Mechanical Characterization of an Eucheuma cottonii White Seaweed-Based Bioplastic Film: Effect of seafood Protein and Sorbitol Plasticizer on Tensile Properties

Abstract: This work reports the preliminary mechanical characterization of a bioplastic film prepared from white Eucheuma cottonii seaweed, using sorbitol as a plasticizer and a small fraction of seafood protein as a reinforcing additive. The film was cast from an acid-extracted seaweed slurry and dried under ambient ventilated conditions. Tensile tests were carried out on four specimens whose geometry was inspired by the ASTM D638 Type V standard, using a manual screw-driven apparatus instrumented with an analog force gauge (capacity 10 N, resolution 0.05 N) and a digital dial indicator (resolution 0.01 mm). After removing the zero-load take-up artifacts observed at the beginning of each test, the mean ultimate tensile strength was found to be 2.67(76) MPa, the mean strain at break 1.01 0.17, and the mean Young’s modulus, determined from a linear regression on the initial elastic region, was 1.97(62) MPa. Optical microscopy revealed millimetre-scale residual porosities and an inhomogeneous through- thickness distribution of unfiltered fibers, which are identified as the primary mechanical weak points of the current formulation. Comparison with the existing literature on Eucheuma cottonii and Gracilaria films suggests that the unusually low stiffness and high apparent strain at break observed here reflect both the high plasticizer- to-polymer ratio of the formulation and the limitations of the testing setup, which are discussed in detail.

Keywords: bioplastic; Eucheuma cottonii; alginate; sorbitol; seafood protein; tensile testing.