In situ tensile deformation of zein films with plasticizers and filler materials

Material deformation is a dynamic process. Visualisation of this deformation can help to understand the local deformation and fracture behaviour. Zein (the prolamin protein from maize) films with different amount of plasticizers (0-25%) and different filler materials (maize oil, Dimodan (R), Vestosint (R)), at 25% (w/w) to protein) were deformed under tension and observed at micron scale in real time by a confocal laser scanning microscope (CLSM). The addition of plasticizers increased strain and decreased stress of zein films. At low level of plasticizers (6.25% and 12%), zein films deformed and fracture through micro-crack formation and propagation normal the tensile axis. At high Plasticization, only micro-pores were observed during tensile deformation. The filler material oil and Dimodan (R)( increased, but Vestosint (R)) decreased tensile strain in comparison to the control. This shows that the fracture dynamic is affected by the filler materials and is indeed observed by the CLSM. Analysis of local strain by Fluospheres (R) as particle tracking showed a good linear correlation with the tensile strain of the plasticized zein films. The local strains of filler materials and zein matrix in the films were different from the overall tensile strain. The combination of CLSM with a fluospheres (R) as particle tracking is a good method to study local deformation in biomaterials to understand the deformation and fracture behaviour of biomaterials. (C) 2006 Elsevier Ltd. All rights reserved.