Date of Award

5-2010

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Packaging Science

Advisor

Cooksey, Kay

Committee Member

Cooksey , Kay

Committee Member

Darby , Duncan

Committee Member

Datt , Greg

Committee Member

Daum , Matthew

Abstract

This research studied expanded polylactic acid cushioning foam and the effect the conditioning environment had on its shock absorbing properties. Polylactic acid, as a polymer, has been available since the 1960s. Only recently has the polymer been adapted to allow expanded foaming. This material's significance to industry lies in its sustainability. With global awareness at all-time highs, the push for sustainable materials is rising. The adaptation of PLA to EPLA is a result of that push. This research represents the first of its kind, by characterizing EPLA for cushioning and also to study the effects temperature and humidity on the material.
Samples of EPLA were obtained from Symbra in densities of 3.7 and 2.8 pcf. To describe the material, cushion curves were created for both densities in each of six environmental conditions ranging from freezing to tropical. Data was collected using ASTM D 1596 and combined using the stress energy method to create cushioning curves. The resulting cushion curves were then compared using linear regression. Accelerations, predicted with the created cushion curves were also compared.
Results of linear regression on stress energy equations showed no statistical difference between EPLA at six different environmental conditions. This was true for both 2.8 and 3.7 pcf material. Low correlations for drops 1 and 2 were observed when computing stress energy equations. These low correlations were the result of variability in material performance. When impact pulses were studied, first impact behavior of the material was descriptive of a non-elastic type cushioning system. Data from drops 2 though 5 typically appeared descriptive of an elastic closed cell cushioning material. Comparison of predicted drops did show changes in cushion behavior with environmental change. While some predicted drops ranged in acceleration level by over 60% for a specific drop, linear regression showed that the overall statistical differences were not significant. Results of this study indicate that EPLA foam behaved inconsistently during first impact and cushioning properties were not statistically changed by temperature and humidity. It should be noted that predicted acceleration levels were reported with high percent differences between environments, however as a whole, the stress energy equations were not statistically different.

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