Natural fiber composites with plant oil-based resin

The goal of this project is to develop new composites using fibers and resins from renewable resources. The ACRES (Affordable Composites from Renewable Sources) group at the University of Delaware has developed new chemistries to synthesize rigid polymers from plant oils. The resins produced contain at least 50% plant triglycerides and have mechanical properties comparable to commercially available synthetic resins such as vinyl esters, polyesters and epoxies. This project explores the development of all-natural composites by using natural fibers such as hemp and flax as reinforcements in the ACRES resins. Replacing synthetic fibers with natural fibers has both environmental and economic advantages. Unlike carbon and glass fibers, natural fibers are abundantly available from renewable resources. In terms of cost, natural fibers are cheaper than the synthetic alternatives. The natural fibers and plant-based resins have been shown to combine to produce a low cost composite with good mechanical properties. Tensile strength in the 30 MPa range has been obtained for a composite containing about 30 wt% Durafibre Grade 2 flax. The tensile modulus was found to be 4.7 GPa for a 40 wt% flax composite. Similar numbers where obtained for the hemp composites obtained from Hemcore Inc. Composites from renewable resources offer significant potential for new high volume, low cost applications.

Composites from Natural Fibers and Soy Oil Resins

All natural composite sandwich beams for structural applications

New sheet molding compound resins from soybean oil. I. Synthesis and characterization

The focus of this work is to synthesize a monomer from a fatty acid methyl ester capable of forming high molecular weight polymers. The mono-unsaturation in the starting material, methyl oleate, was first epoxidized using a peroxy acid. This intermediate material was further modified using acrylic acid. The acrylated molecule is able to participate in free-radical polymerization reactions to form high molecular weight polymers. The rate of polymerization was low because of the long aliphatic structure of the monomer. It is hypothesized that the polymerization reaction occurred in the interface between the particle and water, thereby slowing down the reaction. After 18 h of reaction, a monomer conversion of approximately 91% was achieved. A maximum weight-average molecular weight of approximately 106 g/mol was observed after 14 h of reaction. At early reaction times linear polymers were formed. However, as the reaction time increased, the amount of branching that occurred on the polymer molecule increased, as indicated by gel permeation chromatography and light scattering. This has been attributed to chain transfer to polymer via hydrogen abstraction from a tertiary backbone C–H bond. The resulting polymer may be of considerable interest for pressure-sensitive adhesive applications. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 451–458, 2002; DOI 10.1002/pola.10130

Synthesis and characterization of monomers and polymers for adhesives from methyl oleate

The liquid resins described herein are derived from plant and animal oil triglycerides by suitably functionalizing the triglyceride with chemical groups that render it polymerizable. The triglyceride molecular structure is a combination of various triesters of fatty acids linked together with glycerol. The fatty acid residues are linear carboxylic acids containing from about 4 to about 30 carbon atoms, but preferably from about 14 to about 22 carbons and from about zero to about 4, or preferably from about 2 to 3 carbon-carbon double bonds. As obtained in nature, these double bonds are predominantly in the cis (Z) configuration and, in the case of polyunsaturated acids, not conjugated. The fatty acids derived from triglycerides include, but are not limited to the following: Lauric (C12:0), i.e., 12 carbon atoms long containing zero C=C double bonds, Myristic (C14:0), Palmitic (C16:0), Stearic (C18:0), Oleic (C18:1), Linoleic (C18:2), Linolenic (C18:3), Eicosanoic (C20:0), cis-11-Eicosanoic (C20:1), Docosanoic (C22:0) and cis-13-Docosanoic (C22:1). Typical plant oil triglycerides used for the purpose of this invention contain about 10-20 % saturated, about 20-30 % mono-unsaturated, about 40-60 % di-unsaturated, and about 5-15 % tri-unsaturated fatty acid residues, but other distributions, both narrow and broad, of fatty acid residues can also be used for the thermoset and plastic resins described in this invention.

Guiseppe Palmese

Papers

High modulus polymers and composites from plant oils