Modification of Tung Oil for Bio-Based Coating

Tung oil was used as a diene for modification with acrylate dienophiles via a Diels-Alder reaction. In this thesis, the research was divided into two related parts. In the first part, UV-curable resins were prepared from tung oil and tung oil alkyd for a high solids coating application. In the second part, tung oil alkyd was modified with three different acrylate monomers, possessing either alkoxysilane, triallyl ether, or fluorinated groups. The structures of the modified tung oil and alkyds were characterized by ¹H NMR, ¹³C NMR, MALDI-TOF mass spectroscopy, and gel permeation chromatography(GPC).

Two UV-curable tung oil-based resins in the first part were synthesized via the Diels-Alder cycloaddition. A UV-curable Tung Oil (UVTO) was prepared from bodied tung oil and trimethylolpropane trimethacrylate (TMPTMA) by a two-step reaction. Bodied tung oil was primarily prepared by treatment at high temperature, and then reacted with TMPTMA on the α-eleosterate of tung oil triglyceride via the Diels-Alder reaction. An inhibitor, phenothiazine, was added to avoid homopolymerziaton of TMPTMA. UV-curable Tung Oil Alkyd (UVTA) was prepared by the monoglyceride process, and then reacted with TMPTMA via the Diels-Alder reaction. The UVTO and UVTA were formulated with a free radical reactive diluent, tripropylene glycol diacrylate (TPGDA) and photoinitiator Irgacure 2100. Photo Differential Scanning Calorimeter (Photo-DSC) was used to investigate the curing kinetics of the UVTO and the UVTA. The data showed that the UVTA formula was cured faster than to the UVTO formula.

In the second part, the α-eleosterate pendent fatty acid of tung oil alkyd was functionalized via a Diels-Alder reaction with three different acrylate groups, 2,2,2- trifluoroethyl methacrylate, 3-methacryloxypropyl trimethoxysilane, and triallyl ether acrylate. Drying time and viscoelastic properties of the alkyd-modified film were investigated. Dynamic Mechanical Thermal Analysis (DMTA) was employed to evaluate the viscoelastic properties of the alkyd-modified films. The viscoelastic and drying time result shows that the alkyd modified with siloxane and triallyl group shows a faster drying time, higher crosslink density, and higher glass transition temperature compared to the unmodified alkyd, whereas the fluorinated alkyd showed surface active properties, but lacks in drying and crosslink density.