Synthesis of Dehydrated Ricinoleic Acid/Maleic Anhydride Adduct Based on Diels‐Alder Reaction: Characteristics and its Application in Pressure‐Sensitive Adhesive

Abstract Dehydrated ricinoleic acid (DRA)/maleic anhydride (MA) adducts were prepared through the Diels‐Alder (DA) reaction and then applied for the preparation of pressure‐sensitive adhesives (PSAs). The preparation parameters of the DRA/MA adduct were optimized by investigating the effects of molar ratio, reaction temperature, and reaction time on the adduction degree with acid value (AV) as the evaluation index. Results showed that the optimal parameters were the molar ratio of MA and DRA at 1.2: 1, reaction temperature of 120 °C, and reaction time of 1.5 h, under which the AV of DRA/MA adduct reached up to 298.7 mg KOH/g. Results from Fourier transform infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance spectrum showed that DA reaction effectively occurred between the conjugated diene of DRA and MA. Results from rheology and differential scanning calorimetry showed a higher viscosity and glass transition temperature of DRA/MA adduct than DRA due to the introduction of MA. Thermogravimetric analysis showed that the DRA/MA adduct had good thermal stability. Compared with epoxidized linseed oils‐based PSA (peel strength of 0.217 N/cm and loop tack of 0.390 N), PSA copolymerized by DRA/MA adduct and epoxidized linseed oils had higher adhesion strength (peel strength of 0.309–1.813 N/cm and loop tack of 0.713–7.490 N) and was crosslinked mainly by polyesterifications.