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Title: Rigid polyurethane and kenaf core composite foams

Author
item Nar, Mangesh - University Of North Texas
item Webber Iii, Charles
item D'souza, Nandika - University Of North Texas

Submitted to: Polymer Engineering & Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2014
Publication Date: 2/24/2014
Publication URL: http://handle.nal.usda.gov/10113/62131
Citation: Nar, M., Webber III, C.L., D'Souza, N.A. 2014. Rigid polyurethane and kenaf core composite foams. Polymer Engineering & Science. doi: 10.1002/pen.23868.

Interpretive Summary: Polyurethane foams (PUFs) are used for heat and sound insulation for building structures and appliances, such as refrigerators and freezers. PUFs can be made into flexible and rigid polyurethanes. The development of natural plant-based PUFs has increased the need to identify and evaluate natural fibers that are suitable for reinforcing PUFs to produce rigid PUFs. Kenaf (Hibiscus cannabinus L.) is a potential fiber source for meeting this void. PUFs were produced using both the free expansion and constraint method to determine whether 5, 10, and 15% kenaf core would serve successfully as reinforcement. The research determined that kenaf core fibers successfully reinforced the PUFs when the forms were made using the constraint method. This research provides a successful means for developing both natural and synthetic rigid polyurethane forms using kenaf core material for reinforcement.

Technical Abstract: Rigid polyurethane foams are valuable in many construction applications. Kenaf is a bast fiber plant where the surface stem skin provides bast fibers whose strength-to-weight ratio competes with glass fiber. The higher volume product of the kenaf core is an under-investigated area in composite applications. The naturally porous structure of kenaf-core provides a novel reinforcement particle. In this work, foams of rigid polyurethane with 5, 10, and 15% kenaf-core were formed. To date efforts at using it as reinforcement have proven largely unsuccessful. This was mirrored in this effort when free expansion of the foam was utilized. However introducing constraint during foaming resulted in reinforcement. The environmental scanning electron microscopy is used in conjunction with in–situ microCT compression to capture the change in void fractions before and after deformation. The results show that free foaming resulted in poor reinforcement while a constrained expansion on the foam increased the reinforcement potential of the kenaf core.