trend, and exhibited high correlations (r = 0.89 and 0.86, respectively) with Tg. These parameters were good estimates of phase transition properties of the complex and heterogeneous formulations. As expected, on-line rheological parameters, including flow behavior index, n (0.0438 - 0.304) and consistency coefficient, K (10,500 - 45,700 Pa-sn-1), were functions of in-barrel moisture, and were related to phase transition properties using WLF kinetics. en
dc.description.sponsorship USDA, CSREES, National Research Initiative (NRI) Competitive Grants Program (Award Number 2003-35503-13999). en
dc.language.iso en_US en
dc.publisher Kansas State University en
dc.subject Phase transition en
dc.subject Microstructure en
dc.subject Mechanical en
dc.subject Extrusion en
dc.subject Biopolymeric foams en
dc.title Relationships between material properties and microstructure-mechanical attributes of extruded biopolymeric foams en
dc.type Dissertation en Doctor of Philosophy en
dc.description.level Doctoral en
dc.description.department Department of Grain Science and Industry en
dc.description.advisor Sajid Alavi en
dc.subject.umi Agriculture, Food Science and Technology (0359) en 2007 en August en

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