Honors College

Document Type

Honors Thesis


Marine Science


William Gramlich

Committee Members

Douglas Bousfield, Ian Bricknell, Mark Haggerty, Heather Hamlin

Graduation Year

May 2021

Publication Date

Spring 5-2021


With the growing attention on widespread plastic usage and its impact on the environment and human health, the need for sustainable alternatives to petroleum-based plastics is more important than ever. One of the most promising solutions is bioplastics; however, current bioplastics struggle to compete with the material properties of petroleum- based plastics. Agar is a sustainable algae-derived hydrocolloid polysaccharide that can be used for bioplastics and biofilms. Despite promising characteristics, bioplastics made from agar are brittle. Common additives, such as the plasticizer glycerol, offset brittleness but sacrifice strength in return. This study looks at the impact of natural rubber as an elastomer on the properties of an agar-based bioplastic in comparison to the impact of glycerol.

Agar was first functionalized with norbornene, which has been shown to promote dispersion of natural rubber and prevent layering in plastics made from other biopolymers. Further promoting dispersion, the constituents were then coupled using the thiol-ene reaction. To understand each step of the thiol-norbornene modification and addition of natural rubber, six plastic formulas were created. The viability of each plastic was determined using tensile testing analysis (maximum stress, maximum strain, elastic modulus, and toughness), a four-week degradation study, and a bioassay using Artemia sp. as a model organism for short-term toxicity. The results indicated that addition of natural rubber decreased the stiffness of the plastic with less impact on strength compared to glycerol. Thiol-norbornene modification were successful in coupling the constituents, evidenced by a decrease in degradation speed and toxicity response in Artemia.