Acrylated betulin as a comonomer for bio-based coatings. Part II: Mechanical and optical properties

• To enhance the properties of acrylated epoxidized soybean oil (AESO), a comonomer of acrylated betulin (AB) is added to the matrix.
• MOE and tensile strength of AESO is enhanced significantly by AB.
• Adding AB in AESO coating films increase its hardness and its abrasion resistance.
• The presence of AB in AESO films increase the absorption of UV light, but decrease the transparency of the coatings.
• A yellowing effect is observed with the addition of AB in the AESO polymer matrix.

Acrylated epoxidized soybean oil (AESO) is an interesting bio-based starting material for the development of biomaterials. Betulin, another bio-based product, can be extracted in large amounts from birch trees. Acrylated betulin (AB) was synthesized and added as a comonomer to the AESO at different loading levels (5 wt% and 10 wt%). AESO and AESO-AB mixture were cured photochemically to form films. The properties of the newly formulated coating systems were evaluated. The mechanical properties of cured AESO were affected by addition of AB comonomer. Modulus of elasticity (MOE) and tensile strength, hardness and abrasion resistance of the cured film increased, while strain at break was reduced. AB comonomer addition increased the glass transition temperature (Tg) of the cured AESO polymer while it yellowed AESO formulations and reduced optical clarity (transparency) of the cured film coating.

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