Development of biobased unsaturated polyester resin containing highly functionalized castor oil

• A highly functionalized castor oil product was employed to modify UPR.
• The maleate CC functionality of the castor-oil-based product was high (2.62).
• Properties of the obtained biobased UPRs were comparable to those of the neat UPR.
• This work provides an effective method to prepare high-performance oil-based UPRs.

A highly functionalized castor oil product mainly composed of castor oil pentaerythritol glyceride maleates (COPERMA) was employed to fabricate a partial biobased unsaturated polyester resin (UPR) through blending it with petroleum-based UPR. The COPERMA product synthesized was characterized by FT-IR, 1H NMR, and ESI-MS to determine its possible structure and its functionality. The 1H NMR results showed that the maleate CC functionality of the COPERMA product was high (2.62). This highly functionalized product was then mixed with 35 wt% styrene before blending this mix with petroleum-derived UPR to prepare a new partial biobased UPR. Physical, thermal, and mechanical properties of the UPR/COPERMA resins were carefully studied. Physical properties data indicate that the resultant biobased resins are suitable for liquid molding process and had a less shrinkage than the neat UPR. Compared to the neat UPR, the cured UPR/COPERMA resins demonstrated comparable or even better thermal and mechanical properties when the content of COPERMA resin was up to 10 wt%. When the content of COPERMA resin increased to 20 wt%, the tensile strength and storage modulus at 35 °C decreased gradually, but not as much as reported in other oil/UPR systems, while other properties, such as crosslink density, glass transition temperature, tensile and flexural moduli, and impact strength, were still improved.