May 11, 2010

Midwest Biopolymers & Biocomposites Workshop

 

Poster Abstracts

105: Engineering the Mechanical Properties of Vegetable Oil Based Biopolymers with Electron Beam Irradiation

Mahendra Thunga1, Ying Xia2, Uwe Gohs3, Gert Heinrich3, Richard C. Larock2, and Michael R. Kessler1

1Department of Materials Science and Engineering and 2Department of Chemistry, Iowa State University, Ames, Iowa
3Leibniz-Institute of Polymer Research Dresden, Dresden, Germany


The influence of electron beam (EB) irradiation on the mechanical properties of biopolymers prepared from modified linseed and castor oils is studied. The linseed oil thermoset biopolymer was prepared by copolymerizing norbornenyl-functionalized linseed oil and dicyclopentadiene (DCPD) comonomer, whereas the castor oil-based thermoset was a copolymer of norbornenyl-modified oil and norbornenyl-modified alcohol from castor oil. Both the linseed and castor oil-based polymers were synthesized initially by ring-opening metathesis polymerization (ROMP). EB irradiation of the bulk polymer matrix after ROMP results in a substantial increase in the crosslink density. The residual carbon–carbon double bonds remaining after ROMP were expected to act as further crosslinking sites upon exposure to the energetic EB source. The increase in the crosslink density with increasing irradiation dose was investigated by dynamic mechanical analysis (DMA) and sol-gel fraction measurements. A strong increase in the cross-linking density was observed in both the biopolymers at high irradiation doses while only a marginal increase was observed at low irradiation doses. Mechanical properties from tensile testing, reveal that the Young’s modules and tensile strength were enhanced after crosslinking with EB irradiation. Moderate improvements in the thermal stability of these polymers, as studied by thermogravimetric analysis (TGA), was observed with increasing irradiation.