Date of Award

Summer 8-18-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Biological Engineering

Advisor

Michael Mason

Second Committee Member

David Neivandt

Third Committee Member

Mehdi Tajvidi

Additional Committee Members

Colleen Walker

Abstract

Polyurethane foams have been a staple material for their use in medical positioners, such as post-surgery elevation pillows as well as specific tailored positioners for their use during surgery. Polyurethane foams are preferred because of their lower cost compared to other petroleum derived foams, their versatility, and suitable mechanical properties. However, the environmental impact, including both cost and perception, of these foams is immense. Therefore, alternatives are being explored with biopolymers emerging as a promising class of materials. Cellulose is one such polymer that has recently demonstrated desirable properties. In this study, cellulose nanofibrils (CNF), a household foaming agent, and a majority cellulose wood pulp (

Bleach kraftwood pulp and cellulose nanofibers were sourced from the Process Development Center at the University of Maine. The household foaming agent used was sodium dodecyl sulfate (SDS) purchased from Sigma Aldrich. To fabricate the bio-foams, first the pulp was adjusted to 3 wt%. The CNF and SDS are then mixed into the pulp slowly by hand and transferred to a blender set to low for 10 minutes. After blending the wet stable foam is poured into a 10x10cm mold and left unelevated and level to drain for 10 minutes. If draining occurs too quickly this can be detrimental to the overall morphology of the bio-foams as they lose air and become dense. To completely dry after draining the bio-foams are placed in a 60 °C convection dehydrator. Resilience testing was done on an IDM Instruments Foam Resilience Tester (IDM-F0030-M1) following ASTM D3574-17.

The bio-foams produced in this study have low density (14.29-20.0 mg/cm3) due to the micelle air-fiber network produced by blending with SDS. As well as improved structure and resilience compared to prior pulp-based foams. The air-fiber network allows hydrogen bonding to form between the CNF and the pulp causing a resilient yet supple matrix. The resilience of the bio-foams is tested to be between 25% & 35% which is comparable to current polyurethane foams which test with precision at 35%. Preliminary results suggest that as the weight percentage of CNF increases within the composite the resilience of the bio-foam also increases. As well as, as the level of SDS included in the foams increases the resilience of the foam increases.

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